- Cancer > Radiation Oncology
- Cancer > Thoracic Oncology
- Radiation Oncology
- Radiation Therapy
Cancer Biology Graduate Program Admissions Committee, Stanford University (2012 - Present)
Stem Cell Biology & Regenerative Medicine Graduate Program Admissions Committee, Stanford University (2013 - Present)
Medical Scientist Training Program (MSTP) Admissions Committee, Stanford University (2011 - Present)
Honors & Awards
Thomas Temple Hoopes Prize for outstanding senior thesis, Harvard University (1997)
Medical Scientist Training Program, Stanford University (1997-2004)
Franklin G. Ebaugh, Jr. Award for Research, Department of Medicine, Stanford University (2005)
Annual Meeting Basic Science Travel Grant Award, American Society for Therapeutic Radiology and Oncology (ASTRO) (2006)
Holman Research Pathway, American Board of Radiology (ABR) (2006-2009)
Roentgen Resident/Fellow Research Award, Radiological Society of North America (RSNA) (2008)
ASTRO Residents in Radiation Oncology Research Seed Grant, American Society for Therapeutic Radiology and Oncology (ASTRO) (2006-2008)
RSNA Research Resident/Fellow Grant, Radiological Society of North America (RSNA) (2007-2009)
Malcolm A. Bagshaw Award, Stanford University (2009)
Donald E. and Delia B. Baxter Foundation Faculty Scholar Award, Donald E. and Delia B. Baxter Foundation (2011-2012)
Henry S. Kaplan Memorial Prize for Teaching, Stanford University (2012)
Sidney Kimmel Scholar Award, Sidney Kimmel Foundation (2010-2013)
Edward Mallinckrodt, Jr. Foundation Grant, Edward Mallinckrodt, Jr. Foundation (2010-2014)
Doris Duke Clinical Scientist Development Award, Doris Duke Charitable Foundation (2010-2014)
Lung Cancer Research Program Promising Clinician Research Award, Department of Defense (2012-2014)
Walter H. Coulter Translational Research Grant, Walter H. Coulter Foundation (2013-2014)
V Foundation Scholar Grant, V Foundation (2013-2015)
NIH Director's New Innovator Award, National Institute of Health (2013-2018)
Boards, Advisory Committees, Professional Organizations
Member, American Society for Therapeutic Radiology and Oncology (ASTRO) (2004 - Present)
Member, Radiological Society of North America (RSNA) (2004 - Present)
Member, International Society for Stem Cell Research (ISSCR) (2010 - Present)
Member, International Association for the Study of Lung Cancer (IASLC) (2011 - Present)
Residency:Stanford University Radiation Oncology Residency (2009) CA
Internship:Stanford University School of Medicine (2005) CA
Board Certification: Radiation Oncology, American Board of Radiology (2010)
Medical Education:Stanford University (2004) CA
MD, Stanford University (2004)
PhD, Stanford University, Biophysics (2004)
AB, Harvard College, Biochemical Sciences (1997)
Current Research and Scholarly Interests
My laboratory focuses on two main areas: 1) cancer stem cell biology and its implications for therapy and 2) development of genomics-based biomarkers for identifying the presence of malignant cells (diagnostic), predicting outcome (prognostic), and predicting response to therapy (predictive). Areas of study include cancers of the lung, breast, and gastrointestinal system. We are also interested in developing a deeper molecular understanding of normal and cancer stem cells, including identifying pathways and genes important for survival and self-renewal. Additionally, we are developing methods for overcoming resistance mechanisms to radiotherapy and chemotherapy in cancer stem cells. We employ the tools of cancer genomics, including high throughput sequencing for detecting cancer mutations and quantifying gene expression. Clinically I specialize in the treatment of lung cancer and applications of stereotactic ablative radiotherapy and perform both prospective and retrospective clinical studies.
Independent Studies (16)
- Directed Reading in Cancer Biology
CBIO 299 (Aut, Win, Spr, Sum)
- Directed Reading in Radiation Oncology
RADO 299 (Aut, Win, Spr, Sum)
- Directed Reading in Stem Cell Biology and Regenerative Medicine
STEMREM 299 (Win, Spr)
- Early Clinical Experience in Radiation Oncology
RADO 280 (Aut, Win, Spr, Sum)
- Graduate Research
CBIO 399 (Aut, Win, Spr, Sum)
- Graduate Research
RADO 399 (Aut, Win, Spr, Sum)
- Graduate Research
STEMREM 399 (Aut, Win, Spr, Sum)
- Independent Research and Study
PHYSICS 190 (Aut, Spr, Sum)
- Medical Scholars Research
RADO 370 (Aut, Win, Spr, Sum)
- Medical Scholars Research
STEMREM 370 (Win, Spr)
- Out-of-Department Advanced Research Laboratory in Bioengineering
BIOE 191X (Aut, Win, Spr)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Aut, Win, Spr)
- Readings in Radiation Biology
RADO 101 (Aut, Win, Spr, Sum)
- Teaching in Cancer Biology
CBIO 260 (Spr)
- Undergraduate Research
RADO 199 (Aut, Win, Spr, Sum)
- Undergraduate Research
STEMREM 199 (Aut, Win, Spr, Sum)
- Directed Reading in Cancer Biology
Graduate and Fellowship Programs
Distinct biological subtypes and patterns of genome evolution in lymphoma revealed by circulating tumor DNA
SCIENCE TRANSLATIONAL MEDICINE
2016; 8 (364)
Patients with diffuse large B cell lymphoma (DLBCL) exhibit marked diversity in tumor behavior and outcomes, yet the identification of poor-risk groups remains challenging. In addition, the biology underlying these differences is incompletely understood. We hypothesized that characterization of mutational heterogeneity and genomic evolution using circulating tumor DNA (ctDNA) profiling could reveal molecular determinants of adverse outcomes. To address this hypothesis, we applied cancer personalized profiling by deep sequencing (CAPP-Seq) analysis to tumor biopsies and cell-free DNA samples from 92 lymphoma patients and 24 healthy subjects. At diagnosis, the amount of ctDNA was found to strongly correlate with clinical indices and was independently predictive of patient outcomes. We demonstrate that ctDNA genotyping can classify transcriptionally defined tumor subtypes, including DLBCL cell of origin, directly from plasma. By simultaneously tracking multiple somatic mutations in ctDNA, our approach outperformed immunoglobulin sequencing and radiographic imaging for the detection of minimal residual disease and facilitated noninvasive identification of emergent resistance mutations to targeted therapies. In addition, we identified distinct patterns of clonal evolution distinguishing indolent follicular lymphomas from those that transformed into DLBCL, allowing for potential noninvasive prediction of histological transformation. Collectively, our results demonstrate that ctDNA analysis reveals biological factors that underlie lymphoma clinical outcomes and could facilitate individualized therapy.
View details for DOI 10.1126/scitranslmed.aai8545
View details for Web of Science ID 000389448100006
View details for PubMedID 27831904
Role of KEAP1/NRF2 and TP53 Mutations in Lung Squamous Cell Carcinoma Development and Radiation Resistance.
Lung squamous cell carcinoma (LSCC) pathogenesis remains incompletely understood, and biomarkers predicting treatment response remain lacking. Here, we describe novel murine LSCC models driven by loss of Trp53 and Keap1, both of which are frequently mutated in human LSCCs. Homozygous inactivation of Keap1 or Trp53 promoted airway basal stem cell (ABSC) self-renewal, suggesting that mutations in these genes lead to expansion of mutant stem cell clones. Deletion of Trp53 and Keap1 in ABSCs, but not more differentiated tracheal cells, produced tumors recapitulating histologic and molecular features of human LSCCs, indicating that they represent the likely cell of origin in this model. Deletion of Keap1 promoted tumor aggressiveness, metastasis, and resistance to oxidative stress and radiotherapy (RT). KEAP1/NRF2 mutation status predicted risk of local recurrence after RT in patients with non-small lung cancer (NSCLC) and could be noninvasively identified in circulating tumor DNA. Thus, KEAP1/NRF2 mutations could serve as predictive biomarkers for personalization of therapeutic strategies for NSCLCs.We developed an LSCC mouse model involving Trp53 and Keap1, which are frequently mutated in human LSCCs. In this model, ABSCs are the cell of origin of these tumors. KEAP1/NRF2 mutations increase radioresistance and predict local tumor recurrence in radiotherapy patients. Our findings are of potential clinical relevance and could lead to personalized treatment strategies for tumors with KEAP1/NRF2 mutations. Cancer Discov; 7(1); 86-101. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 1.
View details for PubMedID 27663899
View details for PubMedCentralID PMC5222718
Circulating tumour DNA profiling reveals heterogeneity of EGFR inhibitor resistance mechanisms in lung cancer patients
Circulating tumour DNA (ctDNA) analysis facilitates studies of tumour heterogeneity. Here we employ CAPP-Seq ctDNA analysis to study resistance mechanisms in 43 non-small cell lung cancer (NSCLC) patients treated with the third-generation epidermal growth factor receptor (EGFR) inhibitor rociletinib. We observe multiple resistance mechanisms in 46% of patients after treatment with first-line inhibitors, indicating frequent intra-patient heterogeneity. Rociletinib resistance recurrently involves MET, EGFR, PIK3CA, ERRB2, KRAS and RB1. We describe a novel EGFR L798I mutation and find that EGFR C797S, which arises in ∼33% of patients after osimertinib treatment, occurs in <3% after rociletinib. Increased MET copy number is the most frequent rociletinib resistance mechanism in this cohort and patients with multiple pre-existing mechanisms (T790M and MET) experience inferior responses. Similarly, rociletinib-resistant xenografts develop MET amplification that can be overcome with the MET inhibitor crizotinib. These results underscore the importance of tumour heterogeneity in NSCLC and the utility of ctDNA-based resistance mechanism assessment.
View details for DOI 10.1038/ncomms11815
View details for Web of Science ID 000378007200001
View details for PubMedID 27283993
View details for PubMedCentralID PMC4906406
Integrated digital error suppression for improved detection of circulating tumor DNA
2016; 34 (5): 547-555
High-throughput sequencing of circulating tumor DNA (ctDNA) promises to facilitate personalized cancer therapy. However, low quantities of cell-free DNA (cfDNA) in the blood and sequencing artifacts currently limit analytical sensitivity. To overcome these limitations, we introduce an approach for integrated digital error suppression (iDES). Our method combines in silico elimination of highly stereotypical background artifacts with a molecular barcoding strategy for the efficient recovery of cfDNA molecules. Individually, these two methods each improve the sensitivity of cancer personalized profiling by deep sequencing (CAPP-Seq) by about threefold, and synergize when combined to yield ∼15-fold improvements. As a result, iDES-enhanced CAPP-Seq facilitates noninvasive variant detection across hundreds of kilobases. Applied to non-small cell lung cancer (NSCLC) patients, our method enabled biopsy-free profiling of EGFR kinase domain mutations with 92% sensitivity and >99.99% specificity at the variant level, and with 90% sensitivity and 96% specificity at the patient level. In addition, our approach allowed monitoring of NSCLC ctDNA down to 4 in 10(5) cfDNA molecules. We anticipate that iDES will aid the noninvasive genotyping and detection of ctDNA in research and clinical settings.
View details for DOI 10.1038/nbt.3520
View details for Web of Science ID 000375735000036
View details for PubMedID 27018799
View details for PubMedCentralID PMC4907374
- An ultrasensitive method for quantitating circulating tumor DNA with broad patient coverage NATURE MEDICINE 2014; 20 (5): 552-558
Normal Tissue Constraints for Abdominal and Thoracic Stereotactic Body Radiotherapy.
Seminars in radiation oncology
2017; 27 (3): 197-208
Although stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy has become an established standard of care for the treatment of a variety of malignancies, our understanding of normal tissue dose tolerance with extreme hypofractionation remains immature. Since Timmerman initially proposed normal tissue dose constraints for SBRT in the 2008 issue of Seminars of Radiation Oncology, experience with SBRT has grown, and more long-term clinical outcome data have been reported. This article reviews the modern toxicity literature and provides updated clinically practical and useful recommendations of SBRT dose constraints for extracranial sites. We focus on the major organs of the thoracic and upper abdomen, specifically the liver and the lung.
View details for DOI 10.1016/j.semradonc.2017.02.001
View details for PubMedID 28577827
- Case Series of MET Exon 14 Skipping Mutation-positive Non-Small Cell Lung Cancers and Response to Crizotinib. International journal of radiation oncology, biology, physics 2017; 98 (1): 239-?
Molecular profiling of single circulating tumor cells from lung cancer patients
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2016; 113 (52): E8379-E8386
Circulating tumor cells (CTCs) are established cancer biomarkers for the "liquid biopsy" of tumors. Molecular analysis of single CTCs, which recapitulate primary and metastatic tumor biology, remains challenging because current platforms have limited throughput, are expensive, and are not easily translatable to the clinic. Here, we report a massively parallel, multigene-profiling nanoplatform to compartmentalize and analyze hundreds of single CTCs. After high-efficiency magnetic collection of CTC from blood, a single-cell nanowell array performs CTC mutation profiling using modular gene panels. Using this approach, we demonstrated multigene expression profiling of individual CTCs from non-small-cell lung cancer (NSCLC) patients with remarkable sensitivity. Thus, we report a high-throughput, multiplexed strategy for single-cell mutation profiling of individual lung cancer CTCs toward minimally invasive cancer therapy prediction and disease monitoring.
View details for DOI 10.1073/pnas.1608461113
View details for Web of Science ID 000391090800003
View details for PubMedID 27956614
View details for PubMedCentralID PMC5206556
Control of inflammation by stromal Hedgehog pathway activation restrains colitis.
Proceedings of the National Academy of Sciences of the United States of America
Inflammation disrupts tissue architecture and function, thereby contributing to the pathogenesis of diverse diseases; the signals that promote or restrict tissue inflammation thus represent potential targets for therapeutic intervention. Here, we report that genetic or pharmacologic Hedgehog pathway inhibition intensifies colon inflammation (colitis) in mice. Conversely, genetic augmentation of Hedgehog response and systemic small-molecule Hedgehog pathway activation potently ameliorate colitis and restrain initiation and progression of colitis-induced adenocarcinoma. Within the colon, the Hedgehog protein signal does not act directly on the epithelium itself, but on underlying stromal cells to induce expression of IL-10, an immune-modulatory cytokine long known to suppress inflammatory intestinal damage. IL-10 function is required for the full protective effect of small-molecule Hedgehog pathway activation in colitis; this pharmacologic augmentation of Hedgehog pathway activity and stromal IL-10 expression are associated with increased presence of CD4(+)Foxp3(+) regulatory T cells. We thus identify stromal cells as cellular coordinators of colon inflammation and suggest their pharmacologic manipulation as a potential means to treat colitis.
View details for PubMedID 27815529
View details for PubMedCentralID PMC5127312
Hypofractionated Intensity-Modulated Radiotherapy for Patients With Non-Small-Cell Lung Cancer.
Clinical lung cancer
2016; 17 (6): 588-594
Alternative treatment regimens are needed for patients with non-small cell lung cancer (NSCLC) who cannot receive definitive treatment with concurrent chemoradiotherapy, surgery, or stereotactic ablative radiotherapy (SABR).We report survival, patterns of failure and toxicity outcomes for patients with NSCLC who were not eligible for surgical resection, concurrent chemoradiotherapy, or SABR and underwent hypofractionated intensity-modulated radiotherapy (IMRT). Kaplan-Meier survival analysis was used to evaluate the progression-free and overall survival. Competing risk analysis was used to evaluate in-field, locoregional, and distant failure.A total of 42 patients treated to 52.5 to 60 Gy in 15 fractions were included. Most of the patients had metastatic or recurrent disease (64%) and a relatively large, centrally located tumor burden (74%). The median follow-up period was 13 months (interquartile range, 6-18 months). All patients received the total prescribed dose. The median survival was 15.1 months. The overall and progression-free survival rates at 1 year were 63% and 22.5%, respectively. The pattern of failure was predominantly distant, with only 2% of patients experiencing isolated in-field recurrence. The cumulative incidence of in-field failure at 6 and 12 months was 2.5% (95% confidence interval, 0.4%-15.6%) and 16.1% (95% confidence interval, 7.5%-34.7%), respectively. The risk of esophageal toxicity was associated with the esophageal mean dose, maximal point dose, and dose to the 5 cm(3) volume. The risk of pneumonitis was associated with the lung mean dose and volume receiving 18 Gy.Hypofractionated IMRT without concurrent chemotherapy provides favorable rates of local control and survival for well-selected patients with NSCLC who cannot tolerate standard definitive therapy.
View details for DOI 10.1016/j.cllc.2016.05.024
View details for PubMedID 27378172
Early-Stage Non-Small Cell Lung Cancer: Quantitative Imaging Characteristics of (18)F Fluorodeoxyglucose PET/CT Allow Prediction of Distant Metastasis.
2016; 281 (1): 270-278
Purpose To identify quantitative imaging biomarkers at fluorine 18 ((18)F) positron emission tomography (PET) for predicting distant metastasis in patients with early-stage non-small cell lung cancer (NSCLC). Materials and Methods In this institutional review board-approved HIPAA-compliant retrospective study, the pretreatment (18)F fluorodeoxyglucose PET images in 101 patients treated with stereotactic ablative radiation therapy from 2005 to 2013 were analyzed. Data for 70 patients who were treated before 2011 were used for discovery purposes, while data from the remaining 31 patients were used for independent validation. Quantitative PET imaging characteristics including statistical, histogram-related, morphologic, and texture features were analyzed, from which 35 nonredundant and robust features were further evaluated. Cox proportional hazards regression model coupled with the least absolute shrinkage and selection operator was used to predict distant metastasis. Whether histologic type provided complementary value to imaging by combining both in a single prognostic model was also assessed. Results The optimal prognostic model included two image features that allowed quantification of intratumor heterogeneity and peak standardized uptake value. In the independent validation cohort, this model showed a concordance index of 0.71, which was higher than those of the maximum standardized uptake value and tumor volume, with concordance indexes of 0.67 and 0.64, respectively. The prognostic model also allowed separation of groups with low and high risk for developing distant metastasis (hazard ratio, 4.8; P = .0498, log-rank test), which compared favorably with maximum standardized uptake value and tumor volume (hazard ratio, 1.5 and 2.0, respectively; P = .73 and 0.54, log-rank test, respectively). When combined with histologic types, the prognostic power was further improved (hazard ratio, 6.9; P = .0289, log-rank test; and concordance index, 0.80). Conclusion PET imaging characteristics associated with distant metastasis that could potentially help practitioners to tailor appropriate therapy for individual patients with early-stage NSCLC were identified. (©) RSNA, 2016 Online supplemental material is available for this article.
View details for DOI 10.1148/radiol.2016151829
View details for PubMedID 27046074
Intratumor Partitioning of Serial Computed Tomography and FDG Positron Emission Tomography Images Identifies High-Risk Tumor Subregions and Predicts Patterns of Failure in Non-Small Cell Lung Cancer After Radiation Therapy
58th Annual Meeting of the American-Society-for-Radiation-Oncology (ASTRO)
ELSEVIER SCIENCE INC. 2016: S100–S100
View details for Web of Science ID 000387655804563
Robust Intratumor Partitioning to Identify High-Risk Subregions in Lung Cancer: A Pilot Study.
International journal of radiation oncology, biology, physics
2016; 95 (5): 1504-1512
To develop an intratumor partitioning framework for identifying high-risk subregions from (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) and computed tomography (CT) imaging and to test whether tumor burden associated with the high-risk subregions is prognostic of outcomes in lung cancer.In this institutional review board-approved retrospective study, we analyzed the pretreatment FDG-PET and CT scans of 44 lung cancer patients treated with radiation therapy. A novel, intratumor partitioning method was developed, based on a 2-stage clustering process: first at the patient level, each tumor was over-segmented into many superpixels by k-means clustering of integrated PET and CT images; next, tumor subregions were identified by merging previously defined superpixels via population-level hierarchical clustering. The volume associated with each of the subregions was evaluated using Kaplan-Meier analysis regarding its prognostic capability in predicting overall survival (OS) and out-of-field progression (OFP).Three spatially distinct subregions were identified within each tumor that were highly robust to uncertainty in PET/CT co-registration. Among these, the volume of the most metabolically active and metabolically heterogeneous solid component of the tumor was predictive of OS and OFP on the entire cohort, with a concordance index or CI of 0.66-0.67. When restricting the analysis to patients with stage III disease (n=32), the same subregion achieved an even higher CI of 0.75 (hazard ratio 3.93, log-rank P=.002) for predicting OS, and a CI of 0.76 (hazard ratio 4.84, log-rank P=.002) for predicting OFP. In comparison, conventional imaging markers, including tumor volume, maximum standardized uptake value, and metabolic tumor volume using threshold of 50% standardized uptake value maximum, were not predictive of OS or OFP, with CI mostly below 0.60 (log-rank P>.05).We propose a robust intratumor partitioning method to identify clinically relevant, high-risk subregions in lung cancer. We envision that this approach will be applicable to identifying useful imaging biomarkers in many cancer types.
View details for DOI 10.1016/j.ijrobp.2016.03.018
View details for PubMedID 27212196
The impact of audiovisual biofeedback on 4D functional and anatomic imaging: Results of a lung cancer pilot study.
Radiotherapy and oncology
2016; 120 (2): 267-272
The impact of audiovisual (AV) biofeedback on four dimensional (4D) positron emission tomography (PET) and 4D computed tomography (CT) image quality was investigated in a prospective clinical trial (NCT01172041).4D-PET and 4D-CT images of ten lung cancer patients were acquired with AV biofeedback (AV) and free breathing (FB). The 4D-PET images were analyzed for motion artifacts by comparing 4D to 3D PET for gross tumor volumes (GTVPET) and maximum standardized uptake values (SUVmax). The 4D-CT images were analyzed for artifacts by comparing normalized cross correlation-based scores (NCCS) and quantifying a visual assessment score (VAS). A Wilcoxon signed-ranks test was used for statistical testing.The impact of AV biofeedback varied widely. Overall, the 3D to 4D decrease of GTVPET was 1.2±1.3cm(3) with AV and 0.6±1.8cm(3) for FB. The 4D-PET increase of SUVmax was 1.3±0.9 with AV and 1.3±0.8 for FB. The 4D-CT NCCS were 0.65±0.27 with AV and 0.60±0.32 for FB (p=0.08). The 4D-CT VAS was 0.0±2.7.This study demonstrated a high patient dependence on the use of AV biofeedback to reduce motion artifacts in 4D imaging. None of the hypotheses tested were statistically significant. Future development of AV biofeedback will focus on optimizing the human-computer interface and including patient training sessions for improved comprehension and compliance.
View details for DOI 10.1016/j.radonc.2016.05.016
View details for PubMedID 27256597
Identification and genetic manipulation of human and mouse oesophageal stem cells.
2016; 65 (7): 1077-1086
Human oesophageal stem cell research is hampered by the lack of an optimal assay system to study self-renewal and differentiation. We aimed to identify and characterise human and mouse oesophageal stem/progenitor cells by establishing 3-dimensional organotypic sphere culture systems for both species.Primary oesophageal epithelial cells were freshly isolated and fluorescence-activated cell sorting (FACS)-sorted from human and mouse oesophagus and 3-dimensional organotypic sphere culture systems were developed. The self-renewing potential and differentiation status of novel subpopulations were assessed by sphere-forming ability, cell cycle analysis, immunostaining, qPCR and RNA-Seq.Primary human and mouse oesophageal epithelial cells clonally formed esophagospheres consisting of stratified squamous epithelium. Sphere-forming cells could self-renew and form esophagospheres for over 43 passages in vitro and generated stratified squamous epithelium when transplanted under the kidney capsule of immunodeficient mice. Sphere-forming cells were 10-15-fold enriched among human CD49f(hi)CD24(low) cells and murine CD49f(+)CD24(low)CD71(low) cells compared with the most differentiated cells. Genetic elimination of p63 in mouse and human oesophageal cells dramatically decreased esophagosphere formation and basal gene expression while increasing suprabasal gene expression.We developed clonogenic and organotypic culture systems for the quantitative analyses of human and mouse oesophageal stem/progenitor cells and identified novel cell surface marker combinations that enrich for these cells. Using this system, we demonstrate that elimination of p63 inhibits self-renewal of human oesophageal stem/progenitor cells. We anticipate that these esophagosphere culture systems will facilitate studies of oesophageal stem cell biology and may prove useful for ex vivo expansion of human oesophageal stem cells.
View details for DOI 10.1136/gutjnl-2014-308491
View details for PubMedID 25897018
- Identification and genetic manipulation of human and mouse oesophageal stem cells GUT 2016; 65 (7): 1077-1086
Pre-treatment non-target lung FDG-PET uptake predicts symptomatic radiation pneumonitis following Stereotactic Ablative Radiotherapy (SABR).
Radiotherapy and oncology
2016; 119 (3): 454-460
To determine if pre-treatment non-target lung FDG-PET uptake predicts for symptomatic radiation pneumonitis (RP) following lung stereotactic ablative radiotherapy (SABR).We reviewed a 258 patient database from our institution to identify 28 patients who experienced symptomatic (grade ⩾ 2) RP after SABR, and compared them to 57 controls who did not develop symptomatic RP. We compared clinical, dosimetric and functional imaging characteristics between the 2 cohorts including pre-treatment non-target lung FDG-PET uptake.Median follow-up time was 26.9 months. Patients who experienced symptomatic RP had significantly higher non-target lung FDG-PET uptake as measured by mean SUV (p < 0.0001) than controls. ROC analysis for symptomatic RP revealed area under the curve (AUC) of 0.74, with sensitivity 82.1% and specificity 57.9% with cutoff mean non-target lung SUV > 0.56. Predictive value increased (AUC of 0.82) when mean non-target lung SUV was combined with mean lung dose (MLD). We developed a 0-2 point model using these 2 variables, 1 point each for SUV > 0.56 or MLD > 5.88 Gy equivalent dose in 2 Gy per fraction (EQD2), predictive for symptomatic RP in our cohort with hazard ratio 10.01 for score 2 versus 0 (p < 0.001).Patients with elevated pre-SABR non-target lung FDG-PET uptake are at increased risk of symptomatic RP after lung SABR. Our predictive model suggests patients with mean non-target lung SUV > 0.56 and MLD > 5.88 Gy EQD2 are at highest risk. Our predictive model should be validated in an external cohort before clinical implementation.
View details for DOI 10.1016/j.radonc.2016.05.007
View details for PubMedID 27267049
- SU-D-207B-05: Robust Intra-Tumor Partitioning to Identify High-Risk Subregions for Prognosis in Lung Cancer. Medical physics 2016; 43 (6): 3349-?
- Time course and predictive factors for lung volume reduction following stereotactic ablative radiotherapy (SABR) of lung tumors RADIATION ONCOLOGY 2016; 11
Dosimetric Factors and Toxicity in Highly Conformal Thoracic Reirradiation.
International journal of radiation oncology, biology, physics
2016; 94 (4): 808-815
We determined cumulative dose to critical structures, rates of toxicity, and outcomes following thoracic reirradiation.We retrospectively reviewed our institutional database for patients treated between 2008 and 2014, who received thoracic reirradiation with overlap of 25% prescribed isodose lines. Patients received courses of hyperfractionated (n=5), hypofractionated (n=5), conventionally fractionated (n=21), or stereotactic ablative radiation therapy (n=51). Doses to critical structures were converted to biologically effective dose, expressed as 2 Gy per fraction equivalent dose (EQD2; α/β = 2 for spinal cord; α/β = 3 for other critical structures).We identified 82 courses (44 for retreatment) in 38 patients reirradiated at a median 16 months (range: 1-71 months) following initial RT. Median follow-up was 17 months (range: 3-57 months). Twelve- and 24-month overall survival rates were 79.6% and 57.3%, respectively. Eighteen patients received reirradiation for locoregionally recurrent non-small cell lung cancer with 12-month rates of local failure and regional recurrence and distant metastases rates of 13.5%, 8.1%, and 15.6%, respectively. Critical structures receiving ≥75 Gy EQD2 included spinal cord (1 cm(3); n=1), esophagus (1 cm(3); n=10), trachea (1 cm(3); n=11), heart (1 cm(3); n=9), aorta (1 cm(3); n=16), superior vena cava (1 cm(3); n=12), brachial plexus (0.2 cm(3); n=2), vagus nerve (0.2 cm(3); n=7), sympathetic trunk (0.2 cm(3); n=4), chest wall (30 cm(3); n=12), and proximal bronchial tree (1 cm(3); n=17). Cumulative dose-volume (D cm(3)) toxicity following reirradiation data included esophagitis grade ≥2 (n=3, D1 cm(3) range: 41.0-100.6 Gy), chest wall grade ≥2 (n=4; D30 cm(3) range: 35.0-117.2 Gy), lung grade 2 (n=7; V20combined-lung range: 4.7%-21.7%), vocal cord paralysis (n=2; vagus nerve D0.2 cm(3) range: 207.5-302.2 Gy), brachial plexopathy (n=1; D0.2 cm(3) = 242.5 Gy), and Horner's syndrome (n=1; sympathetic trunk D0.2 cm(3) = 130.8 Gy). No grade ≥4 toxicity was observed.Overlapping courses of reirradiation can be safely delivered with acceptable toxicity. Some toxicities occurred acutely at doses considered safe for a single course of therapy (esophagus). We observed rib fracture, brachial plexopathy, and Horner's syndrome for patients receiving high cumulative doses to corresponding critical structures.
View details for DOI 10.1016/j.ijrobp.2015.12.007
View details for PubMedID 26831903
- Long-Term Survival of a Patient With Non-Small-Cell Lung Cancer Harboring a V600E Mutation in the BRAF Oncogene. Clinical lung cancer 2016; 17 (2): e17-21
Time course and predictive factors for lung volume reduction following stereotactic ablative radiotherapy (SABR) of lung tumors.
2016; 11 (1): 40-?
Stereotactic ablative volume reduction (SAVR) is a potential alternative to lung-volume reduction surgery in patients with severe emphysema and excessive surgical risk. Having previously observed a dose-volume response for localized lobar volume reduction after stereotactic ablative radiotherapy (SABR) for lung tumors, we investigated the time course and factors associated with volume reduction.We retrospectively identified 70 eligible patients receiving lung tumor SABR during 2007-2013. We correlated lobar volume reduction (relative to total, bilateral lung volume [TLV]) with volume receiving high biologically effective doses (VXXBED3) and other pre-treatment factors in all patients, and measured the time course of volume changes on 3-month interval CT scans in patients with large V60BED3 (n = 21, V60BED3 ≥4.1 % TLV).Median CT follow-up was 15 months. Median volume reduction of treated lobes was 4.5 % of TLV (range 0.01-13.0 %), or ~9 % of ipsilateral lung volume (ILV); median expansion of non-target adjacent lobes was 2.2 % TLV (-4.6-9.9 %; ~4 % ILV). Treated lobe volume reduction was significantly greater with larger VXXBED3 (XX = 20-100 Gy, R (2) = 0.52-0.55, p < 0.0001) and smaller with lower pre-treatment FEV1% (R (2) = 0.11, p = 0.005) in a multivariable linear model. Maximum volume reduction was reached by ~12 months and persisted.We identified a multivariable model for lobar volume reduction after SABR incorporating dose-volume and pre-treatment FEV1% and characterized its time course.
View details for DOI 10.1186/s13014-016-0616-8
View details for PubMedID 26975700
View details for PubMedCentralID PMC4791793
Anatomic optimization of lung tumor stereotactic ablative radiation therapy.
Practical radiation oncology
2015; 5 (6): e607-13
The purpose of this study was to demonstrate that anatomic optimization through selection of the degree of breath hold that yields the largest separation between the target and nearby organ at risk could result in dosimetrically superior treatment plans.Thirty patients with 41 plans were included in this planned secondary analysis of a prospective trial. Fifteen plans were created for treatment with use of natural end exhale (NEE), and 26 plans used deep inspiration breath hold (DIBH). To evaluate whether the original plan was dosimetrically optimal, we replanned treatment using the opposite respiratory state with the same beam configuration as the original plan. A treatment plan was deemed superior if it met protocol constraints when the other did not. If both plans met or violated the constraints, the plans were deemed equivalent.Of the 26 plans originally planned with DIBH and replanned with NEE, 3 plans were dosimetrically superior with NEE, 1 plan was dosimetrically superior with DIBH, and 22 plans were dosimetrically equivalent. Of the 15 plans originally planned with NEE, 4 plans were dosimetrically superior with NEE, 2 plans were dosimetrically superior with DIBH, and 9 plans were dosimetrically equivalent.For 10 of 41 plans, planning with 1 respiratory state was superior. To obtain uniformly optimal plans, individual anatomic optimization would be needed.
View details for DOI 10.1016/j.prro.2015.05.008
View details for PubMedID 26231596
Outcomes of Modestly Hypofractionated Radiation for Lung Tumors: Pre- and Mid-Treatment Positron Emission Tomography-Computed Tomography Metrics as Prognostic Factors.
Clinical lung cancer
2015; 16 (6): 475-485
Modestly hypofractionated radiation therapy (HypoRT; 60-66 Gy in 3-Gy fractions) allows patients with locally advanced thoracic tumors and poor performance status to complete treatment within a shorter period without concurrent chemotherapy. We evaluated the outcomes and imaging prognostic factors of HypoRT.We retrospectively reviewed the data from all patients with primary and metastatic intrathoracic tumors treated with HypoRT from 2006 to 2012. We analyzed the survival and toxicity outcomes, including overall survival (OS), progression-free survival (PFS), local recurrence (LR), and distant metastasis. We also evaluated the following tumor metrics in an exploratory analysis: gross tumor volume (GTV), maximum standardized uptake value (SUVMax), and metabolic tumor volume using a threshold of ≥ 50% of the SUVMax (MTV50%) or the maximum gradient of fluorine-18 fluorodeoxyglucose uptake (MTVEdge). We assessed the association of these metrics and their changes from before to mid-RT using positron emission tomography-computed tomography (PET-CT) with OS and PFS.We identified 29 patients, all with pre-RT and 20 with mid-RT PET-CT scans. The median follow-up period was 15 months. The 2-year overall and non-small-cell lung cancer-only rate for OS, PFS, and LR, was 59% and 59%, 52% and 41%, and 27% and 32%, respectively. No grade ≥ 3 toxicities developed. The median decrease in GTV, SUVMax, and MTVEdge was 11%, 24%, and 18%, respectively. Inferior OS was associated with a larger pre-RT MTVEdge (P = .005) and pre-RT MTV50% (P = .007). Inferior PFS was associated with a larger mid-RT SUVMax (P = .003).These findings add to the growing body of data demonstrating promising outcomes and limited toxicity with HypoRT. The pre- and mid-RT PET-CT metrics could be useful for prognostic stratification in future clinical trials.
View details for DOI 10.1016/j.cllc.2015.01.007
View details for PubMedID 25770888
Predicting Radiotherapy Responses and Treatment Outcomes Through Analysis of Circulating Tumor DNA.
Seminars in radiation oncology
2015; 25 (4): 305-312
Tumors continually shed DNA into the blood where it can be detected as circulating tumor DNA (ctDNA). Although this phenomenon has been recognized for decades, techniques that are sensitive and specific enough to robustly detect ctDNA have only become available recently. Quantification of ctDNA represents a new approach for cancer detection and disease burden quantification that has the potential to revolutionize response assessment and personalized treatment in radiation oncology. Analysis of ctDNA has many potential applications, including detection of minimal residual disease following radiotherapy, noninvasive tumor genotyping, and early detection of tumor recurrence. Ultimately, ctDNA-based assays could lead to personalization of therapy based on identification of somatic alterations present in tumors and changes in ctDNA concentrations before and after treatment. In this review, we discuss methods of ctDNA detection and clinical applications of ctDNA-based biomarkers in radiation oncology, with a focus on recently developed techniques that use next-generation sequencing for ctDNA quantification.
View details for DOI 10.1016/j.semradonc.2015.05.001
View details for PubMedID 26384278
View details for PubMedCentralID PMC4575502
- Integrating Tumor and Stromal Gene Expression Signatures With Clinical Indices for Survival Stratification of Early-Stage Non-Small Cell Lung Cancer. Journal of the National Cancer Institute 2015; 107 (10)
Integrating Tumor and Stromal Gene Expression Signatures With Clinical Indices for Survival Stratification of Early-Stage Non-Small Cell Lung Cancer.
Journal of the National Cancer Institute
2015; 107 (10)
Accurate survival stratification in early-stage non-small cell lung cancer (NSCLC) could inform the use of adjuvant therapy. We developed a clinically implementable mortality risk score incorporating distinct tumor microenvironmental gene expression signatures and clinical variables.Gene expression profiles from 1106 nonsquamous NSCLCs were used for generation and internal validation of a nine-gene molecular prognostic index (MPI). A quantitative polymerase chain reaction (qPCR) assay was developed and validated on an independent cohort of formalin-fixed paraffin-embedded (FFPE) tissues (n = 98). A prognostic score using clinical variables was generated using Surveillance, Epidemiology, and End Results data and combined with the MPI. All statistical tests for survival were two-sided.The MPI stratified stage I patients into prognostic categories in three microarray and one FFPE qPCR validation cohorts (HR = 2.99, 95% CI = 1.55 to 5.76, P < .001 in stage IA patients of the largest microarray validation cohort; HR = 3.95, 95% CI = 1.24 to 12.64, P = .01 in stage IA of the qPCR cohort). Prognostic genes were expressed in distinct tumor cell subpopulations, and genes implicated in proliferation and stem cells portended poor outcomes, while genes involved in normal lung differentiation and immune infiltration were associated with superior survival. Integrating the MPI with clinical variables conferred greatest prognostic power (HR = 3.43, 95% CI = 2.18 to 5.39, P < .001 in stage I patients of the largest microarray cohort; HR = 3.99, 95% CI = 1.67 to 9.56, P < .001 in stage I patients of the qPCR cohort). Finally, the MPI was prognostic irrespective of somatic alterations in EGFR, KRAS, TP53, and ALK.The MPI incorporates genes expressed in the tumor and its microenvironment and can be implemented clinically using qPCR assays on FFPE tissues. A composite model integrating the MPI with clinical variables provides the most accurate risk stratification.
View details for DOI 10.1093/jnci/djv211
View details for PubMedID 26286589
- Precision Hypofractionated Radiation Therapy in Poor Performing Patients With Non-Small Cell Lung Cancer: Phase 1 Dose Escalation Trial INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 2015; 93 (1): 72-81
Colorectal Histology Is Associated With an Increased Risk of Local Failure in Lung Metastases Treated With Stereotactic Ablative Radiation Therapy
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2015; 92 (5): 1044-1052
Stereotactic ablative radiation therapy (SABR) is increasingly used to treat lung oligometastases. We set out to determine the safety and efficacy of this approach and to identify factors associated with outcomes.We conducted a retrospective study of patients treated with SABR for metastatic lung tumors at our institution from 2003 to 2014. We assessed the association between various patient and treatment factors with local failure (LF), progression, subsequent treatment, systemic treatment, and overall survival (OS), using univariate and multivariate analyses.We identified 122 tumors in 77 patients meeting inclusion criteria for this study. Median follow-up was 22 months. The 12- and 24-month cumulative incidence rates of LF were 8.7% and 16.2%, respectively; the 24-month cumulative incidence rates of progression, subsequent treatment, and subsequent systemic treatment were 75.2%, 64.5%, and 35.1%, respectively. Twenty-four-month OS was 74.6%, and median OS was 36 months. Colorectal metastases had a significantly higher cumulative incidence of LF at 12 and 24 months (25.5% and 42.2%, respectively), than all other histologies (4.4% and 9.9%, respectively; P<.0004). The 24-month cumulative incidences of LF for colorectal metastases treated with a biologically effective dose at α/β = 10 (BED10) of <100 Gy versus BED10 of ≥100 Gy were 62.5% and 16.7%, respectively (P=.08). Toxicity was minimal, with only a single grade 3 or higher event observed.SABR for metastatic lung tumors appears to be safe and effective with excellent local control, treatment-free intervals, and OS. An exception is metastases from colorectal cancer, which have a high LF rate consistent with a radioresistant phenotype, suggesting a potential role for dose escalation.
View details for DOI 10.1016/j.ijrobp.2015.04.004
View details for Web of Science ID 000357900600024
View details for PubMedID 26025776
3D Riesz-wavelet based Covariance descriptors for texture classification of lung nodule tissue in CT.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference
2015; 2015: 7909-7912
In this paper we present a novel technique for characterizing and classifying 3D textured volumes belonging to different lung tissue types in 3D CT images. We build a volume-based 3D descriptor, robust to changes of size, rigid spatial transformations and texture variability, thanks to the integration of Riesz-wavelet features within a Covariance-based descriptor formulation. 3D Riesz features characterize the morphology of tissue density due to their response to changes in intensity in CT images. These features are encoded in a Covariance-based descriptor formulation: this provides a compact and flexible representation thanks to the use of feature variations rather than dense features themselves and adds robustness to spatial changes. Furthermore, the particular symmetric definite positive matrix form of these descriptors causes them to lay in a Riemannian manifold. Thus, descriptors can be compared with analytical measures, and accurate techniques from machine learning and clustering can be adapted to their spatial domain. Additionally we present a classification model following a "Bag of Covariance Descriptors" paradigm in order to distinguish three different nodule tissue types in CT: solid, ground-glass opacity, and healthy lung. The method is evaluated on top of an acquired dataset of 95 patients with manually delineated ground truth by radiation oncology specialists in 3D, and quantitative sensitivity and specificity values are presented.
View details for DOI 10.1109/EMBC.2015.7320226
View details for PubMedID 26738126
The prognostic landscape of genes and infiltrating immune cells across human cancers
2015; 21 (8): 938-945
Molecular profiles of tumors and tumor-associated cells hold great promise as biomarkers of clinical outcomes. However, existing data sets are fragmented and difficult to analyze systematically. Here we present a pan-cancer resource and meta-analysis of expression signatures from ∼18,000 human tumors with overall survival outcomes across 39 malignancies. By using this resource, we identified a forkhead box MI (FOXM1) regulatory network as a major predictor of adverse outcomes, and we found that expression of favorably prognostic genes, including KLRB1 (encoding CD161), largely reflect tumor-associated leukocytes. By applying CIBERSORT, a computational approach for inferring leukocyte representation in bulk tumor transcriptomes, we identified complex associations between 22 distinct leukocyte subsets and cancer survival. For example, tumor-associated neutrophil and plasma cell signatures emerged as significant but opposite predictors of survival for diverse solid tumors, including breast and lung adenocarcinomas. This resource and associated analytical tools (http://precog.stanford.edu) may help delineate prognostic genes and leukocyte subsets within and across cancers, shed light on the impact of tumor heterogeneity on cancer outcomes, and facilitate the discovery of biomarkers and therapeutic targets.
View details for DOI 10.1038/nm.3909
View details for Web of Science ID 000359181000022
View details for PubMedID 26193342
Inhibition of Mouse Breast Tumor-Initiating Cells by Calcitriol and Dietary Vitamin D
MOLECULAR CANCER THERAPEUTICS
2015; 14 (8): 1951-1961
The anticancer actions of vitamin D and its hormonally active form, calcitriol, have been extensively documented in clinical and preclinical studies. However, the mechanisms underlying these actions have not been completely elucidated. Here, we examined the effect of dietary vitamin D and calcitriol on mouse breast tumor-initiating cells (TICs, also known as cancer stem cells). We focused on MMTV-Wnt1 mammary tumors, for which markers for isolating TICs have previously been validated. We confirmed that these tumors expressed functional vitamin D receptors and estrogen receptors (ER) and exhibited calcitriol-induced molecular responses including ER downregulation. Following orthotopic implantation of MMTV-Wnt1 mammary tumor cells into mice, calcitriol injections or a vitamin D-supplemented diet caused a striking delay in tumor appearance and growth, whereas a vitamin D-deficient diet accelerated tumor appearance and growth. Calcitriol inhibited TIC tumor spheroid formation in a dose-dependent manner in primary cultures and inhibited TIC self-renewal in secondary passages. A combination of calcitriol and ionizing radiation inhibited spheroid formation more than either treatment alone. Further, calcitriol significantly decreased TIC frequency as evaluated by in vivo limiting dilution analyses. Calcitriol inhibition of TIC spheroid formation could be overcome by the overexpression of β-catenin, suggesting that the inhibition of Wnt/β-catenin pathway is an important mechanism mediating the TIC inhibitory activity of calcitriol in this tumor model. Our findings indicate that vitamin D compounds target breast TICs reducing tumor-initiating activity. Our data also suggest that combining vitamin D compounds with standard therapies may enhance anticancer activity and improve therapeutic outcomes.
View details for DOI 10.1158/1535-7163.MCT-15-0066
View details for Web of Science ID 000359324600018
View details for PubMedID 25934710
View details for PubMedCentralID PMC4549392
Analysis of Long-Term 4-Dimensional Computed Tomography Regional Ventilation After Radiation Therapy
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2015; 92 (3): 683-690
To determine whether regional ventilation, as measured using 4-dimensional computed tomography (4D-CT), declines after radiation therapy (RT).We analyzed pretreatment 4D-CT scans associated with 2 RT courses. We quantified regional pulmonary function over equivalent dose in 2 Gy (EQD2α/β=3) intervals of 0 to 5 Gy, 5 to 20 Gy, 20 to 40 Gy, and >40 Gy using percentile-normalized intensity-based (VentInt) and Jacobian-based (VentJac) ventilation metrics. We modeled the impact of dose on mean ventilation (Vent¯) and regional tidal volume (rTV: tidal volume [TV] within a dose interval normalized to total lung TV). We also identified clinical and dosimetric factors that affected regional ventilation changes (ΔVent¯ and ΔrTV) after RT for the >20 Gy dose interval.After RT, Vent¯Int exhibited statistically significant dose-dependent declines within the 20 to 40 Gy (-5.0%; P=.03) and >40 Gy (-6.8%; P<.01) intervals. Vent¯Jac exhibited a declining trend after RT only for the >40 Gy interval (-4.6%; P=.07). Factors associated with ΔVent¯Int for the >20 Gy dose interval included airway stenosis progression (P=.03) and gross tumor volume (P=.09). Both rTVInt and rTVJac were associated with small (<2%) but significant declines after RT for 20 to 40 Gy and >40 Gy intervals. Factors associated with declining rTVInt (P<.05) for the >20 Gy dose interval included airway stenosis progression, greater V20 (volume of lung receiving >20 Gy), and smaller fraction of emphysema in V20. The association between the absence of chronic obstructive pulmonary disease and declining rTV trended toward significance (P=.09).Regional ventilation, as measured using 4D-CT, demonstrates a dose-dependent decline after RT. Our results support the use of 4D-CT ventilation imaging for monitoring regional pulmonary function change after RT.
View details for DOI 10.1016/j.ijrobp.2015.02.037
View details for Web of Science ID 000355636800032
View details for PubMedID 25936813
Stereotactic ablative radiotherapy (SABR) for treatment of central and ultra-central lung tumors
2015; 89 (1): 50-56
Treatment of central and ultra-central lung tumors with stereotactic ablative radiotherapy (SABR) remains controversial due to risks of treatment-related toxicities compared with peripheral tumors. Here we report our institution's experience in treating central and ultra-central lung tumor patients with SABR.We retrospectively reviewed outcomes in 68 patients with single lung tumors, 34 central and 34 peripheral, all treated with SABR consisting of 50 Gy in 4-5 fractions. Tumor centrality was defined per the RTOG 0813 protocol. We defined "ultra-central" tumors as those with GTV directly abutting the central airway.Median follow-up time was 18.4 months and median overall survival was 38.1 months. Two-year overall survival was similar between ultra-central, central, and peripheral NSCLC (80.0% vs. 63.2% vs. 86.6%, P=0.62), as was 2-year local failure (0% vs. 10.0% vs. 16.3%, P=0.64). Toxicity rates were low and comparable between the three groups, with only two cases of grade 3 toxicity (chest wall pain), and one case of grade 4 toxicity (pneumonitis) observed. Patients with ultra-central tumors experienced no symptomatic toxicities over a median follow-up time of 23.6 months. Dosimetric analysis revealed that RTOG 0813 central airway dose constraints were frequently not achieved in central tumor treatment plans, but this did not correlate with increased toxicity rate.Patients with central and ultra-central lung tumors treated with SABR (50 Gy in 4-5 fractions) experienced few toxicities and good outcomes, similar to patients with peripheral lung tumors.
View details for DOI 10.1016/j.lungcan.2015.04.014
View details for Web of Science ID 000356546300010
View details for PubMedID 25997421
Noninvasive monitoring of diffuse large B-cell lymphoma by immunoglobulin high-throughput sequencing.
2015; 125 (24): 3679-3687
Recent studies have shown limited utility of routine surveillance imaging for diffuse large B-cell lymphoma (DLBCL) patients achieving remission. Detection of molecular disease by immunoglobulin high-throughput sequencing (Ig-HTS) from peripheral blood provides an alternate strategy for surveillance. We prospectively evaluated the utility of Ig-HTS within 311 blood and 105 tumor samples from 75 patients with DLBCL, comparing Ig-HTS from the cellular (circulating leukocytes) and acellular (plasma cell-free DNA) compartments of peripheral blood to clinical outcomes and (18)fluoro-deoxyglucose positron emission tomography combined with computed tomography (PET/CT; n = 173). Clonotypic immunoglobulin rearrangements were detected in 83% of patients with adequate tumor samples to enable subsequent monitoring in peripheral blood. Molecular disease measured from plasma, compared with circulating leukocytes, was more abundant and better correlated with radiographic disease burden. Before treatment, molecular disease was detected in the plasma of 82% of patients compared with 71% in circulating cells (P = .68). However, molecular disease was detected significantly more frequently in the plasma at time of relapse (100% vs 30%; P = .001). Detection of molecular disease in the plasma often preceded PET/CT detection of relapse in patients initially achieving remission. During surveillance time points before relapse, plasma Ig-HTS demonstrated improved specificity (100% vs 56%, P < .0001) and similar sensitivity (31% vs 55%, P = .4) compared with PET/CT. Given its high specificity, Ig-HTS from plasma has potential clinical utility for surveillance after complete remission.
View details for DOI 10.1182/blood-2015-03-635169
View details for PubMedID 25887775
View details for PubMedCentralID PMC4463733
TU-AB-201-06: Evaluation of Electromagnetically Guided High- Dose Rate Brachytherapy for Ablative Treatment of Lung Metastases.
2015; 42 (6): 3595-?
The advent of electromagnetic navigation bronchoscopy has enabled minimally invasive access to peripheral lung tumors previously inaccessible by optical bronchoscopes. As an adjunct to Stereotactic Ablative Radiosurgery (SABR), implantation of HDR catheters can provide focal treatments for multiple metastases and sites of retreatments. The authors evaluate a procedure to deliver ablative doses via Electromagnetically-Guided HDR (EMG-HDR) to lung metastases, quantify the resulting dosimetry, and assess its role in the comprehensive treatment of lung cancer.A retrospective study was conducted on ten patients, who, from 2009 to 2011, received a hypo-fractionated SABR regimen with 6MV VMAT to lesions in various lobes ranging from 1.5 to 20 cc in volume. A CT visible pathway was delineated for EM guided placement of an HDR applicator (catheter) and dwell times were optimized to ensure at least 98% prescription dose coverage of the GTV. Normal tissue doses were calculated using inhomogeneity corrections via a grid-based Boltzmann solver (Acuros_BV_1.5.0).With EMG-HDR, an average of 83% (+/-9% standard deviation) of each patient's GTV received over 200% of the prescription dose, as compared to SABR where the patients received an average maximum dose of 125% (+/-5%). EMG-HDR enabled a 59% (+/-12%) decrease in the aorta maximum dose, a 63% (+/-26%) decrease in the spinal cord max dose, and 57% (+/-23%) and 70% (+/-17%) decreases in the volume of the body receiving over 50% and 25% of the prescription dose, respectively.EMG-HDR enables delivery of higher ablative doses to the GTV, while concurrently reducing surrounding normal tissue doses. The single catheter approach shown here is limited to targets smaller than 20 cc. As such, the technique enables ablation of small lesions and a potentially safe and effective retreatment option in situations where external beam utility is limited by normal tissue constraints.
View details for DOI 10.1118/1.4925544
View details for PubMedID 26128845
Robust enumeration of cell subsets from tissue expression profiles.
2015; 12 (5): 453-457
We introduce CIBERSORT, a method for characterizing cell composition of complex tissues from their gene expression profiles. When applied to enumeration of hematopoietic subsets in RNA mixtures from fresh, frozen and fixed tissues, including solid tumors, CIBERSORT outperformed other methods with respect to noise, unknown mixture content and closely related cell types. CIBERSORT should enable large-scale analysis of RNA mixtures for cellular biomarkers and therapeutic targets (http://cibersort.stanford.edu/).
View details for DOI 10.1038/nmeth.3337
View details for PubMedID 25822800
- Robust enumeration of cell subsets from tissue expression profiles NATURE METHODS 2015; 12 (5): 453-?
- To SABR or Not to SABR? Indications and Contraindications for Stereotactic Ablative Radiotherapy in the Treatment of Early-Stage, Oligometastatic, or Oligoprogressive Non-Small Cell Lung Cancer SEMINARS IN RADIATION ONCOLOGY 2015; 25 (2): 78-86
Molecular Determinants of Radiation Response in Non-Small Cell Lung Cancer
SEMINARS IN RADIATION ONCOLOGY
2015; 25 (2): 67-77
Non-small cell lung cancers are now recognized to contain considerable heterogeneity and molecular diversity. Substantial progress has been made regarding molecular determinants of response to targeted agents in advanced lung cancer, and recent findings have revealed subsets of patients with driver mutations that respond rapidly to selective inhibitors. In addition, new approaches to disrupting DNA repair and inflammation and activation of the immune system are being explored. A key question in the field is whether therapeutic multimodality options incorporating radiation therapy can capitalize on the gains made in systemic therapy.
View details for DOI 10.1016/j.semradonc.2014.12.007
View details for Web of Science ID 000351254100002
View details for PubMedID 25771410
- Noninvasive pulmonary nodule elastometry by CT and deformable image registration RADIOTHERAPY AND ONCOLOGY 2015; 115 (1): 35-40
FACTERA: a practical method for the discovery of genomic rearrangements at breakpoint resolution
2014; 30 (23): 3390-3393
For practical and robust de novo identification of genomic fusions and breakpoints from targeted paired-end DNA sequencing data, we developed Fusion And Chromosomal Translocation Enumeration and Recovery Algorithm (FACTERA). Our method has minimal external dependencies, works directly on a preexisting Binary Alignment/Map file and produces easily interpretable output. We demonstrate FACTERA's ability to rapidly identify breakpoint-resolution fusion events with high sensitivity and specificity in patients with non-small cell lung cancer, including novel rearrangements. We anticipate that FACTERA will be broadly applicable to the discovery and analysis of clinically relevant fusions from both targeted and genome-wide sequencing datasets.http://factera.stanford.edu.
View details for DOI 10.1093/bioinformatics/btu549
View details for Web of Science ID 000345827400014
View details for PubMedID 25143292
View details for PubMedCentralID PMC4296148
- Galectin-1 Mediates Radiation-Related Lymphopenia and Attenuates NSCLC Radiation Response CLINICAL CANCER RESEARCH 2014; 20 (21): 5558-5569
- Pulmonary Ventilation Imaging Based on 4-Dimensional Computed Tomography: Comparison With Pulmonary Function Tests and SPECT Ventilation Images INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 2014; 90 (2): 414-422
- Lung Volume Reduction After Stereotactic Ablative Radiation Therapy of Lung Tumors: Potential Application to Emphysema INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 2014; 90 (1): 216-223
Neurotrophic factor GDNF promotes survival of salivary stem cells.
journal of clinical investigation
2014; 124 (8): 3364-3377
Stem cell-based regenerative therapy is a promising treatment for head and neck cancer patients that suffer from chronic dry mouth (xerostomia) due to salivary gland injury from radiation therapy. Current xerostomia therapies only provide temporary symptom relief, while permanent restoration of salivary function is not currently feasible. Here, we identified and characterized a stem cell population from adult murine submandibular glands. Of the different cells isolated from the submandibular gland, this specific population, Lin-CD24+c-Kit+Sca1+, possessed the highest capacity for proliferation, self renewal, and differentiation during serial passage in vitro. Serial transplantations of this stem cell population into the submandibular gland of irradiated mice successfully restored saliva secretion and increased the number of functional acini. Gene-expression analysis revealed that glial cell line-derived neurotrophic factor (Gdnf) is highly expressed in Lin-CD24+c-Kit+Sca1+ stem cells. Furthermore, GDNF expression was upregulated upon radiation therapy in submandibular glands of both mice and humans. Administration of GDNF improved saliva production and enriched the number of functional acini in submandibular glands of irradiated animals and enhanced salisphere formation in cultured salivary stem cells, but did not accelerate growth of head and neck cancer cells. These data indicate that modulation of the GDNF pathway may have potential therapeutic benefit for management of radiation-induced xerostomia.
View details for DOI 10.1172/JCI74096
View details for PubMedID 25036711
View details for PubMedCentralID PMC4109543
Vagal and recurrent laryngeal neuropathy following stereotactic ablative radiation therapy in the chest.
Practical radiation oncology
2014; 4 (4): 272-278
To identify clinical and dosimetric factors associated with vagus nerve (VN) and recurrent laryngeal nerve (RecLN) injury following stereotactic ablative radiation therapy (SABR) in the chest.We examined the clinical courses and SABR plans of 67 patients treated for T1 or T2 non-small cell lung cancer of the upper right or left lung, including 2 who developed vocal cord paresis (VCP) following treatment. After developing a contouring atlas for the VN and RecLN in the thorax, dose to those structures was retrospectively determined for each patient, and we identified 12 patients whose treatment imparted significant dose to either nerve and who were assessable for more than 12 months follow-up. Biologically effective doses using linear-quadratic (LQ) and linear quadratic-linear (LQ-L) modeling were correlated with VN and RecLN toxicity.Of 12 patients, 2 developed VCP. The first underwent repeat SABR and received a cumulative single fraction equivalent dose (alpha/beta = 3; SFED3) of 37.4 or 64.5 Gy to the VN and 13.7 or 15.3 Gy to the RecLN (by LQ or LQ-L modeling, respectively). This was the highest VN dose and fifth highest RecLN dose in the cohort. The second had rheumatoid arthritis and connective tissue disease and received a SFED3 of 16 Gy to the VN and 19.5 Gy to the RecLN (by both LQ and LQ-L modeling). This was in the upper tertile of VN and RecLN doses for the cohort.Following SABR for non-small cell lung cancer, VCP was associated with high cumulative dose to the VN in 1 patient and a moderately high dose to the VN and RecLN in another patient with rheumatoid arthritis and connective tissue disease. Particularly in the setting of reirradiation or connective tissue disease, potential toxicity to the VN or RecLN should be considered.
View details for DOI 10.1016/j.prro.2013.08.005
View details for PubMedID 25012837
- Targeting Unique Metabolic Properties of Breast Tumor Initiating Cells STEM CELLS 2014; 32 (7): 1734-1745
Imaging features associated with disease progression after stereotactic ablative radiotherapy for stage I non-small-cell lung cancer.
Clinical lung cancer
2014; 15 (4): 294-301 e3
The aim of this study was to identify imaging-based predictors of progression in patients treated with SABR for stage I NSCLC.Between March 2003 and December 2012, 117 patients with stage I NSCLC meeting our study criteria were treated with SABR at Stanford University. Median follow-up was 17 months (range, 3-74 months) for all patients and 19 months for living patients (range, 3-74 months). Tumors were classified according to whether or not they contacted the pleura adjacent to the chest wall or mediastinum (MP), according to their maximum dimension based on computed tomography scans, and, for 102 patients who had archived pretreatment fluorine-18 fluorodeoxyglucose positron-emission tomography scans, according to SUVmax.Ten patients (9%) developed local progression, 17 (15%) developed regional progression, and 19 (16%) developed distant metastasis. Two-year freedom from local progression, freedom from regional progression, and freedom from distant metastasis (FFDM) were 88%, 83%, and 83%, respectively. Overall survival was 70% at 2 years. FFDM was significantly associated with MP contact, maximum tumor dimension, and SUVmax, and these variables could be combined into an exploratory prognostic index that identified patients at highest risk for developing metastases.In our cohort, noninvasive, imaging-based features were associated with distant progression after SABR for early stage NSCLC. If validated, our prognostic index could allow identification of patients who might benefit from systemic therapy after SABR.
View details for DOI 10.1016/j.cllc.2013.12.011
View details for PubMedID 24594400
Feasibility and Potential Utility of Multicomponent Exhaled Breath Analysis for Predicting Development of Radiation Pneumonitis After Stereotactic Ablative Radiotherapy
JOURNAL OF THORACIC ONCOLOGY
2014; 9 (7): 957-964
In this prospective pilot study, we evaluated the feasibility and potential utility of measuring multiple exhaled gases as biomarkers of radiation pneumonitis (RP) in patients receiving stereotactic ablative radiotherapy (SABR) for lung tumors.Breath analysis was performed for 26 patients receiving SABR for lung tumors. Concentrations of exhaled nitric oxide (eNO), carbon monoxide (eCO), nitrous oxide (eN2O), and carbon dioxide (eCO2) were measured before and immediately after each fraction using real-time, infrared laser spectroscopy. RP development (CTCAE grade ≥2) was correlated with baseline gas concentrations, acute changes in gas concentrations after each SABR fraction, and dosimetric parameters.Exhaled breath analysis was successfully completed in 77% of patients. Five of 20 evaluable patients developed RP at a mean of 5.4 months after SABR. Acute changes in eNO and eCO concentrations, defined as percent changes between each pre-fraction and post-fraction measurement, were significantly smaller in RP versus non-RP cases (p = 0.022 and 0.015, respectively). In an exploratory analysis, a combined predictor of baseline eNO greater than 24 parts per billion and acute decrease in eCO less than 5.5% strongly correlated with RP incidence (p =0.0099). Neither eN2O nor eCO2 concentrations were significantly associated with RP development. Although generally higher in patients destined to develop RP, dosimetric parameters were not significantly associated with RP development.The majority of SABR patients in this pilot study were able to complete exhaled breath analysis. Baseline concentrations and acute changes in concentrations of exhaled breath components were associated with RP development after SABR. If our findings are validated, exhaled breath analysis may become a useful approach for noninvasive identification of patients at highest risk for developing RP after SABR.
View details for DOI 10.1097/JTO.0000000000000182
View details for Web of Science ID 000338025600015
The effect of arm position on the dosimetry of thoracic stereotactic ablative radiation therapy using volumetric modulated arc therapy.
Practical radiation oncology
2014; 4 (3): 192-197
Patient comfort and positioning stability may be improved in the arms down (AD) compared with the typical arms up (AU) position in thoracic stereotactic ablative radiation therapy (SABR). We compared plan quality for AD vs AU when using volumetric modulated arc therapy (VMAT), and evaluated the sensitivity of AD plans to arm positioning variability.We took plans of 14 patients with 17 lung tumors treated with thoracic SABR using VMAT in the AD position and simulated the same treatments in the AU position by re-optimizing after digitally removing the ipsilateral arm. To evaluate the sensitivity of AD plans to arm positioning variability, all plans were recalculated without re-optimization after assigning water density to the ipsilateral arm (AD-W) and then digitally shifting the arm 2.5 cm anterolaterally (AD-WS).Between AD and AU plans, statistically significant but clinically insignificant (all original planning constraints met) differences were found for the following parameters: mean planning target volume maximum dose, difference of 2.3% of prescription dose (P = .049); mean intermediate dose conformity index, difference of 0.27 (P = .012); median percent lung volume receiving a minimum of 10, 20, and 30 Gy (V10, V20, and V30), differences of 0.5%, 0.2%, and 0.1%, respectively (P = .040, .007, and .001); and median spinal cord maximum dose, difference of 33.5 cGy (P = .017). Similarly, between AD-W and AD-WS plans, statistically significant but clinically insignificant differences were found for median lung V20 and V30, difference of 0.0% for both (P = .034 and .016, by matched pair analysis).Our exploratory planning study suggests that when using VMAT for lung tumor SABR, AD and AU positioning achieve clinically equivalent plan quality, and AD plans are insensitive to relatively large variability in arm position.
View details for DOI 10.1016/j.prro.2013.07.010
View details for PubMedID 24766687
A Population-Based Comparative Effectiveness Study of Radiation Therapy Techniques in Stage III Non-Small Cell Lung Cancer.
International journal of radiation oncology, biology, physics
2014; 88 (4): 872-884
Concerns have been raised about the potential for worse treatment outcomes because of dosimetric inaccuracies related to tumor motion and increased toxicity caused by the spread of low-dose radiation to normal tissues in patients with locally advanced non-small cell lung cancer (NSCLC) treated with intensity modulated radiation therapy (IMRT). We therefore performed a population-based comparative effectiveness analysis of IMRT, conventional 3-dimensional conformal radiation therapy (3D-CRT), and 2-dimensional radiation therapy (2D-RT) in stage III NSCLC.We used the Surveillance, Epidemiology, and End Results (SEER)-Medicare database to identify a cohort of patients diagnosed with stage III NSCLC from 2002 to 2009 treated with IMRT, 3D-CRT, or 2D-RT. Using Cox regression and propensity score matching, we compared survival and toxicities of these treatments.The proportion of patients treated with IMRT increased from 2% in 2002 to 25% in 2009, and the use of 2D-RT decreased from 32% to 3%. In univariate analysis, IMRT was associated with improved overall survival (OS) (hazard ratio [HR] 0.90, P=.02) and cancer-specific survival (CSS) (HR 0.89, P=.02). After controlling for confounders, IMRT was associated with similar OS (HR 0.94, P=.23) and CSS (HR 0.94, P=.28) compared with 3D-CRT. Both techniques had superior OS compared with 2D-RT. IMRT was associated with similar toxicity risks on multivariate analysis compared with 3D-CRT. Propensity score matched model results were similar to those from adjusted models.In this population-based analysis, IMRT for stage III NSCLC was associated with similar OS and CSS and maintained similar toxicity risks compared with 3D-CRT.
View details for DOI 10.1016/j.ijrobp.2013.12.010
View details for PubMedID 24495591
Erythropoietin promotes breast tumorigenesis through tumor-initiating cell self-renewal
JOURNAL OF CLINICAL INVESTIGATION
2014; 124 (2): 553-563
Erythropoietin (EPO) is a hormone that induces red blood cell production. In its recombinant form, EPO is the one of most prescribed drugs to treat anemia, including that arising in cancer patients. In randomized trials, EPO administration to cancer patients has been associated with decreased survival. Here, we investigated the impact of EPO modulation on tumorigenesis. Using genetically engineered mouse models of breast cancer, we found that EPO promoted tumorigenesis by activating JAK/STAT signaling in breast tumor-initiating cells (TICs) and promoted TIC self renewal. We determined that EPO was induced by hypoxia in breast cancer cell lines, but not in human mammary epithelial cells. Additionally, we demonstrated that high levels of endogenous EPO gene expression correlated with shortened relapse-free survival and that pharmacologic JAK2 inhibition was synergistic with chemotherapy for tumor growth inhibition in vivo. These data define an active role for endogenous EPO in breast cancer progression and breast TIC self-renewal and reveal a potential application of EPO pathway inhibition in breast cancer therapy.
View details for DOI 10.1172/JCI69804
View details for Web of Science ID 000331413300017
View details for PubMedID 24435044
Illuminating radiogenomic characteristics of glioblastoma multiforme through integration of MR imaging, messenger RNA expression, and DNA copy number variation.
2014; 270 (1): 1-2
To perform a multilevel radiogenomics study to elucidate the glioblastoma multiforme (GBM) magnetic resonance (MR) imaging radiogenomic signatures resulting from changes in messenger RNA (mRNA) expression and DNA copy number variation (CNV).Radiogenomic analysis was performed at MR imaging in 23 patients with GBM in this retrospective institutional review board-approved HIPAA-compliant study. Six MR imaging features-contrast enhancement, necrosis, contrast-to-necrosis ratio, infiltrative versus edematous T2 abnormality, mass effect, and subventricular zone (SVZ) involvement-were independently evaluated and correlated with matched genomic profiles (global mRNA expression and DNA copy number profiles) in a significant manner that also accounted for multiple hypothesis testing by using gene set enrichment analysis (GSEA), resampling statistics, and analysis of variance to gain further insight into the radiogenomic signatures in patients with GBM.GSEA was used to identify various oncogenic pathways with MR imaging features. Correlations between 34 gene loci were identified that showed concordant variations in gene dose and mRNA expression, resulting in an MR imaging, mRNA, and CNV radiogenomic association map for GBM. A few of the identified gene-to-trait associations include association of the contrast-to-necrosis ratio with KLK3 and RUNX3; association of SVZ involvement with Ras oncogene family members, such as RAP2A, and the metabolic enzyme TYMS; and association of vasogenic edema with the oncogene FOXP1 and PIK3IP1, which is a member of the PI3K signaling network.Construction of an MR imaging, mRNA, and CNV radiogenomic association map has led to identification of MR traits that are associated with some known high-grade glioma biomarkers and association with genomic biomarkers that have been identified for other malignancies but not GBM. Thus, the traits and genes identified on this map highlight new candidate radiogenomic biomarkers for further evaluation in future studies.
View details for DOI 10.1148/radiol.13130078
View details for PubMedID 24056404
Neuregulin Autocrine Signaling Promotes Self-Renewal of Breast Tumor-Initiating Cells by Triggering HER2/HER3 Activation
2014; 74 (1): 341-352
Currently, only patients with HER2-positive tumors are candidates for HER2-targeted therapies. However, recent clinical observations suggest that the survival of patients with HER2-low breast cancers, who lack HER2 amplification, may benefit from adjuvant therapy that targets HER2. In this study, we explored a mechanism through which these benefits may be obtained. Prompted by the hypothesis that HER2/HER3 signaling in breast tumor-initiating cells (TIC) promotes self-renewal and survival, we obtained evidence that neuregulin 1 (NRG1) produced by TICs promotes their proliferation and self-renewal in HER2-low tumors, including in triple-negative breast tumors. Pharmacologic inhibition of EGFR, HER2, or both receptors reduced breast TIC survival and self-renewal in vitro and in vivo and increased TIC sensitivity to ionizing radiation. Through a tissue microarray analysis, we found that NRG1 expression and associated HER2 activation occurred in a subset of HER2-low breast cancers. Our results offer an explanation for why HER2 inhibition blocks the growth of HER2-low breast tumors. Moreover, they argue that dual inhibition of EGFR and HER2 may offer a useful therapeutic strategy to target TICs in these tumors. In generating a mechanistic rationale to apply HER2-targeting therapies in patients with HER2-low tumors, this work shows why these therapies could benefit a considerably larger number of patients with breast cancer than they currently reach.
View details for DOI 10.1158/0008-5472.CAN-13-1055
View details for Web of Science ID 000329297600033
View details for PubMedID 24177178
View details for PubMedCentralID PMC3917843
Clinical implementation of intrafraction cone beam computed tomography imaging during lung tumor stereotactic ablative radiation therapy.
International journal of radiation oncology, biology, physics
2013; 87 (5): 917-923
To develop and clinically evaluate a volumetric imaging technique for assessing intrafraction geometric and dosimetric accuracy of stereotactic ablative radiation therapy (SABR).Twenty patients received SABR for lung tumors using volumetric modulated arc therapy (VMAT). At the beginning of each fraction, pretreatment cone beam computed tomography (CBCT) was used to align the soft-tissue tumor position with that in the planning CT. Concurrent with dose delivery, we acquired fluoroscopic radiograph projections during VMAT using the Varian on-board imaging system. Those kilovolt projections acquired during millivolt beam-on were automatically extracted, and intrafraction CBCT images were reconstructed using the filtered backprojection technique. We determined the time-averaged target shift during VMAT by calculating the center of mass of the tumor target in the intrafraction CBCT relative to the planning CT. To estimate the dosimetric impact of the target shift during treatment, we recalculated the dose to the GTV after shifting the entire patient anatomy according to the time-averaged target shift determined earlier.The mean target shift from intrafraction CBCT to planning CT was 1.6, 1.0, and 1.5 mm; the 95th percentile shift was 5.2, 3.1, 3.6 mm; and the maximum shift was 5.7, 3.6, and 4.9 mm along the anterior-posterior, left-right, and superior-inferior directions. Thus, the time-averaged intrafraction gross tumor volume (GTV) position was always within the planning target volume. We observed some degree of target blurring in the intrafraction CBCT, indicating imperfect breath-hold reproducibility or residual motion of the GTV during treatment. By our estimated dose recalculation, the GTV was consistently covered by the prescription dose (PD), that is, V100% above 0.97 for all patients, and minimum dose to GTV >100% PD for 18 patients and >95% PD for all patients.Intrafraction CBCT during VMAT can provide geometric and dosimetric verification of SABR valuable for quality assurance and potentially for treatment adaptation.
View details for DOI 10.1016/j.ijrobp.2013.08.015
View details for PubMedID 24113060
4D CT lung ventilation images are affected by the 4D CT sorting method.
2013; 40 (10): 101907-?
Four-dimensional (4D) computed tomography (CT) ventilation imaging is a novel promising technique for lung functional imaging. The current standard 4D CT technique using phase-based sorting frequently results in artifacts, which may deteriorate the accuracy of ventilation imaging. The purpose of this study was to quantify the variability of 4D CT ventilation imaging due to 4D CT sorting.4D CT image sets from nine lung cancer patients were each sorted by the phase-based method and anatomic similarity-based method, designed to reduce artifacts, with corresponding ventilation images created for each method. Artifacts in the resulting 4D CT images were quantified with the artifact score which was defined based on the difference between the normalized cross correlation for CT slices within a CT data segment and that for CT slices bordering the interface between adjacent CT data segments. The ventilation variation was quantified using voxel-based Spearman rank correlation coefficients for all lung voxels, and Dice similarity coefficients (DSC) for the spatial overlap of low-functional lung volumes. Furthermore, the correlations with matching single-photon emission CT (SPECT) ventilation images (assumed ground truth) were evaluated for three patients to investigate which sorting method provides higher physiologic accuracy.Anatomic similarity-based sorting reduced 4D CT artifacts compared to phase-based sorting (artifact score, 0.45 ± 0.14 vs 0.58 ± 0.24, p = 0.10 at peak-exhale; 0.63 ± 0.19 vs 0.71 ± 0.31, p = 0.25 at peak-inhale). The voxel-based correlation between the two ventilation images was 0.69 ± 0.26 on average, ranging from 0.03 to 0.85. The DSC was 0.71 ± 0.13 on average. Anatomic similarity-based sorting yielded significantly fewer lung voxels with paradoxical negative ventilation values than phase-based sorting (5.0 ± 2.6% vs 9.7 ± 8.4%, p = 0.05), and improved the correlation with SPECT ventilation regionally.The variability of 4D CT ventilation imaging due to 4D CT sorting was moderate overall and substantial in some cases, suggesting that 4D CT artifacts are an important source of variations in 4D CT ventilation imaging. Reduction of 4D CT artifacts provided more physiologically convincing and accurate ventilation estimates. Further studies are needed to confirm this result.
View details for DOI 10.1118/1.4820538
View details for PubMedID 24089909
Clinical impact of dose overestimation by effective path length calculation in stereotactic ablative radiation therapy of lung tumors.
Practical radiation oncology
2013; 3 (4): 294-300
To determine the clinical impact of calculated dose differences between effective path length (EPL) and Monte Carlo (MC) algorithms in stereotactic ablative radiation therapy (SABR) of lung tumors.We retrospectively analyzed the treatment plans and clinical outcomes of 77 consecutive patients treated with SABR for 82 lung tumors between 2003 and 2009 at our institution. Sixty treatments were originally planned using EPL, and 22 using MC. All plans were recalculated for the same beam specifications using MC and EPL, respectively. The doses covering 95%, 50%, and 5% (D95, D50, D5, respectively) of the target volumes were compared between EPL and MC (assumed to be the actual delivered dose), both as physical dose and biologically effective dose. Time to local recurrence was correlated with dose by Cox regression analysis. The relationship between tumor control probability (TCP) and biologically effective dose was determined via logistic regression and used to estimate the TCP decrements due to prescribing by EPL calculations.EPL overestimated dose compared with MC in all tumor dose-volume histogram parameters in all plans. The difference was >10% of the MC D95 to the planning target volume and gross tumor volume in 60 of 82 (73%) and 52 of 82 plans (63%), respectively. Local recurrence occurred in 13 of 82 tumors. Controlling for gross tumor volume, higher physical and biologically effective planning target volume D95 correlated significantly with local control (P = .007 and P = .045, respectively). Compared with MC, prescribing based on EPL translated to a median TCP decrement of 4.3% (range, 1.2%-37%) and a >5% decrement in 46% of tumors.Clinical follow-up for local lung tumor control in a sizable cohort of patients treated with SABR demonstrates that EPL overestimates dose by amounts that substantially decrease TCP in a large proportion. EPL algorithms should be avoided for lung tumor SABR.
View details for DOI 10.1016/j.prro.2012.09.003
View details for PubMedID 24674401
Migration of implanted markers for image-guided lung tumor stereotactic ablative radiotherapy.
Journal of applied clinical medical physics
2013; 14 (2): 4046-?
The purpose of this study was to quantify postimplantation migration of percutaneously implanted cylindrical gold seeds ("seeds") and platinum endovascular embolization coils ("coils") for tumor tracking in pulmonary stereotactic ablative radiotherapy (SABR). We retrospectively analyzed the migration of markers in 32 consecutive patients with computed tomography scans postimplantation and at simulation. We implanted 147 markers (59 seeds, 88 coils) in or around 34 pulmonary tumors over 32 procedures, with one lesion implanted twice. Marker coordinates were rigidly aligned by minimizing fiducial registration error (FRE), the root mean square of the differences in marker locations for each tumor between scans. To also evaluate whether single markers were responsible for most migration, we aligned with and without the outlier causing the largest FRE increase per tumor. We applied the resultant transformation to all markers. We evaluated migration of individual markers and FRE of each group. Median scan interval was 8 days. Median individual marker migration was 1.28 mm (interquartile range [IQR] 0.78-2.63 mm). Median lesion FRE was 1.56 mm (IQR 0.92-2.95 mm). Outlier identification yielded 1.03 mm median migration (IQR 0.52-2.21 mm) and 1.97 mm median FRE (IQR 1.44-4.32 mm). Outliers caused a mean and median shift in the centroid of 1.22 and 0.80 mm (95th percentile 2.52 mm). Seeds and coils had no statistically significant difference. Univariate analysis suggested no correlation of migration with the number of markers, contact with the chest wall, or time elapsed. Marker migration between implantation and simulation is limited and unlikely to cause geometric miss during tracking.
View details for DOI 10.1120/jacmp.v14i2.4046
View details for PubMedID 23470933
Migration of implanted markers for image-guided lung tumor stereotactic ablative radiotherapy
JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS
2013; 14 (2): 77-89
View details for Web of Science ID 000315898300008
The Optimal Use of Radiotherapy in Small Cell Lung Cancer
JOURNAL OF THE NATIONAL COMPREHENSIVE CANCER NETWORK
2013; 11 (1): 107-114
View details for Web of Science ID 000313575200013
Metabolic imaging metrics correlate with survival in early stage lung cancer treated with stereotactic ablative radiotherapy.
2012; 78 (3): 219-224
To test whether (18)F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) imaging metrics correlate with outcomes in patients with stage I non-small cell lung cancer (NSCLC) treated with stereotactic ablative radiotherapy (SABR).Fifty-four patients with stage I NSCLC underwent pre-SABR PET at simulation and/or post-SABR PET within 6 months. We analyzed maximum standardized uptake value (SUV(max)) and metabolic tumor volume defined using several thresholds (MTV50%, or MTV2, 4, 7, and 10). Endpoints included primary tumor control (PTC), progression-free survival (PFS), overall survival (OS) and cancer-specific survival (CSS). We performed Kaplan-Meier, competing risk, and Cox proportional hazards survival analyses.Patients received 25-60 Gy in 1 to 5 fractions. Median follow-up time was 13.2 months. The 1-year estimated PTC, PFS, OS and CSS were 100, 83, 87 and 94%, respectively. Pre-treatment SUV(max) (p=0.014), MTV(7) (p=0.0077), and MTV(10) (p=0.0039) correlated significantly with OS. In the low-MTV(7)vs. high-MTV(7) sub-groups, 1-year estimated OS was 100 vs. 78% (p=0.0077) and CSS was 100 vs. 88% (p=0.082).In this hypothesis-generating study we identified multiple pre-treatment PET-CT metrics as potential predictors of OS and CSS in patients with NSCLC treated with SABR. These could aid risk-stratification and treatment individualization if validated prospectively.
View details for DOI 10.1016/j.lungcan.2012.08.016
View details for PubMedID 23009727
- Metabolic imaging metrics correlate with survival in early stage lung cancer treated with stereotactic ablative radiotherapy LUNG CANCER 2012; 78 (3): 219-224
Stereotactic Ablative Radiotherapy for Reirradiation of Locally Recurrent Lung Tumors
JOURNAL OF THORACIC ONCOLOGY
2012; 7 (9): 1462-1465
Patients with thoracic tumors that recur after irradiation currently have limited therapeutic options. Retreatment using stereotactic ablative radiotherapy (SABR) is appealing for these patients because of its high conformity but has not been studied extensively. Here we report our experience with SABR for lung tumors in previously irradiated regions.We conducted a retrospective study of patients with primary lung cancer or metastatic lung tumors treated with SABR. We identified 17 such tumors in 15 patients and compared their outcomes with those of a cohort of 135 previously unirradiated lung tumors treated with SABR during the same time period.Twelve-month local control (LC) for retreated tumors was 65.5%, compared with 92.1% for tumors receiving SABR as initial treatment. Twelve-month LC was significantly worse for reirradiated tumors in which the time interval between treatments was 16 months or less (46.7%), compared with those with longer intertreatment intervals (87.5%). SABR reirradiation did not lead to significant increases in treatment-related toxicity.SABR for locally recurrent lung tumors arising in previously irradiated fields seems to be feasible and safe for appropriately selected patients. LC of retreated lesions was significantly lower, likely owing to the lower doses used for retreatment. Shorter time to retreatment was associated with increased risk of local failure, suggesting that these tumors may be particularly radioresistant. Our findings suggest that dose escalation may improve LC while maintaining acceptable levels of toxicity for these patients.
View details for DOI 10.1097/JTO.0b013e31825f22ce
View details for Web of Science ID 000308073300024
View details for PubMedID 22895143
Tumor Volume-Adapted Dosing in Stereotactic Ablative Radiotherapy of Lung Tumors
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2012; 84 (1): 231-237
Current stereotactic ablative radiotherapy (SABR) protocols for lung tumors prescribe a uniform dose regimen irrespective of tumor size. We report the outcomes of a lung tumor volume-adapted SABR dosing strategy.We retrospectively reviewed the outcomes in 111 patients with a total of 138 primary or metastatic lung tumors treated by SABR, including local control, regional control, distant metastasis, overall survival, and treatment toxicity. We also performed subset analysis on 83 patients with 97 tumors treated with a volume-adapted dosing strategy in which small tumors (gross tumor volume <12 mL) received single-fraction regimens with biologically effective doses (BED) <100 Gy (total dose, 18-25 Gy) (Group 1), and larger tumors (gross tumor volume ≥12 mL) received multifraction regimens with BED ≥100 Gy (total dose, 50-60 Gy in three to four fractions) (Group 2).The median follow-up time was 13.5 months. Local control for Groups 1 and 2 was 91.4% and 92.5%, respectively (p = 0.24) at 12 months. For primary lung tumors only (excluding metastases), local control was 92.6% and 91.7%, respectively (p = 0.58). Regional control, freedom from distant metastasis, and overall survival did not differ significantly between Groups 1 and 2. Rates of radiation pneumonitis, chest wall toxicity, and esophagitis were low in both groups, but all Grade 3 toxicities developed in Group 2 (p = 0.02).A volume-adapted dosing approach for SABR of lung tumors seems to provide excellent local control for both small- and large-volume tumors and may reduce toxicity.
View details for DOI 10.1016/j.ijrobp.2011.10.071
View details for Web of Science ID 000308061900060
View details for PubMedID 22381907
Intrafraction Verification of Gated RapidArc by Using Beam-Level Kilovoltage X-Ray Images
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2012; 83 (5): E709-E715
To verify the geometric accuracy of gated RapidArc treatment using kV images acquired during dose delivery.Twenty patients were treated using the gated RapidArc technique with a Varian TrueBeam STx linear accelerator. One to 7 metallic fiducial markers were implanted inside or near the tumor target before treatment simulation. For patient setup and treatment verification purposes, the internal target volume (ITV) was created, corresponding to each implanted marker. The gating signal was generated from the Real-time Position Management (RPM) system. At the beginning of each fraction, individualized respiratory gating amplitude thresholds were set based on fluoroscopic image guidance. During the treatment, we acquired kV images immediately before MV beam-on at every breathing cycle, using the on-board imaging system. After the treatment, all implanted markers were detected, and their 3-dimensional (3D) positions in the patient were estimated using software developed in-house. The distance from the marker to the corresponding ITV was calculated for each patient by averaging over all markers and all fractions.The average 3D distance between the markers and their ITVs was 0.8 ± 0.5 mm (range, 0-1.7 mm) and was 2.1 ± 1.2 mm at the 95th percentile (range, 0-3.8 mm). On average, a left-right margin of 0.6 mm, an anterior-posterior margin of 0.8 mm, and a superior-inferior margin of 1.5 mm is required to account for 95% of the intrafraction uncertainty in RPM-based RapidArc gating.To our knowledge, this is the first clinical report of intrafraction verification of respiration-gated RapidArc treatment in stereotactic ablative radiation therapy. For some patients, the markers deviated significantly from the ITV by more than 2 mm at the beginning of the MV beam-on. This emphasizes the need for gating techniques with beam-on/-off controlled directly by the actual position of the tumor target instead of external surrogates such as RPM.
View details for DOI 10.1016/j.ijrobp.2012.03.006
View details for Web of Science ID 000306128100022
View details for PubMedID 22554582
View details for PubMedCentralID PMC4476315
What the Diagnostic Radiologist Needs to Know about Radiation Oncology
2011; 261 (1): 30-44
Substantial technologic advances in radiation treatment planning and delivery have made possible exquisite tailoring of three-dimensional radiation dose distributions that conform to the tumor treatment volume while avoiding adjacent normal tissues. Although such highly precise treatment can increase the therapeutic ratio, it also introduces the potential that tumor extension outside the target is missed because it is unrecognized at the time of radiation treatment planning. As a result, accurate targeting of the tumor with radiation is of utmost importance to the radiation oncologist. Communication between diagnostic radiologists and radiation oncologists is essential, particularly given the subtleties that accompany image interpretation, to optimize the care of the cancer patient.
View details for DOI 10.1148/radiol.11101688
View details for Web of Science ID 000295039000006
View details for PubMedID 21931140
HIGH RETENTION AND SAFETY OF PERCUTANEOUSLY IMPLANTED ENDOVASCULAR EMBOLIZATION COILS AS FIDUCIAL MARKERS FOR IMAGE-GUIDED STEREOTACTIC ABLATIVE RADIOTHERAPY OF PULMONARY TUMORS
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2011; 81 (1): 85-90
To compare the retention rates of two types of implanted fiducial markers for stereotactic ablative radiotherapy (SABR) of pulmonary tumors, smooth cylindrical gold "seed" markers ("seeds") and platinum endovascular embolization coils ("coils"), and to compare the complication rates associated with the respective implantation procedures.We retrospectively analyzed the retention of percutaneously implanted markers in 54 consecutive patients between January 2004 and June 2009. A total of 270 markers (129 seeds, 141 coils) were implanted in or around 60 pulmonary tumors over 59 procedures. Markers were implanted using a percutaneous approach under computed tomography (CT) guidance. Postimplantation and follow-up imaging studies were analyzed to score marker retention relative to the number of markers implanted. Markers remaining near the tumor were scored as retained. Markers in a distant location (e.g., pleural space) were scored as lost. CT imaging artifacts near markers were quantified on radiation therapy planning scans.Immediately after implantation, 140 of 141 coils (99.3%) were retained, compared to 110 of 129 seeds (85.3%); the difference was highly significant (p<0.0001). Of the total number of lost markers, 45% were reported lost during implantation, but 55% were lost immediately afterwards. No additional markers were lost on longer-term follow-up. Implanted lesions were peripherally located for both seeds (mean distance, 0.33 cm from pleural surface) and coils (0.34 cm) (p=0.96). Incidences of all pneumothorax (including asymptomatic) and pneumothorax requiring chest tube placement were lower in implantation of coils (23% and 3%, respectively) vs. seeds (54% and 29%, respectively; p=0.02 and 0.01). The degree of CT artifact was similar between marker types.Retention of CT-guided percutaneously implanted coils is significantly better than that of seed markers. Furthermore, implanting coils is at least as safe as implanting seeds. Using coils should permit implantation of fewer markers and require fewer repeat implantation procedures owing to lost markers.
View details for DOI 10.1016/j.ijrobp.2010.04.037
View details for Web of Science ID 000294093300012
View details for PubMedID 20675070
Reducing 4D CT artifacts using optimized sorting based on anatomic similarity
2011; 38 (5): 2424-2429
Four-dimensional (4D) computed tomography (CT) has been widely used as a tool to characterize respiratory motion in radiotherapy. The two most commonly used 4D CT algorithms sort images by the associated respiratory phase or displacement into a predefined number of bins, and are prone to image artifacts at transitions between bed positions. The purpose of this work is to demonstrate a method of reducing motion artifacts in 4D CT by incorporating anatomic similarity into phase or displacement based sorting protocols.Ten patient datasets were retrospectively sorted using both the displacement and phase based sorting algorithms. Conventional sorting methods allow selection of only the nearest-neighbor image in time or displacement within each bin. In our method, for each bed position either the displacement or the phase defines the center of a bin range about which several candidate images are selected. The two dimensional correlation coefficients between slices bordering the interface between adjacent couch positions are then calculated for all candidate pairings. Two slices have a high correlation if they are anatomically similar. Candidates from each bin are then selected to maximize the slice correlation over the entire data set using the Dijkstra's shortest path algorithm. To assess the reduction of artifacts, two thoracic radiation oncologists independently compared the resorted 4D datasets pairwise with conventionally sorted datasets, blinded to the sorting method, to choose which had the least motion artifacts. Agreement between reviewers was evaluated using the weighted kappa score.Anatomically based image selection resulted in 4D CT datasets with significantly reduced motion artifacts with both displacement (P = 0.0063) and phase sorting (P = 0.00022). There was good agreement between the two reviewers, with complete agreement 34 times and complete disagreement 6 times.Optimized sorting using anatomic similarity significantly reduces 4D CT motion artifacts compared to conventional phase or displacement based sorting. This improved sorting algorithm is a straightforward extension of the two most common 4D CT sorting algorithms.
View details for DOI 10.1118/1.3577601
View details for Web of Science ID 000290625700016
View details for PubMedID 21776777
Tumor Volume as a Potential Imaging-Based Risk-Stratification Factor in Trimodality Therapy for Locally Advanced Non-small Cell Lung Cancer
JOURNAL OF THORACIC ONCOLOGY
2011; 6 (5): 920-926
The role of trimodality therapy for locally advanced non-small cell lung cancer (NSCLC) continues to be defined. We hypothesized that imaging parameters on pre- and postradiation positron emission tomography (PET)-computed tomography (CT) imaging are prognostic for outcome after preoperative chemoradiotherapy (CRT)/resection/consolidation chemotherapy and could help risk-stratify patients in clinical trials.We enrolled 13 patients on a prospective clinical trial of trimodality therapy for resectable locally advanced NSCLC. PET-CT was acquired for radiation planning and after 45 Gy. Gross tumor volume (GTV) and standardized uptake value were measured at pre- and post-CRT time points and correlated with nodal pathologic complete response, loco-regional and/or distant progression, and overall survival. In addition, we evaluated the performance of automatic deformable image registration (ADIR) software for volumetric response assessment.All patients responded with average total GTV reductions after 45 Gy of 43% (range: 27-64%). Pre- and post-CRT GTVs were highly correlated (R² = 0.9), and their respective median values divided the patients into the same two groups. ADIR measurements agreed closely with manually segmented post-CRT GTVs. Patients with GTV ≥ median (137 ml pre-CRT and 67 ml post-CRT) had 3-year progression-free survival (PFS) of 14% versus 75% for GTV less than median, a significant difference (p = 0.049). Pre- and post-CRT PET-standardized uptake value did not correlate significantly with pathologic complete response, PFS, or overall survival.Preoperative CRT with carboplatin/docetaxel/45 Gy resulted in excellent response rates. In this exploratory analysis, pre- and post-CRT GTV predicted PFS in trimodality therapy, consistent with our earlier studies in a broader cohort of NSCLC. ADIR seems robust enough for volumetric response assessment in clinical trials.
View details for DOI 10.1097/JTO.0b013e31821517db
View details for Web of Science ID 000289554100012
View details for PubMedID 21774104
The Myc Connection: ES Cells and Cancer
2010; 143 (2): 184-186
Gene profiling experiments have revealed similarities between cancer and embryonic stem (ES) cells. Kim et al. (2010) dissect the gene expression signature of ES cells into three functional modules and find that the Myc module, including genes targeted by Myc-interacting proteins, accounts for most of the similarity between ES and cancer cells.
View details for DOI 10.1016/j.cell.2010.09.046
View details for Web of Science ID 000283052200007
View details for PubMedID 20946977
STEREOTACTIC ABLATIVE RADIOTHERAPY SHOULD BE COMBINED WITH A HYPOXIC CELL RADIOSENSITIZER
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
2010; 78 (2): 323-327
To evaluate the effect of tumor hypoxia on the expected level of cell killing by regimens of stereotactic ablative radiotherapy (SABR) and to determine the extent to which the negative effect of hypoxia could be prevented using a clinically available hypoxic cell radiosensitizer.We have calculated the expected level of tumor cell killing from regimens of SABR, both with and without the assumption that 20% of the tumor cells are hypoxic, using the standard linear quadratic model and the universal survival curve modification. We compare the results obtained with our own clinical data for lung tumors of different sizes and with published data from other studies. We also have calculated the expected effect on cell survival of adding the hypoxic cell sensitizer etanidazole at clinically achievable drug concentrations. Modeling tumor cell killing with any of the currently used regimens of SABR produces results that are inconsistent with the majority of clinical findings if tumor hypoxia is not considered. However, with the assumption of tumor hypoxia, the expected level of cell killing is consistent with clinical data. For only some of the smallest tumors are the clinical data consistent with no tumor hypoxia, but there could be other reasons for the sensitivity of these tumors. The addition of etanidazole at clinically achievable tumor concentrations produces a large increase in the expected level of tumor cell killing from the large radiation doses used in SABR.The presence of tumor hypoxia is a major negative factor in limiting the curability of tumors by SABR at radiation doses that are tolerable to surrounding normal tissues. However, this negative effect of hypoxia could be overcome by the addition of clinically tolerable doses of the hypoxic cell radiosensitizer etanidazole.
View details for DOI 10.1016/j.ijrobp.2010.04.070
View details for Web of Science ID 000282147000002
View details for PubMedID 20832663
- Metastatic Cancer Stem Cells: An Opportunity for Improving Cancer Treatment? CELL STEM CELL 2010; 6 (6): 502-503
Identification, molecular characterization, clinical prognosis, and therapeutic targeting of human bladder tumor-initiating cells
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2009; 106 (33): 14016-14021
Major clinical issues in bladder cancer include the identification of prediction markers and novel therapeutic targets for invasive bladder cancer. In the current study, we describe the isolation and characterization of a tumor-initiating cell (T-IC) subpopulation in primary human bladder cancer, based on the expression of markers similar to that of normal bladder basal cells (Lineage-CD44(+)CK5(+)CK20(-)). The bladder T-IC subpopulation was defined functionally by its enriched ability to induce xenograft tumors in vivo that recapitulated the heterogeneity of the original tumor. Further, molecular analysis of more than 300 bladder cancer specimens revealed heterogeneity among activated oncogenic pathways in T-IC (e.g., 80% Gli1, 45% Stat3, 10% Bmi-1, and 5% beta-catenin). Despite this molecular heterogeneity, we identified a unique bladder T-IC gene signature by gene chip analysis. This T-IC gene signature, which effectively distinguishes muscle-invasive bladder cancer with worse clinical prognosis from non-muscle-invasive (superficial) cancer, has significant clinical value. It also can predict the progression of a subset of recurring non-muscle-invasive cancers. Finally, we found that CD47, a protein that provides an inhibitory signal for macrophage phagocytosis, is highly expressed in bladder T-ICs compared with the rest of the tumor. Blockade of CD47 by a mAb resulted in macrophage engulfment of bladder cancer cells in vitro. In summary, we have identified a T-IC subpopulation with potential prognostic and therapeutic value for invasive bladder cancer.
View details for DOI 10.1073/pnas.0906549106
View details for Web of Science ID 000269078700071
View details for PubMedID 19666525
Downregulation of miRNA-200c Links Breast Cancer Stem Cells with Normal Stem Cells
2009; 138 (3): 592-603
Human breast tumors contain a breast cancer stem cell (BCSC) population with properties reminiscent of normal stem cells. We found 37 microRNAs that were differentially expressed between human BCSCs and nontumorigenic cancer cells. Three clusters, miR-200c-141, miR-200b-200a-429, and miR-183-96-182 were downregulated in human BCSCs, normal human and murine mammary stem/progenitor cells, and embryonal carcinoma cells. Expression of BMI1, a known regulator of stem cell self-renewal, was modulated by miR-200c. miR-200c inhibited the clonal expansion of breast cancer cells and suppressed the growth of embryonal carcinoma cells in vitro. Most importantly, miR-200c strongly suppressed the ability of normal mammary stem cells to form mammary ducts and tumor formation driven by human BCSCs in vivo. The coordinated downregulation of three microRNA clusters and the similar functional regulation of clonal expansion by miR-200c provide a molecular link that connects BCSCs with normal stem cells.
View details for DOI 10.1016/j.cell.2009.07.011
View details for Web of Science ID 000268771900022
View details for PubMedID 19665978
Association of reactive oxygen species levels and radioresistance in cancer stem cells
2009; 458 (7239): 780-U123
The metabolism of oxygen, although central to life, produces reactive oxygen species (ROS) that have been implicated in processes as diverse as cancer, cardiovascular disease and ageing. It has recently been shown that central nervous system stem cells and haematopoietic stem cells and early progenitors contain lower levels of ROS than their more mature progeny, and that these differences are critical for maintaining stem cell function. We proposed that epithelial tissue stem cells and their cancer stem cell (CSC) counterparts may also share this property. Here we show that normal mammary epithelial stem cells contain lower concentrations of ROS than their more mature progeny cells. Notably, subsets of CSCs in some human and murine breast tumours contain lower ROS levels than corresponding non-tumorigenic cells (NTCs). Consistent with ROS being critical mediators of ionizing-radiation-induced cell killing, CSCs in these tumours develop less DNA damage and are preferentially spared after irradiation compared to NTCs. Lower ROS levels in CSCs are associated with increased expression of free radical scavenging systems. Pharmacological depletion of ROS scavengers in CSCs markedly decreases their clonogenicity and results in radiosensitization. These results indicate that, similar to normal tissue stem cells, subsets of CSCs in some tumours contain lower ROS levels and enhanced ROS defences compared to their non-tumorigenic progeny, which may contribute to tumour radioresistance.
View details for DOI 10.1038/nature07733
View details for Web of Science ID 000265193600045
View details for PubMedID 19194462
View details for PubMedCentralID PMC2778612
Therapeutic Implications of the Cancer Stem Cell Hypothesis
SEMINARS IN RADIATION ONCOLOGY
2009; 19 (2): 78-86
A growing body of evidence indicates that subpopulations of cancer stem cells (CSCs) drive and maintain many types of human malignancies. These findings have important implications for the development and evaluation of oncologic therapies and present opportunities for potential gains in patient outcome. The existence of CSCs mandates careful analysis and comparison of normal tissue stem cells and CSCs to identify differences between the two cell types. The development of CSC-targeted treatments will face a number of potential hurdles, including normal stem cell toxicity and the acquisition of treatment resistance, which must be considered in order to maximize the chance that such therapies will be successful.
View details for DOI 10.1016/j.semradonc.2008.11.002
View details for Web of Science ID 000264310800003
View details for PubMedID 19249645
Identification of noninvasive imaging surrogates for brain tumor gene-expression modules
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2008; 105 (13): 5213-5218
Glioblastoma multiforme (GBM) is the most common and lethal primary brain tumor in adults. We combined neuroimaging and DNA microarray analysis to create a multidimensional map of gene-expression patterns in GBM that provided clinically relevant insights into tumor biology. Tumor contrast enhancement and mass effect predicted activation of specific hypoxia and proliferation gene-expression programs, respectively. Overexpression of EGFR, a receptor tyrosine kinase and potential therapeutic target, was also directly inferred by neuroimaging and was validated in an independent set of tumors by immunohistochemistry. Furthermore, imaging provided insights into the intratumoral distribution of gene-expression patterns within GBM. Most notably, an "infiltrative" imaging phenotype was identified that predicted patient outcome. Patients with this imaging phenotype had a greater tendency toward having multiple tumor foci and demonstrated significantly shorter survival than their counterparts. Our findings provide an in vivo portrait of genome-wide gene expression in GBM and offer a potential strategy for noninvasively selecting patients who may be candidates for individualized therapies.
View details for DOI 10.1073/pnas.0801279105
View details for Web of Science ID 000254723700047
View details for PubMedID 18362333
View details for PubMedCentralID PMC2278224
Isolation and molecular characterization of cancer stem cells in MMTV-Wnt-1 murine breast tumors
2008; 26 (2): 364-371
In human breast cancers, a phenotypically distinct minority population of tumorigenic (TG) cancer cells (sometimes referred to as cancer stem cells) drives tumor growth when transplanted into immunodeficient mice. Our objective was to identify a mouse model of breast cancer stem cells that could have relevance to the study of human breast cancer. To do so, we used breast tumors of the mouse mammary tumor virus (MMTV)-Wnt-1 mice. MMTV-Wnt-1 breast tumors were harvested, dissociated into single-cell suspensions, and sorted by flow cytometry on Thy1, CD24, and CD45. Sorted cells were then injected into recipient background FVB/NJ female syngeneic mice. In six of seven tumors examined, Thy1+CD24+ cancer cells, which constituted approximately 1%-4% of tumor cells, were highly enriched for cells capable of regenerating new tumors compared with cells of the tumor that did not fit this profile ("not-Thy1+CD24+"). Resultant tumors had a phenotypic diversity similar to that of the original tumor and behaved in a similar manner when passaged. Microarray analysis comparing Thy1+CD24+ tumor cells to not-Thy1+CD24+ cells identified a list of differentially expressed genes. Orthologs of these differentially expressed genes predicted survival of human breast cancer patients from two different study groups. These studies suggest that there is a cancer stem cell compartment in the MMTV-Wnt-1 murine breast tumor and that there is a clinical utility of this model for the study of cancer stem cells.
View details for DOI 10.1634/stemcells.2007-0440
View details for Web of Science ID 000253372600008
View details for PubMedID 17975224
Type I collagen is overexpressed in medulloblastoma as a component of tumor microenvironment
JOURNAL OF NEURO-ONCOLOGY
2008; 86 (2): 133-141
Medulloblastoma is the most common malignant brain tumor of children, and more specific and effective therapeutic management needs to be developed to improve upon existing survival rates and to avoid side-effects from current treatment. Gain of chromosome seven is the most frequent chromosome copy number aberration in medulloblastoma, suggesting that overexpression of genes on chromosome seven might be important for the pathogenesis of medulloblastoma. We used microarrays to identify chromosome seven genes overexpressed in medulloblastoma specimens, and validated using data from published gene expression datasets. The gene encoding the alpha 2 subunit of type I collagen, COL1A2, was overexpressed in all three datasets. Immunohistochemistry of tumor tissues revealed type I collagen in the leptomeninges, and in the extracellular matrix surrounding blood vessels and medulloblastoma cells. Expression of both type I collagen and the beta1 subunit of integrin, a subunit of a known type I collagen receptor, localized to the same area of medulloblastoma. Adherence of D283 medulloblastoma cells to type I collagen matrix in vitro depends on the beta1 subunit of integrin. Because medulloblastoma is characteristic of high vascularity, and because inhibition of type I collagen synthesis has been shown to suppress angiogenesis and tumor growth, our data suggest that type I collagen might be a potential therapeutic target for treating medulloblastoma.
View details for DOI 10.1007/s11060-007-9457-5
View details for Web of Science ID 000251488000002
View details for PubMedID 17653508
- Cancer stem cells and radiotherapy: New insights into tumor radioresistance JOURNAL OF THE NATIONAL CANCER INSTITUTE 2006; 98 (24): 1755-1757
Cell-type specific gene expression profiles of leukocytes in human peripheral blood
Blood is a complex tissue comprising numerous cell types with distinct functions and corresponding gene expression profiles. We attempted to define the cell type specific gene expression patterns for the major constituent cells of blood, including B-cells, CD4+ T-cells, CD8+ T-cells, lymphocytes and granulocytes. We did this by comparing the global gene expression profiles of purified B-cells, CD4+ T-cells, CD8+ T-cells, granulocytes, and lymphocytes using cDNA microarrays.Unsupervised clustering analysis showed that similar cell populations from different donors share common gene expression profiles. Supervised analyses identified gene expression signatures for B-cells (427 genes), T-cells (222 genes), CD8+ T-cells (23 genes), granulocytes (411 genes), and lymphocytes (67 genes). No statistically significant gene expression signature was identified for CD4+ cells. Genes encoding cell surface proteins were disproportionately represented among the genes that distinguished among the lymphocyte subpopulations. Lymphocytes were distinguishable from granulocytes based on their higher levels of expression of genes encoding ribosomal proteins, while granulocytes exhibited characteristic expression of various cell surface and inflammatory proteins.The genes comprising the cell-type specific signatures encompassed many of the genes already known to be involved in cell-type specific processes, and provided clues that may prove useful in discovering the functions of many still unannotated genes. The most prominent feature of the cell type signature genes was the enrichment of genes encoding cell surface proteins, perhaps reflecting the importance of specialized systems for sensing the environment to the physiology of resting leukocytes.
View details for DOI 10.1186/1471-2164-7-115
View details for Web of Science ID 000238364000001
View details for PubMedID 16704732
Genome-scale identification of membrane-associated human mRNAs
2006; 2 (1): 39-50
The subcellular localization of proteins is critical to their biological roles. Moreover, whether a protein is membrane-bound, secreted, or intracellular affects the usefulness of, and the strategies for, using a protein as a diagnostic marker or a target for therapy. We employed a rapid and efficient experimental approach to classify thousands of human gene products as either "membrane-associated/secreted" (MS) or "cytosolic/nuclear" (CN). Using subcellular fractionation methods, we separated mRNAs associated with membranes from those associated with the soluble cytosolic fraction and analyzed these two pools by comparative hybridization to DNA microarrays. Analysis of 11 different human cell lines, representing lymphoid, myeloid, breast, ovarian, hepatic, colon, and prostate tissues, identified more than 5,000 previously uncharacterized MS and more than 6,400 putative CN genes at high confidence levels. The experimentally determined localizations correlated well with in silico predictions of signal peptides and transmembrane domains, but also significantly increased the number of human genes that could be cataloged as encoding either MS or CN proteins. Using gene expression data from a variety of primary human malignancies and normal tissues, we rationally identified hundreds of MS gene products that are significantly overexpressed in tumors compared to normal tissues and thus represent candidates for serum diagnostic tests or monoclonal antibody-based therapies. Finally, we used the catalog of CN gene products to generate sets of candidate markers of organ-specific tissue injury. The large-scale annotation of subcellular localization reported here will serve as a reference database and will aid in the rational design of diagnostic tests and molecular therapies for diverse diseases.
View details for DOI 10.1371/journal.pgen.0020011
View details for Web of Science ID 000239481100004
View details for PubMedID 16415983
Gene expression profiling reveals molecularly and clinically distinct subtypes of glioblastoma multiforme
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2005; 102 (16): 5814-5819
Glioblastoma multiforme (GBM) is the most common form of malignant glioma, characterized by genetic instability, intratumoral histopathological variability, and unpredictable clinical behavior. We investigated global gene expression in surgical samples of brain tumors. Gene expression profiling revealed large differences between normal brain samples and tumor tissues and between GBMs and lower-grade oligodendroglial tumors. Extensive differences in gene expression were found among GBMs, particularly in genes involved in angiogenesis, immune cell infiltration, and extracellular matrix remodeling. We found that the gene expression patterns in paired specimens from the same GBM invariably were more closely related to each other than to any other tumor, even when the paired specimens had strikingly divergent histologies. Survival analyses revealed a set of approximately 70 genes more highly expressed in rapidly progressing tumors that stratified GBMs into two groups that differed by >4-fold in median duration of survival. We further investigated one gene from the group, FABP7, and confirmed its association with survival in two unrelated cohorts totaling 105 patients. Expression of FABP7 enhanced the motility of glioma-derived cells in vitro. Our analyses thus identify and validate a prognostic marker of both biologic and clinical significance and provide a series of putative markers for additional evaluation.
View details for DOI 10.1073/pnas.0402870102
View details for Web of Science ID 000228565200034
View details for PubMedID 15827123
Differential gene expression in anatomical compartments of the human eye
2005; 6 (9)
The human eye is composed of multiple compartments, diverse in form, function, and embryologic origin, that work in concert to provide us with our sense of sight. We set out to systematically characterize the global gene expression patterns that specify the distinctive characteristics of the various eye compartments.We used DNA microarrays representing approximately 30,000 human genes to analyze gene expression in the cornea, lens, iris, ciliary body, retina, and optic nerve. The distinctive patterns of expression in each compartment could be interpreted in relation to the physiology and cellular composition of each tissue. Notably, the sets of genes selectively expressed in the retina and in the lens were particularly large and diverse. Genes with roles in immune defense, particularly complement components, were expressed at especially high levels in the anterior segment tissues. We also found consistent differences between the gene expression patterns of the macula and peripheral retina, paralleling the differences in cell layer densities between these regions. Based on the hypothesis that genes responsible for diseases that affect a particular eye compartment are likely to be selectively expressed in that compartment, we compared our gene expression signatures with genetic mapping studies to identify candidate genes for diseases affecting the cornea, lens, and retina.Through genome-scale gene expression profiling, we were able to discover distinct gene expression 'signatures' for each eye compartment and identified candidate disease genes that can serve as a reference database for investigating the physiology and pathophysiology of the eye.
View details for DOI 10.1186/gb-2005-6-9-r74
View details for Web of Science ID 000232301600008
View details for PubMedID 16168081
A method for detecting and correcting feature misidentification on expression microarrays
Much of the microarray data published at Stanford is based on mouse and human arrays produced under controlled and monitored conditions at the Brown and Botstein laboratories and at the Stanford Functional Genomics Facility (SFGF). Nevertheless, as large datasets based on the Stanford Human array began to accumulate, a small but significant number of discrepancies were detected that required a serious attempt to track down the original source of error. Due to a controlled process environment, sufficient data was available to accurately track the entire process leading to up to the final expression data. In this paper, we describe our statistical methods to detect the inconsistencies in microarray data that arise from process errors, and discuss our technique to locate and fix these errors.To date, the Brown and Botstein laboratories and the Stanford Functional Genomics Facility have together produced 40,000 large-scale (10-50,000 feature) cDNA microarrays. By applying the heuristic described here, we have been able to check most of these arrays for misidentified features, and have been able to confidently apply fixes to the data where needed. Out of the 265 million features checked in our database, problems were detected and corrected on 1.3 million of them.Process errors in any genome scale high throughput production regime can lead to subsequent errors in data analysis. We show the value of tracking multi-step high throughput operations by using this knowledge to detect and correct misidentified data on gene expression microarrays.
View details for DOI 10.1186/1471-2164-5-64
View details for Web of Science ID 000224203400001
View details for PubMedID 15357875
Presynaptic homeostasis at CNS nerve terminals compensates for lack of a key Ca2+ entry pathway
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2004; 101 (10): 3609-3614
At central synapses, P/Q-type Ca(2+) channels normally provide a critical Ca(2+) entry pathway for neurotransmission. Nevertheless, we found that nerve terminals lacking alpha(1A) (Ca(V)2.1), the pore-forming subunit of P/Q-type channels, displayed a remarkable preservation of synaptic function. Two consistent physiological changes reflective of synaptic homeostasis were observed in cultured hippocampal neurons derived from alpha(1A) (-/-) mice. First, the presynaptic response to an ionophore-mediated Ca(2+) elevation was 50% greater, indicating an enhanced Ca(2+) sensitivity of the release machinery. Second, basal miniature excitatory postsynaptic current frequency in alpha(1A) (-/-) neurons was increased 2-fold compared with WT neurons and occluded the normal response of presynaptic terminals to cAMP elevation, suggesting that the compensatory mechanism in alpha(1A) (-/-) synapses and the modulation of presynaptic function by PKA might share a final common pathway. We used cDNA microarray analysis to identify molecular changes underlying homeostatic regulation in the alpha(1A) (-/-) hippocampus. The 40,000 entries in our custom-made array included likely targets of presynaptic homeostasis, along with many other transcripts, allowing a wide-ranging examination of gene expression. The developmental pattern of changes in transcript levels relative to WT was striking; mRNAs at 5 and 11 days postnatal showed little deviation, but clear differences emerged by 22 days. Many of the transcripts that differed significantly in abundance corresponded to known genes that could be incorporated within a logical pattern consistent with the modulation of presynaptic function. Changes in endocytotic proteins, signal transduction kinases, and candidates for Ca(2+)-sensing molecules were consistent with implications of the direct physiological experiments.
View details for DOI 10.1073/pnas.0308188100
View details for Web of Science ID 000220163800052
View details for PubMedID 14990796
T cell receptor-independent basal signaling via Erk and Abl kinases suppresses RAG gene expression.
2003; 1 (2): E53-?
Signal transduction pathways guided by cellular receptors commonly exhibit low-level constitutive signaling in a continuous, ligand-independent manner. The dynamic equilibrium of positive and negative regulators establishes such a tonic signal. Ligand-independent signaling by the precursors of mature antigen receptors regulates development of B and T lymphocytes. Here we describe a basal signal that controls gene expression profiles in the Jurkat T cell line and mouse thymocytes. Using DNA microarrays and Northern blots to analyze unstimulated cells, we demonstrate that expression of a cluster of genes, including RAG-1 and RAG-2, is repressed by constitutive signals requiring the adapter molecules LAT and SLP-76. This TCR-like pathway results in constitutive low-level activity of Erk and Abl kinases. Inhibition of Abl by the drug STI-571 or inhibition of signaling events upstream of Erk increases RAG-1 expression. Our data suggest that physiologic gene expression programs depend upon tonic activity of signaling pathways independent of receptor ligation.
View details for PubMedID 14624253
- T cell receptor-independent basal signaling via Erk and Abl kinases suppresses RAG gene expression PLOS BIOLOGY 2003; 1 (2): 271-287
Gene expression patterns in ovarian carcinomas
MOLECULAR BIOLOGY OF THE CELL
2003; 14 (11): 4376-4386
We used DNA microarrays to characterize the global gene expression patterns in surface epithelial cancers of the ovary. We identified groups of genes that distinguished the clear cell subtype from other ovarian carcinomas, grade I and II from grade III serous papillary carcinomas, and ovarian from breast carcinomas. Six clear cell carcinomas were distinguished from 36 other ovarian carcinomas (predominantly serous papillary) based on their gene expression patterns. The differences may yield insights into the worse prognosis and therapeutic resistance associated with clear cell carcinomas. A comparison of the gene expression patterns in the ovarian cancers to published data of gene expression in breast cancers revealed a large number of differentially expressed genes. We identified a group of 62 genes that correctly classified all 125 breast and ovarian cancer specimens. Among the best discriminators more highly expressed in the ovarian carcinomas were PAX8 (paired box gene 8), mesothelin, and ephrin-B1 (EFNB1). Although estrogen receptor was expressed in both the ovarian and breast cancers, genes that are coregulated with the estrogen receptor in breast cancers, including GATA-3, LIV-1, and X-box binding protein 1, did not show a similar pattern of coexpression in the ovarian cancers.
View details for Web of Science ID 000186738300005
View details for PubMedID 12960427
Individuality and variation in gene expression patterns in human blood
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2003; 100 (4): 1896-1901
The nature and extent of interindividual and temporal variation in gene expression patterns in specific cells and tissues is an important and relatively unexplored issue in human biology. We surveyed variation in gene expression patterns in peripheral blood from 75 healthy volunteers by using cDNA microarrays. Characterization of the variation in gene expression in healthy tissue is an essential foundation for the recognition and interpretation of the changes in these patterns associated with infections and other diseases, and peripheral blood was selected because it is a uniquely accessible tissue in which to examine this variation in patients or healthy volunteers in a clinical setting. Specific features of interindividual variation in gene expression patterns in peripheral blood could be traced to variation in the relative proportions of specific blood cell subsets; other features were correlated with gender, age, and the time of day at which the sample was taken. An analysis of multiple sequential samples from the same individuals allowed us to discern donor-specific patterns of gene expression. These data help to define human individuality and provide a database with which disease-associated gene expression patterns can be compared.
View details for DOI 10.1073/pnas.252784499
View details for Web of Science ID 000181073000082
View details for PubMedID 12578971
SOURCE: a unified genomic resource of functional annotations, ontologies, and gene expression data
NUCLEIC ACIDS RESEARCH
2003; 31 (1): 219-223
The explosion in the number of functional genomic datasets generated with tools such as DNA microarrays has created a critical need for resources that facilitate the interpretation of large-scale biological data. SOURCE is a web-based database that brings together information from a broad range of resources, and provides it in manner particularly useful for genome-scale analyses. SOURCE's GeneReports include aliases, chromosomal location, functional descriptions, GeneOntology annotations, gene expression data, and links to external databases. We curate published microarray gene expression datasets and allow users to rapidly identify sets of co-regulated genes across a variety of tissues and a large number of conditions using a simple and intuitive interface. SOURCE provides content both in gene and cDNA clone-centric pages, and thus simplifies analysis of datasets generated using cDNA microarrays. SOURCE is continuously updated and contains the most recent and accurate information available for human, mouse, and rat genes. By allowing dynamic linking to individual gene or clone reports, SOURCE facilitates browsing of large genomic datasets. Finally, SOURCEs batch interface allows rapid extraction of data for thousands of genes or clones at once and thus facilitates statistical analyses such as assessing the enrichment of functional attributes within clusters of genes. SOURCE is available at http://source.stanford.edu.
View details for DOI 10.1093/nar/gkg014
View details for Web of Science ID 000181079700050
View details for PubMedID 12519986
Genomic expression programs and the integration of the CD28 costimulatory signal in T cell activation
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2002; 99 (18): 11796-11801
Optimal activation of T cells requires effective occupancy of both the antigen-specific T cell receptor and a second coreceptor such as CD28. We used cDNA microarrays to characterize the genomic expression program in human peripheral T cells responding to stimulation of these receptors. We found that CD28 agonists alone elicited few, but reproducible, changes in gene expression, whereas CD3 agonists elicited a multifaceted temporally choreographed gene expression program. The principal effect of simultaneous engagement of CD28 was to increase the amplitude of the CD3 transcriptional response. The induced genes whose expression was most enhanced by costimulation were significantly enriched for known targets of nuclear factor of activated T cells (NFAT) transcription factors. This enhancement was nearly abolished by blocking the nuclear translocation of NFATc by using the calcineurin inhibitor FK506. CD28 signaling promoted phosphorylation, and thus inactivation, of the NFAT nuclear export kinase glycogen synthase kinase-3 (GSK3), coincident with enhanced dephosphorylation of NFATc proteins. These results provide a detailed picture of the transcriptional program of T cell activation and suggest that enhancement of transcriptional activation by NFAT, through inhibition of its nuclear export, plays a key role in mediating the CD28 costimulatory signal.
View details for DOI 10.1073/pnas.092284399
View details for Web of Science ID 000177843100048
View details for PubMedID 12195013
View details for PubMedCentralID PMC129348
Transformation of follicular lymphoma to diffuse large-cell lymphoma: Alternative patterns with increased or decreased expression of c-myc and its regulated genes
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2002; 99 (13): 8886-8891
The natural history of follicular lymphoma (FL) is frequently characterized by transformation to a more aggressive diffuse large B cell lymphoma (DLBCL). We compared the gene-expression profiles between transformed DLBCL and their antecedent FL. No genes were observed to increase or decrease their expression in all of the cases of histological transformation. However, two different gene-expression profiles associated with the transformation process were defined, one in which c-myc and genes regulated by c-myc showed increased expression and one in which these same genes showed decreased expression. Further, there was a striking difference in gene-expression profiles between transformed DLBCL and de novo DLBCL, because the gene-expression profile of transformed DLBCL was more similar to their antecedent FL than to de novo DLBCL. This study demonstrates that transformation from FL to DLBCL can occur by alternative pathways and that transformed DLBCL and de novo DLBCL have very different gene-expression profiles that may underlie the different clinical behaviors of these two types of morphologically similar lymphomas.
View details for DOI 10.1073/pnas.132253599
View details for Web of Science ID 000176478200075
View details for PubMedID 12077300
Transcriptional response of human mast cells stimulated via the Fc(epsilon)RI and identification of mast cells as a source of IL-11.
2002; 3: 5-?
In asthma and other allergic disorders, the activation of mast cells by IgE and antigen induces the cells to release histamine and other mediators of inflammation, as well as to produce certain cytokines and chemokines. To search for new mast cell products, we used complementary DNA microarrays to analyze gene expression in human umbilical cord blood-derived mast cells stimulated via the high-affinity IgE receptor (Fc(epsilon)RI).One to two hours after Fc(epsilon)RI-dependent stimulation, more than 2,400 genes (about half of which are of unknown function) exhibited 2-200 fold changes in expression. The transcriptional program included changes in the expression of IL-11 and at least 30 other cytokines and chemokines. Human mast cells secreted 130-529 pg of IL-11/106 cells by 6 h after stimulation with anti-IgE.Our initial analysis of the transcriptional program induced in in vitro-derived human mast cells stimulated via the Fc(epsilon)RI has identified many products that heretofore have not been associated with this cell type, but which may significantly influence mast cell function in IgE-associated host responses. We also have demonstrated that mast cells stimulated via the Fc(epsilon)RI can secrete IL-11. Based on the previously reported biological effects of IL-11, our results suggest that production of IL-11 may represent one link between IgE-dependent mast cell activation in subjects with allergic asthma and the development of a spectrum of structural changes in the airways of these individuals; such changes, collectively termed "airway remodeling," can constitute an important long term consequence of asthma.
View details for PubMedID 12079505
In vivo regulation of human skeletal muscle gene expression by thyroid hormone
2002; 12 (2): 281-291
Thyroid hormones are key regulators of metabolism that modulate transcription via nuclear receptors. Hyperthyroidism is associated with increased metabolic rate, protein breakdown, and weight loss. Although the molecular actions of thyroid hormones have been studied thoroughly, their pleiotropic effects are mediated by complex changes in expression of an unknown number of target genes. Here, we measured patterns of skeletal muscle gene expression in five healthy men treated for 14 days with 75 microg of triiodothyronine, using 24,000 cDNA element microarrays. To analyze the data, we used a new statistical method that identifies significant changes in expression and estimates the false discovery rate. The 381 up-regulated genes were involved in a wide range of cellular functions including transcriptional control, mRNA maturation, protein turnover, signal transduction, cellular trafficking, and energy metabolism. Only two genes were down-regulated. Most of the genes are novel targets of thyroid hormone. Cluster analysis of triiodothyronine-regulated gene expression among 19 different human tissues or cell lines revealed sets of coregulated genes that serve similar biologic functions. These results define molecular signatures that help to understand the physiology and pathophysiology of thyroid hormone action.
View details for Web of Science ID 000173689600008
View details for PubMedID 11827947
Stereotyped and specific gene expression programs in human innate immune responses to bacteria
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2002; 99 (2): 972-977
The innate immune response is crucial for defense against microbial pathogens. To investigate the molecular choreography of this response, we carried out a systematic examination of the gene expression program in human peripheral blood mononuclear cells responding to bacteria and bacterial products. We found a remarkably stereotyped program of gene expression induced by bacterial lipopolysaccharide and diverse killed bacteria. An intricately choreographed expression program devoted to communication between cells was a prominent feature of the response. Other features suggested a molecular program for commitment of antigen-presenting cells to antigens captured in the context of bacterial infection. Despite the striking similarities, there were qualitative and quantitative differences in the responses to different bacteria. Modulation of this host-response program by bacterial virulence mechanisms was an important source of variation in the response to different bacteria.
View details for Web of Science ID 000173450100078
View details for PubMedID 11805339
View details for PubMedCentralID PMC117415
Transcriptional programs activated by exposure of human prostate cancer cells to androgen
2002; 3 (7)
Androgens are required for both normal prostate development and prostate carcinogenesis. We used DNA microarrays, representing approximately 18,000 genes, to examine the temporal program of gene expression following treatment of the human prostate cancer cell line LNCaP with a synthetic androgen.We observed statistically significant changes in levels of transcripts of more than 500 genes. Many of these genes were previously reported androgen targets, but most were not previously known to be regulated by androgens. The androgen-induced expression programs in three additional androgen-responsive human prostate cancer cell lines, and in four androgen-independent subclones derived from LNCaP, shared many features with those observed in LNCaP, but some differences were observed. A remarkable fraction of the genes induced by androgen appeared to be related to production of seminal fluid and these genes included many with roles in protein folding, trafficking, and secretion.Prostate cancer cell lines retain features of androgen responsiveness that reflect normal prostatic physiology. These results provide a broad view of the effect of androgen signaling on the transcriptional program in these cancer cells, and a foundation for further studies of androgen action.
View details for Web of Science ID 000207581200008
View details for PubMedID 12184806
Comparing functional genomic datasets: lessons from DNA. microarray analyses of host-pathogen interactions
CURRENT OPINION IN MICROBIOLOGY
2001; 4 (1): 95-101
Functional genomic technologies such as high density DNA microarrays allow biologists to study the structure and behavior of thousands of genes in a single experiment. One of the fields in which microarrays have had an increasingly important impact is host-pathogen interactions. Early investigations in this area over the past two years not only emphasize the utility of this approach, but also highlight the stereotyped gene expression responses of different host cells to diverse infectious stimuli, and the potential value of broad dataset comparisons in revealing fundamental features of innate immunity. The comparative analysis of recently published datasets involving human gene expression responses to two bacterial respiratory pathogens illustrates many of these points. Comparisons between these large, highly parallel sets of experimental observations also emphasize important technical and experimental design issues as future challenges.
View details for Web of Science ID 000166840200015
View details for PubMedID 11173041
- Examining the living genome in health and disease with DNA microarrays JAMA-JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION 2000; 283 (17): 2298-2299
Large-scale identification of secreted and membrane-associated gene products using DNA microarrays
2000; 25 (1): 58-62
Membrane-associated and secreted proteins are an important class of proteins and include receptors, transporters, adhesion molecules, hormones and cytokines. Although algorithms have been developed to recognize potential amino-terminal membrane-targeting signals or transmembrane domains in protein sequences, their accuracy is limited and they require knowledge of the entire coding sequence, including the N terminus, which is not currently available for most of the genes in most organisms, including human. Several experimental approaches for identifying secreted and membrane proteins have been described, but none have taken a comprehensive genomic approach. Furthermore, none of these methods allow easy classification of clones from arrayed cDNA libraries, for which large-scale gene-expression data are now becoming available through the use of DNA microarrays. We describe here a rapid and efficient method for identifying genes that encode secreted or membrane proteins. mRNA species bound to membrane-associated polysomes were separated from other mRNAs by sedimentation equilibrium or sedimentation velocity. The distribution of individual transcripts in the 'membrane-bound' and 'cytosolic' fractions was quantitated for thousands of genes by hybridization to DNA microarrays. Transcripts known to encode secreted or membrane proteins were enriched in the membrane-bound fractions, whereas those known to encode cytoplasmic proteins were enriched in the fractions containing mRNAs associated with free and cytoplasmic ribosomes. On this basis, we identified over 275 human genes and 285 yeast genes that are likely to encode previously unrecognized secreted or membrane proteins.
View details for Web of Science ID 000086884000017
View details for PubMedID 10802657
Degradation of proteins from the ER of S-cerevisiae requires an intact unfolded protein response pathway
2000; 5 (4): 729-735
To dissect the requirements of membrane protein degradation from the ER, we expressed the mouse major histocompatibility complex class I heavy chain H-2K(b) in yeast. Like other proteins degraded from the ER, unassembled H-2K(b) heavy chains are not transported to the Golgi but are degraded in a proteasome-dependent manner. The overexpression of H-2K(b) heavy chains induces the unfolded protein response (UPR). In yeast mutants unable to mount the UPR, H-2K(b) heavy chains are greatly stabilized. This defect in degradation is suppressed by the expression of the active form of Hac1p, the transcription factor that upregulates UPR-induced genes. These results indicate that induction of the UPR is required for the degradation of protein substrates from the ER.
View details for Web of Science ID 000086790000013
View details for PubMedID 10882108
Biochemical interactions integrating Itk with the T cell receptor-initiated signaling cascade
JOURNAL OF BIOLOGICAL CHEMISTRY
2000; 275 (3): 2219-2230
Itk, a Tec family tyrosine kinase, acts downstream of Lck and phosphatidylinositol 3'-kinase to facilitate T cell receptor (TCR)-dependent calcium influxes and increases in extracellular-regulated kinase activity. Here we demonstrate interactions between Itk and crucial components of TCR-dependent signaling pathways. First, the inositide-binding pocket of the Itk pleckstrin homology domain directs the constitutive association of Itk with buoyant membranes that are the primary site of TCR activation and are enriched in both Lck and LAT. This association is required for the transphosphorylation of Itk. Second, the Itk proline-rich region binds to Grb2 and LAT. Third, the Itk Src homology (SH3) 3 and SH2 domains interact cooperatively with Syk-phosphorylated SLP-76. Notably, SLP-76 contains a predicted binding motif for the Itk SH2 domain and binds to full-length Itk in vitro. Finally, we show that kinase-inactive Itk can antagonize the SLP-76-dependent activation of NF-AT. The inhibition of NF-AT activation depends on the Itk pleckstrin homology domain, proline-rich region, and SH2 domain. Together, these observations suggest that multivalent interactions recruit Itk to LAT-nucleated signaling complexes and facilitate the activation of LAT-associated phospholipase Cgamma1 by Itk.
View details for Web of Science ID 000084940000092
View details for PubMedID 10636929