Publications by authors named "David S Rickman"

40 Publications

N-Myc-mediated epigenetic reprogramming drives lineage plasticity in advanced prostate cancer.

J Clin Invest 2019 07 1;129(9):3924-3940. Epub 2019 Jul 1.

Department of Pathology and Laboratory Medicine.

Despite recent therapeutic advances, prostate cancer remains a leading cause of cancer-related death. A subset of castration resistant prostate cancers become androgen receptor (AR) signaling-independent and develop neuroendocrine prostate cancer (NEPC) features through lineage plasticity. These NEPC tumors, associated with aggressive disease and poor prognosis, are driven, in part, by aberrant expression of N-Myc, through mechanisms that remain unclear. Integrative analysis of the N-Myc transcriptome, cistrome and interactome using in vivo, in vitro and ex vivo models (including patient-derived organoids) identified a lineage switch towards a neural identity associated with epigenetic reprogramming. N-Myc and known AR-co-factors (e.g., FOXA1 and HOXB13) overlapped, independently of AR, at genomic loci implicated in neural lineage specification. Moreover, histone marks specifically associated with lineage-defining genes were reprogrammed by N-Myc. We also demonstrated that the N-Myc-induced molecular program accurately classifies our cohort of patients with advanced prostate cancer. Finally, we revealed the potential for EZH2 inhibition to reverse the N-Myc-induced suppression of epithelial lineage genes. Altogether, our data provide insights on how N-Myc regulates lineage plasticity and epigenetic reprogramming associated with lineage-specification. The N-Myc signature we defined could also help predict the evolution of prostate cancer and thus better guide the choice of future therapeutic strategies.
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http://dx.doi.org/10.1172/JCI127961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6715370PMC
July 2019

Characterization of the ERG-regulated Kinome in Prostate Cancer Identifies TNIK as a Potential Therapeutic Target.

Neoplasia 2019 04 20;21(4):389-400. Epub 2019 Mar 20.

Cancer Program, Biomedicine Discovery Institute, Monash University, Victoria, Australia; Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia. Electronic address:

Approximately 50% of prostate cancers harbor the TMPRSS2:ERG fusion, resulting in elevated expression of the ERG transcription factor. Despite the identification of this subclass of prostate cancers, no personalized therapeutic strategies have achieved clinical implementation. Kinases are attractive therapeutic targets as signaling networks are commonly perturbed in cancers. The impact of elevated ERG expression on kinase signaling networks in prostate cancer has not been investigated. Resolution of this issue may identify novel therapeutic approaches for ERG-positive prostate cancers. In this study, we used quantitative mass spectrometry-based kinomic profiling to identify ERG-mediated changes to cellular signaling networks. We identified 76 kinases that were differentially expressed and/or phosphorylated in DU145 cells engineered to express ERG. In particular, the Traf2 and Nck-interacting kinase (TNIK) was markedly upregulated and phosphorylated on multiple sites upon ERG overexpression. Importantly, TNIK has not previously been implicated in prostate cancer. To validate the clinical relevance of these findings, we characterized expression of TNIK and TNIK phosphorylated at serine 764 (pS764) in a localized prostate cancer patient cohort and showed that nuclear enrichment of TNIK (pS764) was significantly positively correlated with ERG expression. Moreover, TNIK protein levels were dependent upon ERG expression in VCaP cells and primary cells established from a prostate cancer patient-derived xenograft. Furthermore, reduction of TNIK expression and activity by silencing TNIK expression or using the TNIK inhibitor NCB-0846 reduced cell viability, colony formation and anchorage independent growth. Therefore, TNIK represents a novel and actionable therapeutic target for ERG-positive prostate cancers that could be exploited to develop new treatments for these patients.
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http://dx.doi.org/10.1016/j.neo.2019.02.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6426874PMC
April 2019

A Phase II Trial of the Aurora Kinase A Inhibitor Alisertib for Patients with Castration-resistant and Neuroendocrine Prostate Cancer: Efficacy and Biomarkers.

Clin Cancer Res 2019 01 19;25(1):43-51. Epub 2018 Sep 19.

Department of Medicine, Weill Cornell Medicine, New York, New York.

Purpose: Neuroendocrine prostate cancer (NEPC) is an aggressive variant of prostate cancer that may develop or as a mechanism of treatment resistance. N-myc is capable of driving NEPC progression. Alisertib inhibits the interaction between N-myc and its stabilizing factor Aurora-A, inhibiting N-myc signaling, and suppressing tumor growth.

Patients And Methods: Sixty men were treated with alisertib 50 mg twice daily for 7 days every 21 days. Eligibility included metastatic prostate cancer and at least one: small-cell neuroendocrine morphology; ≥50% neuroendocrine marker expression; new liver metastases without PSA progression; or elevated serum neuroendocrine markers. The primary endpoint was 6-month radiographic progression-free survival (rPFS). Pretreatment biopsies were evaluated by whole exome and RNA-seq and patient-derived organoids were developed.

Results: Median PSA was 1.13 ng/mL (0.01-514.2), number of prior therapies was 3, and 68% had visceral metastases. Genomic alterations involved (55%), (46%), (29%), (29%), and (27%), and there was a range of androgen receptor signaling and NEPC marker expression. Six-month rPFS was 13.4% and median overall survival was 9.5 months (7.3-13). Exceptional responders were identified, including complete resolution of liver metastases and prolonged stable disease, with tumors suggestive of N-myc and Aurora-A overactivity. Patient organoids exhibited concordant responses to alisertib and allowed for the dynamic testing of Aurora-N-myc complex disruption.

Conclusions: Although the study did not meet its primary endpoint, a subset of patients with advanced prostate cancer and molecular features supporting Aurora-A and N-myc activation achieved significant clinical benefit from single-agent alisertib.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-1912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6320304PMC
January 2019

The Expanding World of N-MYC-Driven Tumors.

Cancer Discov 2018 02 22;8(2):150-163. Epub 2018 Jan 22.

Theodor Boveri Institute and Comprehensive Cancer Center Mainfranken, Biocenter, University of Würzburg, Würzburg, Germany.

Enhanced and deregulated expression of N-MYC, a member of the MYC family of transcription factors, drives the development of multiple tumors, including tumors of the nervous and hematologic systems and neuroendocrine tumors in other organs. This review summarizes the cell-of-origin, biological features, associated signaling pathways, and current treatment strategies for N-MYC-driven tumors. We also highlight biological differences within specific tumor types that are driven by the different MYC proteins. N-MYC is a driver of multiple tumor types that are derived through a mechanism that involves direct differentiation within the same lineage (e.g., in the case of neuroblastoma, medulloblastoma, and acute myeloid leukemia) and is often associated with a poor prognosis. Emerging data suggest that N-MYC also drives other tumor types through a mechanism that promotes a lineage switch and that this switch may be exploited for therapeutic purposes.
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http://dx.doi.org/10.1158/2159-8290.CD-17-0273DOI Listing
February 2018

Association with Aurora-A Controls N-MYC-Dependent Promoter Escape and Pause Release of RNA Polymerase II during the Cell Cycle.

Cell Rep 2017 Dec;21(12):3483-3497

Theodor Boveri Institute and Comprehensive Cancer Center Mainfranken, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany. Electronic address:

MYC proteins bind globally to active promoters and promote transcriptional elongation by RNA polymerase II (Pol II). To identify effector proteins that mediate this function, we performed mass spectrometry on N-MYC complexes in neuroblastoma cells. The analysis shows that N-MYC forms complexes with TFIIIC, TOP2A, and RAD21, a subunit of cohesin. N-MYC and TFIIIC bind to overlapping sites in thousands of Pol II promoters and intergenic regions. TFIIIC promotes association of RAD21 with N-MYC target sites and is required for N-MYC-dependent promoter escape and pause release of Pol II. Aurora-A competes with binding of TFIIIC and RAD21 to N-MYC in vitro and antagonizes association of TOP2A, TFIIIC, and RAD21 with N-MYC during S phase, blocking N-MYC-dependent release of Pol II from the promoter. Inhibition of Aurora-A in S phase restores RAD21 and TFIIIC binding to chromatin and partially restores N-MYC-dependent transcriptional elongation. We propose that complex formation with Aurora-A controls N-MYC function during the cell cycle.
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http://dx.doi.org/10.1016/j.celrep.2017.11.090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5746598PMC
December 2017

A germline FANCA alteration that is associated with increased sensitivity to DNA damaging agents.

Cold Spring Harb Mol Case Stud 2017 Sep 3;3(5). Epub 2017 May 3.

Englander Institute for Precision Medicine, Weill Cornell Medicine and New York-Presbyterian Hospital, New York, New York 10065, USA.

Defects in genes involved in DNA damage repair (DDR) pathway are emerging as novel biomarkers and targets for new prostate cancer drug therapies. A previous report revealed an association between an exceptional response to cisplatin treatment and a somatic loss of heterozygosity (LOH) of in a patient with metastatic prostate cancer who also harbored a germline variant (S1088F). Although germline mutations are the most frequent alterations in patients with Fanconi anemia, germline alterations are less common in prostate cancer. We hypothesized that the germline S1088F variant in combination with LOH was deleterious for FANCA function and contributed to the patient's exceptional response to cisplatin. We show that although it properly localizes to the nucleus, the S1088F FANCA mutant protein disrupts the FANC protein complex resulting in increased sensitivity to DNA damaging agents. Because molecular stratification is emerging as a strategy for treating men with metastatic, castrate-resistant prostate cancer harboring specific DDR gene defects, our findings suggest that more biomarker studies are needed to better define clinically relevant germline and somatic alterations.
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http://dx.doi.org/10.1101/mcs.a001487DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5593159PMC
September 2017

Identification of novel prostate cancer drivers using RegNetDriver: a framework for integration of genetic and epigenetic alterations with tissue-specific regulatory network.

Genome Biol 2017 07 27;18(1):141. Epub 2017 Jul 27.

Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, 10065, USA.

We report a novel computational method, RegNetDriver, to identify tumorigenic drivers using the combined effects of coding and non-coding single nucleotide variants, structural variants, and DNA methylation changes in the DNase I hypersensitivity based regulatory network. Integration of multi-omics data from 521 prostate tumor samples indicated a stronger regulatory impact of structural variants, as they affect more transcription factor hubs in the tissue-specific network. Moreover, crosstalk between transcription factor hub expression modulated by structural variants and methylation levels likely leads to the differential expression of target genes. We report known prostate tumor regulatory drivers and nominate novel transcription factors (ERF, CREB3L1, and POU2F2), which are supported by functional validation.
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http://dx.doi.org/10.1186/s13059-017-1266-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5530464PMC
July 2017

Biology and evolution of poorly differentiated neuroendocrine tumors.

Nat Med 2017 Jun;23(6):1-10

Caryl and Israel Englander Institute for Precision Medicine, New York Presbyterian Hospital-Weill Cornell Medicine, New York, New York, USA.

Neuroendocrine (NE) cancers are a diverse group of neoplasms typically diagnosed and treated on the basis of their site of origin. This Perspective focuses on advances in our understanding of the tumorigenesis and treatment of poorly differentiated neuroendocrine tumors. Recent evidence from sequencing indicates that, although neuroendocrine tumors can arise de novo, they can also develop as a result of lineage plasticity in response to pressure from targeted therapies. We discuss the shared genomic alterations of these tumors independently of their site of origin, and we explore potential therapeutic strategies on the basis of recent biological findings.
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http://dx.doi.org/10.1038/nm.4341DOI Listing
June 2017

N-Myc Induces an EZH2-Mediated Transcriptional Program Driving Neuroendocrine Prostate Cancer.

Cancer Cell 2016 10;30(4):563-577

Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY 10065, USA; Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10065, USA; Englander Institute for Precision Medicine, New York-Presbyterian Hospital, Weill Cornell Medicine, New York, NY 10065, USA. Electronic address:

The transition from castration-resistant prostate adenocarcinoma (CRPC) to neuroendocrine prostate cancer (NEPC) has emerged as an important mechanism of treatment resistance. NEPC is associated with overexpression and gene amplification of MYCN (encoding N-Myc). N-Myc is an established oncogene in several rare pediatric tumors, but its role in prostate cancer progression is not well established. Integrating a genetically engineered mouse model and human prostate cancer transcriptome data, we show that N-Myc overexpression leads to the development of poorly differentiated, invasive prostate cancer that is molecularly similar to human NEPC. This includes an abrogation of androgen receptor signaling and induction of Polycomb Repressive Complex 2 signaling. Altogether, our data establishes N-Myc as an oncogenic driver of NEPC.
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http://dx.doi.org/10.1016/j.ccell.2016.09.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5540451PMC
October 2016

A Computational Drug Repositioning Approach for Targeting Oncogenic Transcription Factors.

Cell Rep 2016 06 2;15(11):2348-56. Epub 2016 Jun 2.

Institute for Computational Biomedicine, Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10021, USA; Institute for Precision Medicine, Weill Cornell Medical College, New York, NY 10021, USA. Electronic address:

Mutations in transcription factor (TF) genes are frequently observed in tumors, often leading to aberrant transcriptional activity. Unfortunately, TFs are often considered undruggable due to the absence of targetable enzymatic activity. To address this problem, we developed CRAFTT, a computational drug-repositioning approach for targeting TF activity. CRAFTT combines ChIP-seq with drug-induced expression profiling to identify small molecules that can specifically perturb TF activity. Application to ENCODE ChIP-seq datasets revealed known drug-TF interactions, and a global drug-protein network analysis supported these predictions. Application of CRAFTT to ERG, a pro-invasive, frequently overexpressed oncogenic TF, predicted that dexamethasone would inhibit ERG activity. Dexamethasone significantly decreased cell invasion and migration in an ERG-dependent manner. Furthermore, analysis of electronic medical record data indicates a protective role for dexamethasone against prostate cancer. Altogether, our method provides a broadly applicable strategy for identifying drugs that specifically modulate TF activity.
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http://dx.doi.org/10.1016/j.celrep.2016.05.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4912004PMC
June 2016

Whole-Exome Sequencing of Metastatic Cancer and Biomarkers of Treatment Response.

JAMA Oncol 2015 Jul;1(4):466-74

Institute for Precision Medicine, New York Presbyterian Hospital-Weill Cornell Medical College, New York, New York5Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York.

Importance: Understanding molecular mechanisms of response and resistance to anticancer therapies requires prospective patient follow-up and clinical and functional validation of both common and low-frequency mutations. We describe a whole-exome sequencing (WES) precision medicine trial focused on patients with advanced cancer.

Objective: To understand how WES data affect therapeutic decision making in patients with advanced cancer and to identify novel biomarkers of response.

Design, Setting, And Patients: Patients with metastatic and treatment-resistant cancer were prospectively enrolled at a single academic center for paired metastatic tumor and normal tissue WES during a 19-month period (February 2013 through September 2014). A comprehensive computational pipeline was used to detect point mutations, indels, and copy number alterations. Mutations were categorized as category 1, 2, or 3 on the basis of actionability; clinical reports were generated and discussed in precision tumor board. Patients were observed for 7 to 25 months for correlation of molecular information with clinical response.

Main Outcomes And Measures: Feasibility, use of WES for decision making, and identification of novel biomarkers.

Results: A total of 154 tumor-normal pairs from 97 patients with a range of metastatic cancers were sequenced, with a mean coverage of 95X and 16 somatic alterations detected per patient. In total, 16 mutations were category 1 (targeted therapy available), 98 were category 2 (biologically relevant), and 1474 were category 3 (unknown significance). Overall, WES provided informative results in 91 cases (94%), including alterations for which there is an approved drug, there are therapies in clinical or preclinical development, or they are considered drivers and potentially actionable (category 1-2); however, treatment was guided in only 5 patients (5%) on the basis of these recommendations because of access to clinical trials and/or off-label use of drugs. Among unexpected findings, a patient with prostate cancer with exceptional response to treatment was identified who harbored a somatic hemizygous deletion of the DNA repair gene FANCA and putative partial loss of function of the second allele through germline missense variant. Follow-up experiments established that loss of FANCA function was associated with platinum hypersensitivity both in vitro and in patient-derived xenografts, thus providing biologic rationale and functional evidence for his extreme clinical response.

Conclusions And Relevance: The majority of advanced, treatment-resistant tumors across tumor types harbor biologically informative alterations. The establishment of a clinical trial for WES of metastatic tumors with prospective follow-up of patients can help identify candidate predictive biomarkers of response.
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http://dx.doi.org/10.1001/jamaoncol.2015.1313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4505739PMC
July 2015

ERG induces taxane resistance in castration-resistant prostate cancer.

Nat Commun 2014 Nov 25;5:5548. Epub 2014 Nov 25.

1] Institute of Precision Medicine of Weill Cornell Medical College and New York-Presbyterian Hospital, New York, New York 10065, USA [2] Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York 10065, USA [3] Weill Cornell Cancer Center, New York, New York 10065, USA.

Taxanes are the only chemotherapies used to treat patients with metastatic castration-resistant prostate cancer (CRPC). Despite the initial efficacy of taxanes in treating CRPC, all patients ultimately fail due to the development of drug resistance. In this study, we show that ERG overexpression in in vitro and in vivo models of CRPC is associated with decreased sensitivity to taxanes. ERG affects several parameters of microtubule dynamics and inhibits effective drug-target engagement of docetaxel or cabazitaxel with tubulin. Finally, analysis of a cohort of 34 men with metastatic CRPC treated with docetaxel chemotherapy reveals that ERG-overexpressing prostate cancers have twice the chance of docetaxel resistance than ERG-negative cancers. Our data suggest that ERG plays a role beyond regulating gene expression and functions outside the nucleus to cooperate with tubulin towards taxane insensitivity. Determining ERG rearrangement status may aid in patient selection for docetaxel or cabazitaxel therapy and/or influence co-targeting approaches.
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http://dx.doi.org/10.1038/ncomms6548DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4244604PMC
November 2014

CD30-positive peripheral T-cell lymphomas share molecular and phenotypic features.

Haematologica 2013 Aug 28;98(8):1250-8. Epub 2013 May 28.

University Institute of Pathology, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland.

Peripheral T-cell lymphoma, not otherwise specified is a heterogeneous group of aggressive neoplasms with indistinct borders. By gene expression profiling we previously reported unsupervised clusters of peripheral T-cell lymphomas, not otherwise specified correlating with CD30 expression. In this work we extended the analysis of peripheral T-cell lymphoma molecular profiles to prototypical CD30(+) peripheral T-cell lymphomas (anaplastic large cell lymphomas), and validated mRNA expression profiles at the protein level. Existing transcriptomic datasets from peripheral T-cell lymphomas, not otherwise specified and anaplastic large cell lymphomas were reanalyzed. Twenty-one markers were selected for immunohistochemical validation on 80 peripheral T-cell lymphoma samples (not otherwise specified, CD30(+) and CD30(-); anaplastic large cell lymphomas, ALK(+) and ALK(-)), and differences between subgroups were assessed. Clinical follow-up was recorded. Compared to CD30(-) tumors, CD30(+) peripheral T-cell lymphomas, not otherwise specified were significantly enriched in ALK(-) anaplastic large cell lymphoma-related genes. By immunohistochemistry, CD30(+) peripheral T-cell lymphomas, not otherwise specified differed significantly from CD30(-) samples [down-regulated expression of T-cell receptor-associated proximal tyrosine kinases (Lck, Fyn, Itk) and of proteins involved in T-cell differentiation/activation (CD69, ICOS, CD52, NFATc2); upregulation of JunB and MUM1], while overlapping with anaplastic large cell lymphomas. CD30(-) peripheral T-cell lymphomas, not otherwise specified tended to have an inferior clinical outcome compared to the CD30(+) subgroups. In conclusion, we show molecular and phenotypic features common to CD30(+) peripheral T-cell lymphomas, and significant differences between CD30(-) and CD30(+) peripheral T-cell lymphomas, not otherwise specified, suggesting that CD30 expression might delineate two biologically distinct subgroups.
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http://dx.doi.org/10.3324/haematol.2012.081935DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3729906PMC
August 2013

Oncogenic transcription factors as master regulators of chromatin topology: a new role for ERG in prostate cancer.

Cell Cycle 2012 Sep 23;11(18):3380-3. Epub 2012 Aug 23.

HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA.

The three-dimensional (3D) conformation of the genome is known to be structured and to affect gene transcription, but how chromatin conformation changes in diseases such as cancer is poorly understood. Similarly, oncogenic transcription factors bind to thousands of sites in the genome without a clear transcriptional role on nearby genes. Could these factors play a non-transcriptional role in promoting tumor progression by restructuring the shape of the genome? To address this question, we recently performed unbiased high-resolution mapping of intra- and inter-chromosome interactions upon overexpression of ERG, an oncogenic transcription factor frequently overexpressed in prostate cancer as a result of a gene fusion. By integrating data from genome-wide chromosome conformation capture (Hi-C), ERG binding and gene expression, we have demonstrated that oncogenic transcription factor overexpression is associated with global, reproducible and functionally coherent changes in chromatin organization. Perhaps more importantly, we have identified novel genomic alterations associated with ERG overexpression. These results suggest a yet unappreciated role for transcription factors in promoting genomic alterations through their effect on chromatin architecture.
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http://dx.doi.org/10.4161/cc.21401DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3466547PMC
September 2012

Oncogene-mediated alterations in chromatin conformation.

Proc Natl Acad Sci U S A 2012 Jun 21;109(23):9083-8. Epub 2012 May 21.

Department of Pathology and Laboratory Medicine, HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY 10065, USA.

Emerging evidence suggests that chromatin adopts a nonrandom 3D topology and that the organization of genes into structural hubs and domains affects their transcriptional status. How chromatin conformation changes in diseases such as cancer is poorly understood. Moreover, how oncogenic transcription factors, which bind to thousands of sites across the genome, influence gene regulation by globally altering the topology of chromatin requires further investigation. To address these questions, we performed unbiased high-resolution mapping of intra- and interchromosome interactions upon overexpression of ERG, an oncogenic transcription factor frequently overexpressed in prostate cancer as a result of a gene fusion. By integrating data from genome-wide chromosome conformation capture (Hi-C), ERG binding, and gene expression, we demonstrate that oncogenic transcription factor overexpression is associated with global, reproducible, and functionally coherent changes in chromatin organization. The results presented here have broader implications, as genomic alterations in other cancer types frequently give rise to aberrant transcription factor expression, e.g., EWS-FLI1, c-Myc, n-Myc, and PML-RARα.
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http://dx.doi.org/10.1073/pnas.1112570109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384175PMC
June 2012

Next-generation prostate cancer biobanking: toward a processing protocol amenable for the International Cancer Genome Consortium.

Diagn Mol Pathol 2012 Jun;21(2):61-8

Departments of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065, USA.

Next-generation DNA and RNA sequencing requires intact nucleic acids from high-quality human tissue samples to better elucidate the molecular basis of cancer. We have developed a prostate biobanking protocol to acquire suitable samples for sequencing without compromising the accuracy of clinical diagnosis. To assess the clinical implications of implementing this protocol, we evaluated 105 consecutive radical prostatectomy specimens from November 2008 to February 2009. Alternating levels of prostate samples were submitted to Surgical Pathology as formalin-fixed, paraffin-embedded blocks and to the institutional biobank as frozen blocks. Differences in reported pathologic characteristics between clinical and procured specimens were compared. Clinical staging and grading were not affected by the biobank protocol. Tumor foci on frozen hematoxylin and eosin slides were identified and high-density tumor foci were scored and processed for DNA and RNA extractions for sequencing. Both DNA and RNA were extracted from 22 cases of 44 with high-density tumor foci. Eighty-two percent (18/22) of the samples passed rigorous quality control steps for DNA and RNA sequencing. To date, DNA extracted from 7 cases has undergone whole-genome sequencing, and RNA from 18 cases has been RNA sequenced. This protocol provides prostate tissue for high-throughput biomedical research and confirms the feasibility of actively integrating prostate cancer into The Cancer Genome Atlas Program, a member of the International Cancer Genome Consortium.
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http://dx.doi.org/10.1097/PDM.0b013e31823b6da6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4123125PMC
June 2012

Identification of functionally active, low frequency copy number variants at 15q21.3 and 12q21.31 associated with prostate cancer risk.

Proc Natl Acad Sci U S A 2012 Apr 10;109(17):6686-91. Epub 2012 Apr 10.

Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065, USA.

Copy number variants (CNVs) are a recently recognized class of human germ line polymorphisms and are associated with a variety of human diseases, including cancer. Because of the strong genetic influence on prostate cancer, we sought to identify functionally active CNVs associated with susceptibility of this cancer type. We queried low-frequency biallelic CNVs from 1,903 men of Caucasian origin enrolled in the Tyrol Prostate Specific Antigen Screening Cohort and discovered two CNVs strongly associated with prostate cancer risk. The first risk locus (P = 7.7 × 10(-4), odds ratio = 2.78) maps to 15q21.3 and overlaps a noncoding enhancer element that contains multiple activator protein 1 (AP-1) transcription factor binding sites. Chromosome conformation capture (Hi-C) data suggested direct cis-interactions with distant genes. The second risk locus (P = 2.6 × 10(-3), odds ratio = 4.8) maps to the α-1,3-mannosyl-glycoprotein 4-β-N-acetylglucosaminyltransferase C (MGAT4C) gene on 12q21.31. In vitro cell-line assays found this gene to significantly modulate cell proliferation and migration in both benign and cancer prostate cells. Furthermore, MGAT4C was significantly overexpressed in metastatic versus localized prostate cancer. These two risk associations were replicated in an independent PSA-screened cohort of 800 men (15q21.3, combined P = 0.006; 12q21.31, combined P = 0.026). These findings establish noncoding and coding germ line CNVs as significant risk factors for prostate cancer susceptibility and implicate their role in disease development and progression.
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http://dx.doi.org/10.1073/pnas.1117405109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3340033PMC
April 2012

Molecular characterization of neuroendocrine prostate cancer and identification of new drug targets.

Cancer Discov 2011 Nov;1(6):487-95

Department of Medicine, Weill Cornell Medical College, New York, New York 10065, USA.

Unlabelled: Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer that most commonly evolves from preexisting prostate adenocarcinoma (PCA). Using Next Generation RNA-sequencing and oligonucleotide arrays, we profiled 7 NEPC, 30 PCA, and 5 benign prostate tissue (BEN), and validated findings on tumors from a large cohort of patients (37 NEPC, 169 PCA, 22 BEN) using IHC and FISH. We discovered significant overexpression and gene amplification of AURKA and MYCN in 40% of NEPC and 5% of PCA, respectively, and evidence that that they cooperate to induce a neuroendocrine phenotype in prostate cells. There was dramatic and enhanced sensitivity of NEPC (and MYCN overexpressing PCA) to Aurora kinase inhibitor therapy both in vitro and in vivo, with complete suppression of neuroendocrine marker expression following treatment. We propose that alterations in Aurora kinase A and N-myc are involved in the development of NEPC, and future clinical trials will help determine from the efficacy of Aurora kinase inhibitor therapy.

Significance: We report on the largest in-depth molecular analysis of NEPC and provide new insight into molecular events involved in the progression of prostate cancer.
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http://dx.doi.org/10.1158/2159-8290.CD-11-0130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3290518PMC
November 2011

Combining urinary detection of TMPRSS2:ERG and PCA3 with serum PSA to predict diagnosis of prostate cancer.

Urol Oncol 2013 Jul 19;31(5):566-71. Epub 2011 May 19.

Division of Urology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.

Objectives: We sought to develop a clinical algorithm combining serum PSA with detection of TMPRSS2:ERG fusion and PCA3 in urine collected after digital rectal exam (post-DRE urine) to predict prostate cancer on subsequent biopsy.

Materials And Methods: Post-DRE urine was collected in 48 consecutive patients before prostate biopsy at 2 centers; quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect PCA3 and TMPRSS2:ERG fusion transcript expression. Serum PSA was measured by clinical assay. The performance of TMPRSS2:ERG fusion, PCA3, and serum PSA as biomarkers predicting prostate cancer at biopsy was measured; a clinically practical algorithm combining serum PSA with TMPRSS2:ERG and PCA3 in post-DRE urine to predict prostate cancer was developed.

Results: Post-DRE urine sediment provided informative RNA in 45 patients; prostate cancer was present on subsequent biopsy in 15. TMPRSS2:ERG in post-DRE urine was associated with prostate cancer (OR = 12.02; P < 0.001). PCA3 had the highest sensitivity in predicting prostate cancer diagnosis (93%), whereas TMPRSS2:ERG had the highest specificity (87%). TMPRSS2:ERG had the greatest discriminatory value in predicting prostate cancer (AUC = 0.77 compared with 0.65 for PCA3 and 0.72 for serum PSA alone). Combining serum PSA, PCA3, and TMPRSS2:ERG in a multivariable algorithm optimized for clinical utility improved cancer prediction (AUC = 0.88; specificity = 90% at 80% sensitivity).

Conclusions: A clinical algorithm specifying biopsy for all patients with PSA ≥ 10 ng/ml, while restricting biopsy among those with PSA <10 ng/ml to only those with detectable PCA3 or TMPRSS2:ERG in post-DRE urine, performed better than the individual biomarkers alone in predicting prostate cancer.
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http://dx.doi.org/10.1016/j.urolonc.2011.04.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210917PMC
July 2013

ERG cooperates with androgen receptor in regulating trefoil factor 3 in prostate cancer disease progression.

Neoplasia 2010 Dec;12(12):1031-40

Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY 10065, USA.

To elucidate the role of ETS gene fusions in castration-resistant prostate cancer (CRPC), we characterized the transcriptome of 54 CRPC tumor samples from men with locally advanced or metastatic disease. Trefoil factor 3 (TFF3) emerged as the most highly differentially regulated gene with respect to ERG rearrangement status and resistance to hormone ablation therapy. Conventional chromatin immunoprecipitation (ChIP)-polymerase chain reaction and ChIP followed by DNA sequencing (ChIP-seq) revealed direct binding of ERG to ETS binding sites in the TFF3 promoter in ERG-rearranged prostate cancer cell lines. These results were confirmed in ERG-rearranged hormone-naive prostate cancer (HNPC) and CRPC tissue samples. Functional studies demonstrated that ERG has an inhibitory effect on TFF3 expression in hormone-naive cancer but not in the castration-resistant state. In addition, we provide evidence suggesting an effect of androgen receptor signaling on ERG-regulated TFF3 expression. Furthermore, TFF3 overexpression enhances ERG-mediated cell invasion in CRPC prostate cancer cells. Taken together, our findings reveal a novel mechanism for enhanced tumor cell aggressiveness resulting from ERG rearrangement in the castration-resistant setting through TFF3 gene expression.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3003138PMC
http://dx.doi.org/10.1593/neo.10866DOI Listing
December 2010

Discovery of non-ETS gene fusions in human prostate cancer using next-generation RNA sequencing.

Genome Res 2011 Jan 29;21(1):56-67. Epub 2010 Oct 29.

Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York 10021, USA.

Half of prostate cancers harbor gene fusions between TMPRSS2 and members of the ETS transcription factor family. To date, little is known about the presence of non-ETS fusion events in prostate cancer. We used next-generation transcriptome sequencing (RNA-seq) in order to explore the whole transcriptome of 25 human prostate cancer samples for the presence of chimeric fusion transcripts. We generated more than 1 billion sequence reads and used a novel computational approach (FusionSeq) in order to identify novel gene fusion candidates with high confidence. In total, we discovered and characterized seven new cancer-specific gene fusions, two involving the ETS genes ETV1 and ERG, and four involving non-ETS genes such as CDKN1A (p21), CD9, and IKBKB (IKK-beta), genes known to exhibit key biological roles in cellular homeostasis or assumed to be critical in tumorigenesis of other tumor entities, as well as the oncogene PIGU and the tumor suppressor gene RSRC2. The novel gene fusions are found to be of low frequency, but, interestingly, the non-ETS fusions were all present in prostate cancer harboring the TMPRSS2-ERG gene fusion. Future work will focus on determining if the ETS rearrangements in prostate cancer are associated or directly predispose to a rearrangement-prone phenotype.
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http://dx.doi.org/10.1101/gr.110684.110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3012926PMC
January 2011

ERG rearrangement metastasis patterns in locally advanced prostate cancer.

Urology 2010 Apr;75(4):762-7

Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York 10065, USA.

Objectives: To interrogate multifocal prostate cancer (PCa) to determine its predilection for metastasis, using ERG rearrangement as marker of clonality. A hallmark of PCa is that distinct tumor foci may arise independently, which has important biological and clinical implications. Recent studies characterizing ERG-rearranged PCa possessing intrafocal homogeneity but interfocal heterogeneity support this hypothesis.

Methods: We studied 26 patients who underwent prostatectomy and lymphadenectomy with at least 2 distinct PCa foci and 1 lymph node (LN) metastasis. Each focus was assessed for size, Gleason score, ERG rearrangement, and TMPRSS2-ERG transcript.

Results: Fifteen of 26 cases exhibited interfocal homogeneity with regard to ERG rearrangement (ie, presence vs absence of ERG rearrangement). ERG rearrangement was present in all foci for 6 and absent in all foci for 9 cases. Two cases revealed interfocal heterogeneity with regard to rearrangement mechanism (ie, rearrangement through insertion or deletion). Eight of 26 cases revealed interfocal heterogeneity with regard to rearrangement status. In all cases with at least 1 ERG rearranged focus, we found the corresponding LN metastasis harboring an ERG rearrangement. Interestingly, in a subset of cases the rearrangement status in the LN did not correspond to size or Gleason score. All but 2 ERG rearranged foci had detectable TMPRSS2-ERG transcript levels.

Conclusions: When multifocal PCa demonstrates both ERG-positive and ERG-negative foci, the positive foci have a greater predilection for metastasis. Larger studies are needed to confirm the potential additional risk an ERG rearranged focus confers on the likelihood of disease progression.
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http://dx.doi.org/10.1016/j.urology.2009.10.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850965PMC
April 2010

In situ evidence of KRAS amplification and association with increased p21 levels in non-small cell lung carcinoma.

Am J Clin Pathol 2009 Oct;132(4):500-5

Departments of Pathology, Laboratory MedicineCardiothoracic Surgery, Weill Medical College of Cornell University, New York, NY, USA.

Recent advances in the characterization of the lung cancer genome have suggested that KRAS may frequently be amplified, although little is known regarding the significance of this finding. This is in contrast with activating mutations of KRAS, which occur in approximately 20% of non-small cell lung carcinomas (NSCLCs). We used fluorescence in situ hybridization to provide direct evidence of KRAS amplification for the first time in clinical specimens. We detected amplification in 7 of 100 consecutive NSCLCs, with a concurrent activating KRAS mutation in 4 cases. KRAS amplification was associated with greater expression of p21 as assessed by quantitative immunohistochemical analysis (P = .015). Our data indicate that a sizable subgroup of NSCLCs harbor KRAS amplification, some of which also contain point mutations, and suggest that an increased KRAS copy number may drive p21 overexpression. KRAS amplification may define a unique clinicopathologic subset of NSCLCs with potentially altered responsiveness to targeted therapies.
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http://dx.doi.org/10.1309/AJCPF10ZUNSOLIFGDOI Listing
October 2009

N-myc downstream regulated gene 1 (NDRG1) is fused to ERG in prostate cancer.

Neoplasia 2009 Aug;11(8):804-11

Department of Pathology & Laboratory Medicine, Weill Cornell Medical College, New York, NY 10021, USA.

A step toward the molecular classification of prostate cancer was the discovery of recurrent erythroblast transformation-specific rearrangements, most commonly fusing the androgen-regulated TMPRSS2 promoter to ERG. The TMPRSS2-ERG fusion is observed in around 90% of tumors that overexpress the oncogene ERG. The goal of the current study was to complete the characterization of these ERG-overexpressing prostate cancers. Using fluorescence in situ hybridization and reverse transcription-polymerase chain reaction assays, we screened 101 prostate cancers, identifying 34 cases (34%) with the TMPRSS2-ERG fusion. Seven cases demonstrated ERG rearrangement by fluorescence in situ hybridization without the presence of TMPRSS2-ERG fusion messenger RNA transcripts. Screening for known 5' partners, we determined that three cases harbored the SLC45A3-ERG fusion. To discover novel 5' partners in these ERG-overexpressing and ERG-rearranged cases, we used paired-end RNA sequencing. We first confirmed the utility of this approach by identifying the TMPRSS2-ERG fusion in a known positive prostate cancer case and then discovered a novel fusion involving the androgen-inducible tumor suppressor, NDRG1 (N-myc downstream regulated gene 1), and ERG in two cases. Unlike TMPRSS2-ERG and SCL45A3-ERG fusions, the NDRG1-ERG fusion is predicted to encode a chimeric protein. Like TMPRSS2, SCL45A3 and NDRG1 are inducible not only by androgen but also by estrogen. This study demonstrates that most ERG-overexpressing prostate cancers harbor hormonally regulated TMPRSS2-ERG, SLC45A3-ERG, or NDRG1-ERG fusions. Broader implications of this study support the use of RNA sequencing to discover novel cancer translocations.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2713587PMC
http://dx.doi.org/10.1593/neo.09572DOI Listing
August 2009

WNT/beta-catenin pathway activation in Wilms tumors: a unifying mechanism with multiple entries?

Genes Chromosomes Cancer 2009 Sep;48(9):816-27

Inserm, U574, Hôpital Necker-Enfants Malades, Paris, France.

Based on characterization of both genomic and expression status of WT1 and CTNNB1 (beta-catenin) in a series of 60 Wilms tumor samples, combined with genome-wide expression profiling of these tumors, normal mature and fetal kidney controls, we show that WT1/beta-catenin expression was a better classifier than WT1/CTNNB1 mutations. We present molecular data supporting that the WNT pathway is involved in both tumor classes, with and without WT1/beta-catenin alterations. In the tumor class with WT1/beta-catenin alterations, we identified overexpression of 14 previously unreported WNT target genes, including TWIST1. We show that the TWIST1 protein was specifically expressed in these tumors, where staining was restricted to the stromal, nuclear beta-catenin positive, component. By comparing the state of the WNT pathway in tumors without WT1/beta-catenin alterations and fetal kidneys we provide evidence that suggests that these tumors have a heightened level of pathway activation. We characterized mutations of the WNT pathway regulator gene WTX in 16% of this tumor class. Moreover, genome-transcriptome correlation analysis allowed us to identify three other WNT pathway regulator genes that could participate in the activation of the WNT pathway: BCL9 (1p36.2), CTNNBIP1 (1p36.2), and CBY1 (22q13.1). These genes thus represent new potential important actors in WT tumorigenesis.
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http://dx.doi.org/10.1002/gcc.20686DOI Listing
September 2009

SLC45A3-ELK4 is a novel and frequent erythroblast transformation-specific fusion transcript in prostate cancer.

Cancer Res 2009 Apr 17;69(7):2734-8. Epub 2009 Mar 17.

Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York 10021, USA.

Chromosomal rearrangements account for all erythroblast transformation-specific (ETS) family member gene fusions that have been reported in prostate cancer and have clinical, diagnostic, and prognostic implications. Androgen-regulated genes account for the majority of the 5' genomic regulatory promoter elements fused with ETS genes. TMPRSS2-ERG, TMPRSS2-ETV1, and SLC45A3-ERG rearrangements account for roughly 90% of ETS fusion prostate cancer. ELK4, another ETS family member, is androgen regulated, involved in promoting cell growth, and highly expressed in a subset of prostate cancer, yet the mechanism of ELK4 overexpression is unknown. In this study, we identified a novel ETS family fusion transcript, SLC45A3-ELK4, and found it to be expressed in both benign prostate tissue and prostate cancer. We found high levels of SLC45A3-ELK4 mRNA restricted to a subset of prostate cancer samples. SLC45A3-ELK4 transcript can be detected at high levels in urine samples from men at risk for prostate cancer. Characterization of the fusion mRNA revealed a major variant in which SLC45A3 exon 1 is fused to ELK4 exon 2. Based on quantitative PCR analyses of DNA, unlike other ETS fusions described in prostate cancer, the expression of SLC45A3-ELK4 mRNA is not exclusive to cases harboring a chromosomal rearrangement. Treatment of LNCaP cancer cells with a synthetic androgen (R1881) revealed that SLC45A3-ELK4, and not endogenous ELK4, mRNA expression is androgen regulated. Altogether, our findings show that SLC45A3-ELK4 mRNA expression is heterogeneous, highly induced in a subset of prostate cancers, androgen regulated, and most commonly occurs through a mechanism other than chromosomal rearrangement (e.g., trans-splicing).
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http://dx.doi.org/10.1158/0008-5472.CAN-08-4926DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4063441PMC
April 2009

Distinct genomic aberrations associated with ERG rearranged prostate cancer.

Genes Chromosomes Cancer 2009 Apr;48(4):366-80

Department of Pathology and Laboratory Medicine, Weill Cornell Medical Center, New York, NY 10065.

Emerging molecular and clinical data suggest that ETS fusion prostate cancer represents a distinct molecular subclass, driven most commonly by a hormonally regulated promoter and characterized by an aggressive natural history. The study of the genomic landscape of prostate cancer in the light of ETS fusion events is required to understand the foundation of this molecularly and clinically distinct subtype. We performed genome-wide profiling of 49 primary prostate cancers and identified 20 recurrent chromosomal copy number aberrations, mainly occurring as genomic losses. Co-occurring events included losses at 19q13.32 and 1p22.1. We discovered three genomic events associated with ERG rearranged prostate cancer, affecting 6q, 7q, and 16q. 6q loss in nonrearranged prostate cancer is accompanied by gene expression deregulation in an independent dataset and by protein deregulation of MYO6. To analyze copy number alterations within the ETS genes, we performed a comprehensive analysis of all 27 ETS genes and of the 3 Mbp genomic area between ERG and TMPRSS2 (21q) with an unprecedented resolution (30 bp). We demonstrate that high-resolution tiling arrays can be used to pin-point breakpoints leading to fusion events. This study provides further support to define a distinct molecular subtype of prostate cancer based on the presence of ETS gene rearrangements.
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http://dx.doi.org/10.1002/gcc.20647DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2674964PMC
April 2009

Gene expression profiling reveals a new classification of adrenocortical tumors and identifies molecular predictors of malignancy and survival.

J Clin Oncol 2009 Mar 12;27(7):1108-15. Epub 2009 Jan 12.

Service des Maladies Endocriniennes et Métaboliques, Hôpital Cochin, 27, rue du Faubourg Saint-Jacques, 75014, Paris, France.

Purpose: Adrenocortical tumors, especially cancers, remain challenging both for their diagnosis and prognosis assessment. The aim of this article is to identify molecular predictors of malignancy and of survival.

Patients And Methods: One hundred fifty-three unilateral adrenocortical tumors were studied by microarray (n = 92) or reverse transcription quantitative polymerase chain reaction (n = 148). A two-gene predictor of malignancy was built using the disease-free survival as the end point in a training cohort (n = 47), then validated in an independent validation cohort (n = 104). The best candidate genes were selected using Cox models, and the best gene combination was validated using the log-rank test. Similarly, for malignant tumors, a two-gene predictor of survival was built using the overall survival as the end point in a training cohort (n = 23), then tested in an independent validation cohort (n = 35).

Results: Unsupervised clustering analysis discriminated robustly the malignant and benign tumors, and identified two groups of malignant tumors with very different outcome. The combined expression of DLG7 and PINK1 was the best predictor of disease-free survival (log-rank P approximately 10(-12)), could overcome the uncertainties of intermediate pathological Weiss scores, and remained significant after adjustment to the Weiss score (P < 1.3 x 10(-2)). Among the malignant tumors, the combined expression of BUB1B and PINK1 was the best predictor of overall survival (P < 2 x 10(-6)), and remained significant after adjusting for MacFarlane staging (P < .005).

Conclusion: Gene expression analysis unravels two distinct groups of adrenocortical carcinomas. The molecular predictors of malignancy and of survival are reliable and provide valuable independent information in addition to pathology and tumor staging. These original tools should provide important improvements for adrenal tumors management.
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http://dx.doi.org/10.1200/JCO.2008.18.5678DOI Listing
March 2009

EML4-ALK fusion lung cancer: a rare acquired event.

Neoplasia 2008 Mar;10(3):298-302

Department of Pathology and Laboratory Medicine, Weill Cornell Medical Center, New York, NY, USA.

A recurrent gene fusion between EML4 and ALK in 6.7% of non-small cell lung cancers (NSCLCs) and NKX2-1 (TTF1, TITF1) high-level amplifications in 12% of adenocarcinomas of the lung were independently reported recently. Because the EML4-ALK fusion was only shown by a reverse transcription-polymerase chain reaction approach, we developed fluorescent in situ hybridization assays to interrogate more than 600 NSCLCs using break-apart probes for EML4 and ALK. We found that EML4-ALK fusions occur in less than 3% of NSCLC samples and that EML4 and/or ALK amplifications also occur. We also observed that, in most cases in which an EML4/ALK alteration is detected, not all of the tumor cells harbor the lesion. By using a detailed multi-fluorescent in situ hybridization probe assay and reverse transcription-polymerase chain reaction, we have evidence that other, more common mechanisms besides gene inversion exist including the possibility of other fusion partners for ALK and EML4. Furthermore, we confirmed the NKX2-1 high-level amplification in a significant subset of NSCLC and found this amplification to be mutually exclusive to ALK and EML4 rearrangements.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2259458PMC
http://dx.doi.org/10.1593/neo.07878DOI Listing
March 2008

Stabilization of beta-catenin affects mouse embryonic liver growth and hepatoblast fate.

Hepatology 2008 Jan;47(1):247-58

Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (UMR 8104), Paris, France.

Unlabelled: During hepatogenesis, after the liver has budded out of the endoderm, the hepatoblasts quickly expand and differentiate into either hepatocytes or biliary cells, the latter of which arise only within the ductal plate surrounding the portal vein. Because the Wnt/beta-catenin pathway is involved in liver homeostasis and regeneration and in liver carcinogenesis, we investigated here a role for Wnt/beta-catenin signaling in the embryonic liver. A cyclization recombination (Cre)/locus of X-over P1 (loxP) strategy was chosen to perform adenomatous polyposis coli (Apc) invalidation in order to activate ectopic beta-catenin signaling in hepatoblasts; an appropriate transgenic model expressing the Cre recombinase was used. Phenotypic and immunolocalization studies, together with messenger RNA analyses, by microarray and real-time quantitative polymerase chain reaction approaches were performed on this model during normal hepatogenesis. The loss of Apc allowed beta-catenin activation in the hepatoblasts after the formation of the liver bud and led to embryonic lethality. In this model, the liver became hypoplastic, and hepatocyte differentiation failed, whereas beta-catenin-activated ducts developed and gave rise to fully differentiated bile ducts when transplanted into adult recipient livers. Microarray analyses suggested that beta-catenin plays a role in repressing the hepatocyte genetic program and remodeling the ductal plate. According to these data, in normal embryonic livers, beta-catenin was transiently activated in the nascent bile ducts.

Conclusion: We demonstrated a key role for the Wnt/beta-catenin pathway in liver embryonic growth and in controlling the fate of hepatoblasts, preventing them from differentiating toward the hepatocyte lineage, and guiding them to biliary ductal morphogenesis.
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http://dx.doi.org/10.1002/hep.21952DOI Listing
January 2008