Abstract: OBJECTIVE: To study the role of NOX (NADPH oxidase) in X-ray- induced damage of human androgen-independent prostate cancer PC-3 cells damage，search for potential targets for radiation sensitization. METHODS：The viability of human androgen-independent prostate cancer PC-3 cells induced by 0，1，2，4 and 12 Gy of X rays after 24，48 and 96 h was detected by the MTT assay. The level of ROS after X-ray irradiation for 15，30，60 and 120 min ，and the expression of NOX1-5 protein in PC-3 cells induced by 0，1 and 4 Gy of X rays was analyzed by using DCFH-DA as a probe and by Western blot，respectively. RESULTS：Compared with non-irradiated，the viability of human prostate cancer PC-3 cells induced by 1，2，4 and 12 Gy of X rays was significantly decreased (P<0.05) . The level of ROS reached a maximum at 60 min after 1 and 4 Gy of X-ray irradiation. NOX inhibitor DPI and antioxidant NAC pretreatment could reduce the generation of ROS. Western blotting showed the expressions of NOX1，NOX2 and NOX5 were increased after irradiation. CONCLUSION：X-ray-induced the homologs NOX1，NOX2 and NOX5 of the catalytic subunit gp91phox of NADPH oxidase over-expression，resulting in excessive intracellular ROS which is a new mechanism of X-ray-induced damage of prostate cancer cells.

Key words: NADPH oxidase, reactive oxygen species, human prostate cancer PC-3 cells, X-ray