Effects of mitomycin C on radiation-induced cell death in human cervical squamous cell carcinomas

In order to find an effective protocol for chemoradiotherapy with mitomycin C (MMC) for advanced cervical cancer patients, effects of both MMC and irradiation on chemoradiosensitivity were examined using the radiosensitive human cervical squamous cell carcinoma cell line ME180. MMC and low doses of irradiation did not affect radiosensitivity of the cells. A high dose of gamma-ray irradiation (10 Gy) significantly reduced MMC sensitivity of the cells. All of the four post-irradiation surviving subclones that were established from repetitively irradiated ME180 cells, demonstrated significantly higher MMC sensitivity than that of the non-irradiated parent cells. However, there was no difference in MMC sensitivity among three groups of irradiated cells; (1) cells treated with MMC eight hours before irradiation, (2) cells concurrently treated with MMC and irradiation and (3) cells treated with MMC eight hours after irradiation. These results indicate that MMC injections after completion of radiotherapy may be a better therapy than concurrent chemoradiotherapy with MMC.