Somatic aberrations of BRCA1 gene are associated with progressive and stem cell-like phenotype of prostate cancer

BackgroundBRCA1 is a pivotal tumor suppressor. Its dysfunction is known to play a role in different tumor entities. Among others, BRCA1 germline mutations account for higher risk and more aggressive course of prostate cancer (PCa). In addition, somatic BRCA1 gene loss was demonstrated to be a signature of PCa dissemination to regional lymph nodes and peripheral blood, and indicate worse clinical outcome. In order to substantiate the data for BRCA1 gene loss in PCa and to reveal its phenotypical background, BRCA1 gene status was assessed in a large cohort of PCa patients and compared to different molecular factors.MethodsBRCA1 gene dosage was assessed in 2398 tumor samples from 1199 PCa patients using fluorescent in situ hybridization. It was compared to clinic-pathological parameters, patients’ outcome as well as selected proteins (Ki-67, apoptosis marker, cytokeratins, vimentin, E- and N-cadherin, ALDH1 and EGFR) examined by immunohistcohemistry.ResultsBRCA1 losses were found in 10%, whereas gains appeared in 7% of 603 informative PCa patients. BRCA1 losses correlated to higher T status (p=0.027), Gleason score (p=0.039), shorter time to biochemical recurrence in patients with Gleason score >7 independently of other factors (multivariate analysis, p=0.005) as well as expression of proteins regulating stemness and epithelial-mesenchymal transition i.e. ALDH1 (p=0.021) and EGFR (p=0.011), respectively. BRCA1 gains correlated to shorter time to metastasis (p=0.012) and expression of ALDH1 (p=0.014).ConclusionsThe presented results support the assumption that BRCA1 gene losses contribute to a progressive and stem cell-like phenotype of PCa. Furthermore, they reveal that also BRCA1 gain might mark more invasive tumors.