Androgen sensitivity related proteins in hormone-sensitive and hormone-insensitive prostate cancer cell lines treated by androgen antagonist bicalutamide

Members of the bcl-2 gene family and endogenous inhibitors of cyclin-dependent kinases participate in the regulation of apoptosis and cell cycle in a diverse range of cell types and are implicated in the development of hormone refractory prostate cancer and resistance to anti-cancer therapy. The expression of several of these genes can be regulated by steroid hormones and related agents via their nuclear receptors. However, insufficient information considering the protein expression after the treatment by hormone antagonists is available. The aim of this study was to evaluate the expression of anti- and pro-apoptotic proteins, (Bcl-2, Bax), and to correlate this with the appearance of some nuclear receptors and cell cycle related proteins in androgen sensitive and androgen insensitive prostate cancer cell lines, LNCaP and DU-145, after the treatment by androgen antagonist bicalutamide. Our results revealed that androgen receptor (AR) expression in LNCaP cells decreased, however in DU-145 cells AR slightly increased following anti-androgen treatment. The same agent stimulated expression of p21Waf1/Cip5 and p27Kip1 in LNCaP, as well as in DU-145 cell lines. Bcl-2 level increased slightly in LNCaP cells and, in DU-145 cells was almost undetectable. Bax expression was not changed in LNCaP but significantly decreased in DU-145 cells. Similarly, retinoid X receptor beta (RXRbeta) level was significantly down regulated after 24 hours in DU-145 and also in LNCaP cells after 72 hours. These results confirm that androgen withdrawal therapy employing anti-androgens may elicit different signalling pathways in various types of prostate cancer that may be dependent on AR status and AR sensitivity.