Heat-shock proteins inhibit induction of prostate cancer cell apoptosis

BACKGROUND. Resistance to apoptosis remains a significant problem in the treatment of prostate cancer. Heat-shock proteins (HSP) have been correlated with tumor progression. The role of HSP in prostate cancer resistance to apoptosis is unknown. METHODS. PC-3 and LNCaP prostate cancer cells were heat-shocked and then treated with or without diethyl-maleate, etoposide, cycloheximide, or 3 Gray irradiation. Percent apoptosis was assessed by propidium iodide DNA incorporation. Protein was also extracted for analysis by SDS-PAGE Western blotting. RESULTS. Western blotting confirmed an increase in HSP 27 and 72. These cells were resistant to both chemical- and radiation-induced apoptosis. Cycloheximide and specific oligonucleotides to HSP 72 blocked the increased expression 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-dependent 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.