Dean W. Felsher
Professor of Medicine (Oncology) and of Pathology
Medicine - Oncology
Academic Appointments
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Professor, Medicine - Oncology
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Professor, Pathology
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Member, Bio-X
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Faculty Fellow, Sarafan ChEM-H
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Member, Stanford Cancer Institute
Administrative Appointments
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Director of Translational Research and Applied Medicine, Department of Medicine, Stanford University School of Medicine (2011 - Present)
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Co-Director Cancer Nanotechnology Program, Department of Radiology, Stanford School of Medicine (2016 - Present)
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Director of Admissions/Associate Director, Medical Scientist Training Program (2017 - Present)
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Director of Advanced Residency Training Program, Stanford University School of Medicine (2018 - Present)
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Co-Director of Spectrum KL2 Mentored Development Program, Stanford University, School of Medicine (2019 - Present)
Honors & Awards
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Elected Member, Association of American Physicians (2011)
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Translational Research Award, Burroughs Wellcome Trust (2005-2011)
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Elected Member, American Society of Clinical Investigation (2005)
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Clinical Investigator Award, Damon Runyon Foundation (2003-2008)
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Charles Carrington Prize, Stanford University (2002)
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Esther Ehrman Faculty Scholar Award, Stanford University (2000-2003)
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Physician Post-Doctoral Award, Howard Hughes Medical Institute (1997-1999)
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Emil Bogen Award, University of California, Los Angeles (1992)
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Honors, University of Chicago (1985)
Professional Education
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BA, University of Chicago (1985)
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MD PhD, UCLA, Medicine/Molecular Biology (1992)
Current Research and Scholarly Interests
My laboratory studies how oncogenes such as MYC initiate and maintain cancer. In particular we have shown that shutting down oncogenes even for a brief time can reverse cancer or elicit "Oncogene Addiction"
For a recent review of our work please see: The MYC oncogene - the grand orchestrator of cancer growth and immune evasion Nature Reviews Clinical Oncology, 2022
Examples of project in my laboraory:
We are studying basic mechanisms of Oncogene Addiction: the role of Self-renewal/Stemness, Metabolism, Host Immune System, Protein
Biogenesis, Microbiome, Extracellular Vesicles.
We are developing novel therapeutics using small molecules, nanoparticles, proteins/peptides that can be used to target oncogenes and/or restore the immune response against cancer.
We are developing new diagnostic and imaging methods such as PET, Mass Spec, Nanoproteomics.
Clinical Trials
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Antibiotic Therapy With or Without G-CSF in Treating Children With Neutropenia and Fever Caused by Chemotherapy
Not Recruiting
RATIONALE: Antibiotics may decrease the side effects of neutropenia and fever caused by chemotherapy. Colony-stimulating factors such as G-CSF may increase the number of immune cells found in bone marrow or peripheral blood and may help a person's immune system recover from the side effects of chemotherapy. It is not yet known whether antibiotic therapy plus G-CSF is more effective than antibiotic therapy alone for treating side effects caused by chemotherapy. PURPOSE: Randomized phase III trial to compare the effectiveness of antibiotic therapy with or without G-CSF in treating children who have neutropenia and fever that are caused by chemotherapy.
Stanford is currently not accepting patients for this trial.
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Molecular Analysis of Thoracic Malignancies
Not Recruiting
A research study to learn about the biologic features of cancer development, growth, and spread. We are studying components of blood, tumor tissue, normal tissue, and other fluids, such as urine, cerebrospinal fluid, abdominal or chest fluid in patients with cancer. Our analyses of blood, tissue, and/or fluids may lead to improved diagnosis and treatment of cancer by the identification of markers that predict clinical outcome, markers that predict response to specific therapies, and the identification of targets for new therapies.
Stanford is currently not accepting patients for this trial. For more information, please contact Jordan Preiss, 650-723-1002.
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Perfusion CT Monitoring to Predict Treatment Efficacy in Renal Cell Carcinoma
Not Recruiting
This pilot clinical trial studies perfusion computed tomography (CT) in predicting response to treatment in patients with advanced kidney cancer. Comparing results of diagnostic procedures done before, during, and after targeted therapy may help doctors predict a patient's response to treatment and help plan the best treatment.
Stanford is currently not accepting patients for this trial. For more information, please contact Yoriko Imae, 650-498-5186.
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Phase 2 Study of Atorvastatin Safety and Antitumor Effects in Non-Hodgkin's Lymphoma
Not Recruiting
This is an approach which can inflict significant toxicity. An alternative is to block expression of oncogenes which are over-expressed only in cancer cells, a therapeutic approach which could reduce toxicity to the host while maximizing destruction of the oncogene-dependent malignant cells.
Stanford is currently not accepting patients for this trial. For more information, please contact Alice Fan, 650-736-1285.
2024-25 Courses
- Biologics, advanced therapeutics and drug delivery methods
MED 211 (Aut) - Biotechnology Law
MED 283 (Spr) - Commercialization and Future Healthcare Trends
MED 223C (Spr) - Drug Development and Clinical
MED 223B (Win) - Drug Discovery
MED 223A (Aut) - Translational Research and Applied Medicine
MED 121, MED 221 (Aut, Win, Spr) -
Independent Studies (15)
- Curricular Practical Training
MED 390 (Aut, Win, Spr) - Directed Reading in Cancer Biology
CBIO 299 (Aut, Win, Spr, Sum) - Directed Reading in Immunology
IMMUNOL 299 (Aut, Win, Spr, Sum) - Directed Reading in Medicine
MED 299 (Aut, Win, Spr, Sum) - Early Clinical Experience in Immunology
IMMUNOL 280 (Aut, Win, Spr, Sum) - Early Clinical Experience in Medicine
MED 280 (Aut, Win, Spr, Sum) - Graduate Research
CBIO 399 (Aut, Win, Spr, Sum) - Graduate Research
IMMUNOL 399 (Aut, Win, Spr, Sum) - Graduate Research
MED 399 (Aut, Win, Spr, Sum) - Medical Scholars Research
MED 370 (Aut, Win, Spr, Sum) - TRIP: Translational Research Independent Project required of all MTRAM students
MED 299M (Win) - Teaching in Cancer Biology
CBIO 260 (Aut, Win, Spr) - Teaching in Immunology
IMMUNOL 290 (Aut, Win, Spr, Sum) - Undergraduate Research
IMMUNOL 199 (Aut, Win, Spr, Sum) - Undergraduate Research
MED 199 (Aut, Win, Spr, Sum)
- Curricular Practical Training
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Prior Year Courses
2023-24 Courses
- Biotechnology Law
MED 283 (Spr) - Current Topics in Applied Medicine
MED 211 (Aut) - MTRAM A: Translational Research Methods and Technologies: Cell Based Methods
MED 212A (Aut) - Stanford CTSA Scholars Seminar
EPI 229 (Aut, Win, Spr) - The A to Z of Translational Medicine: Emerging Trends in Drug Development and Next-gen Innovations
MED 251C (Spr) - The A to Z of Translational Medicine: Fundamentals and Technical Considerations of Drug Development
MED 251A (Aut) - The A to Z of Translational Medicine: Strategic Challenges in Drug Development
MED 251B (Win) - Translational Research and Applied Medicine
MED 121, MED 221 (Win, Spr)
2022-23 Courses
- Current Topics in Applied Medicine
MED 211 (Aut) - MTRAM A: Translational Research Methods and Technologies: Cell Based Methods
MED 212A (Aut) - Stanford CTSA Scholars Seminar
EPI 229 (Aut, Win, Spr) - TR Technologies B - (Translational Proteomics)
MED 212B (Win) - Translational Research and Applied Medicine
MED 121, MED 221 (Aut, Win, Spr)
2021-22 Courses
- Stanford CTSA Scholars Seminar
EPI 229 (Aut, Win, Spr) - Translational Research and Applied Medicine
MED 121, MED 221 (Aut, Win, Spr)
- Biotechnology Law
Stanford Advisees
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Doctoral Dissertation Reader (AC)
Andrea Garofalo -
Postdoctoral Faculty Sponsor
Xinyu Chen, Alessia Felici, Vishnu Priya Kanakaveti, Selene Zhou -
Postdoctoral Research Mentor
Xinyu Chen, Alessia Felici, Vishnu Priya Kanakaveti, Selene Zhou
Graduate and Fellowship Programs
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Oncology (Fellowship Program)
All Publications
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Spatial analysis reveals targetable macrophage-mediated mechanisms of immune evasion in hepatocellular carcinoma minimal residual disease.
Nature cancer
2024
Abstract
Hepatocellular carcinoma (HCC) frequently recurs from minimal residual disease (MRD), which persists after therapy. Here, we identified mechanisms of persistence of residual tumor cells using post-chemoembolization human HCC (n = 108 patients, 1.07 million cells) and a transgenic mouse model of MRD. Through single-cell high-plex cytometric imaging, we identified a spatial neighborhood within which PD-L1 + M2-like macrophages interact with stem-like tumor cells, correlating with CD8+ T cell exhaustion and poor survival. Further, through spatial transcriptomics of residual HCC, we showed that macrophage-derived TGFβ1 mediates the persistence of stem-like tumor cells. Last, we demonstrate that combined blockade of Pdl1 and Tgfβ excluded immunosuppressive macrophages, recruited activated CD8+ T cells and eliminated residual stem-like tumor cells in two mouse models: a transgenic model of MRD and a syngeneic orthotopic model of doxorubicin-resistant HCC. Thus, our spatial analyses reveal that PD-L1+ macrophages sustain MRD by activating the TGFβ pathway in stem-like cancer cells and targeting this interaction may prevent HCC recurrence from MRD.
View details for DOI 10.1038/s43018-024-00828-8
View details for PubMedID 39304772
View details for PubMedCentralID 8959995
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A big step for MYC-targeted therapies.
Trends in cancer
2024
Abstract
The MYC proto-oncogene encodes a master transcriptional regulator that is frequently dysregulated in human cancer. Decades of efforts have failed to identify a MYC-targeted therapeutic, and this is still considered to be a holy grail in drug development. We highlight a recent report by Garralda et al. of a Phase 1 clinical trial of OMO-103 in patients with solid malignancies.
View details for DOI 10.1016/j.trecan.2024.03.009
View details for PubMedID 38580534
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Nuclear to cytoplasmic transport is a druggable dependency in MYC-driven hepatocellular carcinoma.
Nature communications
2024; 15 (1): 963
Abstract
The MYC oncogene is often dysregulated in human cancer, including hepatocellular carcinoma (HCC). MYC is considered undruggable to date. Here, we comprehensively identify genes essential for survival of MYChigh but not MYClow cells by a CRISPR/Cas9 genome-wide screen in a MYC-conditional HCC model. Our screen uncovers novel MYC synthetic lethal (MYC-SL) interactions and identifies most MYC-SL genes described previously. In particular, the screen reveals nucleocytoplasmic transport to be a MYC-SL interaction. We show that the majority of MYC-SL nucleocytoplasmic transport genes are upregulated in MYChigh murine HCC and are associated with poor survival in HCC patients. Inhibiting Exportin-1 (XPO1) in vivo induces marked tumor regression in an autochthonous MYC-transgenic HCC model and inhibits tumor growth in HCC patient-derived xenografts. XPO1 expression is associated with poor prognosis only in HCC patients with high MYC activity. We infer that MYC may generally regulate and require altered expression of nucleocytoplasmic transport genes for tumorigenesis.
View details for DOI 10.1038/s41467-024-45128-y
View details for PubMedID 38302473
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Single-Nucleus Chromatin Accessibility Identifies a Critical Role for TWIST1 in IPF Myofibroblast Activity.
The European respiratory journal
2023
Abstract
In idiopathic pulmonary fibrosis (IPF) myofibroblasts are key effectors of fibrosis and architectural distortion by excessive deposition of extracellular matrix and their acquired contractile capacity. Single-cell RNA-sequencing (scRNA-seq) has precisely defined the IPF myofibroblast transcriptome, but identifying critical transcription factor (TF) activity by this approach is imprecise.We performed single-nucleus ATAC sequencing (snATAC-seq) on explanted lungs from patients with IPF (n=3) and donor controls (n=2) and integrated this with a larger scRNA-seq dataset (n=10 IPF, 8 control) to identify differentially accessible chromatin regions and enriched TF motifs within lung cell populations. We performed RNA-sequencing on pulmonary fibroblasts of bleomycin-injured Twist1-overexpressing COL1A2 Cre-ER mice to examine alterations in fibrosis-relevant pathways following Twist1 overexpression in collagen-producing cells.TWIST1, and other E-box TF motifs, were significantly enriched in open chromatin of IPF myofibroblasts compared to both IPF non-myogenic (Log2FC=8.909, adj p-value=1.82E-35) and control fibroblasts (Log2FC=8.975, adj p-value=3.72E-28). TWIST1 expression was selectively upregulated in IPF myofibroblasts (Log2FC=3.136, adj p-value= 1.41E-24), with two regions of TWIST1 having significantly increased accessibility in IPF myofibroblasts. Overexpression of Twist1 in COL1A2-expressing fibroblasts of bleomycin-injured mice resulted in increased collagen synthesis and upregulation of genes with enriched chromatin accessibility in IPF myofibroblasts.Our studies utilizing human multiomic single-cell analyses combined with in vivo murine disease models confirm a critical regulatory function for TWIST1 in IPF myofibroblast activity in the fibrotic lung. Understanding the global process of opening TWIST1 and other E-box TF motifs that govern myofibroblast differentiation may identify new therapeutic interventions for fibrotic pulmonary diseases.
View details for DOI 10.1183/13993003.00474-2022
View details for PubMedID 37142338
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MYC-driven synthesis of Siglec ligands is a glycoimmune checkpoint.
Proceedings of the National Academy of Sciences of the United States of America
2023; 120 (11): e2215376120
Abstract
The Siglecs (sialic acid-binding immunoglobulin-like lectins) are glycoimmune checkpoint receptors that suppress immune cell activation upon engagement of cognate sialoglycan ligands. The cellular drivers underlying Siglec ligand production on cancer cells are poorly understood. We find the MYC oncogene causally regulates Siglec ligand production to enable tumor immune evasion. A combination of glycomics and RNA-sequencing of mouse tumors revealed the MYC oncogene controls expression of the sialyltransferase St6galnac4 and induces a glycan known as disialyl-T. Using in vivo models and primary human leukemias, we find that disialyl-T functions as a "don't eat me" signal by engaging macrophage Siglec-E in mice or the human ortholog Siglec-7, thereby preventing cancer cell clearance. Combined high expression of MYC and ST6GALNAC4 identifies patients with high-risk cancers and reduced tumor myeloid infiltration. MYC therefore regulates glycosylation to enable tumor immune evasion. We conclude that disialyl-T is a glycoimmune checkpoint ligand. Thus, disialyl-T is a candidate for antibody-based checkpoint blockade, and the disialyl-T synthase ST6GALNAC4 is a potential enzyme target for small molecule-mediated immune therapy.
View details for DOI 10.1073/pnas.2215376120
View details for PubMedID 36897988
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MYC Overexpression Drives Immune Evasion in Hepatocellular Carcinoma that is Reversible Through Restoration of Pro-Inflammatory Macrophages.
Cancer research
2022
Abstract
Cancers evade immune surveillance, which can be reversed through immune checkpoint therapy in a small subset of cases. Here we report that the MYC oncogene suppresses innate immune surveillance and drives resistance to immunotherapy. In 33 different human cancers, MYC genomic amplification and overexpression increased immune checkpoint expression, predicted non-responsiveness to immune checkpoint blockade, and was associated with both Th2-like immune profile and reduced CD8 T cell infiltration. MYC transcriptionally suppressed innate immunity and MHCI mediated antigen presentation, which in turn impeded T cell response. Combined, but not individual, blockade of PDL1 and CTLA4 could reverse MYC-driven immune suppression by leading to recruitment of pro-inflammatory antigen-presenting macrophages with increased CD40 and MHCII expression. Depletion of macrophages abrogated the anti-neoplastic effects of PDL1 and CTLA4 blockade in MYC-driven hepatocellular carcinoma (HCC). Hence, MYC is a predictor of immune checkpoint responsiveness and a key driver of immune evasion through the suppression of pro-inflammatory macrophages. The immune evasion by MYC in HCC can be overcome by combined PDL1 and CTLA4 blockade.
View details for DOI 10.1158/0008-5472.CAN-22-0232
View details for PubMedID 36525476
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MYC oncogene elicits tumorigenesis associated with embryonic, ribosomal biogenesis, and tissue-lineage dedifferentiation gene expression changes.
Oncogene
2022
Abstract
MYC is a transcription factor frequently overexpressed in cancer. To determine how MYC drives the neoplastic phenotype, we performed transcriptomic analysis using a panel of MYC-driven autochthonous transgenic mouse models. We found that MYC elicited gene expression changes mostly in a tissue- and lineage-specific manner across B-cell lymphoma, T-cell acute lymphoblastic lymphoma, hepatocellular carcinoma, renal cell carcinoma, and lung adenocarcinoma. However, despite these gene expression changes being mostly tissue-specific, we uncovered a convergence on a common pattern of upregulation of embryonic stem cell gene programs and downregulation of tissue-of-origin gene programs across MYC-driven cancers. These changes are representative of lineage dedifferentiation, that may be facilitated by epigenetic alterations that occur during tumorigenesis. Moreover, while several cellular processes are represented among embryonic stem cell genes, ribosome biogenesis is most specifically associated with MYC expression in human primary cancers. Altogether, MYC's capability to drive tumorigenesis in diverse tissue types appears to be related to its ability to both drive a core signature of embryonic genes that includes ribosomal biogenesis genes as well as promote tissue and lineage specific dedifferentiation.
View details for DOI 10.1038/s41388-022-02458-9
View details for PubMedID 36207533
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Na+/H+-exchanger 1 enhances antitumor activity of engineered NK-92 natural killer cells.
Cancer research communications
2022; 2 (8): 842-856
Abstract
Adoptive cell transfer (ACT) immunotherapy has remarkable efficacy against some hematological malignancies. However, its efficacy in solid tumors is limited by the adverse tumor microenvironment (TME) conditions, most notably that acidity inhibits T and natural killer (NK) cell mTOR complex 1 (mTORC1) activity and impairs cytotoxicity. In several reported studies, systemic buffering of tumor acidity enhanced the efficacy of immune checkpoint inhibitors. Paradoxically, we found in a c-Myc-driven hepatocellular carcinoma model that systemic buffering increased tumor mTORC1 activity, negating inhibition of tumor growth by anti-PD1 treatment. Therefore, in this proof-of-concept study, we tested the metabolic engineering of immune effector cells to mitigate the inhibitory effect of tumor acidity while avoiding side effects associated with systemic buffering. We first overexpressed an activated RHEB in the human NK cell line NK-92, thereby rescuing acid-blunted mTORC1 activity and enhancing cytolytic activity. Then, to directly mitigate the effect of acidity, we ectopically expressed acid extruder proteins. Whereas ectopic expression of carbonic anhydrase IX (CA9) moderately increased mTORC1 activity, it did not enhance effector function. In contrast, overexpressing a constitutively active Na+/H+-exchanger 1 (NHE1; SLC9A1) in NK-92 did not elevate mTORC1 but enhanced degranulation, target engagement, in vitro cytotoxicity, and in vivo antitumor activity. Our findings suggest the feasibility of overcoming the inhibitory effect of the TME by metabolically engineering immune effector cells, which can enhance ACT for better efficacy against solid tumors.
View details for DOI 10.1158/2767-9764.crc-22-0270
View details for PubMedID 36380966
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Bi-steric mTORC1 inhibitor RMC-6272 synergizes with immune checkpoint inhibitors to induce sustained regression of MYC-driven hepatocellular carcinoma
AMER ASSOC CANCER RESEARCH. 2022
View details for Web of Science ID 000892509507274
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A more sensitive approach to cancer imaging using cancer-activated PET reporters
AMER ASSOC CANCER RESEARCH. 2022
View details for Web of Science ID 000892509508243
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Azapodophyllotoxin Causes Lymphoma and Kidney Cancer Regression by Disrupting Tubulin and Monoglycerols.
ACS medicinal chemistry letters
2022; 13 (4): 615-622
Abstract
A natural compound screen identified several anticancer compounds, among which azapodophyllotoxin (AZP) was found to be the most potent. AZP caused decreased viability of both mouse and human lymphoma and renal cell cancer (RCC) tumor-derived cell lines. Novel AZP derivatives were synthesized and screened identifying compound NSC750212 to inhibit the growth of both lymphoma and RCC both in vitro and in vivo. A nanoimmunoassay was used to assess the NSC750212 mode of action in vivo. On the basis of the structure of AZP and its mode of action, AZP disrupts tubulin polymerization. Through desorption electrospray ionization mass spectrometry imaging, NSC750212 was found to inhibit lipid metabolism. NSC750212 suppresses monoglycerol metabolism depleting lipids and thereby inhibits tumor growth. The dual mode of tubulin polymerization disruption and monoglycerol metabolism inhibition makes NSC750212 a potent small molecule against lymphoma and RCC.
View details for DOI 10.1021/acsmedchemlett.1c00673
View details for PubMedID 35450373
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Cyclic adenosine monophosphate/phosphodiesterase 4 pathway associated with immune infiltration and PD-L1 expression in lung adenocarcinoma cells.
Frontiers in oncology
2022; 12: 904969
Abstract
Background: The cyclic adenosine monophosphate/phosphodiesterase 4 (cAMP/PDE4) pathway is involved in inflammation and immune regulation; however, the effect of cAMP/PDE4 on immune infiltration and immune evasion in lung adenocarcinoma (LUAD) remains unclear.Methods: CBioPortal, which is the The Cancer Genome Atlas (TCGA) online database, and the Kaplan Meier plotter were used to analyze the association between genes and the prognosis of TCGA-LUAD. Tumor Immune Estimation Resource (TIMER) was used to analyze the association between gene expression and immune infiltration. The Genecards database was used to identify the transcription factors of related genes. The lung adenocarcinoma cell line H1299 and A549 were treated with cAMP pathway drugs. Flow cytometry and qRT-PCR were used to detect the PD-L1 protein and gene expression, respectively. A one-way analysis of variancewith Tukey's post-hoc test or a Student's t-test were used.Results: It was found that PDE4B and CREB1, which are downstream genes of the cAMP/PDE4 axis, were differentially expressed in LUAD and adjacent tissues and are correlated with the prognosis and immune infiltration of LUAD. In the CBioPortal database, cAMP pathway genes are closely related to programmed cell death-ligand 1 (PD-L1) expression in TCGA-LUAD. The protein-protein interaction revealed that there was a direct interaction between CREB1/CREBBP, which are the downstream molecules of the cAMP/PDE4 axis, and MYC; additionally, MYC was predicted to bind to the PD-L1 transcription site and regulate PD-L1 expression. CREB1 was also predicted to transcriptionally bind to both MYC and PD-L1. These results predicted the interaction network of cAMP/PDE4/CREB1/CREBP/MYC/PD-L1, and the core factor may be related to MYC. In the cell experiment, forskolin (an adenylate cyclase activator) and zardaverine (a PDE4 inhibitor) enhance the cAMP pathway and decrease PD-L1 expression, while SQ2253 (an adenylate cyclase inhibitor) inhibits the cAMP pathway and increases PD-L1 expression of the LUAD cell lines H1299 and A549, and MYC regulation by these drugs was positively correlated with PD-L1 regulation, which verified the regulation of the cAMP/PDE4 pathway on MYC and PD-L1.Conclusions: This study showed that the cAMP/PDE4 pathway may play an important role in PD-L1 regulation and immune infiltration in LUAD.
View details for DOI 10.3389/fonc.2022.904969
View details for PubMedID 35978822
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Tackling heterogeneity in treatment-resistant breast cancer using a broad-spectrum therapeutic approach.
Cancer drug resistance (Alhambra, Calif.)
2022; 5 (4): 917-925
Abstract
Tumor heterogeneity can contribute to the development of therapeutic resistance in cancer, including advanced breast cancers. The object of the Halifax project was to identify new treatments that would address mechanisms of therapeutic resistance through tumor heterogeneity by uncovering combinations of therapeutics that could target the hallmarks of cancer rather than focusing on individual gene products. A taskforce of 180 cancer researchers, used molecular profiling to highlight key targets responsible for each of the hallmarks of cancer and then find existing therapeutic agents that could be used to reach those targets with limited toxicity. In many cases, natural health products and re-purposed pharmaceuticals were identified as potential agents. Hence, by combining the molecular profiling of tumors with therapeutics that target the hallmark features of cancer, the heterogeneity of advanced-stage breast cancers can be addressed.
View details for DOI 10.20517/cdr.2022.40
View details for PubMedID 36627896
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Anti-PD-L1 F(ab) Conjugated PEG-PLGA Nanoparticle Enhances Immune Checkpoint Therapy.
Nanotheranostics
2022; 6 (3): 243-255
Abstract
Background: Immune checkpoint therapies are effective in the treatment of a subset of patients in many different cancers. Immunotherapy offers limited efficacy in part because of rapid drug clearance and off-target associated toxicity. PEG-PLGA is a FDA approved, safe, biodegradable polymer with flexible size control. The delivery of immune checkpoint inhibitors such as anti-PD-L1 (α-PD-L1) via PEG-PLGA polymer has the potential to increase bioavailability and reduce immune clearance to enhance clinical efficacy and reduce toxicity. Methods: The Fc truncated F(ab) portion of α-PD-L1 monoclonal antibody (α-PD-L1 mAb) was attached to a PEG-PLGA polymer. α-PD-L1 F(ab)-PEG-PLGA polymers were incubated in oil-in-water emulsion to form a α-PD-L1 F(ab)-PEG-PLGA nanoparticle (α-PD-L1 NP). α-PD-L1 NP was characterized for size, polarity, toxicity and stability. The relative efficacy of α-PD-L1 NP to α-PD-L1 mAb was measured when delivered either intraperitoneally (IP) or intravenously (IV) in a subcutaneous mouse colon cancer model (MC38). Antibody retention was measured using fluorescence imaging. Immune profile in mice was examined by flow cytometry and immunohistochemistry. Results: Engineered α-PD-L1 NP was found to have pharmacological properties that are potentially advantageous compared to α-PD-L1 mAb. The surface charge of α-PD-L1 NP was optimal for both tumor cell uptake and reduced self-aggregation. The modified size of α-PD-L1 NP reduced renal excretion and mononuclear phagocyte uptake, which allowed the NP to be retained in the host system longer. α-PD-L1 NP was non-toxic in vitro and in vivo. α-PD-L1 NP comparably suppressed MC38 tumor growth. α-PD-L1 NP appeared to elicit an increased immune response as measured by increase in germinal center area in the spleen and in innate immune cell activation in the tumor. Finally, we observed that generally, for both α-PD-L1 NP and α-PD-L1 mAb, the IP route was more effective than IV route for tumor reduction. Conclusion: α-PD-L1 NP is a non-toxic, biocompatible synthetic polymer that can extend α-PD-L1 antibody circulation and reduce renal clearance while retaining anti-cancer activity and potentially enhancing immune activation.
View details for DOI 10.7150/ntno.65544
View details for PubMedID 35145835
View details for PubMedCentralID PMC8824669
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DISTINCT IMMUNE MECHANISMS OF COMBINED PD-L1 AND CTLA-4 BLOCKADE IN HEPATOCELLULAR CARCINOMA (HCC)
WILEY. 2021: 110A
View details for Web of Science ID 000707188000163
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The MYC oncogene - the grand orchestrator of cancer growth and immune evasion.
Nature reviews. Clinical oncology
2021
Abstract
The MYC proto-oncogenes encode a family of transcription factors that are among the most commonly activated oncoproteins in human neoplasias. Indeed, MYC aberrations or upregulation of MYC-related pathways by alternate mechanisms occur in the vast majority of cancers. MYC proteins are master regulators of cellular programmes. Thus, cancers with MYC activation elicit many of the hallmarks of cancer required for autonomous neoplastic growth. In preclinical models, MYC inactivation can result in sustained tumour regression, a phenomenon that has been attributed to oncogene addiction. Many therapeutic agents that directly target MYC are under development; however, to date, their clinical efficacy remains to be demonstrated. In the past few years, studies have demonstrated that MYC signalling can enable tumour cells to dysregulate their microenvironment and evade the host immune response. Herein, we discuss how MYC pathways not only dictate cancer cell pathophysiology but also suppress the host immune response against that cancer. We also propose that therapies targeting the MYC pathway will be key to reversing cancerous growth and restoring antitumour immune responses in patients with MYC-driven cancers.
View details for DOI 10.1038/s41571-021-00549-2
View details for PubMedID 34508258
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A bi-steric mTORC1 inhibitor that selectively reactivates 4EBP1 and induces regression of MYC-driven hepatocellular carcinoma.
AMER ASSOC CANCER RESEARCH. 2021
View details for Web of Science ID 000680263503088
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Twist1 is required for the development of UVB-induced squamous cell carcinoma.
Molecular carcinogenesis
2021
Abstract
The transcription factor Twist1 has been reported to be essential for the formation and invasiveness of chemically induced tumors in mouse skin. However, the impact of keratinocyte-specific Twist1 deletion on skin carcinogenesis caused by UVB radiation has not been reported. Deletion of Twist1 in basal keratinocytes of mouse epidermis using K5.Cre*Twist1flox/flox mice led to significantly reduced UVB-induced epidermal hyperproliferation. In addition, keratinocyte-specific deletion of Twist1 significantly suppressed UVB-induced skin carcinogenesis. Further analyses revealed that deletion of Twist1 in cultured keratinocytes or mouse epidermis in vivo led to keratinocyte differentiation. In this regard, deletion of Twist1 in epidermal keratinocytes showed significant induction of early and late differentiation markers, including TG1, K1, OVOL1, loricrin, and filaggrin. Similar results were obtained with topical application of harmine, a Harmala alkaloid that leads to degradation of Twist1. In contrast, overexpression of Twist1 in cultured keratinocytes suppressed calcium-induced differentiation. Further analyses using both K5.Cre*Twist1flox/flox mice and an inducible system where Twist1 was deleted in bulge region keratinocytes showed loss of expression of hair follicle stem/progenitor markers, including CD34, Lrig1, Lgr5, and Lgr6. These data support the conclusion that Twist1 has a direct role in maintaining the balance between proliferation and differentiation of keratinocytes and keratinocyte stem/progenitor populations. Collectively, these results demonstrate a critical role for Twist1 early in the process of UVB skin carcinogenesis, and that Twist1 may be a novel target for the prevention of cutaneous squamous cell carcinoma.
View details for DOI 10.1002/mc.23296
View details for PubMedID 33713497
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Smart Self-Assembly Amphiphilic Cyclopeptide-Dye for Near-Infrared Window-II Imaging.
Advanced materials (Deerfield Beach, Fla.)
2021: e2006902
Abstract
Development of novel nanomaterials for disease theranostics represents an important direction in chemistry and precision medicine. Fluorescent molecular probes in the second near-infrared window (NIR-II, 1000-1700nm) show high promise because of their exceptional high detection sensitivity, resolution, and deep imaging depth. Here, a sharp pH-sensitive self-assembling cyclopeptide-dye, SIMM1000, as a smart nanoprobe for NIR-II imaging of diseases in living animals, is reported. This small molecule assembled nanoprobe exhibits smart properties by responding to a sharp decrease of pH in the tumor microenvironment (pH 7.0 to 6.8), aggregating from small nanoprobe (80nm at pH 7.0) into large nanoparticles (>500nm at pH 6.8) with 20-30 times enhanced fluorescence compared with the non-self-assembled CH-4T. It yields micrometer-scale resolution in blood vessel imaging and high contrast and resolution in bone and tumor imaging in mice. Because of its self-aggregation in acidic tumor microenvironments in situ, SIMM1000 exhibits high tumor accumulation and extremely long tumor retention (>19 days), while being excretable from normal tissues and safe. This smart self-assembling small molecule strategy can shift the paradigm of designing new nanomaterials for molecular imaging and drug development.
View details for DOI 10.1002/adma.202006902
View details for PubMedID 33709533
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A mathematical model of tumor regression and recurrence after therapeutic oncogene inactivation.
Scientific reports
2021; 11 (1): 1341
Abstract
The targeted inactivation of individual oncogenes can elicit regression of cancers through a phenomenon called oncogene addiction. Oncogene addiction is mediated by cell-autonomous and immune-dependent mechanisms. Therapeutic resistance to oncogene inactivation leads to recurrence but can be counteracted by immune surveillance. Predicting the timing of resistance will provide valuable insights in developing effective cancer treatments. To provide a quantitative understanding of cancer response to oncogene inactivation, we developed a new 3-compartment mathematical model of oncogene-driven tumor growth, regression and recurrence, and validated the model using a MYC-driven transgenic mouse model of T-cell acute lymphoblastic leukemia. Our mathematical model uses imaging-based measurements of tumor burden to predict the relative number of drug-sensitive and drug-resistant cancer cells in MYC-dependent states. We show natural killer (NK) cell adoptive therapy can delay cancer recurrence by reducing the net-growth rate of drug-resistant cells. Our studies provide a novel way to evaluate combination therapy for personalized cancer treatment.
View details for DOI 10.1038/s41598-020-78947-2
View details for PubMedID 33446671
View details for PubMedCentralID PMC7809285
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Generation of a Tetracycline Regulated Mouse Model of MYC-Induced T-Cell Acute Lymphoblastic Leukemia.
Methods in molecular biology (Clifton, N.J.)
2021; 2318: 297-312
Abstract
The tetracycline regulatory system provides a tractable strategy to interrogate the role of oncogenes in the initiation, maintenance, and regression of tumors through both spatial and temporal control of expression. This approach has several potential advantages over conventional methods to generate genetically engineered mouse models. First, continuous constitutive overexpression of an oncogene can be lethal to the host impeding further study. Second, constitutive overexpression fails to model adult onset of disease. Third, constitutive deletion does not permit, whereas conditional overexpression of an oncogene enables the study of the consequences of restoring expression of an oncogene back to endogenous levels. Fourth, the conditional activation of oncogenes enables examination of specific and/or developmental state-specific consequences.Hence, by allowing precise control of when and where a gene is expressed, the tetracycline regulatory system provides an ideal approach for the study of putative oncogenes in the initiation as well as the maintenance of tumorigenesis and the examination of the mechanisms of oncogene addiction. In this protocol, we describe the methods involved in the development of a conditional mouse model of MYC-induced T-cell acute lymphoblastic leukemia.
View details for DOI 10.1007/978-1-0716-1476-1_16
View details for PubMedID 34019298
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Mitochondrial copper depletion suppresses triple-negative breast cancer in mice.
Nature biotechnology
2020
Abstract
Depletion of mitochondrial copper, which shifts metabolism from respiration to glycolysis and reduces energy production, is known to be effective against cancer types that depend on oxidative phosphorylation. However, existing copper chelators are too toxic or ineffective for cancer treatment. Here we develop a safe, mitochondria-targeted, copper-depleting nanoparticle (CDN) and test it against triple-negative breast cancer (TNBC). We show that CDNs decrease oxygen consumption and oxidative phosphorylation, cause a metabolic switch to glycolysis and reduce ATP production in TNBC cells. This energy deficiency, together with compromised mitochondrial membrane potential and elevated oxidative stress, results in apoptosis. CDNs should be less toxic than existing copper chelators because they favorably deprive copper in the mitochondria in cancer cells instead of systemic depletion. Indeed, we demonstrate low toxicity of CDNs in healthy mice. In three mouse models of TNBC, CDN administration inhibits tumor growth and substantially improves survival. The efficacy and safety of CDNs suggest the potential clinical relevance of this approach.
View details for DOI 10.1038/s41587-020-0707-9
View details for PubMedID 33077961
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MYC ASO Impedes Tumorigenesis and Elicits Oncogene Addiction in Autochthonous Transgenic Mouse Models of HCC and RCC
MOLECULAR THERAPY-NUCLEIC ACIDS
2020; 21: 850–59
View details for DOI 10.1016/j.omtn.2020.07.008.
View details for Web of Science ID 000569480600008
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MYC ASO Impedes Tumorigenesis and Elicits Oncogene Addiction in Autochthonous Transgenic Mouse Models of HCC and RCC.
Molecular therapy. Nucleic acids
2020; 21: 850–59
Abstract
The MYC oncogene is dysregulated in most human cancers and hence is an attractive target for cancer therapy. We and others have shown experimentally in conditional transgenic mouse models that suppression of the MYC oncogene is sufficient to induce rapid and sustained tumor regression, a phenomenon known as oncogene addiction. However, it is unclear whether a therapy that targets the MYC oncogene could similarly elicit oncogene addiction. In this study, we report that using antisense oligonucleotides (ASOs) to target and reduce the expression of MYC impedes tumor progression and phenotypically elicits oncogene addiction in transgenic mouse models of MYC-driven primary hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC). Quantitative image analysis of MRI was used to demonstrate the inhibition of HCC and RCC progression. After 4weeks of drug treatment, tumors had regressed histologically. ASOs depleted MYC mRNA and protein expression in primary tumors invivo, as demonstrated by real-time PCR and immunohistochemistry. Treatment with MYC ASO invivo, but not with a control ASO, decreased proliferation, induced apoptosis, increased senescence, and remodeled the tumor microenvironment by recruitment of CD4+ Tcells. Importantly, although MYC ASO reduced both mouse Myc and transgenic human MYC, the ASO was not associated with significant toxicity. Lastly, we demonstrate that MYC ASO inhibits the growth of human liver cancer xenografts invivo. Our results illustrate that targeting MYC expression invivo using ASO can suppress tumorigenesis by phenotypically eliciting both tumor-intrinsic and microenvironment hallmarks of oncogene addiction. Hence, MYC ASO therapy is a promising strategy to treat MYC-driven human cancers.
View details for DOI 10.1016/j.omtn.2020.07.008
View details for PubMedID 32805488
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MYC functions as a switch for natural killer cell-mediated immune surveillance of lymphoid malignancies.
Nature communications
2020; 11 (1): 2860
Abstract
The MYC oncogene drives T- and B- lymphoid malignancies, including Burkitt's lymphoma (BL) and Acute Lymphoblastic Leukemia (ALL). Here, we demonstrate a systemic reduction in natural killer (NK) cell numbers in SRalpha-tTA/Tet-O-MYCON mice bearing MYC-driven T-lymphomas. Residual mNK cells in spleens of MYCON T-lymphoma-bearing mice exhibit perturbations in the terminal NK effector differentiation pathway. Lymphoma-intrinsic MYC arrests NK maturation by transcriptionally repressing STAT1/2 and secretion of Type I Interferons (IFNs). Treating T-lymphoma-bearing mice with Type I IFN improves survival by rescuing NK cell maturation. Adoptive transfer of mature NK cells is sufficient to delay both T-lymphoma growth and recurrence post MYC inactivation. In MYC-driven BL patients, low expression of both STAT1 and STAT2 correlates significantly with the absence of activated NK cells and predicts unfavorable clinical outcomes. Our studies thus provide a rationale for developing NK cell-based therapies to effectively treat MYC-driven lymphomas in the future.
View details for DOI 10.1038/s41467-020-16447-7
View details for PubMedID 32503978
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O-GlcNAcylation is required for mutant KRAS-induced lung tumorigenesis.
AMER ASSOC CANCER RESEARCH. 2020: 59
View details for Web of Science ID 000531799600091
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The gastrointestinal microbiota controls cancer cell intrinsic mechanisms to promote the progression of acute lymphoblastic leukemia.
AMER ASSOC CANCER RESEARCH. 2020: 58–59
View details for Web of Science ID 000526057000081
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The Key Characteristics of Carcinogens: Relationship to the Hallmarks of Cancer, Relevant Biomarkers, and Assays to Measure Them.
Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology
2020
Abstract
BACKGROUND: The key characteristics (KCs) of human carcinogens provide a uniform approach to evaluating mechanistic evidence in cancer hazard identification. Refinements to the approach were requested by organizations and individuals applying the KCs.METHODS: We assembled an expert committee with knowledge of carcinogenesis and experience in applying the KCs in cancer hazard identification. We leveraged this expertise and an examination of the literature to more clearly describe each KC; identify current and emerging assays and in vivo biomarkers that can be used to measure them; and, make recommendations for future assay development.RESULTS: We found that the KCs are clearly distinct from the Hallmarks of Cancer, that interrelationships among the KCs can be leveraged to strengthen the KC approach (and an understanding of environmental carcinogenesis), and that the KC approach is applicable to the systematic evaluation of a broad range of potential cancer hazards in vivo and in vitro. We identified gaps in coverage of the KCs by current assays.CONCLUSION: Future efforts should expand the breadth, specificity and sensitivity of validated assays and biomarkers that can measure the 10 KCs.IMPACT: Refinement of the KC approach will enhance and accelerate carcinogen identification, a first step in cancer prevention.
View details for DOI 10.1158/1055-9965.EPI-19-1346
View details for PubMedID 32152214
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MYC and Twist1 cooperate to drive metastasis by eliciting crosstalk between cancer and innate immunity.
eLife
2020; 9
Abstract
Metastasis is a major cause of cancer mortality. We generated an autochthonous transgenic mouse model whereby conditional expression of MYC and Twist1 enables hepatocellular carcinoma (HCC) to metastasize in >90% of mice. MYC and Twist1 cooperate and their sustained expression is required to elicit a transcriptional program associated with the activation of innate immunity, through secretion of a cytokinome that elicits recruitment and polarization of tumor associated macrophages (TAMs). Systemic treatment with Ccl2 and Il13 induced MYC-HCCs to metastasize; whereas, blockade of Ccl2 and Il13 abrogated MYC/Twist1-HCC metastasis. Further, in 33 human cancers (n = 9502) MYC and TWIST1 predict poor survival (p=4.3*10-10), CCL2/IL13 expression (p<10-109) and TAM infiltration (p<10-96). Finally, in the plasma of patients with HCC (n = 25) but not cirrhosis (n = 10), CCL2 and IL13 were increased and IL13 predicted invasive tumors. Therefore, MYC and TWIST1 generally appear to cooperate in human cancer to elicit a cytokinome that enables metastasis through crosstalk between cancer and immune microenvironment.
View details for DOI 10.7554/eLife.50731
View details for PubMedID 31933479
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Genomic analysis of Vascular Invasion in Hepatocellular Carcinoma (HCC) Reveals Molecular Drivers and Predictive Biomarkers.
Hepatology (Baltimore, Md.)
2020
Abstract
Vascular invasion is a critical risk factor for hepatocellular carcinoma (HCC) recurrence and poor survival. The molecular drivers of vascular invasion in HCC are largely unknown. Deciphering the molecular landscape of invasive HCC will help identify novel therapeutic targets and noninvasive biomarkers. To this end, we undertook this study to evaluate the genomic, transcriptomic, and proteomic profile of tumors with vascular invasion using the multi-platform cancer genome atlas (TCGA) data (n=373). In the TCGA liver hepatocellular carcinoma (LIHC) cohort, macrovascular invasion was present in 5% (n=17) of tumors and microvascular invasion in 25% (n=94) of tumors. Functional pathway analysis revealed that the MYC oncogene was a common upstream regulator of the mRNA, miRNA and proteomic changes in vascular invasion. We performed comparative proteomic analyses of invasive human HCC and MYC driven murine HCC and identified fibronectin to be proteomic biomarker of invasive HCC (mouse Fn1 p= 1.7 X 10-11 ; human FN1 p=1.5 X 10-4 ) conserved across the two species. Mechanistically, we show that FN1 promotes the migratory and invasive phenotype of HCC cancer cells. We demonstrate tissue overexpression of fibronectin in human HCC using a large independent cohort of human HCC tissue microarray (n=153; p<0.001). Lastly, we showed that plasma fibronectin levels were significantly elevated in patients with HCC (n=35, mean=307.7 μg/ml, SEM=35.9) when compared to cirrhosis (n=10, mean=41.8 μg/ml, SEM=13.3; p<0.0001). CONCLUSION: Our study evaluates the molecular landscape of tumors with vascular invasion, identifying distinct transcriptional, epigenetic and proteomic changes driven by the MYC oncogene. We show that MYC upregulates fibronectin expression which promotes HCC invasiveness. In addition, we identify fibronectin to be a promising non-invasive proteomic biomarker of vascular invasion in HCC.
View details for DOI 10.1002/hep.31614
View details for PubMedID 33140851
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The Myc and Ras Partnership in Cancer: Indistinguishable Alliance or Contextual Relationship?
Cancer research
2020
Abstract
Myc and Ras are two of the most commonly activated oncogenes in tumorigenesis. Together and independently they regulate many cancer hallmarks including proliferation, apoptosis and self-renewal. Recently, they were shown to cooperate to regulate host tumor microenvironment programs including host immune responses. But, is their partnership always cooperative or do they have distinguishable functions? Here, we provide one perspective that Myc and Ras cooperation depends on the genetic evolution of a particular cancer. This in turn, dictates when they cooperate via overlapping and identifiably distinct cellular and host immune dependent mechanisms that are cancer type specific.
View details for DOI 10.1158/0008-5472.CAN-20-0787
View details for PubMedID 32732221
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CROSS-SPECIES COMPREHENSIVE PROTEOMIC ANALYSIS OF HEPATOCELLULAR CARCINOMA (HCC) TO IDENTIFY PLASMA BIOMARKERS OF VASCULAR INVASION
WILEY. 2019: 74A
View details for Web of Science ID 000488653500112
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A Tale of Two Complications of Obesity: NASH and Hepatocellular Carcinoma
HEPATOLOGY
2019; 70 (3): 1056–58
View details for DOI 10.1002/hep.30649
View details for Web of Science ID 000483692800023
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Oncogene MYC regulates lipogenesis essential for neoplastic growth
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525055501180
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The MYC Oncogene Cooperates with Sterol-Regulated Element-Binding Protein to Regulate Lipogenesis Essential for Neoplastic Growth.
Cell metabolism
2019
Abstract
Lipid metabolism is frequently perturbed in cancers, but the underlying mechanism is unclear. We present comprehensive evidence that oncogene MYC, in collaboration with transcription factor sterol-regulated element-binding protein (SREBP1), regulates lipogenesis to promote tumorigenesis. We used human and mouse tumor-derived cell lines, tumor xenografts, and four conditional transgenic mouse models of MYC-induced tumors to show that MYC regulates lipogenesis genes, enzymes, and metabolites. We found that MYC induces SREBP1, and they collaborate to activate fatty acid (FA) synthesis and drive FA chain elongation from glucose and glutamine. Further, by employing desorption electrospray ionization mass spectrometry imaging (DESI-MSI), we observed invivo lipidomic changes upon MYC induction across different cancers, for example, aglobal increase in glycerophosphoglycerols. After inhibition of FA synthesis, tumorigenesis was blocked, and tumors regressed in both xenograft and primary transgenic mouse models, revealing the vulnerability of MYC-induced tumors to the inhibition of lipogenesis.
View details for DOI 10.1016/j.cmet.2019.07.012
View details for PubMedID 31447321
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MYC regulates the HIF-2alpha stemness pathway via Nanog and Sox2 to maintain self-renewal in cancer stem cells versus non-stem cancer cells.
Cancer research
2019
Abstract
Cancer stem cells (CSC) maintain both undifferentiated self-renewing CSCs and differentiated, non-self-renewing non-CSCs through cellular division. However, molecular mechanisms that maintain self-renewal in CSCs versus non-CSCs are not yet clear. Here, we report that in a transgenic mouse model of MYC-induced T cell leukemia, MYC maintains self-renewal in Sca1+ CSCs versus Sca-1- non-CSCs. MYC preferentially bound to the promoter and activated HIF-2alpha in Sca-1+ cells only. Further, the reprogramming factors Nanog and Sox2 facilitated MYC regulation of HIF-2alpha in Sca-1+ versus Sca-1- cells. Reduced expression of HIF-2alpha inhibited the self-renewal of Sca-1+ cells; this effect was blocked through suppression of reactive oxygen species (ROS) by N-acetyl cysteine (NAC) or the knock down of p53, Nanog or Sox2. Similar results were seen in ABCG2+ CSCs versus ABCG2- non-CSCs from primary human T cell lymphoma. Thus, MYC maintains self-renewal exclusively in CSCs by selectively binding to the promoter and activating the HIF-2alpha stemness pathway. Identification of this stemness pathway as a unique CSC determinant may have significant therapeutic implications.
View details for DOI 10.1158/0008-5472.CAN-18-2847
View details for PubMedID 31266772
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Mistletoe extract Fraxini inhibits the proliferation of liver cancer by down-regulating c-Myc expression
SCIENTIFIC REPORTS
2019; 9
View details for DOI 10.1038/s41598-019-41444-2
View details for Web of Science ID 000465216700016
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A Tale of Two Complications of Obesity: Nonalcoholic steatohepatitis (NASH) and Hepatocellular carcinoma (HCC).
Hepatology (Baltimore, Md.)
2019
Abstract
Nonalcoholic steatohepatitis (NASH) is the most common cause of chronic liver disease in developed countries and its incidence is rapidly increasing. Cirrhosis, and the dreaded complication of hepatocellular carcinoma (HCC), are the major drivers of morbidity and mortality in NASH. Conventional understanding has been that chronic liver damage leads to a cycle of cell death, regeneration and fibrosis during which HCC precursor cells undergo malignant transformation and lead to cancer initiation. This article is protected by copyright. All rights reserved.
View details for PubMedID 30958566
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Stabilization of the Max Homodimer with a Small Molecule Attenuates Myc-Driven Transcription.
Cell chemical biology
2019
Abstract
The transcription factor Max is a basic-helix-loop-helix leucine zipper (bHLHLZ) protein that forms homodimers or interacts with other bHLHLZ proteins, including Myc and Mxd proteins. Among this dynamic network of interactions, the Myc/Max heterodimer has crucial roles in regulating normal cellular processes, but its transcriptional activity is deregulated in a majority of human cancers. Despite this significance, the arsenal of high-quality chemical probes to interrogate these proteins remains limited. We used small molecule microarrays to identify compounds that bind Max in a mechanistically unbiased manner. We discovered the asymmetric polycyclic lactam, KI-MS2-008, which stabilizes the Max homodimer while reducing Myc protein and Myc-regulated transcript levels. KI-MS2-008 also decreases viable cancer cell growth in a Myc-dependent manner and suppressestumor growth invivo. This approach demonstrates the feasibility of modulating Max with small molecules and supports altering Max dimerization as an alternative approach to targeting Myc.
View details for DOI 10.1016/j.chembiol.2019.02.009
View details for PubMedID 30880155
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Mebendazole for Differentiation Therapy of Acute Myeloid Leukemia Identified by a Lineage Maturation Index.
Scientific reports
2019; 9 (1): 16775
Abstract
Accurate assessment of changes in cellular differentiation status in response to drug treatments or genetic perturbations is crucial for understanding tumorigenesis and developing novel therapeutics for human cancer. We have developed a novel computational approach, the Lineage Maturation Index (LMI), to define the changes in differentiation state of hematopoietic malignancies based on their gene expression profiles. We have confirmed that the LMI approach can detect known changes of differentiation state in both normal and malignant hematopoietic cells. To discover novel differentiation therapies, we applied this approach to analyze the gene expression profiles of HL-60 leukemia cells treated with a small molecule drug library. Among multiple drugs that significantly increased the LMIs, we identified mebendazole, an anti-helminthic clinically used for decades with no known significant toxicity. We tested the differentiation activity of mebendazole using primary leukemia blast cells isolated from human acute myeloid leukemia (AML) patients. We determined that treatment with mebendazole induces dramatic differentiation of leukemia blast cells as shown by cellular morphology and cell surface markers. Furthermore, mebendazole treatment significantly extended the survival of leukemia-bearing mice in a xenograft model. These findings suggest that mebendazole may be utilized as a low toxicity therapeutic for human acute myeloid leukemia and confirm the LMI approach as a robust tool for the discovery of novel differentiation therapies for cancer.
View details for DOI 10.1038/s41598-019-53290-3
View details for PubMedID 31727951
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Mistletoe extract Fraxini inhibits the proliferation of liver cancer by down-regulating c-Myc expression.
Scientific reports
2019; 9 (1): 6428
Abstract
Mistletoe (Viscum album) is a type of parasitic plant reported to have anticancer activity including in hepatocellular carcinoma (HCC). However, the mechanism of mistletoe's anticancer activity, and its effectiveness in treating HCC are not fully understood. We report here that mistletoe extracts, including Fraxini (grown on ash trees) and Iscador Q and M (grown on oak and maple trees), exert strong antiproliferative activity in Hep3B cells, with median inhibitory concentrations (IC50) of 0.5 µg/mL, 7.49 µg/mL, and 7.51 µg/mL, respectively. Results of Reversed Phase Proteomic Array analysis (RPPA) suggests that Fraxini substantially down-regulates c-Myc expression in Hep3B cells. Fraxini-induced growth inhibition (at a concentration of 1.25 μg/ml) was less pronounced in c-Myc knockdown Hep3B cells than in control cells. Furthermore, in the Hep3B xenograft model, Fraxini-treated (8 mg/kg body weight) mice had significantly smaller tumors (34.6 ± 11.9 mm3) than control mice (161.6 ± 79.4 mm3, p < 0.036). Similarly, c-Myc protein expression was reduced in Fraxini treated Hep3B cell xenografts compared to that of control mice. The reduction of c-Myc protein levels in vitro Hep3B cells appears to be mediated by the ubiquitin-proteasome system. Our results suggest the importance of c-Myc in Fraxini's antiproliferative activity, which warrants further investigation.
View details for PubMedID 31015523
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Conditional Upregulation of IFN-α Alone Is Sufficient to Induce Systemic Lupus Erythematosus.
Journal of immunology (Baltimore, Md. : 1950)
2019
Abstract
The cause of systemic lupus erythematosus (SLE) is unknown. IFN-α has been suggested as a causative agent of SLE; however, it was not proven, and to what extent and how IFN-α contributes to the disease is unknown. We studied the contribution of IFN-α to SLE by generating inducible IFN-α transgenic mice and directly show that conditional upregulation of IFN-α alone induces a typical manifestation of SLE in the mice not prone to autoimmunity, such as serum immune complex, autoantibody against dsDNA (anti-dsDNA Ab), and the organ manifestations classical to SLE, such as immune complex-deposited glomerulonephritis, classical splenic onion-skin lesion, alopecia, epidermal liquefaction, and positive lupus band test of the skin. In the spleen of mice, activated effector CD4 T cells, IFN-γ-producing CD8 T cells, B220+CD86+ cells, and CD11c+CD86+ cells were increased, and the T cells produced increased amounts of IL-4, IL-6, IL-17, and IFN-γ and decreased IL-2. In particular, activated CD3+CD4-CD8- double-negative T cells positive for TCRαβ, B220, CD1d-teteramer, PD-1, and Helios (that produced increased amounts of IFN-γ, IL-4, IL-17, and TNF-α) were significantly expanded. They infiltrated into kidney and induced de novo glomerulonephritis and alopecia when transferred into naive recipients. Thus, sole upregulation of IFN-α is sufficient to induce SLE, and the double-negative T cells expanded by IFN-α are directly responsible for the organ manifestations, such as lupus skin disease or nephritis.
View details for DOI 10.4049/jimmunol.1801617
View details for PubMedID 31324723
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MYC Functions As a Master Switch for Natural Killer Cell-Mediated Immune Surveillance of Lymphoid Malignancies
AMER SOC HEMATOLOGY. 2018
View details for DOI 10.1182/blood-2018-99-110472
View details for Web of Science ID 000454837607225
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Lipid nanoparticles that deliver IL-12 messenger RNA suppress tumorigenesis in MYC oncogene-driven hepatocellular carcinoma.
Journal for immunotherapy of cancer
2018; 6 (1): 125
Abstract
Interleukin-12 (IL-12) is a promising candidate for cancer immunotherapy because of its ability to activate a number of host immune subsets that recognize and destroy cancer cells. We found that human hepatocellular carcinoma (HCC) patients with higher than median levels of IL-12 have significantly favorable clinical outcomes. Here, we report that a messenger RNA (mRNA) lipid nanoparticle delivering IL-12 (IL-12-LNP) slows down the progression of MYC oncogene-driven HCC. IL-12-LNP was well distributed within the HCC tumor and was not associated with significant animal toxicity. Treatment with IL-12-LNP significantly reduced liver tumor burden measured by dynamic magnetic resonance imaging (MRI), and increased survival of MYC-induced HCC transgenic mice in comparison to control mice. Importantly, IL-12-LNP exhibited no effect on transgenic MYC levels confirming that its therapeutic efficacy was not related to the downregulation of a driver oncogene. IL-12-LNP elicited marked infiltration of activated CD44+ CD3+ CD4+ T helper cells into the tumor, and increased the production of Interferon gamma (IFNgamma). Collectively, our findings suggest that IL-12-LNP administration may be an effective immunotherapy against HCC.
View details for PubMedID 30458889
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O-GlcNAcylation is required for mutant KRAS-induced lung tumorigenesis
JOURNAL OF CLINICAL INVESTIGATION
2018; 128 (11): 4924–37
Abstract
Mutant KRAS drives glycolytic flux in lung cancer, potentially impacting aberrant protein glycosylation. Recent evidence suggests aberrant KRAS drives flux of glucose into the hexosamine biosynthetic pathway (HBP). HBP is required for various glycosylation processes, such as protein N- or O-glycosylation and glycolipid synthesis. However, its function during tumorigenesis is poorly understood. One contributor and proposed target of KRAS-driven cancers is a developmentally conserved epithelial plasticity program called epithelial-mesenchymal transition (EMT). Here we showed in novel autochthonous mouse models that EMT accelerated KrasG12D lung tumorigenesis by upregulating expression of key enzymes of the HBP pathway. We demonstrated that HBP was required for suppressing KrasG12D-induced senescence, and targeting HBP significantly delayed KrasG12D lung tumorigenesis. To explore the mechanism, we investigated protein glycosylation downstream of HBP and found elevated levels of O-linked β-N-acetylglucosamine (O-GlcNAcylation) posttranslational modification on intracellular proteins. O-GlcNAcylation suppressed KrasG12D oncogene-induced senescence (OIS) and accelerated lung tumorigenesis. Conversely, loss of O-GlcNAcylation delayed lung tumorigenesis. O-GlcNAcylation of proteins SNAI1 and c-MYC correlated with the EMT-HBP axis and accelerated lung tumorigenesis. Our results demonstrated that O-GlcNAcylation was sufficient and required to accelerate KrasG12D lung tumorigenesis in vivo, which was reinforced by epithelial plasticity programs.
View details for PubMedID 30130254
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The glutathione redox system is essential to prevent ferroptosis caused by impaired lipid metabolism in clear cell renal cell carcinoma
ONCOGENE
2018; 37 (40): 5435–50
Abstract
Metabolic reprogramming is a prominent feature of clear cell renal cell carcinoma (ccRCC). Here we investigated metabolic dependencies in a panel of ccRCC cell lines using nutrient depletion, functional RNAi screening and inhibitor treatment. We found that ccRCC cells are highly sensitive to the depletion of glutamine or cystine, two amino acids required for glutathione (GSH) synthesis. Moreover, silencing of enzymes of the GSH biosynthesis pathway or glutathione peroxidases, which depend on GSH for the removal of cellular hydroperoxides, selectively reduced viability of ccRCC cells but did not affect the growth of non-malignant renal epithelial cells. Inhibition of GSH synthesis triggered ferroptosis, an iron-dependent form of cell death associated with enhanced lipid peroxidation. VHL is a major tumour suppressor in ccRCC and loss of VHL leads to stabilisation of hypoxia inducible factors HIF-1α and HIF-2α. Restoration of functional VHL via exogenous expression of pVHL reverted ccRCC cells to an oxidative metabolism and rendered them insensitive to the induction of ferroptosis. VHL reconstituted cells also exhibited reduced lipid storage and higher expression of genes associated with oxidiative phosphorylation and fatty acid metabolism. Importantly, inhibition of β-oxidation or mitochondrial ATP-synthesis restored ferroptosis sensitivity in VHL reconstituted cells. We also found that inhibition of GSH synthesis blocked tumour growth in a MYC-dependent mouse model of renal cancer. Together, our data suggest that reduced fatty acid metabolism due to inhibition of β-oxidation renders renal cancer cells highly dependent on the GSH/GPX pathway to prevent lipid peroxidation and ferroptotic cell death.
View details for PubMedID 29872221
View details for PubMedCentralID PMC6173300
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MYC-driven lymphomas suppress NK surveillance by blocking maturation of early NK cells
AMER ASSOC CANCER RESEARCH. 2018
View details for DOI 10.1158/1538-7445.AM2018-126
View details for Web of Science ID 000468818901199
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The MYC oncogene is a global regulator of the immune response
BLOOD
2018; 131 (18): 2007–15
Abstract
The MYC proto-oncogene is a gene product that coordinates the transcriptional regulation of a multitude of genes that are essential to cellular programs required for normal as well as neoplastic cellular growth and proliferation, including cell cycle, self-renewal, survival, cell growth, metabolism, protein and ribosomal biogenesis, and differentiation. Here, we propose that MYC regulates these programs in a manner that is coordinated with a global influence on the host immune response. MYC had been presumed to contribute to tumorigenesis through tumor cell-intrinsic influences. More recently, MYC expression in tumor cells has been shown to regulate the tumor microenvironment through effects on both innate and adaptive immune effector cells and immune regulatory cytokines. Then, MYC was shown to regulate the expression of the immune checkpoint gene products CD47 and programmed death-ligand 1. Similarly, other oncogenes, which are known to modulate MYC, have been shown to regulate immune checkpoints. Hence, MYC may generally prevent highly proliferative cells from eliciting an immune response. MYC-driven neoplastic cells have coopted this mechanism to bypass immune detection. Thus, MYC inactivation can restore the immune response against a tumor. MYC-induced tumors may be particularly sensitive to immuno-oncology therapeutic interventions.
View details for PubMedID 29514782
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Anti-miR-17 therapy delays tumorigenesis in MYC-driven hepatocellular carcinoma (HCC).
Oncotarget
2018; 9 (5): 5517–28
Abstract
Hepatocellular carcinoma (HCC) remains a significant clinical challenge with few therapeutic options. Genomic amplification and/or overexpression of the MYC oncogene is a common molecular event in HCC, thus making it an attractive target for drug therapy. Unfortunately, currently there are no direct drug therapies against MYC. As an alternative strategy, microRNAs regulated by MYC may be downstream targets for therapeutic blockade. MiR-17 family is a microRNA family transcriptionally regulated by MYC and it is commonly overexpressed in human HCCs. In this study, we performed systemic delivery of a novel lipid nanoparticle (LNP) encapsulating an anti-miR-17 oligonucleotide in a conditional transgenic mouse model of MYC driven HCC. Treatment with anti-miR-17in vivo, but not with a control anti-miRNA, resulted in significant de-repression of direct targets of miR-17, robust apoptosis, decreased proliferation and led to delayed tumorigenesis in MYC-driven HCCs. Global gene expression profiling revealed engagement of miR-17 target genes and inhibition of key transcriptional programs of MYC, including cell cycle progression and proliferation. Hence, anti-miR-17 is an effective therapy for MYC-driven HCC.
View details for PubMedID 29464015
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Administration of low-dose combination anti-CTLA4, anti-CD137, and anti-OX40 into murine tumor or proximal to the tumor draining lymph node induces systemic tumor regression
CANCER IMMUNOLOGY IMMUNOTHERAPY
2018; 67 (1): 47–60
Abstract
The delivery of immunomodulators directly into the tumor potentially harnesses the existing antigen, tumor-specific infiltrating lymphocytes, and antigen presenting cells. This can confer specificity and generate a potent systemic anti-tumor immune response with lower doses and less toxicity compared to systemic administration, in effect an in situ vaccine. Here, we test this concept using the novel combination of immunomodulators anti-CTLA4, -CD137, and -OX40. The triple combination administered intratumorally at low doses to one tumor of a dual tumor mouse model had dramatic local and systemic anti-tumor efficacy in lymphoma (A20) and solid tumor (MC38) models, consistent with an abscopal effect. The minimal effective dose was 10 μg each. The effect was dependent on CD8 T-cells. Intratumoral administration resulted in superior local and distant tumor control compared to systemic routes, supporting the in situ vaccine concept. In a single tumor A20 model, injection close to the tDLN resulted in similar efficacy as intratumoral and significantly better than targeting a non-tDLN, supporting the role of the tDLN as a viable immunotherapy target in addition to the tumor itself. Distribution studies confirmed expected concentration of antibodies in tumor and tDLN, in keeping with the anti-tumor results. Overall intratumoral or peri-tDLN administration of the novel combination of anti-CTLA4, anti-CD137, and anti-OX40, all agents in the clinic or clinical trials, demonstrates potent systemic anti-tumor effects. This immunotherapeutic combination is promising for future clinical development via both these safe and highly efficacious routes of administration.
View details for PubMedID 28905118
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MYC through HIF-2 alpha regulates the altruistic stemness program in human leukemia stem cells.
AMER ASSOC CANCER RESEARCH. 2017: 61–62
View details for Web of Science ID 000418192200065
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MYC is the master switch between tumor dormancy and relapse in Hepatocellular carcinoma (HCC)
WILEY. 2017: 966A
View details for Web of Science ID 000412089802174
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DNMT3B overexpression contributes to aberrant DNA methylation and MYC-driven tumor maintenance in T-ALL and Burkitt's lymphoma
ONCOTARGET
2017; 8 (44): 76898–920
Abstract
Aberrant DNA methylation is a hallmark of cancer. However, our understanding of how tumor cell-specific DNA methylation patterns are established and maintained is limited. Here, we report that in T-cell acute lymphoblastic leukemia (T-ALL) and Burkitt's lymphoma the MYC oncogene causes overexpression of DNA methyltransferase (DNMT) 1 and 3B, which contributes to tumor maintenance. By utilizing a tetracycline-regulated MYC transgene in a mouse T-ALL (EμSRα-tTA;tet-o-MYC) and human Burkitt's lymphoma (P493-6) model, we demonstrated that DNMT1 and DNMT3B expression depend on high MYC levels, and that their transcription decreased upon MYC-inactivation. Chromatin immunoprecipitation indicated that MYC binds to the DNMT1 and DNMT3B promoters, implicating a direct transcriptional regulation. Hence, shRNA-mediated knock-down of endogenous MYC in human T-ALL and Burkitt's lymphoma cell lines downregulated DNMT3B expression. Knock-down and pharmacologic inhibition of DNMT3B in T-ALL reduced cell proliferation associated with genome-wide changes in DNA methylation, indicating a tumor promoter function during tumor maintenance. We provide novel evidence that MYC directly deregulates the expression of both de novo and maintenance DNMTs, showing that MYC controls DNA methylation in a genome-wide fashion. Our finding that a coordinated interplay between the components of the DNA methylating machinery contributes to MYC-driven tumor maintenance highlights the potential of specific DNMTs for targeted therapies.
View details for PubMedID 29100357
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KB004, a first in class monoclonal antibody targeting the receptor tyrosine kinase EphA3, in patients with advanced hematologic malignancies: Results from a phase 1 study (vol 50, pg 123, 2016)
LEUKEMIA RESEARCH
2017; 59: 65
View details for PubMedID 28575698
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MYC activation cooperates with Vhl and Ink4a/Arf loss to induce clear cell renal cell carcinoma
NATURE COMMUNICATIONS
2017; 8: 15770
Abstract
Renal carcinoma is a common and aggressive malignancy whose histopathogenesis is incompletely understood and that is largely resistant to cytotoxic chemotherapy. We present two mouse models of kidney cancer that recapitulate the genomic alterations found in human papillary (pRCC) and clear cell RCC (ccRCC), the most common RCC subtypes. MYC activation results in highly penetrant pRCC tumours (MYC), while MYC activation, when combined with Vhl and Cdkn2a (Ink4a/Arf) deletion (VIM), produce kidney tumours that approximate human ccRCC. RNAseq of the mouse tumours demonstrate that MYC tumours resemble Type 2 pRCC, which are known to harbour MYC activation. Furthermore, VIM tumours more closely simulate human ccRCC. Based on their high penetrance, short latency, and histologic fidelity, these models of papillary and clear cell RCC should be significant contributions to the field of kidney cancer research.
View details for PubMedID 28593993
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Oncogene KRAS activates fatty acid synthase, resulting in specific ERK and lipid signatures associated with lung adenocarcinoma
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2017; 114 (17): 4300-4305
Abstract
KRAS gene mutation causes lung adenocarcinoma. KRAS activation has been associated with altered glucose and glutamine metabolism. Here, we show that KRAS activates lipogenesis, and this activation results in distinct proteomic and lipid signatures. By gene expression analysis, KRAS is shown to be associated with a lipogenesis gene signature and specific induction of fatty acid synthase (FASN). Through desorption electrospray ionization MS imaging (DESI-MSI), specific changes in lipogenesis and specific lipids are identified. By the nanoimmunoassay (NIA), KRAS is found to activate the protein ERK2, whereas ERK1 activation is found in non-KRAS-associated human lung tumors. The inhibition of FASN by cerulenin, a small molecule antibiotic, blocked cellular proliferation of KRAS-associated lung cancer cells. Hence, KRAS is associated with activation of ERK2, induction of FASN, and promotion of lipogenesis. FASN may be a unique target for KRAS-associated lung adenocarcinoma remediation.
View details for DOI 10.1073/pnas.1617709114
View details for PubMedID 28400509
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MYC: Master Regulator of Immune Privilege.
Trends in immunology
2017
Abstract
Cancers are often initiated by genetic events that activate proto-oncogenes or inactivate tumor-suppressor genes. These events are also crucial for sustained tumor cell proliferation and survival, a phenomenon described as oncogene addiction. In addition to this cell-intrinsic role, recent evidence indicates that oncogenes also directly regulate immune responses, leading to immunosuppression. Expression of many oncogenes or loss of tumor suppressors induces the expression of immune checkpoints that regulate the immune response, such as PD-L1. We discuss here how oncogenes, and in particular MYC, suppress immune surveillance, and how oncogene-targeted therapies may restore the immune response against tumors.
View details for DOI 10.1016/j.it.2017.01.002
View details for PubMedID 28233639
View details for PubMedCentralID PMC5378645
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KB004, a first in class monoclonal antibody targeting the receptor tyrosine kinase EphA3, in patients with advanced hematologic malignancies: Results from a phase 1 study.
Leukemia research
2016; 50: 123-131
Abstract
EphA3 is an Ephrin receptor tyrosine kinase that is overexpressed in most hematologic malignancies. We performed a first-in-human multicenter phase I study of the anti-EphA3 monoclonal antibody KB004 in refractory hematologic malignancies in order to determine safety and tolerability, along with the secondary objectives of pharmacokinetics (PK) and pharmacodynamics (PD) assessments, as well as preliminary assessment of efficacy. Patients were enrolled on a dose escalation phase (DEP) initially, followed by a cohort expansion phase (CEP). KB004 was administered by intravenous infusion on days 1, 8, and 15 of each 21-day cycle in escalating doses. A total of 50 patients (AML 39, MDS/MPN 3, MDS 4, DLBCL 1, MF 3) received KB004 in the DEP; an additional 14 patients were treated on the CEP (AML 8, MDS 6). The most common toxicities were transient grade 1 and grade 2 infusion reactions (IRs) in 79% of patients. IRs were dose limiting above 250mg. Sustained exposure exceeding the predicted effective concentration (1ug/mL) and covering the 7-day interval between doses was achieved above 190mg. Responses were observed in patients with AML, MF, MDS/MPN and MDS. In this study, KB004 was well tolerated and clinically active when given as a weekly infusion.
View details for DOI 10.1016/j.leukres.2016.09.012
View details for PubMedID 27736729
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BIM-mediated apoptosis and oncogene addiction.
Aging
2016; 8 (9): 1834-1835
View details for DOI 10.18632/aging.101072
View details for PubMedID 27688082
View details for PubMedCentralID PMC5076438
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Affordable Cancer Medications Are Within Reach but We Need a Different Approach.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology
2016; 34 (18): 2194-5
View details for DOI 10.1200/JCO.2016.67.2436
View details for PubMedID 27161965
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Metabolic vulnerabilities of MYC-induced cancer
ONCOTARGET
2016; 7 (21): 29879–80
View details for PubMedID 26863454
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BIM mediates oncogene inactivation-induced apoptosis in multiple transgenic mouse models of acute lymphoblastic leukemia
ONCOTARGET
2016; 7 (19): 26926-26934
Abstract
Oncogene inactivation in both clinical targeted therapies and conditional transgenic mouse cancer models can induce significant tumor regression associated with the robust induction of apoptosis. Here we report that in MYC-, RAS-, and BCR-ABL-induced acute lymphoblastic leukemia (ALL), apoptosis upon oncogene inactivation is mediated by the same pro-apoptotic protein, BIM. The induction of BIMin the MYC- and RAS-driven leukemia is mediated by the downregulation of miR-17-92. Overexpression of miR-17-92 blocked the induction of apoptosis upon oncogene inactivation in the MYC and RAS-driven but not in the BCR-ABL-driven ALL leukemia. Hence, our results provide novel insight into the mechanism of apoptosis upon oncogene inactivation and suggest that induction of BIM-mediated apoptosis may be an important therapeutic approach for ALL.
View details for DOI 10.18632/oncotarget.8731
View details for Web of Science ID 000377741700001
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BIM mediates oncogene inactivation-induced apoptosis in multiple transgenic mouse models of acute lymphoblastic leukemia.
Oncotarget
2016
Abstract
Oncogene inactivation in both clinical targeted therapies and conditional transgenic mouse cancer models can induce significant tumor regression associated with the robust induction of apoptosis. Here we report that in MYC-, RAS-, and BCR-ABL-induced acute lymphoblastic leukemia (ALL), apoptosis upon oncogene inactivation is mediated by the same pro-apoptotic protein, BIM. The induction of BIMin the MYC- and RAS-driven leukemia is mediated by the downregulation of miR-17-92. Overexpression of miR-17-92 blocked the induction of apoptosis upon oncogene inactivation in the MYC and RAS-driven but not in the BCR-ABL-driven ALL leukemia. Hence, our results provide novel insight into the mechanism of apoptosis upon oncogene inactivation and suggest that induction of BIM-mediated apoptosis may be an important therapeutic approach for ALL.
View details for DOI 10.18632/oncotarget.8731
View details for PubMedID 27095570
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MYC regulates the antitumor immune response through CD47 and PD-L1
SCIENCE
2016; 352 (6282): 227-231
Abstract
TheMYConcogene codes for a transcription factor that is overexpressed in many human cancers. Here we show thatMYCregulates the expression of two immune checkpoint proteins on the tumor cell surface, the innate immune regulator, CD47 ( C: luster of D: ifferentiation 47) and the adaptive immune checkpoint, PD-L1 (programmed death-ligand 1). Suppression of MYC in mouse tumors and human tumor cells caused a reduction in the levels of CD47 and PD-L1 mRNA and protein. MYC was found to bind directly to the promoters of the CD47 and PD-L1 genes. MYC inactivation in mouse tumors down-regulated CD47 and PD-L1 expression and enhanced the anti-tumor immune response. In contrast, when MYC was inactivated in tumors with enforced expression of CD47 or PD-L1, the immune response was suppressed and tumors continued to grow. Thus MYC appears to initiate and maintain tumorigenesis in part through the modulation of immune regulatory molecules.
View details for DOI 10.1126/science.aac9935
View details for Web of Science ID 000373681600047
View details for PubMedID 26966191
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NAFLD causes selective CD4(+) T lymphocyte loss and promotes hepatocarcinogenesis
NATURE
2016; 531 (7593): 253-?
Abstract
Hepatocellular carcinoma (HCC) is the second most common cause of cancer-related death. Non-alcoholic fatty liver disease (NAFLD) affects a large proportion of the US population and is considered to be a metabolic predisposition to liver cancer. However, the role of adaptive immune responses in NAFLD-promoted HCC is largely unknown. Here we show, in mouse models and human samples, that dysregulation of lipid metabolism in NAFLD causes a selective loss of intrahepatic CD4(+) but not CD8(+) T lymphocytes, leading to accelerated hepatocarcinogenesis. We also demonstrate that CD4(+) T lymphocytes have greater mitochondrial mass than CD8(+) T lymphocytes and generate higher levels of mitochondrially derived reactive oxygen species (ROS). Disruption of mitochondrial function by linoleic acid, a fatty acid accumulated in NAFLD, causes more oxidative damage than other free fatty acids such as palmitic acid, and mediates selective loss of intrahepatic CD4(+) T lymphocytes. In vivo blockade of ROS reversed NAFLD-induced hepatic CD4(+) T lymphocyte decrease and delayed NAFLD-promoted HCC. Our results provide an unexpected link between lipid dysregulation and impaired anti-tumour surveillance.
View details for DOI 10.1038/nature16969
View details for Web of Science ID 000371665100046
View details for PubMedID 26934227
View details for PubMedCentralID PMC4786464
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Cancer prevention and therapy through the modulation of the tumor microenvironment.
Seminars in cancer biology
2015; 35: S199-223
Abstract
Cancer arises in the context of an in vivo tumor microenvironment. This microenvironment is both a cause and consequence of tumorigenesis. Tumor and host cells co-evolve dynamically through indirect and direct cellular interactions, eliciting multiscale effects on many biological programs, including cellular proliferation, growth, and metabolism, as well as angiogenesis and hypoxia and innate and adaptive immunity. Here we highlight specific biological processes that could be exploited as targets for the prevention and therapy of cancer. Specifically, we describe how inhibition of targets such as cholesterol synthesis and metabolites, reactive oxygen species and hypoxia, macrophage activation and conversion, indoleamine 2,3-dioxygenase regulation of dendritic cells, vascular endothelial growth factor regulation of angiogenesis, fibrosis inhibition, endoglin, and Janus kinase signaling emerge as examples of important potential nexuses in the regulation of tumorigenesis and the tumor microenvironment that can be targeted. We have also identified therapeutic agents as approaches, in particular natural products such as berberine, resveratrol, onionin A, epigallocatechin gallate, genistein, curcumin, naringenin, desoxyrhapontigenin, piperine, and zerumbone, that may warrant further investigation to target the tumor microenvironment for the treatment and/or prevention of cancer.
View details for DOI 10.1016/j.semcancer.2015.02.007
View details for PubMedID 25865775
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Cancer prevention and therapy through the modulation of the tumor microenvironment.
Seminars in cancer biology
2015; 35: S199-223
Abstract
Cancer arises in the context of an in vivo tumor microenvironment. This microenvironment is both a cause and consequence of tumorigenesis. Tumor and host cells co-evolve dynamically through indirect and direct cellular interactions, eliciting multiscale effects on many biological programs, including cellular proliferation, growth, and metabolism, as well as angiogenesis and hypoxia and innate and adaptive immunity. Here we highlight specific biological processes that could be exploited as targets for the prevention and therapy of cancer. Specifically, we describe how inhibition of targets such as cholesterol synthesis and metabolites, reactive oxygen species and hypoxia, macrophage activation and conversion, indoleamine 2,3-dioxygenase regulation of dendritic cells, vascular endothelial growth factor regulation of angiogenesis, fibrosis inhibition, endoglin, and Janus kinase signaling emerge as examples of important potential nexuses in the regulation of tumorigenesis and the tumor microenvironment that can be targeted. We have also identified therapeutic agents as approaches, in particular natural products such as berberine, resveratrol, onionin A, epigallocatechin gallate, genistein, curcumin, naringenin, desoxyrhapontigenin, piperine, and zerumbone, that may warrant further investigation to target the tumor microenvironment for the treatment and/or prevention of cancer.
View details for DOI 10.1016/j.semcancer.2015.02.007
View details for PubMedID 25865775
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MYC Disrupts the Circadian Clock and Metabolism in Cancer Cells.
Cell metabolism
2015; 22 (6): 1009-1019
Abstract
The MYC oncogene encodes MYC, a transcription factor that binds the genome through sites termed E-boxes (5'-CACGTG-3'), which are identical to the binding sites of the heterodimeric CLOCK-BMAL1 master circadian transcription factor. Hence, we hypothesized that ectopic MYC expression perturbs the clock by deregulating E-box-driven components of the circadian network in cancer cells. We report here that deregulated expression of MYC or N-MYC disrupts the molecular clock in vitro by directly inducing REV-ERBα to dampen expression and oscillation of BMAL1, and this could be rescued by knockdown of REV-ERB. REV-ERBα expression predicts poor clinical outcome for N-MYC-driven human neuroblastomas that have diminished BMAL1 expression, and re-expression of ectopic BMAL1 in neuroblastoma cell lines suppresses their clonogenicity. Further, ectopic MYC profoundly alters oscillation of glucose metabolism and perturbs glutaminolysis. Our results demonstrate an unsuspected link between oncogenic transformation and circadian and metabolic dysrhythmia, which we surmise to be advantageous for cancer.
View details for DOI 10.1016/j.cmet.2015.09.003
View details for PubMedID 26387865
View details for PubMedCentralID PMC4818967
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Designing a broad-spectrum integrative approach for cancer prevention and treatment
SEMINARS IN CANCER BIOLOGY
2015; 35: S276-S304
Abstract
Targeted therapies and the consequent adoption of "personalized" oncology have achieved notable successes in some cancers; however, significant problems remain with this approach. Many targeted therapies are highly toxic, costs are extremely high, and most patients experience relapse after a few disease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistant immortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are not reliant upon the same mechanisms as those which have been targeted). To address these limitations, an international task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspects of relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a wide range of high-priority targets (74 in total) that could be modified to improve patient outcomes. For these targets, corresponding low-toxicity therapeutic approaches were then suggested, many of which were phytochemicals. Proposed actions on each target and all of the approaches were further reviewed for known effects on other hallmark areas and the tumor microenvironment. Potential contrary or procarcinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixed evidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of the relationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. This novel approach has potential to be relatively inexpensive, it should help us address stages and types of cancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for future research is offered.
View details for DOI 10.1016/j.semcancer.2015.09.007
View details for PubMedID 26590477
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ARF: Connecting senescence and innate immunity for clearance
AGING-US
2015; 7 (9): 613-615
Abstract
We have found evidence suggesting that ARF and p53 are essential for tumor regression upon MYC inactivation through distinct mechanisms ARF through p53-independent affect, is required to for MYC to regulate the expression of genes that are required for both the induction of cellular senescence as well as recruitment of innate immune activation. Our observations have possible implications for mechanisms of therapeutic resistance to targeted oncogene inactivation.
View details for PubMedID 26412380
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Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead
CARCINOGENESIS
2015; 36: S254-S296
Abstract
Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety 'Mode of Action' framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.
View details for DOI 10.1093/carcin/bgv039
View details for Web of Science ID 000357048100013
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Targeted inhibition of tumor-specific glutaminase diminishes cell-autonomous tumorigenesis
JOURNAL OF CLINICAL INVESTIGATION
2015; 125 (6): 2293-2306
Abstract
Glutaminase (GLS), which converts glutamine to glutamate, plays a key role in cancer cell metabolism, growth, and proliferation. GLS is being explored as a cancer therapeutic target, but whether GLS inhibitors affect cancer cell-autonomous growth or the host microenvironment or have off-target effects is unknown. Here, we report that loss of one copy of Gls blunted tumor progression in an immune-competent MYC-mediated mouse model of hepatocellular carcinoma. Compared with results in untreated animals with MYC-induced hepatocellular carcinoma, administration of the GLS-specific inhibitor bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES) prolonged survival without any apparent toxicities. BPTES also inhibited growth of a MYC-dependent human B cell lymphoma cell line (P493) by blocking DNA replication, leading to cell death and fragmentation. In mice harboring P493 tumor xenografts, BPTES treatment inhibited tumor cell growth; however, P493 xenografts expressing a BPTES-resistant GLS mutant (GLS-K325A) or overexpressing GLS were not affected by BPTES treatment. Moreover, a customized Vivo-Morpholino that targets human GLS mRNA markedly inhibited P493 xenograft growth without affecting mouse Gls expression. Conversely, a Vivo-Morpholino directed at mouse Gls had no antitumor activity in vivo. Collectively, our studies demonstrate that GLS is required for tumorigenesis and support small molecule and genetic inhibition of GLS as potential approaches for targeting the tumor cell-autonomous dependence on GLS for cancer therapy.
View details for DOI 10.1172/JCI75836
View details for Web of Science ID 000355573900018
View details for PubMedID 25915584
View details for PubMedCentralID PMC4497742
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The effect of environmental chemicals on the tumor microenvironment
CARCINOGENESIS
2015; 36: S160-S183
Abstract
Potentially carcinogenic compounds may cause cancer through direct DNA damage or through indirect cellular or physiological effects. To study possible carcinogens, the fields of endocrinology, genetics, epigenetics, medicine, environmental health, toxicology, pharmacology and oncology must be considered. Disruptive chemicals may also contribute to multiple stages of tumor development through effects on the tumor microenvironment. In turn, the tumor microenvironment consists of a complex interaction among blood vessels that feed the tumor, the extracellular matrix that provides structural and biochemical support, signaling molecules that send messages and soluble factors such as cytokines. The tumor microenvironment also consists of many host cellular effectors including multipotent stromal cells/mesenchymal stem cells, fibroblasts, endothelial cell precursors, antigen-presenting cells, lymphocytes and innate immune cells. Carcinogens can influence the tumor microenvironment through effects on epithelial cells, the most common origin of cancer, as well as on stromal cells, extracellular matrix components and immune cells. Here, we review how environmental exposures can perturb the tumor microenvironment. We suggest a role for disrupting chemicals such as nickel chloride, Bisphenol A, butyltins, methylmercury and paraquat as well as more traditional carcinogens, such as radiation, and pharmaceuticals, such as diabetes medications, in the disruption of the tumor microenvironment. Further studies interrogating the role of chemicals and their mixtures in dose-dependent effects on the tumor microenvironment could have important general mechanistic implications for the etiology and prevention of tumorigenesis.
View details for DOI 10.1093/carcin/bgv035
View details for PubMedID 26106136
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Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead.
Carcinogenesis
2015; 36: S254-96
Abstract
Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety 'Mode of Action' framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.
View details for DOI 10.1093/carcin/bgv039
View details for PubMedID 26106142
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MYC oncogene overexpression drives renal cell carcinoma in a mouse model through glutamine metabolism
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2015; 112 (21): 6539-6544
Abstract
The MYC oncogene is frequently mutated and overexpressed in human renal cell carcinoma (RCC). However, there have been no studies on the causative role of MYC or any other oncogene in the initiation or maintenance of kidney tumorigenesis. Here, we show through a conditional transgenic mouse model that the MYC oncogene, but not the RAS oncogene, initiates and maintains RCC. Desorption electrospray ionization-mass-spectrometric imaging was used to obtain chemical maps of metabolites and lipids in the mouse RCC samples. Gene expression analysis revealed that the mouse tumors mimicked human RCC. The data suggested that MYC-induced RCC up-regulated the glutaminolytic pathway instead of the glycolytic pathway. The pharmacologic inhibition of glutamine metabolism with bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide impeded MYC-mediated RCC tumor progression. Our studies demonstrate that MYC overexpression causes RCC and points to the inhibition of glutamine metabolism as a potential therapeutic approach for the treatment of this disease.
View details for DOI 10.1073/pnas.1507228112
View details for PubMedID 25964345
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p19ARF is a critical mediator of both cellular senescence and an innate immune response associated with MYC inactivation in mouse model of acute leukemia
ONCOTARGET
2015; 6 (6): 3563-3577
Abstract
MYC-induced T-ALL exhibit oncogene addiction. Addiction to MYC is a consequence of both cell-autonomous mechanisms, such as proliferative arrest, cellular senescence, and apoptosis, as well as non-cell autonomous mechanisms, such as shutdown of angiogenesis, and recruitment of immune effectors. Here, we show, using transgenic mouse models of MYC-induced T-ALL, that the loss of either p19ARF or p53 abrogates the ability of MYC inactivation to induce sustained tumor regression. Loss of p53 or p19ARF, influenced the ability of MYC inactivation to elicit the shutdown of angiogenesis; however the loss of p19ARF, but not p53, impeded cellular senescence, as measured by SA-beta-galactosidase staining, increased expression of p16INK4A, and specific histone modifications. Moreover, comparative gene expression analysis suggested that a multitude of genes involved in the innate immune response were expressed in p19ARF wild-type, but not null, tumors upon MYC inactivation. Indeed, the loss of p19ARF, but not p53, impeded the in situ recruitment of macrophages to the tumor microenvironment. Finally, p19ARF null-associated gene signature prognosticated relapse-free survival in human patients with ALL. Therefore, p19ARF appears to be important to regulating cellular senescence and innate immune response that may contribute to the therapeutic response of ALL.
View details for PubMedID 25784651
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miR-17-92 explains MYC oncogene addiction.
Molecular & cellular oncology
2014; 1 (4)
Abstract
MYC regulates tumorigenesis by coordinating the expression of thousands of genes. We found that MYC appears to regulate the decisions between cell survival versus death and self-renewal versus senescence through the microRNA miR-17-92 cluster. Addiction to the MYC oncogene may therefore in fact be an addiction to miR-17-92.
View details for DOI 10.4161/23723548.2014.970092
View details for PubMedID 27308380
View details for PubMedCentralID PMC4905255
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Oncogene addiction: resetting the safety switch?
Oncotarget
2014; 5 (18): 7986-7987
Abstract
Commentary on: Li Y, Choi PS, Casey SC, Dill DL, Felsher DW. MYC through miR-17-92 Suppresses Specific Target Genes to Maintain Survival, Autonomous Proliferation, and a Neoplastic State. Cancer Cell. 2014 ;26:262-72.
View details for PubMedID 25275297
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Activation of Cre Recombinase Alone Can Induce Complete Tumor Regression
PLOS ONE
2014; 9 (9)
View details for DOI 10.1371/journal.pone.0107589
View details for Web of Science ID 000342030300091
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Addiction to multiple oncogenes can be exploited to prevent the emergence of therapeutic resistance.
Proceedings of the National Academy of Sciences of the United States of America
2014; 111 (32): E3316-24
Abstract
Many cancers exhibit sensitivity to the inhibition of a single genetic lesion, a property that has been successfully exploited with oncogene-targeted therapeutics. However, inhibition of single oncogenes often fails to result in sustained tumor regression due to the emergence of therapy-resistant cells. Here, we report that MYC-driven lymphomas frequently acquire activating mutations in β-catenin, including a previously unreported mutation in a splice acceptor site. Tumors with these genetic lesions are highly dependent on β-catenin for their survival and the suppression of β-catenin resulted in marked apoptosis causally related to a decrease in Bcl-xL expression. Using a novel inducible inhibitor of β-catenin, we illustrate that, although MYC withdrawal or β-catenin inhibition alone results in initial tumor regression, most tumors ultimately recurred, mimicking the clinical response to single-agent targeted therapy. Importantly, the simultaneous combined inhibition of both MYC and β-catenin promoted more rapid tumor regression and successfully prevented tumor recurrence. Hence, we demonstrated that MYC-induced tumors are addicted to mutant β-catenin, and the combined inactivation of MYC and β-catenin induces sustained tumor regression. Our results provide a proof of principle that targeting multiple oncogene addicted pathways can prevent therapeutic resistance.
View details for DOI 10.1073/pnas.1406123111
View details for PubMedID 25071175
View details for PubMedCentralID PMC4136575
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Addiction to multiple oncogenes can be exploited to prevent the emergence of therapeutic resistance.
Proceedings of the National Academy of Sciences of the United States of America
2014; 111 (32): E3316-24
View details for DOI 10.1073/pnas.1406123111
View details for PubMedID 25071175
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MYC through miR-17-92 Suppresses Specific Target Genes to Maintain Survival, Autonomous Proliferation, and a Neoplastic State.
Cancer cell
2014; 26 (2): 262-272
Abstract
The MYC oncogene regulates gene expression through multiple mechanisms, and its overexpression culminates in tumorigenesis. MYC inactivation reverses turmorigenesis through the loss of distinguishing features of cancer, including autonomous proliferation and survival. Here we report that MYC via miR-17-92 maintains a neoplastic state through the suppression of chromatin regulatory genes Sin3b, Hbp1, Suv420h1, and Btg1, as well as the apoptosis regulator Bim. The enforced expression of miR-17-92 prevents MYC suppression from inducing proliferative arrest, senescence, and apoptosis and abrogates sustained tumor regression. Knockdown of the five miR-17-92 target genes blocks senescence and apoptosis while it modestly delays proliferative arrest, thus partially recapitulating miR-17-92 function. We conclude that MYC, via miR-17-92, maintains a neoplastic state by suppressing specific target genes.
View details for DOI 10.1016/j.ccr.2014.06.014
View details for PubMedID 25117713
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Alteration of the lipid profile in lymphomas induced by MYC overexpression.
Proceedings of the National Academy of Sciences of the United States of America
2014; 111 (29): 10450-10455
Abstract
Overexpression of the v-myc avian myelocytomatosis viral oncogene homolog (MYC) oncogene is one of the most commonly implicated causes of human tumorigenesis. MYC is known to regulate many aspects of cellular biology including glucose and glutamine metabolism. Little is known about the relationship between MYC and the appearance and disappearance of specific lipid species. We use desorption electrospray ionization mass spectrometry imaging (DESI-MSI), statistical analysis, and conditional transgenic animal models and cell samples to investigate changes in lipid profiles in MYC-induced lymphoma. We have detected a lipid signature distinct from that observed in normal tissue and in rat sarcoma-induced lymphoma cells. We found 104 distinct molecular ions that have an altered abundance in MYC lymphoma compared with normal control tissue by statistical analysis with a false discovery rate of less than 5%. Of these, 86 molecular ions were specifically identified as complex phospholipids. To evaluate whether the lipid signature could also be observed in human tissue, we examined 15 human lymphoma samples with varying expression levels of MYC oncoprotein. Distinct lipid profiles in lymphomas with high and low MYC expression were observed, including many of the lipid species identified as significant for MYC-induced animal lymphoma tissue. Our results suggest a relationship between the appearance of specific lipid species and the overexpression of MYC in lymphomas.
View details for DOI 10.1073/pnas.1409778111
View details for PubMedID 24994904
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Inactivation of MYC reverses tumorigenesis
JOURNAL OF INTERNAL MEDICINE
2014; 276 (1): 52-60
Abstract
The MYC proto-oncogene is an essential regulator of many normal biological programmes. MYC, when activated as an oncogene, has been implicated in the pathogenesis of most types of human cancers. MYC overexpression in normal cells is restrained from causing cancer through multiple genetically and epigenetically controlled checkpoint mechanisms, including proliferative arrest, apoptosis and cellular senescence. When pathologically activated in the correct epigenetic and genetic contexts, MYC bypasses these mechanisms and drives many of the 'hallmark' features of cancer, including uncontrolled tumour growth associated with DNA replication and transcription, cellular proliferation and growth, protein synthesis and altered cellular metabolism. MYC also dictates tumour cell fate by enforcing self-renewal and by abrogating cellular senescence and differentiation programmes. Moreover, MYC influences the tumour microenvironment, including activating angiogenesis and suppressing the host immune response. Provocatively, brief or even partial suppression of MYC back to its physiological levels of activation can lead to the restoration of intrinsic checkpoint mechanisms, resulting in acute and sustained tumour regression associated with tumour cells undergoing proliferative arrest, differentiation, senescence and apoptosis, as well as remodelling of the tumour microenvironment, recruitment of an immune response and shutdown of angiogenesis. Hence, tumours appear to be addicted to the MYC oncogene because of both tumour cell intrinsic and host-dependent mechanisms. MYC is important for the regulation of both the initiation and maintenance of tumorigenesis. This article is protected by copyright. All rights reserved.
View details for DOI 10.1111/joim.12237
View details for Web of Science ID 000337787500006
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Bioorthogonal cyclization-mediated in situ self-assembly of small-molecule probes for imaging caspase activity in vivo.
Nature chemistry
2014; 6 (6): 519-526
Abstract
Directed self-assembly of small molecules in living systems could enable a myriad of applications in biology and medicine, and already this has been used widely to synthesize supramolecules and nano/microstructures in solution and in living cells. However, controlling the self-assembly of synthetic small molecules in living animals is challenging because of the complex and dynamic in vivo physiological environment. Here we employ an optimized first-order bioorthogonal cyclization reaction to control the self-assembly of a fluorescent small molecule, and demonstrate its in vivo applicability by imaging caspase-3/7 activity in human tumour xenograft mouse models of chemotherapy. The fluorescent nanoparticles assembled in situ were imaged successfully in both apoptotic cells and tumour tissues using three-dimensional structured illumination microscopy. This strategy combines the advantages offered by small molecules with those of nanomaterials and should find widespread use for non-invasive imaging of enzyme activity in vivo.
View details for DOI 10.1038/nchem.1920
View details for PubMedID 24848238
View details for PubMedCentralID PMC4031611
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MYC activation is a hallmark of cancer initiation and maintenance.
Cold Spring Harbor perspectives in medicine
2014; 4 (6)
Abstract
The MYC proto-oncogene has been implicated in the pathogenesis of most types of human tumors. MYC activation alone in many normal cells is restrained from causing tumorigenesis through multiple genetic and epigenetically controlled checkpoint mechanisms, including proliferative arrest, apoptosis, and cellular senescence. When pathologically activated in a permissive epigenetic and/or genetic context, MYC bypasses these mechanisms, enforcing many of the "hallmark" features of cancer, including relentless tumor growth associated with DNA replication and transcription, cellular proliferation and growth, protein synthesis, and altered cellular metabolism. MYC mandates tumor cell fate, by inducing stemness and blocking cellular senescence and differentiation. Additionally, MYC orchestrates changes in the tumor microenvironment, including the activation of angiogenesis and suppression of the host immune response. Provocatively, brief or even partial suppression of MYC back to its physiological levels of activation can result in the restoration of intrinsic checkpoint mechanisms, resulting in acute and sustained tumor regression, associated with tumor cells undergoing proliferative arrest, differentiation, senescence, and apoptosis, as well as remodeling of the tumor microenvironment, recruitment of an immune response, and shutdown of angiogenesis. Hence, tumors appear to be "addicted" to MYC because of both tumor cell-intrinsic, cell-autonomous and host-dependent, immune cell-dependent mechanisms. Both the trajectory and persistence of many human cancers require sustained MYC activation. Multiscale mathematical modeling may be useful to predict when tumors will be addicted to MYC. MYC is a hallmark molecular feature of both the initiation and maintenance of tumorigenesis.
View details for DOI 10.1101/cshperspect.a014241
View details for PubMedID 24890832
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MYC Activation Is a Hallmark of Cancer Initiation and Maintenance
COLD SPRING HARBOR PERSPECTIVES IN MEDICINE
2014; 4 (6)
View details for DOI 10.1101/cshperspect.a014241
View details for Web of Science ID 000338021000003
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An essential role for the immune system in the mechanism of tumor regression following targeted oncogene inactivation.
Immunologic research
2014; 58 (2-3): 282-291
Abstract
Tumors are genetically complex and can have a multitude of mutations. Consequently, it is surprising that the suppression of a single oncogene can result in rapid and sustained tumor regression, illustrating the concept that cancers are often "oncogene addicted." The mechanism of oncogene addiction has been presumed to be largely cell autonomous as a consequence of the restoration of normal physiological programs that induce proliferative arrest, apoptosis, differentiation, and/or cellular senescence. Interestingly, it has recently become apparent that upon oncogene inactivation, the immune response is critical in mediating the phenotypic consequences of oncogene addiction. In particular, CD4(+) T cells have been suggested to be essential to the remodeling of the tumor microenvironment, including the shutdown of host angiogenesis and the induction of cellular senescence in the tumor. However, adaptive and innate immune cells are likely involved. Thus, the effectors of the immune system are involved not only in tumor initiation, tumor progression, and immunosurveillance, but also in the mechanism of tumor regression upon targeted oncogene inactivation. Hence, oncogene inactivation may be an effective therapeutic approach because it both reverses the neoplastic state within a cancer cell and reactivates the host immune response that remodels the tumor microenvironment.
View details for DOI 10.1007/s12026-014-8503-6
View details for PubMedID 24791942
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Inactivation of MYC reverses tumorigenesis.
Journal of internal medicine
2014
Abstract
The MYC proto-oncogene is an essential regulator of many normal biological programmes. MYC, when activated as an oncogene, has been implicated in the pathogenesis of most types of human cancers. MYC overexpression in normal cells is restrained from causing cancer through multiple genetically and epigenetically controlled checkpoint mechanisms, including proliferative arrest, apoptosis and cellular senescence. When pathologically activated in the correct epigenetic and genetic contexts, MYC bypasses these mechanisms and drives many of the 'hallmark' features of cancer, including uncontrolled tumour growth associated with DNA replication and transcription, cellular proliferation and growth, protein synthesis and altered cellular metabolism. MYC also dictates tumour cell fate by enforcing self-renewal and by abrogating cellular senescence and differentiation programmes. Moreover, MYC influences the tumour microenvironment, including activating angiogenesis and suppressing the host immune response. Provocatively, brief or even partial suppression of MYC back to its physiological levels of activation can lead to the restoration of intrinsic checkpoint mechanisms, resulting in acute and sustained tumour regression associated with tumour cells undergoing proliferative arrest, differentiation, senescence and apoptosis, as well as remodelling of the tumour microenvironment, recruitment of an immune response and shutdown of angiogenesis. Hence, tumours appear to be addicted to the MYC oncogene because of both tumour cell intrinsic and host-dependent mechanisms. MYC is important for the regulation of both the initiation and maintenance of tumorigenesis. This article is protected by copyright. All rights reserved.
View details for DOI 10.1111/joim.12237
View details for PubMedID 24645771
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Angiocrine factors deployed by tumor vascular niche induce B cell lymphoma invasiveness and chemoresistance.
Cancer cell
2014; 25 (3): 350-365
Abstract
Tumor endothelial cells (ECs) promote cancer progression in ways beyond their role as conduits supporting metabolism. However, it is unknown how vascular niche-derived paracrine factors, defined as angiocrine factors, provoke tumor aggressiveness. Here, we show that FGF4 produced by B cell lymphoma cells (LCs) through activating FGFR1 upregulates the Notch ligand Jagged1 (Jag1) on neighboring ECs. In turn, upregulation of Jag1 on ECs reciprocally induces Notch2-Hey1 in LCs. This crosstalk enforces aggressive CD44(+)IGF1R(+)CSF1R(+) LC phenotypes, including extranodal invasion and chemoresistance. Inducible EC-selective deletion of Fgfr1 or Jag1 in the Eμ-Myc lymphoma model or impairing Notch2 signaling in mouse and human LCs diminished lymphoma aggressiveness and prolonged mouse survival. Thus, targeting the angiocrine FGF4-FGFR1/Jag1-Notch2 loop inhibits LC aggressiveness and enhances chemosensitivity.
View details for DOI 10.1016/j.ccr.2014.02.005
View details for PubMedID 24651014
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Angiocrine Factors Deployed by Tumor Vascular Niche Induce B Cell Lymphoma Invasiveness and Chemoresistance
CANCER CELL
2014; 25 (3): 350-365
Abstract
Tumor endothelial cells (ECs) promote cancer progression in ways beyond their role as conduits supporting metabolism. However, it is unknown how vascular niche-derived paracrine factors, defined as angiocrine factors, provoke tumor aggressiveness. Here, we show that FGF4 produced by B cell lymphoma cells (LCs) through activating FGFR1 upregulates the Notch ligand Jagged1 (Jag1) on neighboring ECs. In turn, upregulation of Jag1 on ECs reciprocally induces Notch2-Hey1 in LCs. This crosstalk enforces aggressive CD44(+)IGF1R(+)CSF1R(+) LC phenotypes, including extranodal invasion and chemoresistance. Inducible EC-selective deletion of Fgfr1 or Jag1 in the Eμ-Myc lymphoma model or impairing Notch2 signaling in mouse and human LCs diminished lymphoma aggressiveness and prolonged mouse survival. Thus, targeting the angiocrine FGF4-FGFR1/Jag1-Notch2 loop inhibits LC aggressiveness and enhances chemosensitivity.
View details for DOI 10.1016/j.ccr.2014.02.005
View details for Web of Science ID 000333233400012
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Development of novel tumor-targeted theranostic nanoparticles activated by membrane-type matrix metalloproteinases for combined cancer magnetic resonance imaging and therapy.
Small
2014; 10 (3): 566-?
Abstract
A major drawback with current cancer therapy is the prevalence of unrequired dose-limiting toxicity to non-cancerous tissues and organs, which is further compounded by a limited ability to rapidly and easily monitor drug delivery, pharmacodynamics and therapeutic response. In this report, the design and characterization of novel multifunctional "theranostic" nanoparticles (TNPs) is described for enzyme-specific drug activation at tumor sites and simultaneous in vivo magnetic resonance imaging (MRI) of drug delivery. TNPs are synthesized by conjugation of FDA-approved iron oxide nanoparticles ferumoxytol to an MMP-activatable peptide conjugate of azademethylcolchicine (ICT), creating CLIO-ICTs (TNPs). Significant cell death is observed in TNP-treated MMP-14 positive MMTV-PyMT breast cancer cells in vitro, but not MMP-14 negative fibroblasts or cells treated with ferumoxytol alone. Intravenous administration of TNPs to MMTV-PyMT tumor-bearing mice and subsequent MRI demonstrates significant tumor selective accumulation of the TNP, an observation confirmed by histopathology. Treatment with CLIO-ICTs induces a significant antitumor effect and tumor necrosis, a response not observed with ferumoxytol. Furthermore, no toxicity or cell death is observed in normal tissues following treatment with CLIO-ICTs, ICT, or ferumoxytol. These findings demonstrate proof of concept for a new nanotemplate that integrates tumor specificity, drug delivery and in vivo imaging into a single TNP entity through attachment of enzyme-activated prodrugs onto magnetic nanoparticles. This novel approach holds the potential to significantly improve targeted cancer therapies, and ultimately enable personalized therapy regimens.
View details for DOI 10.1002/smll.201301456
View details for PubMedID 24038954
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Development of novel tumor-targeted theranostic nanoparticles activated by membrane-type matrix metalloproteinases for combined cancer magnetic resonance imaging and therapy.
Small
2014; 10 (3): 566-575
View details for DOI 10.1002/smll.201301456
View details for PubMedID 24038954
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Oncogene withdrawal engages the immune system to induce sustained cancer regression.
Journal for immunotherapy of cancer
2014; 2: 24-?
Abstract
The targeted inactivation of a single oncogene can induce dramatic tumor regression, suggesting that cancers are "oncogene addicted." Tumor regression following oncogene inactivation has been thought to be a consequence of restoration of normal physiological programs that induce proliferative arrest, apoptosis, differentiation, and cellular senescence. However, recent observations illustrate that oncogene addiction is highly dependent upon the host immune cells. In particular, CD4(+) helper T cells were shown to be essential to the mechanism by which MYC or BCR-ABL inactivation elicits "oncogene withdrawal." Hence, immune mediators contribute in multiple ways to the pathogenesis, prevention, and treatment of cancer, including mechanisms of tumor initiation, progression, and surveillance, but also oncogene inactivation-mediated tumor regression. Data from both the bench and the bedside illustrates that the inactivation of a driver oncogene can induce activation of the immune system that appears to be essential for sustained tumor regression.
View details for DOI 10.1186/2051-1426-2-24
View details for PubMedID 25089198
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Activation of Cre recombinase alone can induce complete tumor regression.
PloS one
2014; 9 (9)
Abstract
The Cre/loxP system is a powerful tool for generating conditional genomic recombination and is often used to examine the mechanistic role of specific genes in tumorigenesis. However, Cre toxicity due to its non-specific endonuclease activity has been a concern. Here, we report that tamoxifen-mediated Cre activation in vivo induced the regression of primary lymphomas in p53-/- mice. Our findings illustrate that Cre activation alone can induce the regression of established tumors.
View details for DOI 10.1371/journal.pone.0107589
View details for PubMedID 25208064
View details for PubMedCentralID PMC4160265
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STK38 is a critical upstream regulator of MYC's oncogenic activity in human B-cell lymphoma
ONCOGENE
2013; 32 (45): 5283-5291
Abstract
The MYC protooncogene is associated with the pathogenesis of most human neoplasia. Conversely, its experimental inactivation elicits oncogene addiction. Besides constituting a formidable therapeutic target, MYC also has an essential function in normal physiology, thus creating the need for context-specific targeting strategies. The analysis of post-translational MYC activity modulation yields novel targets for MYC inactivation. Specifically, following regulatory network analysis in human B-cells, we identify a novel role of the STK38 kinase as a regulator of MYC activity and a candidate target for abrogating tumorigenesis in MYC-addicted lymphoma. We found that STK38 regulates MYC protein stability and turnover in a kinase activity-dependent manner. STK38 kinase inactivation abrogates apoptosis following B-cell receptor activation, whereas its silencing significantly decreases MYC levels and increases apoptosis. Moreover, STK38 knockdown suppresses growth of MYC-addicted tumors in vivo, thus providing a novel viable target for treating these malignancies.Oncogene advance online publication, 26 November 2012; doi:10.1038/onc.2012.543.
View details for DOI 10.1038/onc.2012.543
View details for Web of Science ID 000326922100004
View details for PubMedID 23178486
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Real-time nanoscale proteomic analysis of the novel multi-kinase pathway inhibitor rigosertib to measure the response to treatment of cancer.
Expert opinion on investigational drugs
2013; 22 (11): 1495-1509
Abstract
Rigosertib (ON01910.Na), is a targeted therapeutic that inhibits multiple kinases, including PI3K and PIk-1. Rigosertib has been found to induce the proliferative arrest and apoptosis of myeloblasts but not of other normal hematopoietic cells. Rigosertib has significant clinical activity as a therapy for patients with high-risk myelodysplastic syndrome who are otherwise refractory to DNA methyltransferase inhibitors. Moreover, rigosertib has potential clinical activity in a multitude of solid tumors.The objective of this review is to evaluate the mechanism of activity, efficacy and dosing of rigosertib. Furthermore, the challenge in the clinical development of rigosertib, to identify the specific patients that are most likely to benefit from this therapeutic agent, is discussed. A PubMed search was performed using the following key words: rigosertib and ON01910.Na.We describe the application of a novel nanoscale proteomic assay, the nanoimmunoassay, a tractable approach for measuring the activity and predicting the efficacy of rigosertib, in real-time, using limited human clinical specimens. Our strategy suggests a possible paradigm where proteomic analysis during the pre-clinical and clinical development of a therapy can be used to uncover biomarkers for the analysis and prediction of efficacy in human patients.
View details for DOI 10.1517/13543784.2013.829453
View details for PubMedID 23937225
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Regulation of accumulation and function of myeloid derived suppressor cells in different murine models of hepatocellular carcinoma
JOURNAL OF HEPATOLOGY
2013; 59 (5): 1007-1013
Abstract
Myeloid derived suppressor cells (MDSC) are immature myeloid cells with immunosuppressive activity. They accumulate in tumor-bearing mice and humans with different types of cancer, including hepatocellular carcinoma (HCC). The aim of this study was to examine the biology of MDSC in murine HCC models and to identify a model, which mimics the human disease.The comparative analysis of MDSC was performed in mice, bearing transplantable, diethylnitrosoamine (DEN)-induced and MYC-expressing HCC at different ages.An accumulation of MDSC was found in mice with HCC irrespectively of the model tested. Transplantable tumors rapidly induced systemic recruitment of MDSC, in contrast to slow-growing DEN-induced or MYC-expressing HCC, where MDSC numbers only increased intra-hepatically in mice with advanced tumors. MDSC derived from mice with subcutaneous tumors were more suppressive than those from mice with DEN-induced HCC. Enhanced expression of genes associated with MDSC generation (GM-CSF, VEGF, IL-6, IL-1 and migration (MCP-1, KC, S100A8, S100A9) was observed in mice with subcutaneous tumors. In contrast, only KC levels increased in mice with DEN-induced HCC. Both KC and GM-CSF over-expression or anti-KC and anti-GM-CSF treatment controlled MDSC frequency in mice with HCC. Finally, the frequency of MDSC decreased upon successful anti-tumor treatment with sorafenib.Our data indicate that MDSC accumulation is a late event during hepatocarcinogenesis and differs significantly depending on the tumor model studied.
View details for Web of Science ID 000325754200016
View details for PubMedID 23796475
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BCL-2 inhibition with ABT-737 prolongs survival in an NRAS/BCL-2 mouse model of AML by targeting primitive LSK and progenitor cells.
Blood
2013; 122 (16): 2864-2876
Abstract
Myelodysplastic syndrome (MDS) transforms into an acute myelogenous leukemia (AML) with associated increased bone marrow (BM) blast infiltration. Using a transgenic mouse model, MRP8[NRASD12/hBCL-2], in which the NRAS:BCL-2 complex at the mitochondria induces MDS progressing to AML with dysplastic features, we studied the therapeutic potential of a BCL-2 homology domain 3 mimetic inhibitor, ABT-737. Treatment significantly extended lifespan, increased survival of lethally irradiated secondary recipients transplanted with cells from treated mice compared with cells from untreated mice, with a reduction of BM blasts, Lin-/Sca-1(+)/c-Kit(+), and progenitor populations by increased apoptosis of infiltrating blasts of diseased mice assessed in vivo by technicium-labeled annexin V single photon emission computed tomography and ex vivo by annexin V/7-amino actinomycin D flow cytometry, terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling, caspase 3 cleavage, and re-localization of the NRAS:BCL-2 complex from mitochondria to plasma membrane. Phosphoprotein analysis showed restoration of wild-type (WT) AKT or protein kinase B, extracellular signal-regulated kinase 1/2 and mitogen-activated protein kinase patterns in spleen cells after treatment, which showed reduced mitochondrial membrane potential. Exon specific gene expression profiling corroborates the reduction of leukemic cells, with an increase in expression of genes coding for stem cell development and maintenance, myeloid differentiation, and apoptosis. Myelodysplastic features persist underscoring targeting of BCL-2-mediated effects on MDS-AML transformation and survival of leukemic cells.
View details for DOI 10.1182/blood-2012-07-445635
View details for PubMedID 23943652
View details for PubMedCentralID PMC3799000
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A c-Myc Activation Sensor-Based High-Throughput Drug Screening Identifies an Antineoplastic Effect of Nitazoxanide.
Molecular cancer therapeutics
2013; 12 (9): 1896-1905
Abstract
Deregulation of c-Myc plays a central role in the tumorigenesis of many human cancers. Yet, the development of drugs regulating c-Myc activity has been challenging. To facilitate the identification of c-Myc inhibitors, we developed a molecular imaging sensor based high throughput-screening (HTS) system. This system uses a cell-based assay to detect c-Myc activation in a HTS format, which is established from a pure clone of a stable breast cancer cell line that constitutively expresses a c-Myc activation sensor. Optimization of the assay performance in the HTS format resulted in uniform and robust signals at the baseline. Using this system, we performed a quantitative HTS against approximately 5,000 existing bioactive compounds from five different libraries. Thirty-nine potential hits were identified, including currently known c-Myc inhibitors. There are a few among the top potent hits that are not known for anti-c-Myc activity. One of these hits is nitazoxanide (NTZ), a thiazolide for treating human protozoal infections. Validation of NTZ in different cancer cell lines revealed a high potency for c-Myc inhibition with IC50 ranging between 10 - 500nM. Oral administration of NTZ in breast cancer xenograft mouse models significantly suppressed tumor growth by inhibition of c-Myc and induction of apoptosis. These findings suggest a potential of NTZ to be repurposed as a new anti-tumor agent for inhibition of c-Myc associated neoplasia. Our work also demonstrated the unique advantage of molecular imaging in accelerating discovery of drugs for c-Myc targeted cancer therapy.
View details for DOI 10.1158/1535-7163.MCT-12-1243
View details for PubMedID 23825064
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A tumor-immune mathematical model of CD4+ T helper cell dependent tumor regression by oncogene inactivation.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
2013; 2013: 4529-4532
Abstract
Understanding the complex dynamics between the tumor cells and the host immune system will be key to improved therapeutic strategies against cancer. We propose an ODE-based mathematical model of both the tumor and immune system and how they respond to inactivation of the driving oncogene. Our model supports experimental results showing that cellular senescence of tumor cells is dependent on CD4+ T helper cells, leading to relapse of tumors in immunocompromised hosts.
View details for DOI 10.1109/EMBC.2013.6610554
View details for PubMedID 24110741
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Characterization of MYC-Induced Tumorigenesis by in Situ Lipid Profiling
ANALYTICAL CHEMISTRY
2013; 85 (9): 4259-4262
Abstract
We apply desorption electrospray ionization mass spectrometry imaging (DESI-MSI) to provide an in situ lipidomic profile of genetically modified tissues from a conditional transgenic mouse model of MYC-induced hepatocellular carcinoma (HCC). This unique, label-free approach of combining DESI-MSI with the ability to turn specific genes on and off has led to the discovery of highly specific lipid molecules associated with MYC-induced tumor onset. We are able to distinguish normal from MYC-induced malignant cells. Our approach provides a strategy to define a precise molecular picture at a resolution of about 200 μm that may be useful in identifying lipid molecules that define how the MYC oncogene initiates and maintains tumorigenesis.
View details for DOI 10.1021/ac400479j
View details for Web of Science ID 000318756100008
View details for PubMedID 23560736
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[F-18]CAIP a smart PET tracer for imaging caspase-3 induced Apoptosis
WILEY-BLACKWELL. 2013: S6–S6
View details for Web of Science ID 000318694100007
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Role of MYCN in retinoblastoma
LANCET ONCOLOGY
2013; 14 (4): 270-271
View details for DOI 10.1016/S1470-2045(13)70070-6
View details for Web of Science ID 000317390300022
View details for PubMedID 23498720
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Noncanonical roles of the immune system in eliciting oncogene addiction.
Current opinion in immunology
2013; 25 (2): 246-258
Abstract
Cancer is highly complex. The magnitude of this complexity makes it highly surprising that even the brief suppression of an oncogene can sometimes result in rapid and sustained tumor regression, illustrating that cancers can be 'oncogene addicted' [1-10]. The essential implication is that oncogenes may not only fuel the initiation of tumorigenesis, but in some cases must be excessively activated to maintain a neoplastic state [11]. Oncogene suppression acutely restores normal physiological programs that effectively overrides secondary genetic events and a cancer collapses [12,13]. Oncogene addiction is the description of the dramatic and sustained regression of some cancers upon the specific inactivation of a single oncogene [1-13,14(••),15,16(••)], that can occur through tumor intrinsic [1,2,4,12], but also host immune mechanisms [17-23]. Notably, oncogene inactivation elicits a host immune response that involves specific immune effectors and cytokines that facilitate a remodeling of the tumor microenvironment including the shut down of angiogenesis and the induction of cellular senescence of tumor cells [16(••)]. Hence, immune effectors are not only critically involved in tumor prevention, initiation [17-19], and progression [20], but also appear to be essential to tumor regression upon oncogene inactivation [21,22(••),23(••)]. Understanding how the inactivation of an oncogene elicits a systemic signal in the host that prompts a deconstruction of a tumor could have important implications. The combination of oncogene-targeted therapy together with immunomodulatory therapy may be ideal for the development of both robust tumor intrinsic and immunological responses, effectively leading to sustained tumor regression.
View details for DOI 10.1016/j.coi.2013.02.003
View details for PubMedID 23571026
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Metabolic changes in cancer cells upon suppression of MYC.
Cancer & metabolism
2013; 1 (1): 7-?
Abstract
Cancer cells engage in aerobic glycolysis and glutaminolysis to fulfill their biosynthetic and energetic demands in part by activating MYC. Previous reports have characterized metabolic changes in proliferating cells upon MYC loss or gain of function. However, metabolic differences between MYC-dependent cancer cells and their isogenic differentiated counterparts have not been characterized upon MYC suppression in vitro.Here we report metabolic changes between MYC-dependent mouse osteogenic sarcomas and differentiated osteoid cells induced upon MYC suppression. While osteogenic sarcoma cells increased oxygen consumption and spare respiratory capacity upon MYC suppression, they displayed minimal changes in glucose and glutamine consumption as well as their respective contribution to the citrate pool. However, glutamine significantly induced oxygen consumption in the presence of MYC which was dependent on aminotransferases. Furthermore, inhibition of aminotransferases selectively diminished cell proliferation and survival of osteogenic sarcoma MYC-expressing cells. There were minimal changes in ROS levels and cell death sensitivity to reactive oxygen species (ROS)-inducing agents between osteoid cells and osteogenic sarcoma cells. Nevertheless, the mitochondrial-targeted antioxidant Mito-Vitamin E still diminished proliferation of MYC-dependent osteogenic sarcoma cells.These data highlight that aminotransferases and mitochondrial ROS might be attractive targets for cancer therapy in MYC-driven tumors.
View details for DOI 10.1186/2049-3002-1-7
View details for PubMedID 24280108
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Dissection of the role of the tumor microenvironment in oncogene addiction by ex vivo and in situ imaging
AACR/SNMMI Joint Conference on State-of-the-Art Molecular Imaging in Cancer Biology and Therapy
SOC NUCLEAR MEDICINE INC. 2013: 25–25
View details for Web of Science ID 000314691400075
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CD271(+) bone marrow mesenchymal stem cells may provide a niche for dormant Mycobacterium tuberculosis.
Science translational medicine
2013; 5 (170): 170ra13-?
Abstract
Mycobacterium tuberculosis (Mtb) can persist in hostile intracellular microenvironments evading immune cells and drug treatment. However, the protective cellular niches where Mtb persists remain unclear. We report that Mtb may maintain long-term intracellular viability in a human bone marrow (BM)-derived CD271(+)/CD45(-) mesenchymal stem cell (BM-MSC) population in vitro. We also report that Mtb resides in an equivalent population of BM-MSCs in a mouse model of dormant tuberculosis infection. Viable Mtb was detected in CD271(+)/CD45(-) BM-MSCs isolated from individuals who had successfully completed months of anti-Mtb drug treatment. These results suggest that CD271(+) BM-MSCs may provide a long-term protective intracellular niche in the host in which dormant Mtb can reside.
View details for DOI 10.1126/scitranslmed.3004912
View details for PubMedID 23363977
View details for PubMedCentralID PMC3616630
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CD271(+) Bone Marrow Mesenchymal Stem Cells May Provide a Niche for Dormant Mycobacterium tuberculosis
SCIENCE TRANSLATIONAL MEDICINE
2013; 5 (170)
View details for DOI 10.1126/scitranslmed.3004912
View details for Web of Science ID 000314343100003
View details for PubMedID 23363977
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Tumor dormancy, oncogene addiction, cellular senescence, and self-renewal programs.
Advances in experimental medicine and biology
2013; 734: 91-107
Abstract
Cancers are frequently addicted to initiating oncogenes that elicit aberrant cellular proliferation, self-renewal, and apoptosis. Restoration of oncogenes to normal physiologic regulation can elicit dramatic reversal of the neoplastic phenotype, including reduced proliferation and increased apoptosis of tumor cells (Science 297(5578):63-64, 2002). In some cases, oncogene inactivation is associated with compete elimination of a tumor. However, in other cases, oncogene inactivation induces a conversion of tumor cells to a dormant state that is associated with cellular differentiation and/or loss of the ability to self-replicate. Importantly, this dormant state is reversible, with tumor cells regaining the ability to self-renew upon oncogene reactivation. Thus, understanding the mechanism of oncogene inactivation-induced dormancy may be crucial for predicting therapeutic outcome of targeted therapy. One important mechanistic insight into tumor dormancy is that oncogene addiction might involve regulation of a decision between self-renewal and cellular senescence. Recent evidence suggests that this decision is regulated by multiple mechanisms that include tumor cell-intrinsic, cell-autonomous mechanisms and host-dependent, tumor cell-non-autonomous programs (Mol Cell 4(2):199-207, 1999; Science 297(5578):102-104, 2002; Nature 431(7012):1112-1117, 2004; Proc Natl Acad Sci U S A 104(32):13028-13033, 2007). In particular, the tumor microenvironment, which is known to be critical during tumor initiation (Cancer Cell 7(5):411-423, 2005; J Clin Invest 121(6):2436-2446, 2011), prevention (Nature 410(6832):1107-1111, 2001), and progression (Cytokine Growth Factor Rev 21(1):3-10, 2010), also appears to dictate when oncogene inactivation elicits the permanent loss of self-renewal through induction of cellular senescence (Nat Rev Clin Oncol 8(3):151-160, 2011; Science 313(5795):1960-1964, 2006; N Engl J Med 351(21):2159-21569, 2004). Thus, oncogene addiction may be best modeled as a consequence of the interplay amongst cell-autonomous and host-dependent programs that define when a therapy will result in tumor dormancy.
View details for DOI 10.1007/978-1-4614-1445-2_6
View details for PubMedID 23143977
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In Vivo Imaging-Based Mathematical Modeling Techniques That Enhance the Understanding of Oncogene Addiction in relation to Tumor Growth
COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE
2013
Abstract
The dependence on the overexpression of a single oncogene constitutes an exploitable weakness for molecular targeted therapy. These drugs can produce dramatic tumor regression by targeting the driving oncogene, but relapse often follows. Understanding the complex interactions of the tumor's multifaceted response to oncogene inactivation is key to tumor regression. It has become clear that a collection of cellular responses lead to regression and that immune-mediated steps are vital to preventing relapse. Our integrative mathematical model includes a variety of cellular response mechanisms of tumors to oncogene inactivation. It allows for correct predictions of the time course of events following oncogene inactivation and their impact on tumor burden. A number of aspects of our mathematical model have proven to be necessary for recapitulating our experimental results. These include a number of heterogeneous tumor cell states since cells following different cellular programs have vastly different fates. Stochastic transitions between these states are necessary to capture the effect of escape from oncogene addiction (i.e., resistance). Finally, delay differential equations were used to accurately model the tumor growth kinetics that we have observed. We use this to model oncogene addiction in MYC-induced lymphoma, osteosarcoma, and hepatocellular carcinoma.
View details for DOI 10.1155/2013/802512
View details for Web of Science ID 000316905000001
View details for PubMedID 23573174
View details for PubMedCentralID PMC3616361
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Generation of a Tetracycline Regulated Mouse Model of MYC-Induced T-Cell Acute Lymphoblastic Leukemia.
Methods in molecular biology (Clifton, N.J.)
2013; 1012: 221-235
Abstract
The tetracycline regulatory system provides a tractable strategy to interrogate the role of oncogenes in the initiation and maintenance of tumorigenesis through both spatial and temporal control of expression. This approach has several potential advantages over conventional methods to generate genetically engineered mouse models. First, continuous constitutive overexpression of an oncogene can be lethal to the host impeding further study. Second, constitutive overexpression fails to model adult onset of disease. Third, constitutive deletion does not permit, whereas conditional overexpression of an oncogene enables the study of the consequences of restoring expression of an oncogene back to endogenous levels. Fourth, the conditional activation of oncogenes enables examination of specific and/or developmental state-specific consequences.Hence, by allowing precise control of when and where a gene is expressed, the tetracycline regulatory system provides an ideal approach for the study of putative oncogenes in both the initiation and maintenance of tumorigenesis. In this protocol, we describe the methods involved in the development of a conditional mouse model of MYC-induced T-cell acute lymphoblastic leukemia.
View details for DOI 10.1007/978-1-62703-429-6_15
View details for PubMedID 24006068
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In vivo imaging-based mathematical modeling techniques that enhance the understanding of oncogene addiction in relation to tumor growth.
Computational and mathematical methods in medicine
2013; 2013: 802512-?
Abstract
The dependence on the overexpression of a single oncogene constitutes an exploitable weakness for molecular targeted therapy. These drugs can produce dramatic tumor regression by targeting the driving oncogene, but relapse often follows. Understanding the complex interactions of the tumor's multifaceted response to oncogene inactivation is key to tumor regression. It has become clear that a collection of cellular responses lead to regression and that immune-mediated steps are vital to preventing relapse. Our integrative mathematical model includes a variety of cellular response mechanisms of tumors to oncogene inactivation. It allows for correct predictions of the time course of events following oncogene inactivation and their impact on tumor burden. A number of aspects of our mathematical model have proven to be necessary for recapitulating our experimental results. These include a number of heterogeneous tumor cell states since cells following different cellular programs have vastly different fates. Stochastic transitions between these states are necessary to capture the effect of escape from oncogene addiction (i.e., resistance). Finally, delay differential equations were used to accurately model the tumor growth kinetics that we have observed. We use this to model oncogene addiction in MYC-induced lymphoma, osteosarcoma, and hepatocellular carcinoma.
View details for DOI 10.1155/2013/802512
View details for PubMedID 23573174
View details for PubMedCentralID PMC3616361
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SIRT1 and c-Myc Promote Liver Tumor Cell Survival and Predict Poor Survival of Human Hepatocellular Carcinomas
PLOS ONE
2012; 7 (9)
Abstract
The increased expression of SIRT1 has recently been identified in numerous human tumors and a possible correlation with c-Myc oncogene has been proposed. However, it remains unclear whether SIRT1 functions as an oncogene or tumor suppressor. We sought to elucidate the role of SIRT1 in liver cancer under the influence of c-Myc and to determine the prognostic significance of SIRT1 and c-Myc expression in human hepatocellular carcinoma. The effect of either over-expression or knock down of SIRT1 on cell proliferation and survival was evaluated in both mouse and human liver cancer cells. Nicotinamide, an inhibitor of SIRT1, was also evaluated for its effects on liver tumorigenesis. The prognostic significance of the immunohistochemical detection of SIRT1 and c-Myc was evaluated in 154 hepatocellular carcinoma patients. SIRT1 and c-Myc regulate each other via a positive feedback loop and act synergistically to promote hepatocellular proliferation in both mice and human liver tumor cells. Tumor growth was significantly inhibited by nicotinamide in vivo and in vitro. In human hepatocellular carcinoma, SIRT1 expression positively correlated with c-Myc, Ki67 and p53 expression, as well as high á-fetoprotein level. Moreover, the expression of SIRT1, c-Myc and p53 were independent prognostic indicators of hepatocellular carcinoma. In conclusion, this study demonstrates that SIRT1 expression supports liver tumorigenesis and is closely correlated with oncogenic c-MYC expression. In addition, both SIRT1 and c-Myc may be useful prognostic indicators of hepatocellular carcinoma and SIRT1 targeted therapy may be beneficial in the treatment of hepatocellular carcinoma.
View details for DOI 10.1371/journal.pone.0045119
View details for Web of Science ID 000308860100058
View details for PubMedID 23024800
View details for PubMedCentralID PMC3443243
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HIF-2 alpha Suppresses p53 to Enhance the Stemness and Regenerative Potential of Human Embryonic Stem Cells
STEM CELLS
2012; 30 (8): 1685-1695
Abstract
Human embryonic stem cells (hESCs) have been reported to exert cytoprotective activity in the area of tissue injury. However, hypoxia/oxidative stress prevailing in the area of injury could activate p53, leading to death and differentiation of hESCs. Here we report that when exposed to hypoxia/oxidative stress, a small fraction of hESCs, namely the SSEA3+/ABCG2+ fraction undergoes a transient state of reprogramming to a low p53 and high hypoxia inducible factor (HIF)-2α state of transcriptional activity. This state can be sustained for a period of 2 weeks and is associated with enhanced transcriptional activity of Oct-4 and Nanog, concomitant with high teratomagenic potential. Conditioned medium obtained from the post-hypoxia SSEA3+/ABCG2+ hESCs showed cytoprotection both in vitro and in vivo. We termed this phenotype as the "enhanced stemness" state. We then demonstrated that the underlying molecular mechanism of this transient phenotype of enhanced stemness involved high Bcl-2, fibroblast growth factor (FGF)-2, and MDM2 expression and an altered state of the p53/MDM2 oscillation system. Specific silencing of HIF-2α and p53 resisted the reprogramming of SSEA3+/ABCG2+ to the enhanced stemness phenotype. Thus, our studies have uncovered a unique transient reprogramming activity in hESCs, the enhanced stemness reprogramming where a highly cytoprotective and undifferentiated state is achieved by transiently suppressing p53 activity. We suggest that this transient reprogramming is a form of stem cell altruism that benefits the surrounding tissues during the process of tissue regeneration.
View details for DOI 10.1002/stem.1142
View details for Web of Science ID 000306684900011
View details for PubMedID 22689594
View details for PubMedCentralID PMC3584519
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Twist1 Suppresses Senescence Programs and Thereby Accelerates and Maintains Mutant Kras-Induced Lung Tumorigenesis
PLOS GENETICS
2012; 8 (5)
Abstract
KRAS mutant lung cancers are generally refractory to chemotherapy as well targeted agents. To date, the identification of drugs to therapeutically inhibit K-RAS have been unsuccessful, suggesting that other approaches are required. We demonstrate in both a novel transgenic mutant Kras lung cancer mouse model and in human lung tumors that the inhibition of Twist1 restores a senescence program inducing the loss of a neoplastic phenotype. The Twist1 gene encodes for a transcription factor that is essential during embryogenesis. Twist1 has been suggested to play an important role during tumor progression. However, there is no in vivo evidence that Twist1 plays a role in autochthonous tumorigenesis. Through two novel transgenic mouse models, we show that Twist1 cooperates with Kras(G12D) to markedly accelerate lung tumorigenesis by abrogating cellular senescence programs and promoting the progression from benign adenomas to adenocarcinomas. Moreover, the suppression of Twist1 to physiological levels is sufficient to cause Kras mutant lung tumors to undergo senescence and lose their neoplastic features. Finally, we analyzed more than 500 human tumors to demonstrate that TWIST1 is frequently overexpressed in primary human lung tumors. The suppression of TWIST1 in human lung cancer cells also induced cellular senescence. Hence, TWIST1 is a critical regulator of cellular senescence programs, and the suppression of TWIST1 in human tumors may be an effective example of pro-senescence therapy.
View details for DOI 10.1371/journal.pgen.1002650
View details for Web of Science ID 000304864000004
View details for PubMedID 22654667
View details for PubMedCentralID PMC3360067
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Immunology in the clinic review series; focus on cancer: multiple roles for the immune system in oncogene addiction
CLINICAL AND EXPERIMENTAL IMMUNOLOGY
2012; 167 (2): 188-194
Abstract
Despite complex genomic and epigenetic abnormalities, many cancers are irrevocably dependent on an initiating oncogenic lesion whose restoration to a normal physiological activation can elicit a dramatic and sudden reversal of their neoplastic properties. This phenomenon of the reversal of tumorigenesis has been described as oncogene addiction. Oncogene addiction had been thought to occur largely through tumour cell-autonomous mechanisms such as proliferative arrest, apoptosis, differentiation and cellular senescence. However, the immune system plays an integral role in almost every aspect of tumorigenesis, including tumour initiation, prevention and progression as well as the response to therapeutics. Here we highlight more recent evidence suggesting that oncogene addiction may be integrally dependent upon host immune-mediated mechanisms, including specific immune effectors and cytokines that regulate tumour cell senescence and tumour-associated angiogenesis. Hence, the host immune system is essential to oncogene addiction.
View details for DOI 10.1111/j.1365-2249.2011.04514.x
View details for Web of Science ID 000299037700002
View details for PubMedID 22235994
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Loss of Dnmt3b function upregulates the tumor modifier Ment and accelerates mouse lymphomagenesis
JOURNAL OF CLINICAL INVESTIGATION
2012; 122 (1): 163-177
Abstract
DNA methyltransferase 3B (Dnmt3b) belongs to a family of enzymes responsible for methylation of cytosine residues in mammals. DNA methylation contributes to the epigenetic control of gene transcription and is deregulated in virtually all human tumors. To better understand the generation of cancer-specific methylation patterns, we genetically inactivated Dnmt3b in a mouse model of MYC-induced lymphomagenesis. Ablation of Dnmt3b function using a conditional knockout in T cells accelerated lymphomagenesis by increasing cellular proliferation, which suggests that Dnmt3b functions as a tumor suppressor. Global methylation profiling revealed numerous gene promoters as potential targets of Dnmt3b activity, the majority of which were demethylated in Dnmt3b-/- lymphomas, but not in Dnmt3b-/- pretumor thymocytes, implicating Dnmt3b in maintenance of cytosine methylation in cancer. Functional analysis identified the gene Gm128 (which we termed herein methylated in normal thymocytes [Ment]) as a target of Dnmt3b activity. We found that Ment was gradually demethylated and overexpressed during tumor progression in Dnmt3b-/- lymphomas. Similarly, MENT was overexpressed in 67% of human lymphomas, and its transcription inversely correlated with methylation and levels of DNMT3B. Importantly, knockdown of Ment inhibited growth of mouse and human cells, whereas overexpression of Ment provided Dnmt3b+/+ cells with a proliferative advantage. Our findings identify Ment as an enhancer of lymphomagenesis that contributes to the tumor suppressor function of Dnmt3b and suggest it could be a potential target for anticancer therapies.
View details for DOI 10.1172/JCI57292
View details for Web of Science ID 000298769400022
View details for PubMedID 22133874
View details for PubMedCentralID PMC3248285
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Mathematical Modeling of the Interactions between Cellular Programs in Response to Oncogene Inactivation
12th IEEE International Conference on BioInformatics and BioEngineering (BIBE)
IEEE. 2012: 454–459
View details for Web of Science ID 000315332900087
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Treatment of higher risk myelodysplastic syndrome patients unresponsive to hypomethylating agents with ON 01910.Na
LEUKEMIA RESEARCH
2012; 36 (1): 98-103
Abstract
In a Phase I/II clinical trial, 13 higher risk red blood cell-dependent myelodysplastic syndrome (MDS) patients unresponsive to hypomethylating therapy were treated with the multikinase inhibitor ON 01910.Na. Responses occurred in all morphologic, prognostic risk and cytogenetic subgroups, including four patients with marrow complete responses among eight with stable disease, associated with good drug tolerance. In a subset of patients, a novel nanoscale immunoassay showed substantially decreased AKT2 phosphorylation in CD34+ marrow cells from patients responding to therapy but not those who progressed on therapy. These data demonstrate encouraging efficacy and drug tolerance with ON 01910.Na treatment of higher risk MDS patients.
View details for DOI 10.1016/j.leukres.2011.08.022
View details for PubMedID 21924492
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"Picolog," a Synthetically-Available Bryostatin Analog, Inhibits Growth of MYC-Induced Lymphoma In Vivo
ONCOTARGET
2012; 3 (1): 58-66
Abstract
Bryostatin 1 is a naturally occurring complex macrolide with potent anti-neoplastic activity. However, its extremely low natural occurrence has impeded clinical advancement. We developed a strategy directed at the design of simplified and synthetically more accessible bryostatin analogs. Our lead analog, "picolog", can be step-economically produced. Picolog, compared to bryostatin, exhibited superior growth inhibition of MYC-induced lymphoma in vitro. A key mechanism of picolog's (and bryostatin's) activity is activation of PKC. A novel nano-immunoassay (NIA) revealed that picolog treatment increased phospho-MEK2 in the PKC pathway. Moreover, the inhibition of PKC abrogated picolog's activity. Finally, picolog was highly potent at 100 micrograms/kg and well tolerated at doses ranging from 100 micrograms/kg to 1 milligram/kg in vivo for the treatment of our aggressive model of MYC-induced lymphoma. We provide the first in vivo validation that the bryostatin analog, picolog, is a potential therapeutic agent for the treatment of cancer and other diseases.
View details for PubMedID 22308267
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Cryptococcal osteomyelitis and meningitis in a patient with non-hodgkin's lymphoma treated with PEP-C.
BMJ case reports
2012; 2012
Abstract
The authors present the first case report of a patient with lymphoma who developed disseminated cryptococcal osteomyelitis and meningitis while being treated with the PEP-C (prednisone, etoposide, procarbazine and cyclophosphamide) chemotherapy regimen. During investigation of fever and new bony lesions, fungal culture from a rib biopsy revealed that the patient had cryptococcal osteomyelitis. Further evaluation demonstrated concurrent cryptococcal meningitis. The patient's disseminated cryptococcal infections completely resolved after a full course of antifungal treatment. Cryptococcal osteomyelitis is itself an extremely rare diagnosis, and the unique presentation with concurrent cryptococcal meningitis in our patient with lymphoma was likely due to his PEP-C treatment. It is well recognised that prolonged intensive chemotherapeutic regimens place patients at risk for atypical infections; yet physicians should recognise that even chronic low-dose therapies can put patients at risk for fungal infections. Physicians should consider fungal infections as part of the infectious investigation of a lymphopaenic patient on PEP-C.
View details for DOI 10.1136/bcr.08.2011.4578
View details for PubMedID 22962380
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High throughput automated chromatin immunoprecipitation as a platform for drug screening and antibody validation
LAB ON A CHIP
2012; 12 (12): 2190-2198
Abstract
Chromatin immunoprecipitation (ChIP) is an assay for interrogating protein-DNA interactions that is increasingly being used for drug target discovery and screening applications. Currently the complexity of the protocol and the amount of hands-on time required for this assay limits its use to low throughput applications; furthermore, variability in antibody quality poses an additional obstacle in scaling up ChIP for large scale screening purposes. To address these challenges, we report HTChIP, an automated microfluidic-based platform for performing high-throughput ChIP screening measurements of 16 different targets simultaneously, with potential for further scale-up. From chromatin to analyzable PCR results only takes one day using HTChIP, as compared to several days up to one week for conventional protocols. HTChIP can also be used to test multiple antibodies and select the best performer for downstream ChIP applications, saving time and reagent costs of unsuccessful ChIP assays as a result of poor antibody quality. We performed a series of characterization assays to demonstrate that HTChIP can rapidly and accurately evaluate the epigenetic states of a cell, and that it is sensitive enough to detect the changes in the epigenetic state induced by a cytokine stimulant over a fine temporal resolution. With these results, we believe that HTChIP can introduce large improvements in routine ChIP, antibody screening, and drug screening efficiency, and further facilitate the use of ChIP as a valuable tool for research and discovery.
View details for DOI 10.1039/c2lc21290k
View details for PubMedID 22566096
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Hypoxia-microRNA-16 downregulation induces VEGF expression in anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphomas
LEUKEMIA
2011; 25 (12): 1882-1890
Abstract
The anaplastic lymphoma kinase (ALK), tyrosine kinase oncogene is implicated in a wide variety of cancers. In this study we used conditional onco-ALK (NPM-ALK and TPM3-ALK) mouse MEF cell lines (ALK+ fibroblasts) and transgenic models (ALK+ B-lymphoma) to investigate the involvement and regulation of angiogenesis in ALK tumor development. First, we observed that ALK expression leads to downregulation of miR-16 and increased Vascular Endothelial Growth Factor (VEGF) levels. Second, we found that modification of miR-16 levels in TPM3-ALK MEF cells greatly affected VEGF levels. Third, we demonstrated that miR-16 directly interacts with VEGF mRNA at the 3'-untranslated region and that the regulation of VEGF by miR-16 occurs at the translational level. Fourth, we showed that expression of both the ALK oncogene and hypoxia-induced factor 1α (HIF1α) is a prerequisite for miR-16 downregulation. Fifth, in vivo, miR-16 gain resulted in reduced angiogenesis and tumor growth. Finally, we highlighted an inverse correlation between the levels of miR-16 and VEGF in human NPM-ALK+ Anaplastic Large Cell Lymphomas (ALCL). Altogether, our results demonstrate, for the first time, the involvement of angiogenesis in ALK+ ALCL and strongly suggest an important role for hypoxia-miR-16 in regulating VEGF translation.
View details for DOI 10.1038/leu.2011.168
View details for Web of Science ID 000298405500012
View details for PubMedID 21778999
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A Novel Nano-Immunoassay (NIA) Reveals Inhibition of PI3K and MAPK Pathways in CD34+Bone Marrow Cells of Patients with Myelodysplastic Syndrome (MDS) Treated with the Multi-Kinase Inhibitor On 01910.Na (Rigosertib)
53rd Annual Meeting and Exposition of the American-Society-of-Hematology (ASH)
AMER SOC HEMATOLOGY. 2011: 1626–26
View details for Web of Science ID 000299597105536
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Lymphomas that recur after MYC suppression continue to exhibit oncogene addiction
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2011; 108 (42): 17432-17437
Abstract
The suppression of oncogenic levels of MYC is sufficient to induce sustained tumor regression associated with proliferative arrest, differentiation, cellular senescence, and/or apoptosis, a phenomenon known as oncogene addiction. However, after prolonged inactivation of MYC in a conditional transgenic mouse model of Eμ-tTA/tetO-MYC T-cell acute lymphoblastic leukemia, some of the tumors recur, recapitulating what is frequently observed in human tumors in response to targeted therapies. Here we report that these recurring lymphomas express either transgenic or endogenous Myc, albeit in many cases at levels below those in the original tumor, suggesting that tumors continue to be addicted to MYC. Many of the recurring lymphomas (76%) harbored mutations in the tetracycline transactivator, resulting in expression of the MYC transgene even in the presence of doxycycline. Some of the remaining recurring tumors expressed high levels of endogenous Myc, which was associated with a genomic rearrangement of the endogenous Myc locus or activation of Notch1. By gene expression profiling, we confirmed that the primary and recurring tumors have highly similar transcriptomes. Importantly, shRNA-mediated suppression of the high levels of MYC in recurring tumors elicited both suppression of proliferation and increased apoptosis, confirming that these tumors remain oncogene addicted. These results suggest that tumors induced by MYC remain addicted to overexpression of this oncogene.
View details for DOI 10.1073/pnas.1107303108
View details for PubMedID 21969595
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Survival and Death Signals Can Predict Tumor Response to Therapy After Oncogene Inactivation
SCIENCE TRANSLATIONAL MEDICINE
2011; 3 (103)
Abstract
Cancers can exhibit marked tumor regression after oncogene inhibition through a phenomenon called "oncogene addiction." The ability to predict when a tumor will exhibit oncogene addiction would be useful in the development of targeted therapeutics. Oncogene addiction is likely the consequence of many cellular programs. However, we reasoned that many of these inputs may converge on aggregate survival and death signals. To test this, we examined conditional transgenic models of K-ras(G12D)--or MYC-induced lung tumors and lymphoma combined with quantitative imaging and an in situ analysis of biomarkers of proliferation and apoptotic signaling. We then used computational modeling based on ordinary differential equations (ODEs) to show that oncogene addiction could be modeled as differential changes in survival and death intracellular signals. Our mathematical model could be generalized to different imaging methods (computed tomography and bioluminescence imaging), different oncogenes (K-ras(G12D) and MYC), and several tumor types (lung and lymphoma). Our ODE model could predict the differential dynamics of several putative prosurvival and prodeath signaling factors [phosphorylated extracellular signal-regulated kinase 1 and 2, Akt1, Stat3/5 (signal transducer and activator of transcription 3/5), and p38] that contribute to the aggregate survival and death signals after oncogene inactivation. Furthermore, we could predict the influence of specific genetic lesions (p53⁻/⁻, Stat3-d358L, and myr-Akt1) on tumor regression after oncogene inactivation. Then, using machine learning based on support vector machine, we applied quantitative imaging methods to human patients to predict both their EGFR genotype and their progression-free survival after treatment with the targeted therapeutic erlotinib. Hence, the consequences of oncogene inactivation can be accurately modeled on the basis of a relatively small number of parameters that may predict when targeted therapeutics will elicit oncogene addiction after oncogene inactivation and hence tumor regression.
View details for DOI 10.1126/scitranslmed.3002018
View details for PubMedID 21974937
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Functional Interactions between Retinoblastoma and c-MYC in a Mouse Model of Hepatocellular Carcinoma
PLOS ONE
2011; 6 (5)
Abstract
Inactivation of the RB tumor suppressor and activation of the MYC family of oncogenes are frequent events in a large spectrum of human cancers. Loss of RB function and MYC activation are thought to control both overlapping and distinct cellular processes during cell cycle progression. However, how these two major cancer genes functionally interact during tumorigenesis is still unclear. Here, we sought to test whether loss of RB function would affect cancer development in a mouse model of c-MYC-induced hepatocellular carcinoma (HCC), a deadly cancer type in which RB is frequently inactivated and c-MYC often activated. We found that RB inactivation has minimal effects on the cell cycle, cell death, and differentiation features of liver tumors driven by increased levels of c-MYC. However, combined loss of RB and activation of c-MYC led to an increase in polyploidy in mature hepatocytes before the development of tumors. There was a trend for decreased survival in double mutant animals compared to mice developing c-MYC-induced tumors. Thus, loss of RB function does not provide a proliferative advantage to c-MYC-expressing HCC cells but the RB and c-MYC pathways may cooperate to control the polyploidy of mature hepatocytes.
View details for DOI 10.1371/journal.pone.0019758
View details for PubMedID 21573126
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Reactive Oxygen Species Regulate Nucleostemin Oligomerization and Protein Degradation
JOURNAL OF BIOLOGICAL CHEMISTRY
2011; 286 (13): 11035-11046
Abstract
Nucleostemin (NS) is a nucleolar-nucleoplasmic shuttle protein that regulates cell proliferation, binds p53 and Mdm2, and is highly expressed in tumor cells. We have identified NS as a target of oxidative regulation in transformed hematopoietic cells. NS oligomerization occurs in HL-60 leukemic cells and Raji B lymphoblasts that express high levels of c-Myc and have high intrinsic levels of reactive oxygen species (ROS); reducing agents dissociate NS into monomers and dimers. Exposure of U2OS osteosarcoma cells with low levels of intrinsic ROS to hydrogen peroxide (H(2)O(2)) induces thiol-reversible disulfide bond-mediated oligomerization of NS. Increased exposure to H(2)O(2) impairs NS degradation, immobilizes the protein within the nucleolus, and results in detergent-insoluble NS. The regulation of NS by ROS was validated in a murine lymphoma tumor model in which c-Myc is overexpressed and in CD34+ cells from patients with chronic myelogenous leukemia in blast crisis. In both instances, increased ROS levels were associated with markedly increased expression of NS protein and thiol-reversible oligomerization. Site-directed mutagenesis of critical cysteine-containing regions of nucleostemin altered both its intracellular localization and its stability. MG132, a potent proteasome inhibitor and activator of ROS, markedly decreased degradation and increased nucleolar retention of NS mutants, whereas N-acetyl-L-cysteine largely prevented the effects of MG132. These results indicate that NS is a highly redox-sensitive protein. Increased intracellular ROS levels, such as those that result from oncogenic transformation in hematopoietic malignancies, regulate the ability of NS to oligomerize, prevent its degradation, and may alter its ability to regulate cell proliferation.
View details for DOI 10.1074/jbc.M110.208470
View details for PubMedID 21242306
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MYC Phosphorylation, Activation, and Tumorigenic Potential in Hepatocellular Carcinoma Are Regulated by HMG-CoA Reductase
CANCER RESEARCH
2011; 71 (6): 2286-2297
Abstract
MYC is a potential target for many cancers but is not amenable to existing pharmacologic approaches. Inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) by statins has shown potential efficacy against a number of cancers. Here, we show that inhibition of HMG-CoA reductase by atorvastatin (AT) blocks both MYC phosphorylation and activation, suppressing tumor initiation and growth in vivo in a transgenic model of MYC-induced hepatocellular carcinoma (HCC) as well as in human HCC-derived cell lines. To confirm specificity, we show that the antitumor effects of AT are blocked by cotreatment with the HMG-CoA reductase product mevalonate. Moreover, by using a novel molecular imaging sensor, we confirm that inhibition of HMG-CoA reductase blocks MYC phosphorylation in vivo. Importantly, the introduction of phosphorylation mutants of MYC at Ser62 or Thr58 into tumors blocks their sensitivity to inhibition of HMG-CoA reductase. Finally, we show that inhibition of HMG-CoA reductase suppresses MYC phosphorylation through Rac GTPase. Therefore, HMG-CoA reductase is a critical regulator of MYC phosphorylation, activation, and tumorigenic properties. The inhibition of HMG-CoA reductase may be a useful target for the treatment of MYC-associated HCC as well as other tumors.
View details for DOI 10.1158/0008-5472.CAN-10-3367
View details for Web of Science ID 000288381300028
View details for PubMedID 21262914
View details for PubMedCentralID PMC3059327
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Definition of an Enhanced Immune Cell Therapy in Mice That Can Target Stem-Like Lymphoma Cells
CANCER RESEARCH
2010; 70 (23): 9837-9845
Abstract
Current treatments of high-grade lymphoma often have curative potential, but unfortunately many patients relapse and develop therapeutic resistance. Thus, there remains a need for novel therapeutics that can target the residual cancer cells whose phenotypes are distinct from the bulk tumor and that are capable of reforming tumors from very few cells. Oncolytic viruses offer an approach to destroy tumors by multiple mechanisms, but they cannot effectively reach residual disease or micrometastases, especially within the lymphatic system. To address these limitations, we have generated immune cells infected with oncolytic viruses as a therapeutic strategy that can combine effective cellular delivery with synergistic tumor killing. In this study, we tested this approach against minimal disease states of lymphomas characterized by the persistence of cancer cells that display stem cell-like properties and resistance to conventional therapies. We found that the immune cells were capable of trafficking to and targeting residual cancer cells. The combination biotherapy used prevented relapse by creating a long-term, disease-free state, with acquired immunity to the tumor functioning as an essential mediator of this effect. Immune components necessary for this acquired immunity were identified. We further demonstrated that the dual biotherapy could be applied before or after conventional therapy. Our approach offers a potentially powerful new way to clear residual cancer cells, showing how restoring immune surveillance is critical for maintenance of a disease-free state.
View details for DOI 10.1158/0008-5472.CAN-10-2650
View details for PubMedID 20935221
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TGFß-dependent gene expression shows that senescence correlates with abortive differentiation along several lineages in Myc-induced lymphomas.
Cell cycle
2010; 9 (23): 4622-4626
Abstract
Deregulated expression of Myc under the control of an immunoglobulin enhancer induces lymphoma formation in mice. The development of lymphomas is limited by TGFβ-dependent senescence and high levels of Myc expression are continuously required to antagonize senescence. The biological processes underlying senescence are not fully resolved. We report here a comprehensive analysis of TGFβ-dependent alterations in gene expression when the Myc transgene is switched off. Our data show that Myc-induced target genes are downregulated in a TGFβ-independent manner. In contrast, TGFβ is required to upregulate a broad spectrum of genes that are characteristic of different T-cell lineages when Myc is turned off. The analysis reveals a significant overlap between these Myc-repressed genes with genes that are targets of polycomb repressive complexes in embryonic stem cells. Therefore, TGFβ-dependent senescence is associated with gene expression patterns indicative of abortive cellular differentiation along several lineages.
View details for PubMedID 21127397
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TGFbeta-dependent gene expression shows that senescence correlates with abortive differentiation along several lineages in Myc-induced lymphomas
CELL CYCLE
2010; 9 (23): 4622-4626
View details for DOI 10.4161/cc.9.23.14211
View details for Web of Science ID 000284833200012
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ABT-737 Targets Leukemic Stem Cells In Mouse Models of Mutant NRASD12/hBCL-2-Mediated Acute Myeloid Leukemia progression with Increased Survival
52nd Annual Meeting and Exposition of the American-Society-of-Hematology (ASH)
AMER SOC HEMATOLOGY. 2010: 1355–56
View details for Web of Science ID 000289662203639
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Treatment of Higher Risk Myelodysplastic Syndrome Patients Unresponsive to Hypomethylating Agents with ON 01910.Na
52nd Annual Meeting and Exposition of the American-Society-of-Hematology (ASH)
AMER SOC HEMATOLOGY. 2010: 1635–35
View details for Web of Science ID 000289662204430
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CD4(+) T Cells Contribute to the Remodeling of the Microenvironment Required for Sustained Tumor Regression upon Oncogene Inactivation
CANCER CELL
2010; 18 (5): 485-498
Abstract
Oncogene addiction is thought to occur cell autonomously. Immune effectors are implicated in the initiation and restraint of tumorigenesis, but their role in oncogene inactivation-mediated tumor regression is unclear. Here, we show that an intact immune system, specifically CD4(+) T cells, is required for the induction of cellular senescence, shutdown of angiogenesis, and chemokine expression resulting in sustained tumor regression upon inactivation of the MYC or BCR-ABL oncogenes in mouse models of T cell acute lymphoblastic lymphoma and pro-B cell leukemia, respectively. Moreover, immune effectors knocked out for thrombospondins failed to induce sustained tumor regression. Hence, CD4(+) T cells are required for the remodeling of the tumor microenvironment through the expression of chemokines, such as thrombospondins, in order to elicit oncogene addiction.
View details for DOI 10.1016/j.ccr.2010.10.002
View details for PubMedID 21035406
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PET Imaging of Tumor Neovascularization in a Transgenic Mouse Model with a Novel Cu-64-DOTA-Knottin Peptide
CANCER RESEARCH
2010; 70 (22): 9022-9030
Abstract
Due to the high mortality of lung cancer, there is a critical need to develop diagnostic procedures enabling early detection of the disease while at a curable stage. Targeted molecular imaging builds on the positive attributes of positron emission tomography/computed tomography (PET/CT) to allow for a noninvasive detection and characterization of smaller lung nodules, thus increasing the chances of positive treatment outcome. In this study, we investigate the ability to characterize lung tumors that spontaneously arise in a transgenic mouse model. The tumors are first identified with small animal CT followed by characterization with the use of small animal PET with a novel 64Cu-1,4,7,10-tetra-azacylododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-knottin peptide that targets integrins upregulated during angiogenesis on the tumor associated neovasculature. The imaging results obtained with the knottin peptide are compared with standard 18F-fluorodeoxyglucose (FDG) PET small animal imaging. Lung nodules as small as 3 mm in diameter were successfully identified in the transgenic mice by small animal CT, and both 64Cu-DOTA-knottin 2.5F and FDG were able to differentiate lung nodules from the surrounding tissues. Uptake and retention of the 64Cu-DOTA-knottin 2.5F tracer in the lung tumors combined with a low background in the thorax resulted in a statistically higher tumor to background (normal lung) ratio compared with FDG (6.01±0.61 versus 4.36±0.68; P<0.05). Ex vivo biodistribution showed 64Cu-DOTA-knottin 2.5F to have a fast renal clearance combined with low nonspecific accumulation in the thorax. Collectively, these results show 64Cu-DOTA-knottin 2.5F to be a promising candidate for clinical translation for earlier detection and improved characterization of lung cancer.
View details for DOI 10.1158/0008-5472.CAN-10-1338
View details for Web of Science ID 000284213300008
View details for PubMedID 21062977
View details for PubMedCentralID PMC3057960
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Hypoxia in Models of Lung Cancer: Implications for Targeted Therapeutics
CLINICAL CANCER RESEARCH
2010; 16 (19): 4843-4852
Abstract
To efficiently translate experimental methods from bench to bedside, it is imperative that laboratory models of cancer mimic human disease as closely as possible. In this study, we sought to compare patterns of hypoxia in several standard and emerging mouse models of lung cancer to establish the appropriateness of each for evaluating the role of oxygen in lung cancer progression and therapeutic response.Subcutaneous and orthotopic human A549 lung carcinomas growing in nude mice as well as spontaneous K-ras or Myc-induced lung tumors grown in situ or subcutaneously were studied using fluorodeoxyglucose and fluoroazomycin arabinoside positron emission tomography, and postmortem by immunohistochemical observation of the hypoxia marker pimonidazole. The response of these models to the hypoxia-activated cytotoxin PR-104 was also quantified by the formation of γH2AX foci in vitro and in vivo. Finally, our findings were compared with oxygen electrode measurements of human lung cancers.Minimal fluoroazomycin arabinoside and pimonidazole accumulation was seen in tumors growing within the lungs, whereas subcutaneous tumors showed substantial trapping of both hypoxia probes. These observations correlated with the response of these tumors to PR-104, and with the reduced incidence of hypoxia in human lung cancers relative to other solid tumor types.These findings suggest that in situ models of lung cancer in mice may be more reflective of the human disease, and encourage judicious selection of preclinical tumor models for the study of hypoxia imaging and antihypoxic cell therapies.
View details for DOI 10.1158/1078-0432.CCR-10-1206
View details for Web of Science ID 000282647900017
View details for PubMedID 20858837
View details for PubMedCentralID PMC2948600
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Noninvasive molecular imaging of c-Myc activation in living mice
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2010; 107 (36): 15892-15897
Abstract
The cytoplasmic Myc protein (c-Myc) regulates various human genes and is dysregulated in many human cancers. Phosphorylation mediates the protein activation of c-Myc and is essential for the function of this transcription factor in normal cell behavior and tumor growth. To date, however, the targeting of Myc as a therapeutic approach for cancer treatment has been achieved primarily at the nonprotein level. We have developed a molecular imaging sensor for noninvasive imaging of c-Myc activity in living subjects using a split Firefly luciferase (FL) complementation strategy to detect and quantify the phosphorylation-mediated interaction between glycogen synthase kinase 3beta (GSK3beta) and c-Myc. This sensor system consists of two fusion proteins, GSK 35-433-CFL and NFL-c-Myc, in which specific fragments of GSK3beta and c-Myc are fused with C-terminal and N-terminal fragments of the split FL, respectively. The sensor detects phosphorylation-specific GSK3beta-c-Myc interaction, the imaging signal of which correlates with the steady-state and temporal regulation of c-Myc phosphorylation in cell culture. The sensor also detects inhibition of c-Myc activity via differential pathways, allowing noninvasive monitoring of c-Myc-targeted drug efficacy in intact cells and living mice. Notably, this drug inhibition is detected before changes in tumor size are apparent in mouse xenograft and liver tumor models. This reporter system not only provides an innovative way to investigate the role of functional c-Myc in normal and cancer-related biological processes, but also facilitates c-Myc-targeted drug development by providing a rapid quantitative approach to assessing cancer response to therapy in living subjects.
View details for DOI 10.1073/pnas.1007443107
View details for PubMedID 20713710
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DEVELOPMENT OF A MICRO-COMPUTED TOMOGRAPHY-BASED IMAGE-GUIDED CONFORMAL RADIOTHERAPY SYSTEM FOR SMALL ANIMALS
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2010; 78 (1): 297-305
Abstract
To report on the physical aspects of a system in which radiotherapy functionality was added to a micro-computed tomography (microCT) scanner, to evaluate the accuracy of this instrument, and to and demonstrate the application of this technology for irradiating tumors growing within the lungs of mice.A GE eXplore RS120 microCT scanner was modified by the addition of a two-dimensional subject translation stage and a variable aperture collimator. Quality assurance protocols for these devices, including measurement of translation stage positioning accuracy, collimator aperture accuracy, and collimator alignment with the X-ray beam, were devised. Use of this system for image-guided radiotherapy was assessed by irradiation of a solid water phantom as well as of two mice bearing spontaneous MYC-induced lung tumors. Radiation damage was assessed ex vivo by immunohistochemical detection of gammaH2AX foci.The positioning error of the translation stage was found to be <0.05 mm, whereas after alignment of the collimator with the X-ray axis through adjustment of its displacement and rotation, the collimator aperture error was <0.1 mm measured at isocenter. Computed tomography image-guided treatment of a solid water phantom demonstrated target localization accuracy to within 0.1 mm. Gamma-H2AX foci were detected within irradiated lung tumors in mice, with contralateral lung tissue displaying background staining.Addition of radiotherapy functionality to a microCT scanner is an effective means of introducing image-guided radiation treatments into the preclinical setting. This approach has been shown to facilitate small-animal conformal radiotherapy while leveraging existing technology.
View details for DOI 10.1016/j.ijrobp.2009.11.008
View details for Web of Science ID 000281304600041
View details for PubMedID 20395069
View details for PubMedCentralID PMC2906632
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Impact of Hydrodynamic Injection and phiC31 Integrase on Tumor Latency in a Mouse Model of MYC-Induced Hepatocellular Carcinoma
PLOS ONE
2010; 5 (6)
Abstract
Hydrodynamic injection is an effective method for DNA delivery in mouse liver and is being translated to larger animals for possible clinical use. Similarly, phiC31 integrase has proven effective in mediating long-term gene therapy in mice when delivered by hydrodynamic injection and is being considered for clinical gene therapy applications. However, chromosomal aberrations have been associated with phiC31 integrase expression in tissue culture, leading to questions about safety.To study whether hydrodynamic delivery alone, or in conjunction with delivery of phiC31 integrase for long-term transgene expression, could facilitate tumor formation, we used a transgenic mouse model in which sustained induction of the human C-MYC oncogene in the liver was followed by hydrodynamic injection. Without injection, mice had a median tumor latency of 154 days. With hydrodynamic injection of saline alone, the median tumor latency was significantly reduced, to 105 days. The median tumor latency was similar, 106 days, when a luciferase donor plasmid and backbone plasmid without integrase were administered. In contrast, when active or inactive phiC31 integrase and donor plasmid were supplied to the mouse liver, the median tumor latency was 153 days, similar to mice receiving no injection.Our data suggest that phiC31 integrase does not facilitate tumor formation in this C-MYC transgenic mouse model. However, in groups lacking phiC31 integrase, hydrodynamic injection appeared to contribute to C-MYC-induced hepatocellular carcinoma in adult mice. Although it remains to be seen to what extent these findings may be extrapolated to catheter-mediated hydrodynamic delivery in larger species, they suggest that caution should be used during translation of hydrodynamic injection to clinical applications.
View details for DOI 10.1371/journal.pone.0011367
View details for Web of Science ID 000279369900016
View details for PubMedID 20614008
View details for PubMedCentralID PMC2894073
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The interaction between Myc and Miz1 is required to antagonize TGFbeta-dependent autocrine signaling during lymphoma formation and maintenance.
Genes & development
2010; 24 (12): 1281-1294
Abstract
The Myc protein suppresses the transcription of several cyclin-dependent kinase inhibitors (CKIs) via binding to Miz1; whether this interaction is important for Myc's ability to induce or maintain tumorigenesis is not known. Here we show that the oncogenic potential of a point mutant of Myc (MycV394D) that is selectively deficient in binding to Miz1 is greatly attenuated. Binding of Myc to Miz1 is continuously required to repress CKI expression and inhibit accumulation of trimethylated histone H3 at Lys 9 (H3K9triMe), a hallmark of cellular senescence, in T-cell lymphomas. Lymphomas that arise express high amounts of transforming growth factor beta-2 (TGFbeta-2) and TGFbeta-3. Upon Myc suppression, TGFbeta signaling is required to induce CKI expression and cellular senescence and suppress tumor recurrence. Binding of Myc to Miz1 is required to antagonize growth suppression and induction of senescence by TGFbeta. We demonstrate that, since lymphomas express high levels of TGFbeta, they are poised to elicit an autocrine program of senescence upon Myc inactivation, demonstrating that TGFbeta is a key factor that establishes oncogene addiction of T-cell lymphomas.
View details for DOI 10.1101/gad.585710
View details for PubMedID 20551174
View details for PubMedCentralID PMC2885663
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The interaction between Myc and Miz1 is required to antagonize TGF beta-dependent autocrine signaling during lymphoma formation and maintenance
GENES & DEVELOPMENT
2010; 24 (12): 1281-1294
View details for DOI 10.1101/gad.585710
View details for Web of Science ID 000278778200008
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MYC Inactivation Elicits Oncogene Addiction through Both Tumor Cell-Intrinsic and Host-Dependent Mechanisms.
Genes & cancer
2010; 1 (6): 597-604
Abstract
Tumorigenesis is generally caused by genetic changes that activate oncogenes or inactivate tumor suppressor genes. The targeted inactivation of oncogenes can be associated with tumor regression through the phenomenon of oncogene addiction. One of the most common oncogenic events in human cancer is the activation of the MYC oncogene. The inactivation of MYC may be a general and effective therapy for human cancer. Indeed, it has been experimentally shown that the inactivation of MYC can result in dramatic and sustained tumor regression in lymphoma, leukemia, osteosarcoma, hepatocellular carcinoma, squamous carcinoma, and pancreatic carcinoma through a multitude of mechanisms, including proliferative arrest, terminal differentiation, cellular senescence, induction of apoptosis, and the shutdown of angiogenesis. Cell-autonomous and cell-dependent mechanisms have both been implicated, and recent results suggest a critical role for autocrine factors, including thrombospondin-1 and TGF-β. Hence, targeting the inactivation of MYC appears to elicit oncogene addiction and, thereby, tumor regression through both tumor cell-intrinsic and host-dependent mechanisms.
View details for DOI 10.1177/1947601910377798
View details for PubMedID 21037952
View details for PubMedCentralID PMC2965623
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Conditional TPM3-ALK and NPM-ALK transgenic mice develop reversible ALK-positive early B-cell lymphoma/leukemia
BLOOD
2010; 115 (20): 4061-4070
Abstract
NPM-ALK (nucleophosmin-anaplastic lymphoma kinase) and TPM3-ALK (nonmuscular tropomyosin 3-anaplastic lymphoma kinase) are oncogenic tyrosine kinases implicated in the pathogenesis of human ALK-positive lymphoma. We report here the development of novel conditional mouse models for ALK-induced lymphomagenesis, with the use of the tetracycline regulatory system under the control of the EmuSRalpha enhancer/promoter. The expression of either oncogene resulted in the arrest of the differentiation of early B cells and lymphomagenesis. We also observed the development of skin keratoacanthoma lesions, probably because of aberrant ALK expression in keratinocytes. The inactivation of the ALK oncogene on doxycycline treatment was sufficient to induce sustained regression of both hematopoietic tumors and skin disease. Importantly, treatment with the specific ALK inhibitor (PF-2341066) also reversed the pathologic states, showing the value of these mouse models for the validation of ALK tyrosine kinase inhibitors. Thus, our results show (1) that NPM-ALK and TPM3-ALK oncogenes are sufficient for lymphoma/leukemia development and required for tumor maintenance, hence validating ALK as potentially effective therapeutic target; and (2) for the first time, in vivo, the equal tumorigenic potential of the NPM-ALK and TPM3-ALK oncogenic tyrosine kinases. Our models offer a new tool to investigate in vivo the molecular mechanisms associated with ALK-induced lymphoproliferative disorders.
View details for DOI 10.1182/blood-2008-06-163386
View details for Web of Science ID 000277923600011
View details for PubMedID 20223922
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MYC as a regulator of ribosome biogenesis and protein synthesis
NATURE REVIEWS CANCER
2010; 10 (4): 301-309
Abstract
MYC regulates the transcription of thousands of genes required to coordinate a range of cellular processes, including those essential for proliferation, growth, differentiation, apoptosis and self-renewal. Recently, MYC has also been shown to serve as a direct regulator of ribosome biogenesis. MYC coordinates protein synthesis through the transcriptional control of RNA and protein components of ribosomes, and of gene products required for the processing of ribosomal RNA, the nuclear export of ribosomal subunits and the initiation of mRNA translation. We discuss how the modulation of ribosome biogenesis by MYC may be essential to its physiological functions as well as its pathological role in tumorigenesis.
View details for DOI 10.1038/nrc2819
View details for Web of Science ID 000275932700013
View details for PubMedID 20332779
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Myc and a Cdk2 senescence switch
NATURE CELL BIOLOGY
2010; 12 (1): 7-9
Abstract
Cdk2 has been shown to have an unanticipated role in suppressing Myc-induced senescence. This has implications for how c-Myc overcomes failsafe mechanisms to induce tumorigenesis and suggests that the inhibition of Cdk2 may have therapeutic efficacy in the treatment of cancer.
View details for DOI 10.1038/ncb0110-7
View details for Web of Science ID 000272973800006
View details for PubMedID 20027199
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Low-level shRNA Cytotoxicity Can Contribute to MYC-induced Hepatocellular Carcinoma in Adult Mice
MOLECULAR THERAPY
2010; 18 (1): 161-170
Abstract
Short hairpin RNAs (shRNAs) have emerged as a novel therapeutic modality, but there is increasing concern over nonspecific effects in vivo. Here, we used viral vectors to express shRNAs against endogenous p53 in livers of conditional MYC-transgenic mice. As expected, the shRNAs silenced hepatic p53 and accelerated liver tumorigenesis when MYC was concurrently expressed. Surprisingly, various irrelevant control shRNAs similarly induced a rapid onset of tumorigenesis, comparable to carbon tetrachloride (CCl4), a potent carcinogen. We found that even marginal shRNA doses can already trigger histologically detectable hepatoxicity and increased hepatocyte apoptosis. Moreover, we noted that shRNA expression globally dysregulated hepatic microRNA (miRNA) expression, and that shRNA levels and activity further increased in the presence of MYC. In MYC-expressing transgenic mice, the marginal shRNA-induced liver injury sufficed to further stimulate hepatocellular division that was in turn associated with markedly increased expression of the mitotic cyclin B1. Hence, even at low doses, shRNAs can cause low-level hepatoxicity that can facilitate the ability of the MYC oncogene to induce liver tumorigenesis. Our data warrant caution regarding the possible carcinogenic potential of shRNAs when used as clinical agent, particularly in circumstances where tissues are genetically predisposed to cellular transformation and proliferation.
View details for DOI 10.1038/mt.2009.222
View details for Web of Science ID 000274447200023
View details for PubMedID 19844192
View details for PubMedCentralID PMC2839214
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Cell Cycle Re-Entry and Mitochondrial Defects in Myc-Mediated Hypertrophic Cardiomyopathy and Heart Failure
PLOS ONE
2009; 4 (9)
Abstract
While considerable evidence supports the causal relationship between increases in c-Myc (Myc) and cardiomyopathy as a part of a "fetal re-expression" pattern, the functional role of Myc in mechanisms of cardiomyopathy remains unclear. To address this, we developed a bitransgenic mouse that inducibly expresses Myc under the control of the cardiomyocyte-specific MHC promoter. In adult mice the induction of Myc expression in cardiomyocytes in the heart led to the development of severe hypertrophic cardiomyopathy followed by ventricular dysfunction and ultimately death from congestive heart failure. Mechanistically, following Myc activation, cell cycle markers and other indices of DNA replication were significantly increased suggesting that cell cycle-related events might be a primary mechanism of cardiac dysfunction. Furthermore, pathological alterations at the cellular level included alterations in mitochondrial function with dysregulation of mitochondrial biogenesis and defects in electron transport chain complexes I and III. These data are consistent with the known role of Myc in several different pathways including cell cycle activation, mitochondrial proliferation, and apoptosis, and indicate that Myc activation in cardiomyocytes is an important regulator of downstream pathological sequelae. Moreover, our findings indicate that the induction of Myc in cardiomyocytes is sufficient to cause cardiomyopathy and heart failure, and that sustained induction of Myc, leading to cell cycle re-entry in adult cardiomyocytes, represents a maladaptive response for the mature heart.
View details for DOI 10.1371/journal.pone.0007172
View details for Web of Science ID 000270176200013
View details for PubMedID 19779629
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Nanofluidic proteomic assay for serial analysis of oncoprotein activation in clinical specimens
NATURE MEDICINE
2009; 15 (5): 566-571
Abstract
Current methods of protein detection are insensitive to detecting subtle changes in oncoprotein activation that underlie key cancer signaling processes. The requirement for large numbers of cells precludes serial tumor sampling for assessing a response to therapeutics. Therefore, we have developed a nanofluidic proteomic immunoassay (NIA) to quantify total and low-abundance protein isoforms in nanoliter volumes. Our method can quantify amounts of MYC oncoprotein and B cell lymphoma protein-2 (BCL2) in Burkitt's and follicular lymphoma; identify changes in activation of extracellular signal-related kinases-1 (ERK1) and ERK2, mitogen-activated kinase-1 (MEK), signal transducer and activator of transcription protein-3 (STAT3) and STAT5, c-Jun N-terminal kinase (JNK) and caspase-3 in imatinib-treated chronic myelogeneous leukemia (CML) cells; measure an unanticipated change in the phosphorylation of an ERK2 isomer in individuals with CML who responded to imatinib; and detect a decrease in STAT3 and STAT5 phosphorylation in individuals with lymphoma who were treated with atorvastatin. Therefore, we have described a new and highly sensitive method for determining oncoprotein expression and phosphorylation in clinical specimens for the development of new therapeutics for cancer.
View details for DOI 10.1038/nm.1903
View details for PubMedID 19363496
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SPECT and PET Imaging of EGF Receptors with Site-Specifically Labeled EGF and Dimeric EGF
BIOCONJUGATE CHEMISTRY
2009; 20 (4): 742-749
Abstract
We describe a new generation of tracers for molecular imaging of the cell surface receptors for epidermal growth factor (EGF). These receptors play a key role in the progression of many tumors and are major drug development targets. Our tracers are based on a recombinant human EGF expressed with a cysteine-containing tag that enables facile site-specific radiolabeling with (99m)Tc for single photon emission computed tomography or site-specific conjugation of (64)Cu PEGylated chelators for positron emission tomography. These tracers retain EGF activities in vitro and display selective and highly specific focal uptake in tumors in vivo. We expect that nuclear imaging of EGF receptors with these tracers will be useful for clinical diagnosis, therapeutic monitoring, and development of new drugs and treatment regimens.
View details for DOI 10.1021/bc800443w
View details for PubMedID 19320434
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Apoptosis-stimulating protein of p53 (ASPP2) heterozygous mice are tumor-prone and have attenuated cellular damage-response thresholds
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2009; 106 (11): 4390-4395
Abstract
The expression of ASPP2 (53BP2L), a proapoptotic member of a family of p53-binding proteins, is frequently suppressed in many human cancers. Accumulating evidence suggests that ASPP2 inhibits tumor growth; however, the mechanisms by which ASPP2 suppresses tumor formation remain to be clarified. To study this, we targeted the ASPP2 allele in a mouse by replacing exons 10-17 with a neoR gene. ASPP2(-/-) mice were not viable because of an early embryonic lethal event. Although ASPP2(+/-) mice appeared developmentally normal, they displayed an increased incidence of a variety of spontaneous tumors as they aged. Moreover, gamma-irradiated 6-week-old ASPP2(+/-) mice developed an increased incidence of high-grade T cell lymphomas of thymic origin compared with ASPP2(+/+) mice. Primary thymocytes derived from ASPP2(+/-) mice exhibited an attenuated apoptotic response to gamma-irradiation compared with ASPP2(+/+) thymocytes. Additionally, ASPP2(+/-) primary mouse embryonic fibroblasts demonstrated a defective G(0)/G(1) cell cycle checkpoint after gamma-irradiation. Our results demonstrate that ASPP2 is a haploinsufficient tumor suppressor and, importantly, open new avenues for investigation into the mechanisms by which disruption of ASPP2 pathways could play a role in tumorigenesis and response to therapy.
View details for DOI 10.1073/pnas.0809080106
View details for PubMedID 19251665
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The Neuronal Expression of MYC Causes a Neurodegenerative Phenotype in a Novel Transgenic Mouse
AMERICAN JOURNAL OF PATHOLOGY
2009; 174 (3): 891-897
Abstract
Many different proteins associated with the cell cycle, including cyclins, cyclin-dependent kinases, and proto-oncogenes such as c-MYC (MYC), are increased in degenerating neurons. Consequently, an ectopic activation of the cell cycle machinery in neurons has emerged as a potential pathogenic mechanism of neuronal dysfunction and death in many neurodegenerative diseases, including Alzheimer's disease. However, the exact role of cell cycle re-entry during disease pathogenesis is unclear, primarily because of the lack of relevant research models to study the effects of cell cycle re-entry on mature neurons in vivo. To address this issue, we developed a new transgenic mouse model in which forebrain neurons (CaMKII-MYC) can be induced to enter the cell cycle using the physiologically relevant proto-oncogene MYC to drive cell cycle re-entry. We show that such cell cycle re-entry results in neuronal cell death, gliosis, and cognitive deficits. These findings provide compelling evidence that dysregulation of cell cycle re-entry results in neurodegeneration in vivo. Our current findings, coupled with those of previous reports, strengthen the hypothesis that neurodegeneration in Alzheimer's disease, similar to cellular proliferation in cancer, is a disease that results from inappropriate cell cycle control.
View details for DOI 10.2353/ajpath.2009.080583
View details for Web of Science ID 000263612600017
View details for PubMedID 19164506
View details for PubMedCentralID PMC2665749
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Autochthonous Liver Tumors Induce Systemic T Cell Tolerance Associated with T Cell Receptor Down-Modulation
HEPATOLOGY
2009; 49 (2): 471-481
Abstract
The reason the adaptive immune system fails in advanced liver tumors is largely unclear. To address this question, we have developed a novel murine model that combines c-myc-induced autochthonous tumorigenesis with expression of a cognate antigen, ovalbumin (OVA). When c-myc/OVA transgenic mice were crossed with liver-specific inducer mice, multifocal hepatocellular carcinomas co-expressing OVA developed in a tetracycline-dependent manner with a short latency and 100% penetrance. Transferred OVA-specific T cells, although infiltrating the tumor at high numbers, were hyporesponsive, as evidenced by a lack of in vivo cytotoxicity and interferon gamma production. This allowed the tumor to progress even in the presence of large numbers of antigen-specific T cells and even after vaccination (OVA+CpG-DNA). Interestingly, T cell receptor down-modulation was observed, which may explain antigen-specific hyporesponsiveness. This model is helpful in understanding liver cancer-specific mechanisms of T cell tolerance and dissection of antigen-specific and nonspecific mechanisms of immunotherapies in the preclinical phase.
View details for DOI 10.1002/hep.22652
View details for Web of Science ID 000262923300019
View details for PubMedID 19105207
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Supramolecular Stacking of Doxorubicin on Carbon Nanotubes for In Vivo Cancer Therapy
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2009; 48 (41): 7668-7672
View details for DOI 10.1002/anie.200902612
View details for PubMedID 19760685
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The current STATe of biomarkers to predict the response to anti-angiogenic therapies
CANCER BIOLOGY & THERAPY
2008; 7 (12): 2004-2006
View details for Web of Science ID 000262318700024
View details for PubMedID 19158482
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F-18 and (18)FDG PET imaging of osteosarcoma to non-invasively monitor in situ changes in cellular proliferation and bone differentiation upon MYC inactivation
CANCER BIOLOGY & THERAPY
2008; 7 (12): 1947-1951
Abstract
Osteosarcoma is one of the most common pediatric cancers. Accurate imaging of osteosarcoma is important for proper clinical staging of the disease and monitoring of the tumor's response to therapy. The MYC oncogene has been commonly implicated in the pathogenesis of human osteosarcoma. Previously, we have described a conditional transgenic mouse model of MYC-induced osteosarcoma. These tumors are highly invasive and are frequently associated with pulmonary metastases. In our model, upon MYC inactivation osteosarcomas lose their neoplastic properties, undergo proliferative arrest and differentiate into mature bone. We reasoned that we could use our model system to develop noninvasive imaging modalities to interrogate the consequences of MYC inactivation on tumor cell biology in situ. We performed positron emission tomography (PET) combining the use of both (18)F-fluorodeoxyglucose ((18)FDG) and (18)F-flouride ((18)F) to detect metabolic activity and bone mineralization/remodeling. We found that upon MYC inactivation, tumors exhibited a slight reduction in uptake of (18)FDG and a significant increase in the uptake of (18)F along with associated histological changes. Thus, these cells have apparently lost their neoplastic properties based upon both examination of their histology and biologic activity. However, these tumors continue to accumulate (18)FDG at levels significantly elevated compared to normal bone. Therefore, PET can be used to distinguish normal bone cells from tumors that have undergone differentiation upon oncogene inactivation. In addition, we found that (18)F is a highly sensitive tracer for detection of pulmonary metastasis. Collectively, we conclude that combined modality PET/CT imaging incorporating both (18)FDG and (18)F is a highly sensitive means to non-invasively measure osteosarcoma growth and the therapeutic response, as well as to detect tumor cells that have undergone differentiation upon oncogene inactivation.
View details for Web of Science ID 000262318700015
View details for PubMedID 18981708
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A quantitative PCR method to detect blood microRNAs associated with tumorigenesis in transgenic mice
MOLECULAR CANCER
2008; 7
Abstract
MicroRNA (miRNA) dysregulation frequently occurs in cancer. Analysis of whole blood miRNA in tumor models has not been widely reported, but could potentially lead to novel assays for early detection and monitoring of cancer. To determine whether miRNAs associated with malignancy could be detected in the peripheral blood, we used real-time reverse transcriptase-PCR to determine miRNA profiles in whole blood obtained from transgenic mice with c-MYC-induced lymphoma, hepatocellular carcinoma and osteosarcoma. The PCR-based assays used in our studies require only 10 nanograms of total RNA, allowing serial mini-profiles (20 - 30 miRNAs) to be carried out on individual animals over time. Blood miRNAs were measured from mice at different stages of MYC-induced lymphomagenesis and regression. Unsupervised hierarchical clustering of the data identified specific miRNA expression profiles that correlated with tumor type and stage. The miRNAs found to be altered in the blood of mice with tumors frequently reverted to normal levels upon tumor regression. Our results suggest that specific changes in blood miRNA can be detected during tumorigenesis and tumor regression.
View details for DOI 10.1186/1476-4598-7-74
View details for PubMedID 18826639
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An efficient and versatile system for acute and chronic modulation of renal tubular function in transgenic mice
NATURE MEDICINE
2008; 14 (9): 979-984
Abstract
We describe a transgenic mouse line, Pax8-rtTA, which, under control of the mouse Pax8 promoter, directs high levels of expression of the reverse tetracycline-dependent transactivator (rtTA) to all proximal and distal tubules and the entire collecting duct system of both embryonic and adult kidneys. Using crosses of Pax8-rtTA mice with tetracycline-responsive c-MYC mice, we established a new, inducible model of polycystic kidney disease that can mimic adult onset and that shows progression to renal malignant disease. When targeting the expression of transforming growth factor beta-1 to the kidney, we avoided early lethality by discontinuous treatment and successfully established an inducible model of renal fibrosis. Finally, a conditional knockout of the gene encoding tuberous sclerosis complex-1 was achieved, which resulted in the early outgrowth of giant polycystic kidneys reminiscent of autosomal recessive polycystic kidney disease. These experiments establish Pax8-rtTA mice as a powerful tool for modeling renal diseases in transgenic mice.
View details for DOI 10.1038/nm.1865
View details for Web of Science ID 000258988600032
View details for PubMedID 18724376
View details for PubMedCentralID PMC3446847
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Genomic and proteomic analysis reveals a threshold level of MYC required for tumor maintenance
CANCER RESEARCH
2008; 68 (13): 5132-5142
Abstract
MYC overexpression has been implicated in the pathogenesis of most types of human cancers. MYC is likely to contribute to tumorigenesis by its effects on global gene expression. Previously, we have shown that the loss of MYC overexpression is sufficient to reverse tumorigenesis. Here, we show that there is a precise threshold level of MYC expression required for maintaining the tumor phenotype, whereupon there is a switch from a gene expression program of proliferation to a state of proliferative arrest and apoptosis. Oligonucleotide microarray analysis and quantitative PCR were used to identify changes in expression in 3,921 genes, of which 2,348 were down-regulated and 1,573 were up-regulated. Critical changes in gene expression occurred at or near the MYC threshold, including genes implicated in the regulation of the G(1)-S and G(2)-M cell cycle checkpoints and death receptor/apoptosis signaling. Using two-dimensional protein analysis followed by mass spectrometry, phospho-flow fluorescence-activated cell sorting, and antibody arrays, we also identified changes at the protein level that contributed to MYC-dependent tumor regression. Proteins involved in mRNA translation decreased below threshold levels of MYC. Thus, at the MYC threshold, there is a loss of its ability to maintain tumorigenesis, with associated shifts in gene and protein expression that reestablish cell cycle checkpoints, halt protein translation, and promote apoptosis.
View details for DOI 10.1158/0008-5472.CAN-07-6192
View details for PubMedID 18593912
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Tumor dormancy and oncogene addiction
APMIS
2008; 116 (7-8): 629-637
Abstract
Cancer is caused by genetic changes that activate oncogenes or inactivate tumor suppressor genes. The repair or inactivation of mutant genes may be effective in the treatment of cancer. Indeed, drugs that target oncogenes can be effective in the treatment of cancer. However, it is still unclear why the inactivation of a single cancer-associated gene would ever result in the elimination of tumor cells. In experimental transgenic mouse models the consequences of oncogene inactivation depend upon the genetic and cellular context. In some cases, oncogene inactivation results in the elimination of all or almost all tumor cells through apoptosis by the phenomenon described as oncogene addiction. In other cases, oncogene inactivation predominantly results in the terminal differentiation or cellular senescence of tumor cells. In yet others, oncogene inactivation results in the apparent loss of the neoplastic properties of tumor cells, which now appear and behave like normal cells; however, upon oncogene reactivation at least some of these cells rapidly recover their neoplastic phenotype. Thus, oncogene inactivation can result in a state of tumor dormancy. Hence, understanding when and how oncogene inactivation induces apoptosis, differentiation, and senescence within a tumor will be important when developing effective strategies for the treatment of cancer.
View details for Web of Science ID 000259037600009
View details for PubMedID 18834407
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Hepatotoxin-Induced Changes in the Adult Murine Liver Promote MYC-Induced Tumorigenesis
PLOS ONE
2008; 3 (6)
Abstract
Overexpression of the human c-MYC (MYC) oncogene is one of the most frequently implicated events in the pathogenesis of hepatocellular carcinoma (HCC). Previously, we have shown in a conditional transgenic mouse model that MYC overexpression is restrained from inducing mitotic cellular division and tumorigenesis in the adult liver; whereas, in marked contrast, MYC induces robust proliferation associated with the very rapid onset of tumorigenesis in embryonic and neonatal mice.Here, we show that non-genotoxic hepatotoxins induce changes in the liver cellular context associated with increased cellular proliferation and enhanced tumorigenesis. Both 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) and carbon tetrachloride (CCl(4)) cooperate with MYC to greatly accelerate the onset of liver cancer in an adult host to less than 7 days versus a mean latency of onset of over 35 weeks for MYC alone. These hepatotoxin-enhanced liver tumors grossly and histologically resemble embryonic and neonatal liver tumors. Importantly, we found that MYC overexpression is only capable of inducing expression of the mitotic Cyclin B1 in embryonic/neonatal hosts or adult hosts that were treated with either carcinogen.Our results suggest a model whereby oncogenes can remain latently activated, but exposure of the adult liver to hepatotoxins that promote hepatocyte proliferation can rapidly uncover their malignant potential.
View details for DOI 10.1371/journal.pone.0002493
View details for Web of Science ID 000263280700056
View details for PubMedID 18560566
View details for PubMedCentralID PMC2423614
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Combined Analysis of Murine and Human Microarrays and ChIP Analysis Reveals Genes Associated with the Ability of MYC To Maintain Tumorigenesis
PLOS GENETICS
2008; 4 (6)
Abstract
The MYC oncogene has been implicated in the regulation of up to thousands of genes involved in many cellular programs including proliferation, growth, differentiation, self-renewal, and apoptosis. MYC is thought to induce cancer through an exaggerated effect on these physiologic programs. Which of these genes are responsible for the ability of MYC to initiate and/or maintain tumorigenesis is not clear. Previously, we have shown that upon brief MYC inactivation, some tumors undergo sustained regression. Here we demonstrate that upon MYC inactivation there are global permanent changes in gene expression detected by microarray analysis. By applying StepMiner analysis, we identified genes whose expression most strongly correlated with the ability of MYC to induce a neoplastic state. Notably, genes were identified that exhibited permanent changes in mRNA expression upon MYC inactivation. Importantly, permanent changes in gene expression could be shown by chromatin immunoprecipitation (ChIP) to be associated with permanent changes in the ability of MYC to bind to the promoter regions. Our list of candidate genes associated with tumor maintenance was further refined by comparing our analysis with other published results to generate a gene signature associated with MYC-induced tumorigenesis in mice. To validate the role of gene signatures associated with MYC in human tumorigenesis, we examined the expression of human homologs in 273 published human lymphoma microarray datasets in Affymetrix U133A format. One large functional group of these genes included the ribosomal structural proteins. In addition, we identified a group of genes involved in a diverse array of cellular functions including: BZW2, H2AFY, SFRS3, NAP1L1, NOLA2, UBE2D2, CCNG1, LIFR, FABP3, and EDG1. Hence, through our analysis of gene expression in murine tumor models and human lymphomas, we have identified a novel gene signature correlated with the ability of MYC to maintain tumorigenesis.
View details for DOI 10.1371/journal.pgen.1000090
View details for Web of Science ID 000260410300026
View details for PubMedID 18535662
View details for PubMedCentralID PMC2390767
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Combined Inactivation of MYC and K-Ras Oncogenes Reverses Tumorigenesis in Lung Adenocarcinomas and Lymphomas
PLOS ONE
2008; 3 (5)
Abstract
Conditional transgenic models have established that tumors require sustained oncogene activation for tumor maintenance, exhibiting the phenomenon known as "oncogene-addiction." However, most cancers are caused by multiple genetic events making it difficult to determine which oncogenes or combination of oncogenes will be the most effective targets for their treatment.To examine how the MYC and K-ras(G12D) oncogenes cooperate for the initiation and maintenance of tumorigenesis, we generated double conditional transgenic tumor models of lung adenocarcinoma and lymphoma. The ability of MYC and K-ras(G12D) to cooperate for tumorigenesis and the ability of the inactivation of these oncogenes to result in tumor regression depended upon the specific tissue context. MYC-, K-ras(G12D)- or MYC/K-ras(G12D)-induced lymphomas exhibited sustained regression upon the inactivation of either or both oncogenes. However, in marked contrast, MYC-induced lung tumors failed to regress completely upon oncogene inactivation; whereas K-ras(G12D)-induced lung tumors regressed completely. Importantly, the combined inactivation of both MYC and K-ras(G12D) resulted more frequently in complete lung tumor regression. To account for the different roles of MYC and K-ras(G12D) in maintenance of lung tumors, we found that the down-stream mediators of K-ras(G12D) signaling, Stat3 and Stat5, are dephosphorylated following conditional K-ras(G12D) but not MYC inactivation. In contrast, Stat3 becomes dephosphorylated in lymphoma cells upon inactivation of MYC and/or K-ras(G12D). Interestingly, MYC-induced lung tumors that failed to regress upon MYC inactivation were found to have persistent Stat3 and Stat5 phosphorylation.Taken together, our findings point to the importance of the K-Ras and associated down-stream Stat effector pathways in the initiation and maintenance of lymphomas and lung tumors. We suggest that combined targeting of oncogenic pathways is more likely to be effective in the treatment of lung cancers and lymphomas.
View details for DOI 10.1371/journal.pone.0002125
View details for PubMedID 18461184
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Oncogene addiction versus oncogene amnesia: Perhaps more than just a bad habit?
CANCER RESEARCH
2008; 68 (9): 3081-3086
Abstract
Cancer is a multistep process whereby genetic events that result in the activation of proto-oncogenes or the inactivation of tumor suppressor genes usurp physiologic programs mandating relentless proliferation and growth. Experimental evidence surprisingly illustrates that the inactivation of even a single oncogene can be sufficient to induce sustained tumor regression. These observations suggest the hypothesis that tumors become irrevocably addicted to the oncogenes that initiated tumorigenesis. The proposed explanation for this phenomenon is that activated oncogenes result in a signaling state in which the sudden abatement of oncogene activity balances towards proliferative arrest and apoptosis. Indeed, substantial evidence supports this hypothesis. Here, we propose an alternative, although not necessarily mutually exclusive, explanation for how oncogenes initiate and sustain tumorigenesis. We suggest that oncogene activation initiates tumorigenesis precisely because it directly overrides physiologic programs inducing a state of cellular amnesia, not only inducing relentless cellular proliferation, but also bypassing checkpoint mechanisms that are essential for cellular mortality, self-renewal, and genomic integrity. Because no single oncogenic lesion is sufficient to overcome all of these physiologic barriers, oncogenes are restrained from inducing tumorigenesis. Correspondingly, in a tumor that has acquired the complete complement of oncogenic lesions required to overcome all of these safety mechanisms, the inactivation of a single oncogene can restore some of these pathways resulting in proliferative arrest, differentiation, cellular senescence, and/or apoptosis. Thus, oncogenes induce cancer because they induce a cellular state of enforced oncogenic amnesia in which, only upon oncogene inactivation, the tumor becomes aware of its transgression.
View details for DOI 10.1158/0008-5472.CAN-07-5832
View details for Web of Science ID 000255602600003
View details for PubMedID 18451131
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Reversing cancer from inside and out: oncogene addiction, cellular senescence, and the angiogenic switch.
Lymphatic research and biology
2008; 6 (3-4): 149-154
Abstract
Cancer is largely caused by genetic events that result in the mutation of oncogenes or tumor suppressor genes, leading to cell autonomous proliferation and growth. The repair of these mutant gene products may be expected to subvert this neoplastic behavior. Indeed, oncogene inactivation can result in the elimination of all or almost all tumor cells by various mechanisms through the phenomena described as oncogene addiction. Recently, we have shown that oncogene addiction occurs through at least two broad classes of mechanisms: tumor cell intrinsic mechanisms of cellular senescence and apoptosis; and tumor cell extrinsic host-dependent mechanisms that include the shut-down of angiogenesis. We have argued that the abatement of oncogenic activity within a cancer cell not only leads to the demise of a tumor from within but also through the instruction of the restoration of the microenvironment.
View details for DOI 10.1089/lrb.2008.63403
View details for PubMedID 19093787
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MYC potentiates DNA damage response dependent cellular senescence
50th Annual Meeting of the American-Society-for-Therapeutic-Radiology-and-Oncology (ASTRO)
ELSEVIER SCIENCE INC. 2008: S693–S693
View details for Web of Science ID 000258805302452
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BCL-2 and mutant NRAS interact physically and functionally in a mouse model of progressive myelodysplasia
CANCER RESEARCH
2007; 67 (24): 11657-11667
Abstract
Myelodysplastic syndromes (MDS) are clonal stem cell hematologic disorders that evolve to acute myeloid leukemia (AML) and thus model multistep leukemogenesis. Activating RAS mutations and overexpression of BCL-2 are prognostic features of MDS/AML transformation. Using NRASD12 and BCL-2, we created two distinct models of MDS and AML, where human (h)BCL-2 is conditionally or constitutively expressed. Our novel transplantable in vivo models show that expression of hBCL-2 in a primitive compartment by mouse mammary tumor virus-long terminal repeat results in a disease resembling human MDS, whereas the myeloid MRP8 promoter induces a disease with characteristics of human AML. Expanded leukemic stem cell (Lin(-)/Sca-1(+)/c-Kit(+)) populations and hBCL-2 in the increased RAS-GTP complex within the expanded Sca-1(+) compartment are described in both MDS/AML-like diseases. Furthermore, the oncogenic compartmentalizations provide the proapoptotic versus antiapoptotic mechanisms, by activating extracellular signal-regulated kinase and AKT signaling, in determination of the neoplastic phenotype. When hBCL-2 is switched off with doxycycline in the MDS mice, partial reversal of the phenotype was observed with persistence of bone marrow blasts and tissue infiltration as RAS recruits endogenous mouse (m)BCL-2 to remain active, thus demonstrating the role of the complex in the disease. This represents the first in vivo progression model of MDS/AML dependent on the formation of a BCL-2:RAS-GTP complex. The colocalization of BCL-2 and RAS in the bone marrow of MDS/AML patients offers targeting either oncogene as a therapeutic strategy.
View details for DOI 10.1158/0008-5472.CAN-07-0196
View details for Web of Science ID 000251857900025
View details for PubMedID 18089795
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A novel nano-immunoassay system capable of absolute protein measurements from 400 tumor-derived stem cells.
AMER ASSOC CANCER RESEARCH. 2007: 3556S–3556S
View details for Web of Science ID 000251969000677
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Inhibition of HMGcoA reductase by atorvastatin prevents and reverses MYC-induced lymphomagenesis
BLOOD
2007; 110 (7): 2674-2684
Abstract
Statins are a class of drugs that inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMGcoA) reductase, a critical enzyme in the mevalonate pathway. Several reports document that statins may prevent different human cancers. However, whether or not statins can prevent cancer is controversial due to discordant results. One possible explanation for these conflicting conclusions is that only some tumors or specific statins may be effective. Here, we demonstrate in an in vivo transgenic model in which atorvastatin reverses and prevents the onset of MYC-induced lymphomagenesis, but fails to reverse or prevent tumorigenesis in the presence of constitutively activated K-Ras (G12D). Using phosphoprotein fluorescence-activated cell sorter (FACS) analysis, atorvastatin treatment was found to result in the inactivation of the Ras and ERK1/2 signaling pathways associated with the dephosphorylation and inactivation of MYC. Correspondingly, tumors with a constitutively activated K-Ras (G12D) did not exhibit dephosphorylation of ERK1/2 and MYC. Atorvastatin's effects on MYC were specific to the inhibition of HMGcoA reductase, as treatment with mevalonate, the product of HMG-CoA reductase activity, abrogated these effects and inhibited the ability of atorvastatin to reverse or suppress tumorigenesis. Also, RNAi directed at HMGcoA reductase was sufficient to abrogate the neoplastic properties of MYC-induced tumors. Thus, atorvastatin, by inhibiting HMGcoA reductase, induces changes in phosphoprotein signaling that in turn prevent MYC-induced lymphomagenesis.
View details for DOI 10.1182/blood-2006-09-048033
View details for PubMedID 17622571
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Specific tumor suppressor function for E2F2 in Myc-induced T cell lymphomagenesis
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2007; 104 (39): 15400-15405
Abstract
Deregulation of the Myc pathway and deregulation of the Rb pathway are two of the most common abnormalities in human malignancies. Recent in vitro experiments suggest a complex cross-regulatory relationship between Myc and Rb that is mediated through the control of E2F. To evaluate the functional connection between Myc and E2Fs in vivo, we used a bitransgenic mouse model of Myc-induced T cell lymphomagenesis and analyzed tumor progression in mice deficient for E2f1, E2f2, or E2f3. Whereas the targeted inactivation of E2f1 or E2f3 had no significant effect on tumor progression, loss of E2f2 accelerated lymphomagenesis. Interestingly, loss of a single copy of E2f2 also accelerated tumorigenesis, albeit to a lesser extent, suggesting a haploinsufficient function for this locus. The combined ablation of E2f1 or E2f3, along with E2f2, did not further accelerate tumorigenesis. Myc-overexpressing T cells were more resistant to apoptosis in the absence of E2f2, and the reintroduction of E2F2 into these tumor cells resulted in an increase of apoptosis and inhibition of tumorigenesis. These results identify the E2f2 locus as a tumor suppressor through its ability to modulate apoptosis.
View details for DOI 10.1073/pnas.0706307104
View details for Web of Science ID 000249806900042
View details for PubMedID 17881568
View details for PubMedCentralID PMC2000495
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CpG island methylation in a mouse model of lymphoma is driven by the genetic configuration of tumor cells
PLOS GENETICS
2007; 3 (9): 1757-1769
Abstract
Hypermethylation of CpG islands is a common epigenetic alteration associated with cancer. Global patterns of hypermethylation are tumor-type specific and nonrandom. The biological significance and the underlying mechanisms of tumor-specific aberrant promoter methylation remain unclear, but some evidence suggests that this specificity involves differential sequence susceptibilities, the targeting of DNA methylation activity to specific promoter sequences, or the selection of rare DNA methylation events during disease progression. Using restriction landmark genomic scanning on samples derived from tissue culture and in vivo models of T cell lymphomas, we found that MYC overexpression gave rise to a specific signature of CpG island hypermethylation. This signature reflected gene transcription profiles and was detected only in advanced stages of disease. The further inactivation of the Pten, p53, and E2f2 tumor suppressors in MYC-induced lymphomas resulted in distinct and diagnostic CpG island methylation signatures. Our data suggest that tumor-specific DNA methylation in lymphomas arises as a result of the selection of rare DNA methylation events during the course of tumor development. This selection appears to be driven by the genetic configuration of tumor cells, providing experimental evidence for a causal role of DNA hypermethylation in tumor progression and an explanation for the tremendous epigenetic heterogeneity observed in the evolution of human cancers. The ability to predict genome-wide epigenetic silencing based on relatively few genetic alterations will allow for a more complete classification of tumors and understanding of tumor cell biology.
View details for DOI 10.1371/journal.pgen.0030167
View details for Web of Science ID 000249767800018
View details for PubMedID 17907813
View details for PubMedCentralID PMC1994712
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HIF-dependent antitumorigenic effect of antioxidants in vivo
CANCER CELL
2007; 12 (3): 230-238
Abstract
The antitumorigenic activity of antioxidants has been presumed to arise from their ability to squelch DNA damage and genomic instability mediated by reactive oxygen species (ROS). Here, we report that antioxidants inhibited three tumorigenic models in vivo. Inhibition of a MYC-dependent human B lymphoma model was unassociated with genomic instability but was linked to diminished hypoxia-inducible factor (HIF)-1 levels in a prolyl hydroxylase 2 and von Hippel-Lindau protein-dependent manner. Ectopic expression of an oxygen-independent, stabilized HIF-1 mutant rescued lymphoma xenografts from inhibition by two antioxidants: N-acetylcysteine and vitamin C. These findings challenge the paradigm that antioxidants diminish tumorigenesis primarily through decreasing DNA damage and mutations and provide significant support for a key antitumorigenic effect of diminishing HIF levels.
View details for DOI 10.1016/j.ccr.2007.08.004
View details for Web of Science ID 000249514500006
View details for PubMedID 17785204
View details for PubMedCentralID PMC2084208
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Cellular senescence is an important mechanism of tumor regression upon c-Myc inactivation
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2007; 104 (32): 13028-13033
Abstract
Oncogene-induced senescence is an important mechanism by which normal cells are restrained from malignant transformation. Here we report that the suppression of the c-Myc (MYC) oncogene induces cellular senescence in diverse tumor types including lymphoma, osteosarcoma, and hepatocellular carcinoma. MYC inactivation was associated with prototypical markers of senescence, including acidic beta-gal staining, induction of p16INK4a, and p15INK4b expression. Moreover, MYC inactivation induced global changes in chromatin structure associated with the marked reduction of histone H4 acetylation and increased histone H3 K9 methylation. Osteosarcomas engineered to be deficient in p16INK4a or Rb exhibited impaired senescence and failed to exhibit sustained tumor regression upon MYC inactivation. Similarly, only after lymphomas were repaired for p53 expression did MYC inactivation induce robust senescence and sustained tumor regression. The pharmacologic inhibition of signaling pathways implicated in oncogene-induced senescence including ATM/ATR and MAPK did not prevent senescence associated with MYC inactivation. Our results suggest that cellular senescence programs remain latently functional, even in established tumors, and can become reactivated, serving as a critical mechanism of oncogene addiction associated with MYC inactivation.
View details for DOI 10.1073/pnas.0701953104
View details for PubMedID 17664422
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Development of a conditional bioluminescent transplant model for TPM3-ALK-induced tumorigenesis as a tool to validate ALK-Dependent cancer targeted therapy
CANCER BIOLOGY & THERAPY
2007; 6 (8): 1318-1323
Abstract
Overexpression and activation of TPM3-ALK tyrosine kinase fusion protein is a causal oncogenic event in the development of Anaplastic Large Cell Lymphoma and Inflammatory Myofibroblastic ALK-positive tumors. Thus, the development of ALK specific tyrosine kinase inhibitors is a current therapeutic challenge. Animal models are essential to assess, in vivo, the efficiency of ALK-oncogene inhibitors and to identify new and/or additional therapeutic targets in the ALK tumorigenesis pathway. Using the tetracycline system to allow conditional and concomitant TPM3-ALK and luciferase expression, we have developed a unique transplant model for bioluminescent TPM3-ALK-induced fibroblastic tumors in athymic nude mice. The reversible TPM3-ALK expression allowed us to demonstrate that this oncogene is essential for the tumor growth and its maintenance. In addition, we showed that this model could be used to precisely assess tumor growth inhibition upon ALK chemical inactivation. As proof of principle, we used the general tyrosine kinase inhibitor herbimycin A to inhibit ALK oncoprotein activity. As expected, herbimycin A treatment reduced tumor growth as assessed both by tumor volume measurement and bioluminescent imaging. We conclude that this transplant model for TPM3-ALK-induced tumors represents a valuable tool not only to accurately and rapidly evaluate in vivo ALK-targeted therapies but also to gain insight into the mechanism of ALK-positive tumor development.
View details for Web of Science ID 000252666800038
View details for PubMedID 17660712
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Enhanced NFATc1 nuclear occupancy causes T cell activation independent of CD28 costimulation
JOURNAL OF IMMUNOLOGY
2007; 178 (7): 4315-4321
Abstract
TCR signals induce the nuclear localization of NFATc proteins, which are removed from the nucleus after rephosphorylation by glycogen synthase kinase 3 and other kinases. Rapid nuclear export might allow continuous monitoring of receptor occupancy, making the transcriptional response proportional to the duration of TCR/CD28 signaling. To investigate this possibility, we analyzed mice in which T cells express a NFATc1 variant (NFATc1(nuc)) with serine-to-alanine changes at the glycogen synthase kinase 3 phosphorylation sites. NFATc1(nuc) T cells have constitutively nuclear NFATc1, enhanced T cell activation in vivo, and calcineurin-independent proliferation in vitro. NFATc1(nuc) T cells are hypersensitive to TCR/CD3 stimulation, resulting in enhanced proliferation and cytokine production that is independent of CD28 costimulation. These results support the notion that CD28 inhibits nuclear export of NFATc transcription factors. In addition, NFATc1(nuc) destabilizes a positive feedback loop in which NFATc1 activates its own transcription as well as its targets, such as CD40 ligand and Th1/Th2 cytokines.
View details for Web of Science ID 000245197300038
View details for PubMedID 17371988
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Identifying critical signaling molecules for the treatment of cancer.
Recent results in cancer research. Fortschritte der Krebsforschung. Progrès dans les recherches sur le cancer
2007; 172: 5-24
View details for PubMedID 17607933
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Predictive modeling of tumor regression kinetics using a murine model of oncogene-addicted lung cancers
49th Annual Meeting of the American-Society-for-Therapeutic-Radiology-and-Oncology (ASTRO)
ELSEVIER SCIENCE INC. 2007: S596–S597
View details for Web of Science ID 000249950201402
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ASPP2 haploinsufficiency promotes tumor formation in a mouse model.
48th Annual Meeting of the American-Society-of-Hematology
AMER SOC HEMATOLOGY. 2006: 162B–162B
View details for Web of Science ID 000242440401020
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Sustained regression of tumors upon MYC inactivation requires p53 or thrombospondin-1 to reverse the angiogenic switch
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2006; 103 (44): 16266-16271
Abstract
The targeted inactivation of oncogenes offers a rational therapeutic approach for the treatment of cancer. However, the therapeutic inactivation of a single oncogene has been associated with tumor recurrence. Therefore, it is necessary to develop strategies to override mechanisms of tumor escape from oncogene dependence. We report here that the targeted inactivation of MYC is sufficient to induce sustained regression of hematopoietic tumors in transgenic mice, except in tumors that had lost p53 function. p53 negative tumors were unable to be completely eliminated, as demonstrated by the kinetics of tumor cell elimination revealed by bioluminescence imaging. Histological examination revealed that upon MYC inactivation, the loss of p53 led to a deficiency in thrombospondin-1 (TSP-1) expression, a potent antiangiogenic protein, and the subsequent inability to shut off angiogenesis. Restoration of p53 expression in these tumors re-established TSP-1 expression. This permitted the suppression of angiogenesis and subsequent sustained tumor regression upon MYC inactivation. Similarly, the restoration of TSP-1 alone in p53 negative tumors resulted in the shut down of angiogenesis and led to sustained tumor regression upon MYC inactivation. Hence, the complete regression of tumor mass driven by inactivation of the MYC oncogene requires the p53-dependent induction of TSP-1 and the shut down of angiogenesis. Notably, overexpression of TSP-1 alone did not influence tumor growth. Therefore, the combined inactivation of oncogenes and angiogenesis may be a more clinically effective treatment of cancer. We conclude that angiogenesis is an essential component of oncogene addiction.
View details for DOI 10.1073/pnas.0608017103
View details for PubMedID 17056717
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Tumor dormancy - Death and resurrection of cancer as seen through transgenic mouse models
CELL CYCLE
2006; 5 (16): 1808-1811
Abstract
Cancer is caused by genetic changes that activate oncogenes or inactivate tumor suppressor genes. The repair or inactivation of mutant genes may be effective in the treatment of cancer. Drugs that target oncogenes have shown to be effective in the treatment of some cancers. However, it is still unclear why the inactivation of a single cancer associated gene would ever result in the elimination of tumor cells. In experimental transgenic mouse models the consequences of oncogene inactivation depend upon the genetic and cellular context. In some cases, oncogene inactivation results in the elimination of all or almost all tumor cells through apoptosis or terminal differentiation. However, in other cases, oncogene inactivation results in the apparent loss of the neoplastic properties of tumor cells, that now appear and behave like normal cells, however, upon oncogene reactivation rapidly recover their neoplastic phenotype. These observations illustrate that oncogene inactivation can result in a state of tumor dormancy. Understanding when and how oncogene inactivation induces sustained tumor regression will be important towards the development of successful therapeutic strategies for cancer.
View details for Web of Science ID 000240698600011
View details for PubMedID 16929172
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Conditional transgenic models define how MYC initiates and maintains tumorigenesis
SEMINARS IN CANCER BIOLOGY
2006; 16 (4): 313-317
Abstract
MYC is one of the most commonly overexpressed oncogenes in human cancer. The targeted inactivation of MYC is a possible therapy for neoplasia. Conditional transgenic mouse model systems are tractable methods to precisely dissect how and when the inactivation of MYC might be effective in the treatment for human cancer. From these model systems, several general principles emerge. MYC inactivation stereotypically results in the proliferative arrest, differentiation and/or apoptosis of tumor cells. The specific consequences of MYC inactivation appear to depend both on the type of cancer as well as the constellation of genetic events unique to a given tumor. Tumors can escape from dependence upon MYC by acquiring compensatory genetic events. MYC inactivation can uncover the stem cell properties of tumor cells that differentiate into normal appearing cells. In some cases, these differentiated cells are actually dormant tumor cells that recover their neoplastic properties upon MYC reactivation. In other cases, even brief MYC inactivation is sufficient to induce sustained tumor regression. Insights from conditional transgenic mouse models will be useful in the development of therapies that target MYC for the treatment of cancer.
View details for DOI 10.1016/j.semcancer.2006.07.012
View details for Web of Science ID 000241107600008
View details for PubMedID 16935001
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c-Myc is an important direct target of Notch1 in T-cell acute lymphoblastic leukemia/lymphoma
GENES & DEVELOPMENT
2006; 20 (15): 2096-2109
Abstract
Human acute T-cell lymphoblastic leukemias and lymphomas (T-ALL) are commonly associated with gain-of-function mutations in Notch1 that contribute to T-ALL induction and maintenance. Starting from an expression-profiling screen, we identified c-myc as a direct target of Notch1 in Notch-dependent T-ALL cell lines, in which Notch accounts for the majority of c-myc expression. In functional assays, inhibitors of c-myc interfere with the progrowth effects of activated Notch1, and enforced expression of c-myc rescues multiple Notch1-dependent T-ALL cell lines from Notch withdrawal. The existence of a Notch1-c-myc signaling axis was bolstered further by experiments using c-myc-dependent murine T-ALL cells, which are rescued from withdrawal of c-myc by retroviral transduction of activated Notch1. This Notch1-mediated rescue is associated with the up-regulation of endogenous murine c-myc and its downstream transcriptional targets, and the acquisition of sensitivity to Notch pathway inhibitors. Additionally, we show that primary murine thymocytes at the DN3 stage of development depend on ligand-induced Notch signaling to maintain c-myc expression. Together, these data implicate c-myc as a developmentally regulated direct downstream target of Notch1 that contributes to the growth of T-ALL cells.
View details for DOI 10.1101/gad.1450406
View details for Web of Science ID 000239504500014
View details for PubMedID 16847353
View details for PubMedCentralID PMC1536060
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MYC can induce DNA breaks in vivo and in vitro independent of reactive oxygen species
CANCER RESEARCH
2006; 66 (13): 6598-6605
Abstract
MYC overexpression is thought to initiate tumorigenesis by inducing cellular proliferation and growth and to be restrained from causing tumorigenesis by inducing cell cycle arrest, cellular senescence, and/or apoptosis. Here we show that MYC can induce DNA breaks both in vitro and in vivo independent of increased production of reactive oxygen species (ROS). We provide an insight into the specific circumstances under which MYC generates ROS in vitro and propose a possible mechanism. We found that MYC induces DNA double-strand breaks (DSBs) independent of ROS production in murine lymphocytes in vivo as well as in normal human foreskin fibroblasts (NHFs) in vitro in normal (10%) serum, as measured by gammaH2AX staining. However, NHFs cultured in vitro in low serum (0.05%) and/or ambient oxygen saturation resulted in ROS-associated oxidative damage and DNA single-strand breaks (SSBs), as measured by Ape-1 staining. In NHFs cultured in low versus normal serum, MYC induced increased expression of CYP2C9, a gene product well known to be associated with ROS production. Specific inhibition of CYP2C9 by small interfering RNA was shown to partially inhibit MYC-induced ROS production. Hence, MYC overexpression can induce ROS and SSBs under some conditions, but generally induces widespread DSBs in vivo and in vitro independent of ROS production.
View details for DOI 10.1158/0008-5472.CAN-05-3115
View details for PubMedID 16818632
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CDK2 is required by MYC to induce apoptosis
CELL CYCLE
2006; 5 (12): 1342-1347
Abstract
Depending upon the cellular and physiologic context, the overexpression of the MYC proto-oncogene results in rapid cell growth, proliferation, induction of apoptosis and/or proliferative arrest. What determines the precise consequences upon MYC activation is not clear. We have found that cyclin-dependent kinase 2 (CDK2) is required by MYC to induce apoptosis. MYC-induced apoptosis was suppressed in mouse embryonic fibroblasts (MEF) knocked out for Cdk2 or normal human fibroblasts (NHF) upon expression of the CDK2 inhibitor p27 or treated with RNAi directed at CDK2. Knockout of Cdk2 did not prevent MYC from inducing p53 and Bim. The inhibition of CDK2 did not prevent apoptosis induced by the DNA damaging agent etoposide. Our results surprisingly suggest that CDK2 defines whether MYC induction causes apoptosis.
View details for Web of Science ID 000238581200019
View details for PubMedID 16760655
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MYC can enforce cell cycle transit from G(1) to S and G(2) to S, but not mitotic cellular division, independent of p27-mediated inihibition of Cyclin E/CDK2
CELL CYCLE
2006; 5 (12): 1348-1355
Abstract
Overexpression of the MYC proto-oncogene exerts protean biological effects that may contribute to its ability to induce tumorigenesis including enforcing cellular growth and proliferation and inducing genomic instability. MYC overexpression may induce genomic damage at least in part by causing inappropriate DNA replication. MYC may induce inappropriate DNA replication through the activation of Cyclin E/CDK2. To address this possibility, the effects of ectopic p27 expression in immortal rat fibroblasts or human breast epithelial cell lines on MYC-induced endo-reduplication was determined. p27 inhibited Cyclin E/CDK2 associated kinase activity, but failed to prevent MYC from inducing transit from G1 to S phase; inhibited at lower but not higher levels of MYC transit from G2 to S and endo-reduplication; however, MYC failed to enforce mitotic cellular division. In addition, MYC was found to induce Cyclin E; and Cyclin E in turn was found to be able to induce endo-reduplication. Hence, MYC appears induce inappropriate cell cycle transit, but not mitotic cellular division independent of p27 mediated inhibition of Cyclin E/Cdk2. Our results have implications for the mechanisms by which MYC overexpression dysregulates cell cycle transit, causes genomic destabilization and is restrained from causing tumorigenesis.
View details for Web of Science ID 000238581200020
View details for PubMedID 16760657
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Lethal cutaneous disease in transgenic mice conditionally expressing type I human T cell leukemia virus tax
JOURNAL OF BIOLOGICAL CHEMISTRY
2005; 280 (42): 35713-35722
Abstract
Type I human T cell leukemia virus (HTLV-I) is etiologically linked with adult T cell leukemia, an aggressive and usually fatal expansion of activated CD4+ T lymphocytes that frequently traffic to skin. T cell transformation induced by HTLV-I involves the action of the 40-kDa viral Tax transactivator protein. Tax both stimulates the HTLV-I long terminal repeat and deregulates the expression of select cellular genes by altering the activity of specific host transcription factors, including cyclic AMP-responsive element-binding protein (CREB)/activating transcription factor, NF-kappaB/Rel, and serum response factor. To study initiating events involved in HTLV-I Tax-induced T cell transformation, we generated "Tet-off" transgenic mice conditionally expressing in a lymphocyte-restricted manner (EmuSR alpha promoter-enhancer) either wild-type Tax or mutant forms of Tax that selectively compromise the NF-kappaB (M22) or CREB/activating transcription factor (M47) activation pathways. Wild-type Tax and M47 Tax-expressing mice, but not M22-Tax expressing mice, developed progressive alopecia, hyperkeratosis, and skin lesions containing profuse activated CD4 T cell infiltrates with evidence of deregulated inflammatory cytokine production. In addition, these animals displayed systemic lymphadenopathy and splenomegaly. These findings suggest that Tax-mediated activation of NF-kappaB plays a key role in the development of this aggressive skin disease that shares several features in common with the skin disease occurring during the preleukemic stage in HTLV-I-infected patients. Of note, this skin disease completely resolved when Tax transgene expression was suppressed by administration of doxycycline, emphasizing the key role played by this viral oncoprotein in the observed pathology.
View details for DOI 10.1074/jbc.M504848200
View details for Web of Science ID 000232561200074
View details for PubMedID 16105841
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Comparative genomic hybridization on mouse cDNA microarrays and its application to a murine lymphoma model
ONCOGENE
2005; 24 (40): 6101-6107
Abstract
Microarray-based formats offer a high-resolution alternative to conventional, chromosome-based comparative genomic hybridization (CGH) methods for assessing DNA copy number alteration (CNA) genome-wide in human cancer. For murine tumors, array CGH should provide even greater advantage, since murine chromosomes are more difficult to individually discern. We report here the adaptation and evaluation of a cDNA microarray-based CGH method for the routine characterization of CNAs in murine tumors, using mouse cDNA microarrays representing approximately 14,000 different genes, thereby providing an average mapping resolution of 109 kb. As a first application, we have characterized CNAs in a set of 10 primary and recurrent lymphomas derived from a Myc-induced murine lymphoma model. In primary lymphomas and more commonly in Myc-independent relapses, we identified a recurrent genomic DNA loss at chromosome 3G3-3H4, and recurrent amplifications at chromosome 3F2.1-3G3 and chromosome 15E1/E2-15F3, the boundaries of which we defined with high resolution. Further, by profiling gene expression using the same microarray platform, we identified within CNAs the relevant subset of candidate cancer genes displaying comparably altered expression, including Mcl1 (myeloid cell leukemia sequence 1), a highly expressed antiapoptotic gene residing within the chr 3 amplicon peak. CGH on mouse cDNA microarrays therefore represents a reliable method for the high-resolution characterization of CNAs in murine tumors, and a powerful approach for elucidating the molecular events in tumor development and progression in murine models.
View details for DOI 10.1038/sj.onc.1208751
View details for Web of Science ID 000231718100004
View details for PubMedID 16007205
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Conditionally MYC : insights from novel transgenic models
CANCER LETTERS
2005; 226 (2): 95-99
Abstract
MYC was one of the first oncogenes identified to be associated with chromosomal aberrations and one of the most common oncogenes involved in the pathogenesis of cancer. However, until recently it was not clear if MYC would be a good target for the treatment of cancer. New conditional transgenic models have been used to demonstrate that even the brief inactivation of MYC can reverse tumorigenesis. Here we review results from recent experimental model systems, which demonstrate that the inactivation of MYC may be a specific and effective treatment for many types of cancer.
View details for DOI 10.1016/j.canlet.2004.10.043
View details for Web of Science ID 000231161800001
View details for PubMedID 16039948
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Suppression of p53 by Notch in lymphomagenesis: Implications for initiation and regression
CANCER RESEARCH
2005; 65 (16): 7159-7168
Abstract
Aberrant Notch signaling contributes to more than half of all human T-cell leukemias, and accumulating evidence indicates Notch involvement in other human neoplasms. We developed a tetracycline-inducible mouse model (Top-Notch(ic)) to examine the genetic interactions underlying the development of Notch-induced neoplastic disease. Using this model, we show that Notch suppresses p53 in lymphomagenesis through repression of the ARF-mdm2-p53 tumor surveillance network. Attenuation of Notch expression resulted in a dramatic increase in p53 levels that led to tumor regression by an apoptotic program. This shows that continued Notch activity is required to maintain the disease state. However, all tumors relapsed with rapid kinetics, most of which, by reactivation of Notch expression. Furthermore, by directly inhibiting the mdm2-p53 interaction by using either ionizing radiation or the novel small molecule therapeutic Nutlin, p53 can be activated and cause tumor cell death, even in the presence of sustained Notch activity. Therefore, it is the suppression of p53 that provides the Achilles heel for Notch-induced tumors, as activation of p53 in the presence of Notch signaling drives tumor regression. Our study provides proof-of-principle for the rational targeting of therapeutics against the mdm2-p53 pathway in Notch-induced neoplasms. Furthermore, we propose that suppression of p53 by Notch is a key mechanism underlying the initiation of T-cell lymphoma.
View details for DOI 10.1158/0008-5472.CAN-05-1664
View details for Web of Science ID 000231188600020
View details for PubMedID 16103066
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Rehabilitation of cancer through oncogene inactivation
TRENDS IN MOLECULAR MEDICINE
2005; 11 (7): 316-321
Abstract
The inactivation of the MYC oncogene alone can reverse tumorigenesis. Upon MYC inactivation, tumors stereotypically reverse, undergoing proliferative arrest, cellular differentiation and/or apoptosis. The precise consequences of MYC inactivation appear to depend upon both genetic and epigenetic parameters. In some types of cancer following MYC inactivation, tumor cells become well differentiated and biologically and histologically normal, inducing sustained tumor regression. However, in some cases, these normal-appearing cells are actually dormant tumor cells and upon MYC reactivation they rapidly recover their tumorigenic properties. Future therapies to treat cancer will need to address the possibility that tumor cells can camouflage a normal phenotype following treatment, resting in a dormant, latently cancerous state.
View details for Web of Science ID 000231084900005
View details for PubMedID 15955741
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Getting at MYC through RAS
CLINICAL CANCER RESEARCH
2005; 11 (12): 4278-4281
View details for Web of Science ID 000229725900002
View details for PubMedID 15958607
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Tumor dormancy and MYC inactivation: Pushing cancer to the brink of normalcy
CANCER RESEARCH
2005; 65 (11): 4471-4474
Abstract
Upon MYC inactivation, tumors variously undergo proliferative arrest, cellular differentiation, and apoptosis and in some cases, apparently permanently revoking tumorigenesis. In liver tumor cells, we recently showed that MYC inactivation uncovers stem cell properties and triggers differentiation, but in this case, their neoplastic properties are restorable by MYC reactivation. Thus, whereas oncogene inactivation can push cancer to the brink of normalcy, some cells retain the latent capacity to turn cancerous again, arguing that they may exist in a state of tumor dormancy.
View details for Web of Science ID 000229407800002
View details for PubMedID 15930260
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Developmental context determines latency of MYC-induced tumorigenesis
PLOS BIOLOGY
2004; 2 (11): 1785-1798
Abstract
One of the enigmas in tumor biology is that different types of cancers are prevalent in different age groups. One possible explanation is that the ability of a specific oncogene to cause tumorigenesis in a particular cell type depends on epigenetic parameters such as the developmental context. To address this hypothesis, we have used the tetracycline regulatory system to generate transgenic mice in which the expression of a c-MYC human transgene can be conditionally regulated in murine hepatocytes. MYC's ability to induce tumorigenesis was dependent upon developmental context. In embryonic and neonatal mice, MYC overexpression in the liver induced marked cell proliferation and immediate onset of neoplasia. In contrast, in adult mice MYC overexpression induced cell growth and DNA replication without mitotic cell division, and mice succumbed to neoplasia only after a prolonged latency. In adult hepatocytes, MYC activation failed to induce cell division, which was at least in part mediated through the activation of p53. Surprisingly, apoptosis is not a barrier to MYC inducing tumorigenesis. The ability of oncogenes to induce tumorigenesis may be generally restrained by developmentally specific mechanisms. Adult somatic cells have evolved mechanisms to prevent individual oncogenes from initiating cellular growth, DNA replication, and mitotic cellular division alone, thereby preventing any single genetic event from inducing tumorigenesis.
View details for DOI 10.1371/journal.pbio.0020332
View details for Web of Science ID 000225160300011
View details for PubMedID 15455033
View details for PubMedCentralID PMC519000
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MYC inactivation uncovers pluripotent differentiation and tumour dormancy in hepatocellular cancer
NATURE
2004; 431 (7012): 1112-1117
Abstract
Hepatocellular carcinoma is generally refractory to clinical treatment. Here, we report that inactivation of the MYC oncogene is sufficient to induce sustained regression of invasive liver cancers. MYC inactivation resulted en masse in tumour cells differentiating into hepatocytes and biliary cells forming bile duct structures, and this was associated with rapid loss of expression of the tumour marker alpha-fetoprotein, the increase in expression of liver cell markers cytokeratin 8 and carcinoembryonic antigen, and in some cells the liver stem cell marker cytokeratin 19. Using in vivo bioluminescence imaging we found that many of these tumour cells remained dormant as long as MYC remain inactivated; however, MYC reactivation immediately restored their neoplastic features. Using array comparative genomic hybridization we confirmed that these dormant liver cells and the restored tumour retained the identical molecular signature and hence were clonally derived from the tumour cells. Our results show how oncogene inactivation may reverse tumorigenesis in the most clinically difficult cancers. Oncogene inactivation uncovers the pluripotent capacity of tumours to differentiate into normal cellular lineages and tissue structures, while retaining their latent potential to become cancerous, and hence existing in a state of tumour dormancy.
View details for DOI 10.1038/nature03043
View details for Web of Science ID 000224730800044
View details for PubMedID 15475948
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Putting oncogenes into a developmental context
CANCER BIOLOGY & THERAPY
2004; 3 (10): 942-944
Abstract
Cancer is largely caused by genomic events that activate oncogenes or inactivate tumor suppressor genes. To date, the mechanisms by which these mutant gene products contribute to tumorigenesis has been studied mostly in experimental model systems that have not been able to interrogate the potential contribution of developmental factors in the etiology of neoplasia. Recently, we employed a conditional transgenic model system to demonstrate that the ability of the MYC oncogene to induce tumorigenesis is influenced by the developmental age of the host. MYC induced in embryonic of neonatal tissues cellular proliferation and the rapid onset of tumorigenesis; whereas MYC activation in adult tissues induces cellular hypertrophy. Thus, differences in the frequency and spectrum of cancers observed in different aged hosts may reflect the influence of developmental context. Cancer may generally be better thought of as a consequence of genetic events that occur in a permissive epigenetic state. Developmental context may be a critical determinant in the pathogenesis of neoplasia.
View details for Web of Science ID 000227440300012
View details for PubMedID 15611633
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The human BCL6 transgene promotes the development of lymphomas in the mouse
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2004; 101 (39): 14198-14203
Abstract
BCL6, a gene on chromosome 3, band q27, encodes a zinc finger transcriptional repressor that is needed for germinal center formation and has been implicated in the pathogenesis of some human lymphomas when it is mutated or involved in chromosomal rearrangements. To explore further the mechanisms of action of BCL6 in lymphomagenesis, we developed a transgenic mouse model mimicking a common translocation, the t(3, 14)(q27;q32), in human lymphomas. The transgenic mice develop normally and express the transgenic BCL6 protein constitutively in lymphocytes. A small fraction of the animals develop B and T cell lymphomas after a long latency period, but the incidence is dramatically enhanced following administration of N-ethyl-N-nitrosourea, a carcinogen that induces DNA mutations. The N-ethyl-N-nitrosourea-induced lymphomas spread widely, were exclusively T cell, expressed the BCL6 protein, and occurred only in the transgenic mice. Because BCL6 expression has been reported in a number of T cell tumors as well as in the more commonly occurring B cell lymphomas in humans, our transgenic mice provide a model for the study of human lymphomas.
View details for DOI 10.1073/pnas.0406138101
View details for Web of Science ID 000224211400043
View details for PubMedID 15375218
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The E47 transcription factor negatively regulates CD5 expression during thymocyte development
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2004; 101 (11): 3898-3902
Abstract
The expression of CD5 increases progressively as thymocytes mature. We have shown that CD5 expression is controlled by a tissue-specific regulatory promoter located upstream of the CD5 translation start sites. Deletion of this regulatory promoter, which contains three potential transcription factor binding sites (CCAAT, kappa E2, and ets) reduces the promoter activity to basal level. Of these sites, only ets proved essential for CD5 expression in T cell lines. Here, we introduce a role for the E47 transcription factor and the CD5 promoter kappa E2 site in regulating CD5 expression during thymocyte development. Using T cell lines, we show that (i) mutation of the kappa E2 site in the CD5 regulatory promoter results in a significant elevation of CD5 promoter activity; (ii) the E47 transcription factor binds to the kappa E2 site; and (iii) overexpression of E47 inhibits CD5 expression. We then show, in high-dimensional fluorescence-activated cell sorting studies with primary thymocytes at successive developmental stages, that (i) intracellular E47 levels decrease as surface CD5 expression increases; (ii) E47 expression is down-regulated and CD5 expression is correspondingly up-regulated in DN3 thymocytes in RAG-2-deficient mice injected with anti-CD3 to mimic pre-T cell receptor stimulation; and (iii) E47 expression is down-regulated and CD5 expression is up-regulated when double positive thymocytes are stimulated in vitro with anti-CD3. Based on these data, we propose that E47 negatively regulates CD5 expression by interacting with the kappa E2 site in the CD5 regulatory promoter and that decreases in E47 in response to developmental signals are critical to the progressive increase in CD5 expression as thymocytes mature.
View details for DOI 10.1073/pnas.0308764101
View details for Web of Science ID 000220314500034
View details for PubMedID 15001710
View details for PubMedCentralID PMC374341
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Reversibility of oncogene-induced cancer
CURRENT OPINION IN GENETICS & DEVELOPMENT
2004; 14 (1): 37-42
Abstract
Cancer can largely be conceived as a consequence of genomic catastrophes resulting in genetic events that usurp physiologic function of a normal cell. These genetic events mediate their pathologic effects by either activating oncogenes or inactivating tumor-suppressor genes. The targeted repair or inactivation of these damaged gene products may counteract the effects of these genetic events, reversing tumorigenesis and thereby serve as an effective therapy for cancer. However, because they are the result of many genetic events, the inactivation of no single mutant gene product may be sufficient to reverse cancer. Despite this caveat, compelling recent evidence suggests that there are circumstances when even the brief interruption of activation of a single oncogene can be sufficient to reverse tumorigenesis. Understanding how and when oncogene inactivation reverses cancer will be important in both defining the molecular pathogenesis of cancer as well as developing new molecularly based treatments.
View details for Web of Science ID 000188978200007
View details for PubMedID 15108803
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Oncogenes as therapeutic targets
SEMINARS IN CANCER BIOLOGY
2004; 14 (1): 1-1
View details for DOI 10.1016/j.semcancer.2003.11.001
View details for Web of Science ID 000189081200001
View details for PubMedID 14757530
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Conditional animal models: a strategy to define when oncogenes will be effective targets to treat cancer
SEMINARS IN CANCER BIOLOGY
2004; 14 (1): 3-11
Abstract
The ability to model cancer in the mouse has provided a robust methodology to dissect the molecular etiology of cancer. These models serve as potentially powerful platforms to preclinically evaluate novel therapeutics. In particular, the recent development of strategies to conditionally induce the or knockout the function of genes in a tissue specific manner has enabled investigators to engineer mice to demonstrate that the targeted inactivation of specific oncogenes can be effective in inducing sustained regression of tumors. Thus, these animal models will be useful to define the specific genes that will be therapeutically useful to target for the treatment of particular human cancers.
View details for DOI 10.1016/j.semcancer.2003.11.002
View details for PubMedID 14757531
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RAS and BCL-2 co-operate in a mouse model of myelodysplasia (MDS).
45th Annual Meeting and Exhibition of the American-Society-of-Hematology
AMER SOC HEMATOLOGY. 2003: 145A–145A
View details for Web of Science ID 000186536700499
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Defective double-strand DNA break repair and chromosomal translocations by MYC overexpression
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2003; 100 (17): 9974-9979
Abstract
DNA repair mechanisms are essential for the maintenance of genomic integrity. Disruption of gene products responsible for DNA repair can result in chromosomal damage. Improperly repaired chromosomal damage can result in the loss of chromosomes or the generation of chromosomal deletions or translocations, which can lead to tumorigenesis. The MYC protooncogene is a transcription factor whose overexpression is frequently associated with human neoplasia. MYC has not been previously implicated in a role in DNA repair. Here we report that the overexpression of MYC disrupts the repair of double-strand DNA breaks, resulting in a several-magnitude increase in chromosomal breaks and translocations. We found that MYC inhibited the repair of gamma irradiation DNA breaks in normal human cells and blocked the repair of a single double-strand break engineered to occur in an immortal cell line. By spectral karyotypic analysis, we found that MYC even within one cell division cycle resulted in a several-magnitude increase in the frequency of chromosomal breaks and translocations in normal human cells. Hence, MYC overexpression may be a previously undescribed example of a dominant mutator that may fuel tumorigenesis by inducing chromosomal damage.
View details for DOI 10.1073/pnas.1732638100
View details for PubMedID 12909717
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How cancers escape their oncogene habit.
Cell cycle
2003; 2 (4): 329-332
Abstract
Many recent reports demonstrate that at least initially, the inactivation of an oncogene can induce sustained regression of even a highly invasive and genetically complex cancer. However, upon prolonged oncogene inactivation, some cancers ultimately relapse, becoming independent of the very oncogene that initiated the process of tumorigenesis. Understanding the specific mechanisms by which cancers can escape dependence upon a particular oncogene will be critical to anticipate mechanisms by which human cancers will evade therapies that target individual oncogenes. Thereby, more effective strategies will be developed to clinically treat cancer.
View details for PubMedID 12851484
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Pharmacological inactivation of MYC for the treatment of cancer
DRUG NEWS & PERSPECTIVES
2003; 16 (6): 370-374
Abstract
The overexpression of the MYC proto-oncogene has been implicated in the pathogenesis of most types of human cancer. Recent experimental observations indicate that the inactivation of MYC may be effective in the treatment of neoplasia. Several different strategies have been employed to develop novel drugs that may be effective to target the inactivation of MYC for the treatment of cancer. Some of these strategies are discussed.
View details for Web of Science ID 000185723900007
View details for PubMedID 12973448
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Cancer revoked: oncogenes as therapeutic targets
NATURE REVIEWS CANCER
2003; 3 (5): 375-380
Abstract
Recent findings show that even the brief inactivation of a single oncogene might be sufficient to result in the sustained loss of a neoplastic phenotype. It is therefore possible that the targeted inactivation of oncogenes could be a specific and effective treatment for cancer. So why does oncogene inactivation cause tumour regression and will this be a generally successful approach for the treatment of human neoplasia?
View details for DOI 10.1038/nrc1070
View details for Web of Science ID 000183007900016
View details for PubMedID 12724735
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Genomically complex lymphomas undergo sustained tumor regression upon MYC inactivation unless they acquire novel chromosomal translocations
BLOOD
2003; 101 (7): 2797-2803
Abstract
The targeted inactivation of oncogenes may be a specific and effective treatment for cancer. However, because human cancers are the consequence of multiple genetic changes, the inactivation of one oncogene may not be sufficient to cause sustained tumor regression. Moreover, cancers are genomically unstable and may readily compensate for the inactivation of a single oncogene. Here we confirm by spectral karyotypic analysis that MYC-induced hematopoietic tumors are highly genetically complex and genomically unstable. Nevertheless, the inactivation of MYC alone was found to be sufficient to induce sustained tumor regression. After prolonged MYC inactivation, some tumors exhibited a distinct propensity to relapse. When tumors relapsed, they no longer required the overexpression of MYC but instead acquired novel chromosomal translocations. We conclude that even highly genetically complex cancers are reversible on the inactivation of MYC, unless they acquire novel genetic alterations that can sustain a neoplastic phenotype.
View details for DOI 10.1182/blood-2002-10-3091
View details for Web of Science ID 000181823600058
View details for PubMedID 12517816
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How Cancers Escape Their Oncogene Habit
CELL CYCLE
2003; 2 (4): 329-332
View details for DOI 10.4161/cc.2.4.415
View details for Web of Science ID 000209691300018
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Sustained loss of a neoplastic phenotype by brief inactivation of MYC
SCIENCE
2002; 297 (5578): 102-104
Abstract
Pharmacological inactivation of oncogenes is being investigated as a possible therapeutic strategy for cancer. One potential drawback is that cessation of such therapy may allow reactivation of the oncogene and tumor regrowth. We used a conditional transgenic mouse model for MYC-induced tumorigenesis to demonstrate that brief inactivation of MYC results in the sustained regression of tumors and the differentiation of osteogenic sarcoma cells into mature osteocytes. Subsequent reactivation of MYC did not restore the cells' malignant properties but instead induced apoptosis. Thus, brief MYC inactivation appears to cause epigenetic changes in tumor cells that render them insensitive to MYC-induced tumorigenesis. These results raise the possibility that transient inactivation of MYC may be an effective therapy for certain cancers.
View details for Web of Science ID 000176711000043
View details for PubMedID 12098700
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C-Myc is a critical target for C/EBP alpha in granulopoiesis
MOLECULAR AND CELLULAR BIOLOGY
2001; 21 (11): 3789-3806
Abstract
CCAAT/enhancer binding protein alpha (C/EBPalpha) is an integral factor in the granulocytic developmental pathway, as myeloblasts from C/EBPalpha-null mice exhibit an early block in differentiation. Since mice deficient for known C/EBPalpha target genes do not exhibit the same block in granulocyte maturation, we sought to identify additional C/EBPalpha target genes essential for myeloid cell development. To identify such genes, we used both representational difference analysis and oligonucleotide array analysis with RNA derived from a C/EBPalpha-inducible myeloid cell line. From each of these independent screens, we identified c-Myc as a C/EBPalpha negatively regulated gene. We mapped an E2F binding site in the c-Myc promoter as the cis-acting element critical for C/EBPalpha negative regulation. The identification of c-Myc as a C/EBPalpha target gene is intriguing, as it has been previously shown that down-regulation of c-Myc can induce myeloid differentiation. Here we show that stable expression of c-Myc from an exogenous promoter not responsive to C/EBPalpha-mediated down-regulation forces myeloblasts to remain in an undifferentiated state. Therefore, C/EBPalpha negative regulation of c-Myc is critical for allowing early myeloid precursors to enter a differentiation pathway. This is the first report to demonstrate that C/EBPalpha directly affects the level of c-Myc expression and, thus, the decision of myeloid blasts to enter into the granulocytic differentiation pathway.
View details for Web of Science ID 000168706600017
View details for PubMedID 11340171
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Over-expression of MYC causes p53-dependent G2 arrest of normal fibroblasts
AMER SOC CELL BIOLOGY. 2000: 239A–239A
View details for Web of Science ID 000165525901249
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Overexpression of MYC causes p53-dependent G(2) arrest of normal fibroblasts
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2000; 97 (19): 10544-10548
Abstract
Overexpression of the proto-oncogene MYC has been implicated in the genesis of diverse human cancers. One explanation for the role of MYC in tumorigenesis has been that this gene might drive cells inappropriately through the division cycle, leading to the relentless proliferation characteristic of the neoplastic phenotype. Herein, we report that the overexpression of MYC alone cannot sustain the division cycle of normal cells but instead leads to their arrest in G(2). We used an inducible form of the MYC protein to stimulate normal human and rodent fibroblasts. The stimulated cells passed through G(1) and S but arrested in G(2) and frequently became aneuploid, presumably as a result of inappropriate reinitiation of DNA synthesis. Absence of the tumor suppressor gene p53 or its downstream effector p21 reduced the frequency of both G(2) arrest and aneuploidy, apparently by compromising the G(2) checkpoint control. Thus, relaxation of the G(2) checkpoint may be an essential early event in tumorigenesis by MYC. The loss of p53 function seems to be one mechanism by which this relaxation commonly occurs. These findings dramatize how multiple genetic events can collaborate to produce neoplastic cells.
View details for Web of Science ID 000089341400047
View details for PubMedID 10962037
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Reversible tumorigenesis by MYC in hematopoietic lineages
MOLECULAR CELL
1999; 4 (2): 199-207
Abstract
The targeted repair of mutant protooncogenes or the inactivation of their gene products may be a specific and effective therapy for human neoplasia. To examine this possibility, we have used the tetracycline regulatory system to generate transgenic mice that conditionally express the MYC protooncogene in hematopoietic cells. Sustained expression of the MYC transgene culminated in the formation of malignant T cell lymphomas and acute myleoid leukemias. The subsequent inactivation of the transgene caused regression of established tumors. Tumor regression was associated with rapid proliferative arrest, differentiation and apoptosis of tumor cells, and resumption of normal host hematopoiesis. We conclude that even though tumorigenesis is a multistep process, remediation of a single genetic lesion may be sufficient to reverse malignancy.
View details for Web of Science ID 000082387700006
View details for PubMedID 10488335
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Transient excess of MYC activity can elicit genomic instability and tumorigenesis
NATL ACAD SCIENCES. 1999: 3940–44
Abstract
Overexpression of the MYC protooncogene has been implicated in the genesis of diverse human tumors. Tumorigenesis induced by MYC has been attributed to sustained effects on proliferation and differentiation. Here we report that MYC may also contribute to tumorigenesis by destabilizing the cellular genome. A transient excess of MYC activity increased tumorigenicity of Rat1A cells by at least 50-fold. The increase persisted for >30 days after the return of MYC activity to normal levels. The brief surfeit of MYC activity was accompanied by evidence of genomic instability, including karyotypic abnormalities, gene amplification, and hypersensitivity to DNA-damaging agents. MYC also induced genomic destabilization in normal human fibroblasts, although these cells did not become tumorigenic. Stimulation of Rat1A cells with MYC accelerated their passage through G1/S. Moreover, MYC could force normal human fibroblasts to transit G1 and S after treatment with N-(phosphonoacetyl)-L-aspartate (PALA) at concentrations that normally lead to arrest in S phase by checkpoint mechanisms. Instead, the cells subsequently appeared to arrest in G2. We suggest that the accelerated passage through G1 was mutagenic but that the effect of MYC permitted a checkpoint response only after G2 had been reached. Thus, MYC may contribute to tumorigenesis through a dominant mutator effect.
View details for Web of Science ID 000079507900107
View details for PubMedID 10097142
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A NOVEL OCTAMER REGULATORY ELEMENT IN THE V(H)11 LEADER EXON OF B-1 CELLS
JOURNAL OF IMMUNOLOGY
1995; 154 (9): 4546-4556
Abstract
B-1 cells (CD5 B cells) represent an initial fetal wave of B cell lymphopoiesis. B-1 cells have fundamental properties that are unique from conventional B cells, including a restricted Ab repertoire. We investigated the mechanism for the overrepresentation of one such Ig H chain variable-region gene, VH11, by murine B-1 cells. We postulated that a cis-regulatory element contributed to the use of VH11. We observed that the DNA encoding the leader peptide of VH11 was atypically A/T rich and thus was a candidate for nuclear protein binding. By electrophoretic mobility shift analysis, we found that the VH11 leader DNA specifically bound to three protein complexes present in the nucleus of the B-1 cell line AJ9. Of these bands, one was ubiquitous for all cells examined (lymphoid and nonlymphoid); another band was present only in B cells, and the third band was specific for B-1 cells that expressed VH11 or VH12. In addition to its binding properties, the VH11 leader sequence also displayed modest tissue-specific enhancer activity. By DNA footprint analysis, all three protein complexes were found to bind to an octamer motif embedded within the VH11 leader DNA. To identify the octamer-binding proteins, a panel of octamer-specific Abs was used. We found that the ubiquitous band was Oct-1, and the B cell-specific band was Oct-2. The B-1 cell-specific nuclear binding protein was neither Oct-1 nor Oct-2, but may be a novel POU domain protein. We hypothesize that the VH11 leader octamer site may target this gene for preferential rearrangement and/or expression and therefore would be a contributing factor in the increased use of this gene by B-1 cells.
View details for Web of Science ID A1995QU82500033
View details for PubMedID 7722308
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C-MYC, MHCI, AND NK RESISTANCE IN IMMUNODEFICIENCY LYMPHOMAS
ANNALS OF THE NEW YORK ACADEMY OF SCIENCES
1992; 651: 467-469
View details for Web of Science ID A1992JM21900060
View details for PubMedID 1599133
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C-MYC, MHCI, AND NK RESISTANCE IN IMMUNODEFICIENCY LYMPHOMAS
CONF ON CD5 B-CELLS IN DEVELOPMENT AND DISEASE
NEW YORK ACAD SCIENCES. 1992: 467–469
View details for Web of Science ID A1992BW41S00060
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INDEPENDENT REARRANGEMENT OF IG LAMBDA-GENES IN TISSUE CULTURE-DERIVED MURINE B-CELL LINES
INTERNATIONAL IMMUNOLOGY
1991; 3 (7): 711-718
Abstract
Rearrangement of the lambda light chain locus is considered a late event in pre-B cell differentiation which occurs after successful heavy chain and unsuccessful kappa light chain rearrangement. However, this view has recently been challenged by the observation of apparently independent lambda rearrangement in certain B cell lines and Ig transgenic populations. In this study we have examined the pattern of Ig rearrangements and expression in several tissue culture-derived murine B cell lines. One pre-B cell line (BDL-1) displayed germline heavy and kappa light chain genes despite the presence of a productive lambda 1 light chain rearrangement. Two other cell lines (DAC-2, BDL-2) had multiple lambda rearrangements despite the presence of productive kappa chain rearrangements. These cell lines provide new precedents for rearrangement of the lambda locus independent of the kappa locus. Their phenotype suggests that accessibility at the different Ig loci may be controlled by a non-sequential mechanism.
View details for Web of Science ID A1991FX13700013
View details for PubMedID 1911542
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A MURINE MODEL FOR B-CELL LYMPHOMAGENESIS IN IMMUNOCOMPROMISED HOSTS - NATURAL-KILLER-CELLS ARE AN IMPORTANT COMPONENT OF HOST-RESISTANCE TO PREMALIGNANT B-CELL LINES
CANCER RESEARCH
1990; 50 (21): 7050-7056
Abstract
The accompanying paper (D. W. Felsher et al., Cancer Res., 50:7042-7049, 1990) describes a new panel of cloned murine B-cell lines with a premalignant phenotype and in vivo-derived malignant variants. This paper assesses the contribution of immune mediated antitumor mechanisms which might account for host resistance to the tumorigenicity of these cell lines. Conventional T-cell-dependent responses did not appear to be critical to host resistance. In vivo elimination of T-helper cells with anti-L3T4 monoclonal antibody did not reduce host resistance to the tumorigenicity of these cell lines, nor did these cell lines elicit cytotoxic T-cell activity. However, a strong correlation was found between tumorigenicity and host natural killer (NK) activity. In vitro studies demonstrated that the cell lines were as NK sensitive as the prototypical NK target, YAC-1, whereas the malignant variants fully tumorigenic in normal hosts were greater than 20-fold less NK sensitive than were the parent cell lines. In vivo depletion of NK cells with anti-asialo-GM1 in BALB/c strongly diminished host resistance to cell line tumorigenicity, whereas polydeoxyinosinic-deoxycytidilic acid induction of NK cells enhanced host resistance. These findings indicate that NK function is a critical component to host resistance in this system and suggest that endogenous cellular mechanisms which overcome NK sensitivity could be a target for secondary transforming events in B-cell lymphomagenesis. They also raise the unexpected possibility that a non-antigen-dependent (versus immune cytotoxic T-lymphocytes) effector mechanism may be the key deficit promoting B-cell neoplasia in the setting of immunocompromised states.
View details for Web of Science ID A1990EF20500049
View details for PubMedID 2208172
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A MURINE MODEL FOR B-CELL LYMPHOMAGENESIS IN IMMUNOCOMPROMISED HOSTS - C-MYC-REARRANGED B-CELL LINES WITH A PREMALIGNANT PHENOTYPE
CANCER RESEARCH
1990; 50 (21): 7042-7049
Abstract
Activation of c-myc or bcl-2 protooncogene is a common event in B-cell lymphomagenesis. Alone, each is insufficient to produce lymphoma, prompting the search for the additional steps required to complete the malignant phenotype. Among the existing systems of murine or human B-cell neoplasia, no commonly occurring complementary oncogenic activation has been found. This study introduces a new series of murine B-cell lines with a phenotype suggesting that such additional events might not involve intrinsic growth control, but instead host immune mechanisms which normally suppress tumorigenicity of premalignant B-cells. Four murine B-cell lines were isolated from the long-term culture of normal lymphoid tissue bearing a premalignant phenotype. (a) Their phenotype resembled naturally occurring lymphoid tumors of immunocompromised hosts with regard to c-myc activation, aberrant or absent immunoglobulin expression, preferential rearrangement of the lambda light chain locus, and a distinctive pattern of tissue invasion and tumor histology. (b) Their tumorigenicity was strictly dependent on host permissiveness correlated with immunodeficient status: C.B-17-scid greater than BALB/c-nu/nu greater than normal BALB/c much greater than other H-2d strains (NZB x NZW F1, NZB, DBA/2). (c) Host passage selected for malignant variants distinguished by a 10(4)-fold increase in tumorigenicity (as judged by limiting cell dose) and by novel tumorigenicity in nonpermissive syngeneic hosts. These features are analogous to properties of human lymphomas arising in immunocompromised states and, to our knowledge, unique among previously reported murine B-cell lines.
View details for Web of Science ID A1990EF20500048
View details for PubMedID 2208171
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A RAPID METHOD FOR THE PURIFICATION OF MONOMERIC AND OR DIMERIC PHOSPHOLIPASES A2 IN CROTALID SNAKE-VENOMS
TOXICON
1985; 23 (5): 747-754
Abstract
We have developed a simple two-step procedure for the separation of monomeric (14,000 mol. wt) and dimeric (28,000 mol. wt) phospholipases A2 from the venoms of Crotalidae family snakes. All venom phospholipases A2 studied thus far exist as monomers under acidic conditions and are chromatographed as such on a column of G-50 Sephadex (superfine) equilibrated in 5% acetic acid. Separation of dimeric phospholipases A2 from any monomeric enzyme(s) in pools of enzyme thus obtained is achieved by chromatography on a second column of G-50 Sephadex (superfine) identical to the first but developed in 1% ammonium bicarbonate. This method has been applied to an investigation of the prevalence of monomeric and/or dimeric enzymes in venoms of the Crotalidae family. The distribution of monomeric and dimeric phospholipases correlates well with phylogeny. In the more primitive Crotalidae genera, such as Trimeresurus and Agkistrodon, monomeric phospholipases A2 are predominant. In the more highly evolved Crotalus genus, only dimeric enzymes are found.
View details for Web of Science ID A1985AVE1800004
View details for PubMedID 4089870