Radiosensitization of hormone-refractory prostate cancer cells by gossypol treatment.

Purpose: many drugs have been tested to increase the sensitivity of prostate cancer cells to radiotherapy. Gossypol, a natural polyphenolic compound extracted from the cotton plant, is one of the agents the efficacy of which has been investigated in the treatment of prostate cancer for this purpose. The main aim of this study was to investigate the best gossypol application with irradiation, when gossypol was applied either sequentially (24 h before and after irradiation) or concurrently in PC-3 hormone-refractory and radioresistant prostate cancer cells.

Methods: The XTT viability assay was used to evaluate the cytotoxicity of different concentrations of gossypol in PC- 3 cells. Irradiation was applied to PC-3 cells via 6 MV photon linear accelerator and delivered 24 h before, 24 h after radiation or at the same time with gossypol administration.

Results: gossypol caused radiosensitization of PC-3 cells that are known to be radioresistant, with high Bcl-2 levels. Among different applications of gossypol and irradiation (before, after and concurrent) in prostate cancer cells, the best results were observed by the application of gossypol 24 h before irradiation.

Conclusion: our study suggests that gossypol represents a promising novel anticancer treatment for radiosensitization of human hormone-refractory prostate cancer cells.