Abstract: Preliminary experiments confirmed that evodiamine (EVO) has radiosensitizing effect on the tongue squamous cell carcinoma cell line Tca8113.We wonder the efficacy of EVO combined radiotherapy with different treatment schedules on human gastric cancer cells SGC7901.Cell proliferation inhibitory rates of SGC7901 cells were detected by MTT method at different time points after treatment with EVO at different concentrations.The colony-formation ability of SGC7901 cells treated with EVO plus radiation was detected by colony-formation assay.Cell cycle was detected to compare the difference between radiotherapy and EVO with different doses of radio-therapies by flow cytometry.Western blot assay was conducted to determine the expression of Caspase3 in the cell lines.The grouping of EVO administration was as follows:Group A,administration 24 h before irradiation;Group B,administration after irradiation;inhibition rates of SGC7901 cells were increased as EVO increased in concentration and time.Survival fraction,D₀, D_q, SF₂ of combination groups were lower than that in the radiation and combination groups.The effect of Group A was superior to that of Group B.G2/M blockage rates of the EVO in combination was higher than other groups.The protein expression of caspase3 in the combination group was markedly increasing compared with radiation group.The radiosensitizing effect was affected by different time series of administration,in which the effect of the administration before radiotherapy ranked the first.The mechanism of radiosensitization effect may relate to G2/M cell cycle arrest and increase expression of Caspase3.

Key words: evodimine, radiosensitization, gastric cancer, cell cycle, caspase3