- Pediatric Hematology-Oncology
Chief, Division of Pediatric Hematology/Oncology/Stem Cell Transplantation/Cancer Biology, Bass Cancer Center, Lucile Packard Children's Hospital (2011 - Present)
Fellowship Program Director, Division of Pediatric Hematology-Oncology, Stanford University School of Medicine (2011 - 2013)
Honors & Awards
Standing Member, NIDDK-D Study Section for Training Grants and K awards (2011-present)
Chair, Myeloid Biology Subcommittee, American Society of Hematology (2011)
Brett Ely Visiting Professor in Pediatric Oncology, University of Colorado and Children's Hospital Denver (2011)
Outstanding advances in cancer research award, Mendiburu Magic Foundation (2010)
Fernbach Distinguished Visiting Professor Lectureship, Texas Children's Cancer Center (2009)
Gift of Hope Award, Pediatric Cancer Research Foundation (2008)
Junior Faculty Ross Research Award, Western Society for Pediatric Research (1996)
Young Investigator Award, American Society of Pediatric Hematology/Oncology (1994)
STOP Cancer Career Development award, UCLA Jonsson Comprehensive Cancer Center (1992)
Victor E. Stork Award, Children's Hospital of Los Angeles (1988)
Fellowship:Children's Hospital Los Angeles (1991) CA
Board Certification: Pediatrics, American Board of Pediatrics (1989)
Residency:Children's Hospital Los Angeles (1988) CA
Board Certification: Pediatric Hematology-Oncology, American Board of Pediatrics (1992)
Medical Education:University of Cincinnati College of Medicine (1985) OH
B.A., Williams College, Biology (1979)
M.D., University of Cincinnati College of Medicine, Medicine (1985)
Ph.D., California Institute of Technology, Biology (2004)
Internship and Residency, Children's Hospital Los Angeles, Pediatrics (1988)
Fellowship, Children's Hospital Los Angeles, Pediatric Hematology/Oncology (1991)
Postdoctoral Fellowship, UCLA School of Medicine, Hematopoietic growth factors and signal transduction (1992)
Current Research and Scholarly Interests
Transcriptional regulation in leukemogenesis
CREB is a leucine zipper transcription factor that controls cell proliferation, differentiation, and survival. CREB is overexpressed in bone marrow cells from the majority of patients with acute lymphoblastic and myeloid leukemia. CREB transgenic mice develop myeloproliferative disease, i.e. preleukemia, but not acute leukemia. Therefore, CREB is an oncogene that requires additional mutations. We are studying other cooperating oncogenes that contribute to leukemogenesis. In addition, downstream target genes are being explored. We are also studying a small molecule inhibitor of CREB for the treatment of acute leukemia.
Targeted therapy for leukemia and other cancers
In collaboration with pharmaceutical companies, we are testing novel compounds to target specific signaling molecules in AML. Among the small molecules being studied in vitro and in vivo are inhibitors of receptor tyrosine kinases, aurora kinases, and anti-apoptotic proteins. Mechanistic pathways are being investigated.
Protacs are chimeric molecules to target cancer causing proteins for ubiquitination and degradation. We have demonstrated the feasibility of using this approach in prostate and breast cancer cell lines to target the androgen and estrogen receptors for ubiquitination and degradation, resulting in apoptosis. Approaches are being developed to design Protacs for clinical trials in humans.
Signaling Pathways in bone marrow failure syndromes
Defects in ribosome biogenesis have been associated with specific bone marrow failure syndromes, such as Diamond Blackfan Anemia. We are studying the signaling pathways that are altered by deficiency in specific ribosomal protein subunits. Zebrafish, mouse, and human cells are being used to characterize p53-dependent and independent pathways mediating aberrant erythropoiesis and increased risk of cancer in these patients. Novel drugs are being tested.
Genome, Proteome and Tissue Microarray in Childhood Acute Leukemia
We will study gene and protein expression in leukemia cells of children diagnosed with acute leukemia. We hope to identify genes or proteins which can help us grade leukemia at diagnosis in order to: (a) develop better means of diagnosis and (b) more accurately choose the best therapy for each patient.
Independent Studies (8)
- Directed Reading in Cancer Biology
CBIO 299 (Aut, Win, Spr, Sum)
- Directed Reading in Pediatrics
PEDS 299 (Aut, Win, Sum)
- Early Clinical Experience
PEDS 280 (Aut, Win, Spr, Sum)
- Graduate Research
CBIO 399 (Aut, Win, Spr, Sum)
- Graduate Research
PEDS 399 (Aut, Win, Spr, Sum)
- Medical Scholars Research
PEDS 370 (Aut, Win, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Aut, Win, Spr)
- Undergraduate Directed Reading/Research
PEDS 199 (Aut, Win, Sum)
- Directed Reading in Cancer Biology
Graduate and Fellowship Programs
The Multitargeted Receptor Tyrosine Kinase Inhibitor Linifanib (ABT-869) Induces Apoptosis through an Akt and Glycogen Synthase Kinase 3 beta-Dependent Pathway
MOLECULAR CANCER THERAPEUTICS
2011; 10 (6): 949-959
The FMS-like receptor tyrosine kinase 3 (FLT3) plays an important role in controlling differentiation and proliferation of hematopoietic cells. Activating mutations in FLT3 occur in patients with acute myeloid leukemia (AML; 15%-35%), resulting in abnormal cell proliferation. Furthermore, both adult and pediatric patients with AML harboring the FLT3 internal tandem duplication (ITD) mutation have a poor prognosis. Several inhibitors have been developed to target mutant FLT3 for the treatment of AML, yet the molecular pathways affected by drug inhibition of the mutated FLT3 receptor alone have not been characterized as yet. Linifanib (ABT-869) is a multitargeted tyrosine kinase receptor inhibitor that suppresses FLT3 signaling. In this article, we show that treatment with linifanib inhibits proliferation and induces apoptosis in ITD mutant cells in vitro and in vivo. We show that treatment with linifanib reduces phosphorylation of Akt and glycogen synthase kinase 3? (GSK3?). In addition, we show that inhibition of GSK3? decreases linifanib-induced apoptosis. This study shows the importance of GSK3 as a potential target for AML therapy, particularly in patients with FLT3 ITD mutations.
View details for DOI 10.1158/1535-7163.MCT-10-0904
View details for Web of Science ID 000291428000004
View details for PubMedID 21471285
CREB and leukemogenesis.
Critical reviews in oncogenesis
2011; 16 (1-2): 37-46
Acute myeloid leukemia (AML) is one of the most common leukemias with a 20% 5-year event-free survival in adults and 50% overall survival in children, despite aggressive chemotherapy treatment and bone marrow transplantation. The incidence and mortality rates for acute leukemia have only slightly decreased over the last 20 years, and therefore greater understanding of the molecular mechanisms associated with leukemic progression is needed. To this end, a number of transcription factors that appear to play a central role in leukemogenesis are being investigated; among them is the cAMP response element binding protein (CREB). CREB is a transcription factor that can regulate downstream targets involving in various cellular functions including cell proliferation, survival, and differentiation. In several studies, the majority of bone marrow samples from patients with acute lymphoid and myeloid leukemia demonstrate CREB overexpression. Moreover, CREB overexpression is associated with a poor outcome in AML patients. This review summarizes the role of CREB in leukemogenesis.
View details for PubMedID 22150306
Ribosomal protein S19 deficiency in zebrafish leads to developmental abnormalities and defective erythropoiesis through activation of p53 protein family
2008; 112 (13): 5228-5237
Mutations in several ribosomal proteins (RPs) lead to Diamond-Blackfan anemia (DBA), a syndrome characterized by defective erythropoiesis, congenital anomalies, and increased frequency of cancer. RPS19 is the most frequently mutated RP in DBA. RPS19 deficiency impairs ribosomal biogenesis, but how this leads to DBA or cancer remains unknown. We have found that rps19 deficiency in ze-brafish results in hematopoietic and developmental abnormalities resembling DBA. Our data suggest that the rps19-deficient phenotype is mediated by dysregulation of deltaNp63 and p53. During gastrulation, deltaNp63 is required for specification of nonneural ectoderm and its up-regulation suppresses neural differentiation, thus contributing to brain/craniofacial defects. In rps19-deficient embryos, deltaNp63 is induced in erythroid progenitors and may contribute to blood defects. We have shown that suppression of p53 and deltaNp63 alleviates the rps19-deficient phenotypes. Mutations in other ribosomal proteins, such as S8, S11, and S18, also lead to up-regulation of p53 pathway, suggesting it is a common response to ribosomal protein deficiency. Our finding provides new insights into pathogenesis of DBA. Ribosomal stress syndromes represent a broader spectrum of human congenital diseases caused by genotoxic stress; therefore, imbalance of p53 family members may become a new target for therapeutics.
View details for DOI 10.1182/blood-2008-01-132290
View details for Web of Science ID 000261513400057
View details for PubMedID 18515656
The role of CREB as a proto-oncogene in hematopoiesis and in acute myeloid leukemia
2005; 7 (4): 351-362
CREB is a transcription factor that functions in glucose homeostasis, growth factor-dependent cell survival, and memory. In this study, we describe a role of CREB in human cancer. CREB overexpression is associated with increased risk of relapse and decreased event-free survival. CREB levels are elevated in blast cells from patients with acute myeloid leukemia. To understand the role of CREB in leukemogenesis, we studied the biological consequences of CREB overexpression in primary human leukemia cells, leukemia cell lines, and transgenic mice. Our results demonstrate that CREB promotes abnormal proliferation and survival of myeloid cells in vitro and in vivo through upregulation of specific target genes. Thus, we report that CREB is implicated in myeloid cell transformation.
View details for Web of Science ID 000228741700010
View details for PubMedID 15837624
Ubistatins inhibit proteasome-dependent degradation by binding the ubiquitin chain
2004; 306 (5693): 117-120
To identify previously unknown small molecules that inhibit cell cycle machinery, we performed a chemical genetic screen in Xenopus extracts. One class of inhibitors, termed ubistatins, blocked cell cycle progression by inhibiting cyclin B proteolysis and inhibited degradation of ubiquitinated Sic1 by purified proteasomes. Ubistatins blocked the binding of ubiquitinated substrates to the proteasome by targeting the ubiquitin-ubiquitin interface of Lys(48)-linked chains. The same interface is recognized by ubiquitin-chain receptors of the proteasome, indicating that ubistatins act by disrupting a critical protein-protein interaction in the ubiquitin-proteasome system.
View details for Web of Science ID 000224304000050
View details for PubMedID 15459393
Development of protacs to target cancer-promoting proteins for ubiquitination and degradation
MOLECULAR & CELLULAR PROTEOMICS
2003; 2 (12): 1350-1358
The proteome contains hundreds of proteins that in theory could be excellent therapeutic targets for the treatment of human diseases. However, many of these proteins are from functional classes that have never been validated as viable candidates for the development of small molecule inhibitors. Thus, to exploit fully the potential of the Human Genome Project to advance human medicine, there is a need to develop generic methods of inhibiting protein activity that do not rely on the target protein's function. We previously demonstrated that a normally stable protein, methionine aminopeptidase-2 or MetAP-2, could be artificially targeted to an Skp1-Cullin-F-box (SCF) ubiquitin ligase complex for ubiquitination and degradation through a chimeric bridging molecule or Protac (proteolysis targeting chimeric molecule). This Protac consisted of an SCF(beta-TRCP)-binding phosphopeptide derived from IkappaBalpha linked to ovalicin, which covalently binds MetAP-2. In this study, we employed this approach to target two different proteins, the estrogen (ER) and androgen (AR) receptors, which have been implicated in the progression of breast and prostate cancer, respectively. We show here that an estradiol-based Protac can enforce the ubiquitination and degradation of the alpha isoform of ER in vitro, and a dihydroxytestosterone-based Protac introduced into cells promotes the rapid disappearance of AR in a proteasome-dependent manner. Future improvements to this technology may yield a general approach to treat a number of human diseases, including cancer.
View details for DOI 10.1074/mcp.T300009-MCP200
View details for Web of Science ID 000187250900010
View details for PubMedID 14525958
Protacs: Chimeric molecules that target proteins to the Skp1-Cullin-F box complex for ubiquitination and degradation
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2001; 98 (15): 8554-8559
The intracellular levels of many proteins are regulated by ubiquitin-dependent proteolysis. One of the best-characterized enzymes that catalyzes the attachment of ubiquitin to proteins is a ubiquitin ligase complex, Skp1-Cullin-F box complex containing Hrt1 (SCF). We sought to artificially target a protein to the SCF complex for ubiquitination and degradation. To this end, we tested methionine aminopeptidase-2 (MetAP-2), which covalently binds the angiogenesis inhibitor ovalicin. A chimeric compound, protein-targeting chimeric molecule 1 (Protac-1), was synthesized to recruit MetAP-2 to SCF. One domain of Protac-1 contains the I kappa B alpha phosphopeptide that is recognized by the F-box protein beta-TRCP, whereas the other domain is composed of ovalicin. We show that MetAP-2 can be tethered to SCF(beta-TRCP), ubiquitinated, and degraded in a Protac-1-dependent manner. In the future, this approach may be useful for conditional inactivation of proteins, and for targeting disease-causing proteins for destruction.
View details for Web of Science ID 000169967000064
View details for PubMedID 11438690
Net1 stimulates RNA polymerase I transcription and regulates nucleolar structure independently of controlling mitotic exit
2001; 8 (1): 45-55
The budding yeast RENT complex, consisting of at least three proteins (Net1, Cdc14, Sir2), is anchored to the nucleolus by Net1. RENT controls mitotic exit, nucleolar silencing, and nucleolar localization of Nop1. Here, we report two new functions of Net1. First, Net1 directly binds Pol I and stimulates rRNA synthesis both in vitro and in vivo. Second, Net1 modulates nucleolar structure by regulating rDNA morphology and proper localization of multiple nucleolar antigens, including Pol I. Importantly, we show that the nucleolar and previously described cell cycle functions of the RENT complex can be uncoupled by a dominant mutant allele of CDC14. The independent functions of Net1 link a key event in the cell cycle to nucleolar processes that are fundamental to cell growth.
View details for Web of Science ID 000170081900008
View details for PubMedID 11511359
MicroRNA-34b promoter hypermethylation induces CREB overexpression and contributes to myeloid transformation.
2013; 98 (4): 602-610
MicroRNA-34b down-regulation in acute myeloid leukemia was previously shown to induce CREB overexpression, thereby causing leukemia proliferation in vitro and in vivo. The role of microRNA-34b and CREB in patients with myeloid malignancies has never been evaluated. We examined microRNA-34b expression and the methylation status of its promoter in cells from patients diagnosed with myeloid malignancies. We used gene expression profiling to identify signatures of myeloid transformation. We established that microRNA-34b has suppressor ability and that CREB has oncogenic potential in primary bone marrow cell cultures and in vivo. MicroRNA-34b was found to be up-regulated in pediatric patients with juvenile myelomonocytic leukemia (n=17) and myelodysplastic syndromes (n=28), but was down-regulated in acute myeloid leukemia patients at diagnosis (n=112). Our results showed that hypermethylation of the microRNA-34b promoter occurred in 66% of cases of acute myeloid leukemia explaining the low microRNA-34b levels and CREB overexpression, whereas preleukemic myelodysplastic syndromes and juvenile myelomonocytic leukemia were not associated with hypermethylation or CREB overexpression. In paired samples taken from the same patients when they had myelodysplastic syndrome and again during the subsequent acute myeloid leukemia, we confirmed microRNA-34b promoter hypermethylation at leukemia onset, with 103 CREB target genes differentially expressed between the two disease stages. This subset of CREB targets was confirmed to associate with high-risk myelodysplastic syndromes in a separate cohort of patients (n=20). Seventy-eight of these 103 CREB targets were also differentially expressed between healthy samples (n=11) and de novo acute myeloid leukemia (n=72). Further, low microRNA-34b and high CREB expression levels induced aberrant myelopoiesis through CREB-dependent pathways in vitro and in vivo. In conclusion, we suggest that microRNA-34b controls CREB expression and contributes to myeloid transformation from both healthy bone marrow and myelodysplastic syndromes. We identified a subset of CREB target genes that represents a novel transcriptional network that may control myeloid transformation.
View details for DOI 10.3324/haematol.2012.070664
View details for PubMedID 23100280
Increased Abscess Formation and Defective Chemokine Regulation in CREB Transgenic Mice
2013; 8 (2)
Cyclic AMP-response element-binding protein (CREB) is a transcription factor implicated in growth factor-dependent cell proliferation and survival, glucose homeostasis, spermatogenesis, circadian rhythms, and synaptic plasticity associated with memory. To study the phenotype of CREB overexpression in vivo, we generated CREB transgenic (TG) mice in which a myeloid specific hMRP8 promoter drives CREB expression. CREB TG mice developed spontaneous skin abscesses more frequently than wild type (WT) mice. To understand the role of CREB in myeloid function and innate immunity, chemokine expression in bone marrow derived macrophages (BMDMs) from CREB TG mice were compared with BMDMs from WT mice. Our results demonstrated decreased Keratinocyte-derived cytokine (KC) in CREB TG BMDMs but not TNF? protein production in response to lipid A (LPA). In addition, mRNA expression of KC and IL-1? (Interleukin)-1? was decreased in CREB TG BMDMs; however, there was no difference in the mRNA expression of TNF?, MCP-1, IL-6 and IL-12p40. The mRNA expression of IL-1RA and IL-10 was decreased in response to LPA. Nuclear factor kappa B (NF?B) expression and a subset of its target genes were upregulated in CREB TG mouse BMDMs. Although neutrophil migration was the same in both CREB TG and WT mice, Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was significantly increased in neutrophils from CREB TG mice. Taken together, CREB overexpression in myeloid cells results in increased abscess formation in vivo and aberrant cytokine and chemokine response, and neutrophil function in vitro.
View details for DOI 10.1371/journal.pone.0055866
View details for Web of Science ID 000315153400169
View details for PubMedID 23405224
Identification of somatic and germline mutations using whole exome sequencing of congenital acute lymphoblastic leukemia
Acute lymphoblastic leukemia (ALL) diagnosed within the first month of life is classified as congenital ALL and has a significantly worse outcome than ALL diagnosed in older children. This suggests that congenital ALL is a biologically different disease, and thus may be caused by a distinct set of mutations. To understand the somatic and germline mutations contributing to congenital ALL, the protein-coding regions in the genome were captured and whole-exome sequencing was employed for the identification of single-nucleotide variants and small insertion and deletions in the germlines as well as the primary tumors of four patients with congenital ALL.Exome sequencing was performed on Illumina GAIIx or HiSeq 2000 (Illumina, San Diego, California). Reads were aligned to the human reference genome and the Genome Analysis Toolkit was used for variant calling. An in-house developed Ensembl-based variant annotator was used to richly annotate each variant.There were 1-3 somatic, protein-damaging mutations per ALL, including a novel mutation in Sonic Hedgehog. Additionally, there were many germline mutations in genes known to be associated with cancer predisposition, as well as genes involved in DNA repair.This study is the first to comprehensively characterize the germline and somatic mutational profile of all protein-coding genes patients with congenital ALL. These findings identify potentially important therapeutic targets, as well as insight into possible cancer predisposition genes.
View details for DOI 10.1186/1471-2407-13-55
View details for Web of Science ID 000315027900001
View details for PubMedID 23379653
Sox4 cooperates with CREB in myeloid transformation
2012; 120 (1): 155-165
The cAMP response element-binding protein (CREB) is a nuclear transcription factor that is critical for normal and neoplastic hematopoiesis. Previous studies have demonstrated that CREB is a proto-oncogene whose overexpression promotes cellular proliferation in hematopoietic cells. Transgenic mice that overexpress CREB in myeloid cells develop a myeloproliferative disease with splenomegaly and aberrant myelopoiesis. However, CREB overexpressing mice do not spontaneously develop acute myeloid leukemia. In this study, we used retroviral insertional mutagenesis to identify genes that accelerate leukemia in CREB transgenic mice. Our mutagenesis screen identified several integration sites, including oncogenes Gfi1, Myb, and Ras. The Sox4 transcription factor was identified by our screen as a gene that cooperates with CREB in myeloid leukemogenesis. We show that the transduction of CREB transgenic mouse bone marrow cells with a Sox4 retrovirus increases survival and self-renewal of cells in vitro. Furthermore, leukemic blasts from the majority of acute myeloid leukemia patients have higher CREB, phosphorylated CREB, and Sox 4 protein expression. Sox4 transduction of mouse bone marrow cells results in increased expression of CREB target genes. We also demonstrate that CREB is a direct target of Sox4 by chromatin immunoprecipitation assays. These results indicate that Sox4 and CREB cooperate and contribute to increased proliferation of hematopoietic progenitor cells.
View details for DOI 10.1182/blood-2011-05-357418
View details for Web of Science ID 000307411100023
View details for PubMedID 22627767
The neutropenic diet... still ageless?
Oncology (Williston Park, N.Y.)
2012; 26 (6): 586-?
View details for PubMedID 22870544
- Editorial: Granulopoiesis versus monopoiesis: a consequence of transcription factors dancing with the right partners JOURNAL OF LEUKOCYTE BIOLOGY 2011; 90 (4): 637-638
Tubacin suppresses proliferation and induces apoptosis of acute lymphoblastic leukemia cells
LEUKEMIA & LYMPHOMA
2011; 52 (8): 1544-1555
Over the past decade, histone deacetylase inhibitors have increasingly been used to treat various malignancies. Tubacin (tubulin acetylation inducer) is a small molecule that inhibits histone deacetylase 6 (HDAC6) and induces acetylation of ?-tubulin. We observed a higher antiproliferative effect of tubacin in acute lymphoblastic leukemia (ALL) cells than in normal hematopoietic cells. Treatment with tubacin led to the induction of apoptotic pathways in both pre-B and T cell ALL cells at a 50% inhibitory concentration (IC(50)) of low micromolar concentrations. Acetylation of ?-tubulin increases within the first 30?min following treatment of ALL cells with tubacin. We also observed an accumulation of polyubiquitinated proteins and poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, the signaling pathways activated by tubacin appear to be distinct from those observed in multiple myeloma. In this article, we demonstrate that tubacin enhances the effects of chemotherapy to treat primary ALL cells in vitro and in vivo. These results suggest that targeting HDAC6 alone or in combination with chemotherapy could provide a novel approach to treat ALL.
View details for DOI 10.3109/10428194.2011.570821
View details for Web of Science ID 000292747300021
View details for PubMedID 21699378
Increasing Diversity in Pediatric Hematology/Oncology
PEDIATRIC BLOOD & CANCER
2011; 57 (1): 147-152
Diversity is necessary for the survival and success of both biological and social systems including societies. There is a lack of diversity, particularly the proportion of women and minorities in leadership positions, within medicine [Leadley. AAMC 2009. Steinecke and Terrell. Acad Med 2010;85:236-245]. In 2009 a group of ASPHO members recognized the need to support the career advancement of women and minority members. This article reports the results of a survey designed to characterize the comparative career pathway experience of women and minority ASPHO members.A group of ASPHO members modified a published Faculty Worklife survey [Pribbenow et al. High Educ Policy 2010;23:17-38] for use by Pediatric Hematologist-Oncologists (PHOs). A link to an online version of the survey was sent to all ASPHO members.Of 1,228 ASPHO members polled, 213 responded (17%). Women and minority PHOs reported less satisfaction than their counterparts on 70 of the 90 issues addressed in the survey including the hiring process, access to resources as well as integration and satisfaction with their organizations. Women also expressed greater dissatisfaction with issues of work-life balance, support for family obligations and personal health.The current literature suggests that there are significant disparities in career opportunities, compensation and satisfaction for women compared to men and minority compared to majority faculty in academic medicine [Nivet. J Vasc Surg 2010;51:53S-58S; Peterson et al. J Gen Intern Med 2004;19:259-265; DesRoches et al. Acad Med 2010;85:631-639; Castillo-Page. AAMC 2008]. Our data, derived from a survey of ASPHO members, suggests that this holds true for PHOs as well.
View details for DOI 10.1002/pbc.22977
View details for Web of Science ID 000290452400024
View details for PubMedID 21284078
The Role of HDAC6 in Cancer
JOURNAL OF BIOMEDICINE AND BIOTECHNOLOGY
Histone deacetylase 6 (HDAC6), a member of the HDAC family whose major substrate is ?-tubulin, has become a target for drug development to treat cancer due to its major contribution in oncogenic cell transformation. Overexpression of HDAC6 correlates with tumorigenesis and improved survival; therefore, HDAC6 may be used as a marker for prognosis. Previous work demonstrated that in multiple myeloma cells, inhibition of HDAC6 results in apoptosis. Furthermore, HDAC6 is required for the activation of heat-shock factor 1 (HSF1), an activator of heat-shock protein encoding genes (HSPs) and CYLD, a cylindromatosis tumor suppressor gene. HDAC6 contributes to cancer metastasis since its upregulation increases cell motility in breast cancer MCF-7 cells and its interaction with cortactin regulates motility. HDAC6 also affects transcription and translation by regulating the heat-shock protein 90 (Hsp90) and stress granules (SGs), respectively. This review will discuss the role of HDAC6 in the pathogenesis and treatment of cancer.
View details for DOI 10.1155/2011/875824
View details for Web of Science ID 000285611100001
View details for PubMedID 21076528
Self-Renewal of Acute Lymphocytic Leukemia Cells Is Limited by the Hedgehog Pathway Inhibitors Cyclopamine and IPI-926
2010; 5 (12)
Conserved embryonic signaling pathways such as Hedgehog (Hh), Wingless and Notch have been implicated in the pathogenesis of several malignancies. Recent data suggests that Hh signaling plays a role in normal B-cell development, and we hypothesized that Hh signaling may be important in precursor B-cell acute lymphocytic leukemia (B-ALL). We found that the expression of Hh pathway components was common in human B-ALL cell lines and clinical samples. Moreover, pathway activity could be modulated by Hh ligand or several pathway inhibitors including cyclopamine and the novel SMOOTHENED (SMO) inhibitor IPI-926. The inhibition of pathway activity primarily impacted highly clonogenic B-ALL cells expressing aldehyde dehydrogenase (ALDH) by limiting their self-renewal potential both in vitro and in vivo. These data demonstrate that Hh pathway activation is common in B-ALL and represents a novel therapeutic target regulating self-renewal and persistence of the malignant clone.
View details for DOI 10.1371/journal.pone.0015262
View details for Web of Science ID 000285792500027
View details for PubMedID 21203400
The Role of the Transcription Factor CREB in Immune Function
JOURNAL OF IMMUNOLOGY
2010; 185 (11): 6413-6419
CREB is a transcription factor that regulates diverse cellular responses, including proliferation, survival, and differentiation. CREB is induced by a variety of growth factors and inflammatory signals and subsequently mediates the transcription of genes containing a cAMP-responsive element. Several immune-related genes possess this cAMP-responsive element, including IL-2, IL-6, IL-10, and TNF-?. In addition, phosphorylated CREB has been proposed to directly inhibit NF-?B activation by blocking the binding of CREB binding protein to the NF-?B complex, thereby limiting proinflammatory responses. CREB also induces an antiapoptotic survival signal in monocytes and macrophages. In T and B cells, CREB activation promotes proliferation and survival and differentially regulates Th1, Th2, and Th17 responses. Finally, CREB activation is required for the generation and maintenance of regulatory T cells. This review summarizes current advances involving CREB in immune function--a role that is continually being defined.
View details for DOI 10.4049/jimmunol.1001829
View details for Web of Science ID 000284311500004
View details for PubMedID 21084670
Germline CBL mutations cause developmental abnormalities and predispose to juvenile myelomonocytic leukemia
2010; 42 (9): 794-U93
CBL encodes a member of the Cbl family of proteins, which functions as an E3 ubiquitin ligase. We describe a dominant developmental disorder resulting from germline missense CBL mutations, which is characterized by impaired growth, developmental delay, cryptorchidism and a predisposition to juvenile myelomonocytic leukemia (JMML). Some individuals experienced spontaneous regression of their JMML but developed vasculitis later in life. Importantly, JMML specimens from affected children show loss of the normal CBL allele through acquired isodisomy. Consistent with these genetic data, the common p.371Y>H altered Cbl protein induces cytokine-independent growth and constitutive phosphorylation of ERK, AKT and S6 only in hematopoietic cells in which normal Cbl expression is reduced by RNA interference. We conclude that germline CBL mutations have developmental, tumorigenic and functional consequences that resemble disorders that are caused by hyperactive Ras/Raf/MEK/ERK signaling and include neurofibromatosis type 1, Noonan syndrome, Costello syndrome, cardiofaciocutaneous syndrome and Legius syndrome.
View details for DOI 10.1038/ng.641
View details for Web of Science ID 000281388400018
View details for PubMedID 20694012
Targeting CREB for Cancer Therapy: Friend or Foe
CURRENT CANCER DRUG TARGETS
2010; 10 (4): 384-391
The cyclic-AMP response element-binding protein (CREB) is a nuclear transcription factor activated by phosphorylation at Ser133 by multiple serine/threonine (Ser/Thr) kinases. Upon phosphorylation, CREB binds the transcriptional co-activator, CBP (CREB-binding protein), to initiate CREB-dependent gene transcription. CREB is a critical regulator of cell differentiation, proliferation and survival in the nervous system. Recent studies have shown that CREB is involved tumor initiation, progression and metastasis, supporting its role as a proto-oncogene. Overexpression and over-activation of CREB were observed in cancer tissues from patients with prostate cancer, breast cancer, non-small-cell lung cancer and acute leukemia while down-regulation of CREB in several distinct cancer cell lines resulted in inhibition of cell proliferation and induction of apoptosis, suggesting that CREB may be a promising target for cancer therapy. Although CREB, as a transcription factor, is a challenging target for small molecules, various small molecules have been discovered to inhibit CREB phosphorylation, CREB-DNA, or CREB-CBP interaction. These results suggest that CREB is a suitable transcription factor for drug targeting and therefore targeting CREB could represent a novel strategy for cancer therapy.
View details for Web of Science ID 000279868900003
View details for PubMedID 20370681
Macroautophagy modulates cellular response to proteasome inhibitors in cancer therapy
DRUG RESISTANCE UPDATES
2010; 13 (3): 87-92
Macroautophagy and the ubiquitin-proteasome system are two complementary pathways for protein degradation. The former degrades long-lived proteins and damaged organelles while the later degrades short-lived proteins. Recent findings indicate that suppression of the ubiquitin-proteasome system by proteasome inhibitors induces macroautophagy through multiple pathways, including (1) accumulation of ubiquitinated proteins and activation of HDAC6; (2) activation of the IRE1-JNK pathway; (3) proteasomal stabilization of ATF4; (4) inhibition of mTOR complex 1 signaling; (5) reduced proteasomal degradation of LC3. Induction of macroautophagy attenuates the antitumor effect of proteasome inhibitors in various types of cancer. These findings suggest that inhibition of macroautophagy may represent a novel strategy to enhance cellular sensitivity to proteasome inhibition.
View details for DOI 10.1016/j.drup.2010.04.003
View details for Web of Science ID 000279649500004
View details for PubMedID 20462785
Targeting steroid hormone receptors for ubiquitination and degradation in breast and prostate cancer
2008; 27 (57): 7201-7211
Proteolysis targeting chimeric molecules (Protacs) target proteins for destruction by exploiting the ubiquitin-dependent proteolytic system of eukaryotic cells. We designed two Protacs that contain the peptide 'degron' from hypoxia-inducible factor-1alpha, which binds to the Von-Hippel-Lindau (VHL) E3 ubiquitin ligase complex, linked to either dihydroxytestosterone that targets the androgen receptor (AR; Protac-A), or linked to estradiol (E2) that targets the estrogen receptor-alpha (ERalpha; Protac-B). We hypothesized that these Protacs would recruit hormone receptors to the VHL E3 ligase complex, resulting in the degradation of receptors, and decreased proliferation of hormone-dependent cell lines. Treatment of estrogen-dependent breast cancer cells with Protac-B induced the degradation of ERalpha in a proteasome-dependent manner. Protac-B inhibited the proliferation of ERalpha-dependent breast cancer cells by inducing G(1) arrest, inhibition of retinoblastoma phosphorylation and decreasing expression of cyclin D1, progesterone receptors A and B. Protac-B treatment did not affect the proliferation of estrogen-independent breast cancer cells that lacked ERalpha expression. Similarly, Protac-A treatment of androgen-dependent prostate cancer cells induced G(1) arrest but did not affect cells that do not express AR. Our results suggest that Protacs specifically inhibit the proliferation of hormone-dependent breast and prostate cancer cells through degradation of the ERalpha and AR, respectively.
View details for DOI 10.1038/onc.2008.320
View details for Web of Science ID 000261384100007
View details for PubMedID 18794799
CREB is a critical regulator of normal hematopoiesis and leukemogenesis
2008; 111 (3): 1182-1192
The cAMP-responsive element binding protein (CREB) is a 43-kDa nuclear transcription factor that regulates cell growth, memory, and glucose homeostasis. We showed previously that CREB is amplified in myeloid leukemia blasts and expressed at higher levels in leukemia stem cells from patients with myeloid leukemia. CREB transgenic mice develop myeloproliferative disease after 1 year, but not leukemia, suggesting that CREB contributes to but is not sufficient for leukemogenesis. Here, we show that CREB is most highly expressed in lineage negative hematopoietic stem cells (HSCs). To understand the role of CREB in hematopoietic progenitors and leukemia cells, we examined the effects of RNA interference (RNAi) to knock down CREB expression in vitro and in vivo. Transduction of primary HSCs or myeloid leukemia cells with lentiviral CREB shRNAs resulted in decreased proliferation of stem cells, cell- cycle abnormalities, and inhibition of CREB transcription. Mice that received transplants of bone marrow transduced with CREB shRNA had decreased committed progenitors compared with control mice. Mice injected with Ba/F3 cells expressing either Bcr-Abl wild-type or T315I mutation with CREB shRNA had delayed leukemic infiltration by bioluminescence imaging and prolonged median survival. Our results suggest that CREB is critical for normal myelopoiesis and leukemia cell proliferation.
View details for DOI 10.1182/blood-blood-2007-04-083600
View details for Web of Science ID 000252792900040
View details for PubMedID 17975014
Expression profile of CREB knockdown in myeloid leukemia cells.
2008; 8: 264-?
The cAMP Response Element Binding Protein, CREB, is a transcription factor that regulates cell proliferation, differentiation, and survival in several model systems, including neuronal and hematopoietic cells. We demonstrated that CREB is overexpressed in acute myeloid and leukemia cells compared to normal hematopoietic stem cells. CREB knockdown inhibits leukemic cell proliferation in vitro and in vivo, but does not affect long-term hematopoietic reconstitution.To understand downstream pathways regulating CREB, we performed expression profiling with RNA from the K562 myeloid leukemia cell line transduced with CREB shRNA.By combining our expression data from CREB knockdown cells with prior ChIP data on CREB binding we were able to identify a list of putative CREB regulated genes. We performed extensive analyses on the top genes in this list as high confidence CREB targets. We found that this list is enriched for genes involved in cancer, and unexpectedly, highly enriched for histone genes. Furthermore, histone genes regulated by CREB were more likely to be specifically expressed in hematopoietic lineages. Decreased expression of specific histone genes was validated in K562, TF-1, and primary AML cells transduced with CREB shRNA.We have identified a high confidence list of CREB targets in K562 cells. These genes allow us to begin to understand the mechanisms by which CREB contributes to acute leukemia. We speculate that regulation of histone genes may play an important role by possibly altering the regulation of DNA replication during the cell cycle.
View details for DOI 10.1186/1471-2407-8-264
View details for PubMedID 18801183
Expression of cyclic adenosine monophosphate response-element binding protein in acute leukemia
2002; 99 (7): 2617-2619
Cyclic adenosine monophosphate response-element binding protein (CREB) is a nuclear protein that regulates expression of genes that control cell proliferation, differentiation, and survival. To analyze CREB expression in leukemia cells, we conducted Western blot analysis of bone marrow cells obtained from patients with acute lymphoblastic leukemia, patients with acute myeloid leukemia, and patients without active leukemia. CREB was expressed at a higher frequency in bone marrow cells from patients with acute lymphoid or myeloid leukemia than in patients with leukemia remission or without leukemia. Our results indicate that CREB expression could be a useful marker for leukemia in patients with acute disease and suggest a role for CREB in leukemogenesis.
View details for Web of Science ID 000174559300051
View details for PubMedID 11895805