Hypermethylation-mediated transcriptional repression of TMPRSS2 in androgen receptor-negative prostate cancer cells.

Prostate cancer is the most common type of cancer for men in the developed world. Androgen receptor (AR) is very important in prostate cancer progression. TMPRSS2 is an AR signaling downstream gene and closely related to prostate carcinogenesis. DNA methylation is a key mechanism to influence gene expression. Though previous reports have shown that AR signaling plays a critical role in the regulation of TMPRSS2 in prostate cancer, hardly any studies have examined whether the DNA methylation has been involved in the regulation of TMPRSS2. In the present study, we demonstrated that AR-negative prostate cancer (PCa) cells showed low expression levels and hypermethylation of TMPRSS2. In contrast, AR-positive PCa cells displayed high levels and hypomethylation of TMPRSS2. Treatment with the DNA methylation inhibitor 5-Aza-2'-deoxycytidine reversed the low expression levels of TMPRSS2 in the AR-negative PCa cells. Additionally, we found that the level of DNA methyltransferases 1 (DNMT1) was high in AR-negative PCa cells, in which hypermethylation of TMPRSS2 and low expression level of TMPRSS2 were observed. Collectively, these data suggest that the high level of DNMT1 might be the mechanism for the hypermethylation-mediated transcriptional repression of TMPRSS2 in AR-negative PCa cells.