Abstract: Background and purpose: Quinonoids can change the cell cycle distribution of tumor cells, and effect the radiosensitizing. This study aimed to investigate the radiosensitization effects, cell cycle and apoptosis of cryptotanshinone on H22 hepatoma-bearing mice. Methods: The mouse hepatoma H22 model was established, then divided into blank control group, irradiation alone group, high dose of cryptotanshinone group, cryptotanshinone (low, medium and high) + IR groups. After irradiated, observed the growth of tumor’s conditions, record epigenetic tumor irradiation time, calculated the delay time of tumor growth and enhancement factor (EF). After 22 days, mice were killed, stripped tumor, and calculated the inhibition rate. The cell cycle distribution and apoptosis were measured by flow cytometry. Results: Cryptotanshinone (low, medium and high) groups inhibited the tumor growth better than the blank group, and had the significant radiosensitizing effect. The enhancement factor was 1.22, 1.43,2.19, respectively. Cells were treated with cryptotanshinone which had significant effects on cell cycle, and induced apoptosis, which indicated significant G₂/M phase arrest and a decrease in S phase. Conclusion: Cryptotanshinone inhibited the tumor growth and had the radiosensitizing effects on H22 hepatoma-bearing mice. One of the mechanism may be that it might make significant G₂/M phase arrest and S phase decreased, and induced apoptosis. So cells were more sensitive to radiation.

Key words: Cryptotanshinone, H22 hepatoma, Radiosensitization, Cell cycle, Apoptosis