Heat-shock proteins inhibit induction of prostate cancer cell apoptosis

BACKGROUND. Resistance to apoptosis remains a significant problem in the tr eatment of prostate cancer. Heat-shock proteins (HSP) have been correlated with tumor progression. The role of HSP in prostate cancer resistance to ap optosis is unknown. METHODS. PC-3 and LNCaP prostate cancer cells were heat-shocked and then tr eated with or without diethyl-maleate, etoposide, cycloheximide, or 3 Gray irradiation. Percent apoptosis was assessed by propidium iodide DNA incorpo ration. Protein was also extracted for analysis by SDS-PAGE Western blottin g. RESULTS. Western blotting confirmed an increase in HSP 27 and 72. These cel ls were resistant to both chemical- and radiation-induced apoptosis. Cycloh eximide and specific oligonucleotides to HSP 72 blocked the increased expre ssion of HSP 72 and the resistance to apoptosis. Mcl-1, Bcl-2, Bcl-X-L, and glutathione-S-transferase (GST) expression were increased in a time-depend ent manner after heat shock. CONCLUSIONS. This study demonstrates that HSP expression, specifically HSP 72, inhibits apoptosis in prostate tumor cell lines, which may be mediated by the production of survival factors. (C) 2000 Wiley-Liss, Inc.