Protection of androgen-dependent human prostate cancer cells from oxidative stress-induced DNA damage by overexpression of clusterin and its modulation by androgen

BACKGROUND. Recent studies reported that oxidative stress is one of the major factors associated with the progression of prostate cancer through the accumulation of DNA damage. In the present study, we investigated the effect of oxidative stress on cell injury using androgen-dependent human prostate cancer LNCaP cells overexpressing clusterin, which has been shown to play crucial roles in the acquisition of resistance to several apoptotic stimuli. METHODS. We introduced clusterin cDNA into LNCaP cells which do not express a detectable level of clusterin expression, and generated a clusterin-overexpressing cell line (LNCaP/Cl) and a control vector only-transfected cell line (LNCaP/Co). The effects of hydrogen peroxide (H2O2) treatment on the LNCaP sublines with and without the addition of dihydrotestosterone (DHT) were analyzed using the in vitro mitogenic assay and lipid peroxidation assay, and morphological changes in the LNCaP sublines after H2O2 treatment were examined by staining with Hoechst 33258. The degrees of DNA damage induced by H2O2 into the LNCaP sublines were evaluated by the measurement of 8-hydroxy-2'-deoxyguanosine (8-OHdG) level. RESULTS. H2O2-induced apoptosis in LNCaP/Cl was significantly suppressed compared with that in LNCaP/Co through the inhibition of membrane damage; however, the measurement of 8-OHdG level demonstrated that DNA damage was more intensively accumulated in LNCaP/Cl cells than LNCaP/Co cells. Furthermore, DHT suppressed the incidence of apoptotic cell death and enhanced the formation of 8-OHdG in both LNCaP/Cl and LNCaP / Co cells after H2O2 treatment in a dose-dependent manner. CONCLUSIONS. These findings suggest that clusterin may contribute to conferring resistance to oxidative stress-mediated cellular injury on prostate cancer cells, especially in the presence of androgen. (C) 2004 Wiley-Liss, Inc.