Identification and Mechanistic Investigation of Recurrent Functional Genomic and Transcriptional Alterations in Advanced Prostate Cancer

Abstract

Novel functionally altered transcripts may be recurrent in prostate cancer (PCa) and may underlie lethal and advanced disease and the neuroendocrine small cell carcinoma (SCC) phenotype. We conducted an RNASeq survey of the LuCaP series of 24 PCa xenograft tumors from 19 men, and validated observations on metastatic tumors and PCa cell lines. Key findings include discovery and validation of 40 novel fusion transcripts including one recurrent chimera, many SCC-specific and castration resistance (CR) -specific novel splice isoforms, new observations on SCC-specific and TMPRSS2-ERG specific differential expression, the allele-specific expression of certain recurrent non-synonymous somatic single nucleotide variants (nsSNVs) previously discovered via exome sequencing of the same tumors, rgw ubiquitous A-to-I RNA editing of base excision repair (BER) gene NEIL1 as well as CDK13, a kinase involved in RNA splicing, and the SCC expression of a previously unannotated long noncoding RNA (lncRNA) at Chr6p22.2. Mechanistic investigation of the novel lncRNA indicates expression is regulated by derepression by master neuroendocrine regulator RE1-silencing transcription factor (REST), and may regulate some genes of axonogenesis and angiogenesis. Taken together these variant transcripts offer insight into aggressive metastatic PCa, both broadly and with regard to castration-resistant and neuroendocrine disease.