Radiation- and heat-induced apoptosis in PC-3 prostate cancer cells.

Radiation therapy is used to treat all stages of localized prostate cancer. However, both clinical and radiobiological evidence indicate that prostate cancer cells are relatively resistant to radiation. New modalities which can induce apoptosis in androgen-independent cells are of interest for developing novel treatments for prostate cancer. Both radiation and hyperthermia have been shown to be able to induce apoptosis in a variety of cells. However, it is not known whether heat- or radiation-induced apoptosis plays a role in the mechanism of cell killing for prostate cancer cells. We examined radiation- and heat-induced apoptosis in PC-3 prostate cancer cells and found that apoptosis is an important mode of death in heated cells. However, apoptosis is not an important mechanism of death in irradiated cells. Apoptosis-inducing modalities such as hyperthermia may supplement radiation therapy in the future management of prostate cancer. No significant apoptosis was observed when cells were heated at 42 degrees C for 240 min. Thus a heating temperature of 43 degrees C and above may be required to induce significant apoptosis in a clinically feasible duration of time.