CCAAT enhancer binding protein β promotes tumor growth and inhibits apoptosis in prostate cancer by methylating estrogen receptor β

The CCAAT enhancer binding protein 3 (C/EBPP) is overexpressed at late stages in carcinogenesis of prostate cancer (PCa), suggesting that it could potentially contribute to progression of PCa. Estrogen receptor beta (ERP) is a tmnor suppressor gene in PCa. However, whether C/EBP beta could regulate ERP by promoter methylation is still poorly understood. In this study, expression levels of C/EBP beta and ERI in two PC lines (LNCap and PC-3), prostatic epithelial cell line (RWPE-1), forty-eight paired non-cancerous and cancerous peripheral blood samples were examined via qRT-PCR, western blotting and methylation-specific PCR. In addition, PCa cell line was infected with peDII-C/EBP beta and pLK0.1-C/ EBp beta and expression levels of C/EBP beta, ERP and DNA methyltransferases were detected. Finally, the role of C/EBP beta in proliferation and apoptosis of PCa cell lines was examined by MIT and flow cytometer assay. Our results show a higher frequency of promoter methylation of ERP levels in blood samples from PCa patients (16 of 18 cases) compared with that from healthy controls (3 of 48). Besides, elevated expression levels of C/EBP beta were found in PCa patients and two PCa lines (LNCap and PC-3) compared to non-cancerous cases or prostatic epithelial cell line (RWPE-1), while opposite expression levels of ERP were found. Overexpression of C/EBP beta could regulate ERP expression, DNA methyltransferases expression, cell proliferation and apoptosis. Our results support the conclusion that C/EBP beta down-regulated ERP expression through increasing its promoter methylation, and then regulated proliferation and apoptosis in PCa.