NCOR1 may be a potential biomarker of a novel molecular subtype of prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed male cancer. An earlier study of a cohort of 333 primary prostate carcinomas showed that 74% of these tumors fell into one of seven subtypes of a molecular taxonomy defined by specific gene fusions (ERG, ETV1/4 and FLI1) or mutations (SPOP, FOXA1 and IDH1). Molecular subtypes may aid in distinguishing indolent cases from aggressive cases and improving management of the disease. However, molecular features of PCa outside the seven subtypes are still not well studied. Here we report molecular features of PCa cases without typical features of the established subtypes. We performed comprehensive genomic analysis of 91 patients, including 54 primary and 37 metastatic cases, by whole-exome sequencing. TP53, SPOP, FOXA1, AR (androgen receptor) and a TMPRSS2-ERG fusion emerged as the most commonly altered genes in primary cases, whereas AR, FOXA1, PTEN, CDK12, APC and TP53 were the most commonly altered genes in metastatic cases. Nuclear receptor corepressor (NCOR1) genomic alterations have been identified in 5% of cases, which are nontypical molecular features of PCa subtypes. A novel NCOR1 c.2182G>C (p.Val728Leu) was identified in tumor. RT-PCR was used to show that this mutation caused loss of NCOR1 exon 19 and might be oncogenic in PCa. NCOR1 is involved in maintenance of mitochondrial membrane potential in PCa cells, and loss of NCOR1 might contribute to PCa progression. Therefore, NCOR1 may be a potential molecular marker of a subtype of PCa.