Silencing of Heat Shock Protein 27 Expression Accelerates Doxazosin-induced Apoptosis in Prostate Cancer Cell Line PC-3

ABSTRACT

PURPOSE: Heat shock proteins (HSPs) are highly expressed during stress responses and cellular adaptation to environmental changes. One such protein is HSP27, a 27kDa protein that prevents cell death induced by many pro-apoptotic agents. Therefore, the aim of this study was to investigate the correlation between HSP27 expression and apoptosis induced by doxazosin treatment in prostate cancer cell line PC-3. MATERIALS AND METHODS: RT-PCR, Western blotting, and immunocytochemical staining were performed to determine whether HSP27 mRNA and protein are expressed in PC-3 cells. Next, to investigate the effects of doxazosin on apoptosis and HSP27 protein expression in PC-3 cells, the cells were stained using a TUNEL kit (to detect apoptotic cells) and with HSP27 antibody (to assess HSP27 protein expression) 6, 12, 24, and 48h after treatment with 25microM doxazosin. In addition, to determine whether HSP27 mRNA interference accelerates doxazosin-induced apoptosis of PC-3, we knocked down HSP27 with siRNA and then evaluated the rate of apoptosis after doxazosin treatment. RESULTS: HSP27 mRNA and protein were expressed in PC-3 cells. Furthermore, HSP27 mRNA and protein levels increased until 12 hours after 25microM doxazosin treatment, whereas the rate of apoptosis did not increased dramatically. After 12 hours, HSP27 expression decreased and then apoptosis was accelerated. In addition, siRNA-mediated knockdown of HSP27 induce higher apoptosis rate of PC-3 cells even before 12hrs after doxazosin treatment. CONCLUSIONS: By inhibiting apoptosis, HSP27 expression might play an important role in inhibiting progression to castration-refractory prostate cancer and resistance to anti-cancer treatment.