Effects of N-acetylcystein on bleomycin-induced apoptosis in malignant testicular germ cell tumors

摘要

Oxidative stress has been shown to induce apoptosis in cancer cells. Therefore, one might suspect that antioxidants may inhibit reactive oxygen species (ROS) and prevent apoptosis of cancer cells. No study has been carried out so far to elucidate the effects of N-acetylcysteine (NAC) on bleomycin-induced apoptosis in human testicular cancer (NCCIT) cells. We investigated the molecular mechanisms of apoptosis induced by bleomycin and the effect of NAC in NCCIT cells. We compared the effects of bleomycin on apoptosis with H2O2 which directly produces ROS. Strong antioxidant NAC was evaluated alone and in combination with bleomycin or H2O2 in germ cell tumor-derived NCCIT cell line (embryonal carcinoma, being the nonseminomatous stem cell component). We determined the cytotoxic effect of bleomycin and H2O2 on NCCIT cells and measured apoptosis markers such as caspase-3, caspase-8, and caspase-9 activities and Bcl-2, Bax, and cytochrome c (Cyt-c) levels in NCCIT cells incubated with bleomycin, H2O2, and/or NAC. We found half of the lethal dose (LD50) of bleomycin on NCCIT cell viability as 120 μg/ml after incubation for 72 h. Incubation with bleomycin (LD50) induced increases in caspase-3, caspase-8, and caspase-9 activities and Cyt-c and Bax protein levels and a decrease in Bcl-2 level. Co-incubation of NCCIT cells with bleomycin and 10 mM NAC abolished bleomycin-induced increases in caspase-3 and caspase-9 activities, Bax, and Cyt-c levels and bleomycin-induced decrease in Bcl-2 level. Our results indicate that bleomycin induces apoptosis in NICCT cells and that NAC diminishes bleomycin-induced apoptosis via inhibiting the mitochondrial pathway. We conclude that NAC has negative effects on bleomycin-induced apoptosis in NICCT cells and causes resistance to apoptosis, which is not a desirable effect in the fight against cancer.