Dataset Information

Discovery of Non-ETS Gene Fusions using RNA Sequencing

ABSTRACT:

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 employed 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 five 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.

PROVIDER: phs000310 | dbGaP |

SECONDARY ACCESSION(S): PRJNA74905PRJNA74907

REPOSITORIES: dbGaP

ACCESS DATA

Dataset's files

Source:

			Action	DRS
	GapExchange_phs000310.v1.p1.xml	Xml
	dbGaPEx2.1.5.xsd	Other
	Study_Report.phs000310.NonETS_Fusions.v1.p1.MULTI.pdf	Pdf
	manifest_phs000310.NonETS_Fusions.v1.p1.c1.PPC.pdf	Pdf
	datadict_v2.xsl	Other

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Project description:Characterization of the prostate cancer transcriptome and genome has identified chromosomal rearrangements and copy number gains/losses, including ETS gene fusions, PTEN loss and androgen receptor (AR) amplification, that drive prostate cancer development and progression to lethal, metastatic castrate resistant prostate cancer (CRPC)1. As less is known about the role of mutations2-4, here we sequenced the exomes of 50 lethal, heavily-pretreated metastatic CRPCs obtained at rapid autopsy (including three different foci from the same patient) and 11 treatment naïve, high-grade localized prostate cancers. We identified low overall mutation rates even in heavily treated CRPC (2.00/Mb) and confirmed the monoclonal origin of lethal CRPC. Integrating exome copy number analysis identified disruptions of CHD1, which define a subtype of ETS? prostate cancer. Similarly, we demonstrate that ETS2, which is deleted in ~1/3 of CRPCs (commonly through TMPRSS2:ERG fusions), is a prostate cancer tumor suppressor that can also be deregulated through mutation. Further, we identified recurrent mutations in multiple chromatin/histone modifying genes, including MLL2 (mutated in 8.6% of prostate cancers), and demonstrate interaction of the MLL complex with AR, which is required for AR mediated signaling. We also identified novel recurrent mutations in the AR collaborating factor FOXA1, which is mutated in 5 of 147 (3.4%) prostate cancers (both untreated localized prostate cancer and CRPC) , and showed that mutated FOXA1 represses androgen signaling and increases tumor growth in vitro and in vivo. Proteins that physically interact with AR, such as the ERG gene fusion product, FOXA1, MLL2, UTX, and ASXL1 were found to be mutated in CRPC, suggesting novel drivers of prostate cancer progression and potential resistance mechanisms to anti-androgen therapies. In summary, we describe the mutational landscape of a heavily treated metastatic cancer, identify novel mechanisms of AR signaling deregulated in prostate cancer, and prioritize candidates for future study. Gene expression profiling and array CGH (aCGH) was performed on matched benign prostate tissues (n=28), localized prostate cancer (n=59), and metastatic castrate resistant prostate cancer (CRPC, n=35). For gene expression profiling, frozen prostate tissue samples (channel 2), were hybridized against a commercial pool of benign prostate tissue (Clontech, channel 1). For aCGH, frozen prostate tissue samples (channel 2) were hybridized against a commerical sample of Human Male Genomic DNA (Promega, channel 1).

Project description:Characterization of the prostate cancer transcriptome and genome has identified chromosomal rearrangements and copy number gains/losses, including ETS gene fusions, PTEN loss and androgen receptor (AR) amplification, that drive prostate cancer development and progression to lethal, metastatic castrate resistant prostate cancer (CRPC)1. As less is known about the role of mutations2-4, here we sequenced the exomes of 50 lethal, heavily-pretreated metastatic CRPCs obtained at rapid autopsy (including three different foci from the same patient) and 11 treatment naïve, high-grade localized prostate cancers. We identified low overall mutation rates even in heavily treated CRPC (2.00/Mb) and confirmed the monoclonal origin of lethal CRPC. Integrating exome copy number analysis identified disruptions of CHD1, which define a subtype of ETS‑ prostate cancer. Similarly, we demonstrate that ETS2, which is deleted in ~1/3 of CRPCs (commonly through TMPRSS2:ERG fusions), is a prostate cancer tumor suppressor that can also be deregulated through mutation. Further, we identified recurrent mutations in multiple chromatin/histone modifying genes, including MLL2 (mutated in 8.6% of prostate cancers), and demonstrate interaction of the MLL complex with AR, which is required for AR mediated signaling. We also identified novel recurrent mutations in the AR collaborating factor FOXA1, which is mutated in 5 of 147 (3.4%) prostate cancers (both untreated localized prostate cancer and CRPC) , and showed that mutated FOXA1 represses androgen signaling and increases tumor growth in vitro and in vivo. Proteins that physically interact with AR, such as the ERG gene fusion product, FOXA1, MLL2, UTX, and ASXL1 were found to be mutated in CRPC, suggesting novel drivers of prostate cancer progression and potential resistance mechanisms to anti-androgen therapies. In summary, we describe the mutational landscape of a heavily treated metastatic cancer, identify novel mechanisms of AR signaling deregulated in prostate cancer, and prioritize candidates for future study.

Project description:Common epithelial cancers are believed to become more aggressive through the accumulation of multiple independent molecular events that lead to the deregulation of cell signaling. However, the discovery that the majority of prostate cancers harbor gene fusions of the 5'-untranslated region of androgen regulated TMPRSS2 promoter with ETS transcription factor family members has brought this paradigm into question1,2. TMPRSS2-ERG gene fusion is the most common molecular sub-type of prostate cancer. Recent work suggests that the TMPRSS2-ERG fusion is associated with a more aggressive clinical phenotype3. In the most advanced castration resistant prostate cancers where the androgen receptor has been inactivated, the TMPRSS2-ERG fusion remains functionally active. Here we show compelling clinical and gene expression data supporting the existence of a TMPRSS2-ERG fusion prostate cancer subclass. Using expression array profiling on 455 primary prostate tumors, we identified an 87 gene expression signature, distinguishing TMPRSS2-ERG fusion prostate cancer as a discrete molecular entity. Computational analysis suggested that this fusion signature was associated with estrogen receptor signaling. Functional studies demonstrated regulation of the TMPRSS2-ERG fusion transcript by estrogenic compounds. These data identify a previously unrecognized mechanism for regulation of the TMPRSS2-ERG, even in the absence of a functional androgen receptor, and thus may have broader implications in the treatment of prostate cancer. Keywords: Prostate cancer, Expression array, Illumina, gene fusion, TMPRSS2, ERG, Signatures, Estrogen Test Cohort: 388 cases from the population based Swedish-Watchful Waiting cohort. The cohort consists of men with localized prostate cancer (clinical stage T1-T2, Mx, N0); Validation cohort: The PhysiciansM-bM-^@M-^Y Health Study (PHS) cohort included 116 US men diagnosed with incidental prostate cancer between 1983 and 2003; 455 cases were annotated for TMPRSS2-ERG fusion. Test Set: GSM208029 ... GSM208392 Validation Set: GSM208404 ... GSM208512

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Discovery of Non-ETS Gene Fusions using RNA Sequencing

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