Abstract
英文摘要（English abstract）Experiments in animal models of carcinogenesis suggest that soy consumption decreases tumor number and incidence. Genistein, an isoflavone which is present in soy at high concentrations, has been considered to be the primary antitumor constituent in soy. Up to now, studies on the biological effects of the genistein are quite limited. In this work, we investigated the biological responses of cells when exposed to genistein. First, we examined whether genistein could produce cytotoxic in cells. RKO cells were treated with various concentrations of genistein for 8 hours. We find out that dose-dependent cytotoxic effect and time-dependent cytotoxic effect were observed. Then we examined the effect of genistein on the cell cycle progression by flow cytometry. The results show that genistein induced G2/M arrest in RKO cells but it is reversal after several hours later. Since cells arrest in G2/M phase we investigated whether cyclin B and cdc2 level change and the cyclin B/cdc2 complex activity change after genistein treatment. It is found that cyclin B and cdc2 level were not affected by genistein. However, there is a time-dependent effect in cyclin B/cdc2 complex activity. It is concluded that genistein may block cell cycle progression at G2 phase of RKO cells.To investigate whether the delay of G2 phase relates to the repair efficiency of cell damage, we therefore irradiated the genistein pretreated and co-treated cells and estimated the survival fraction. The results show that genistein more enhanced the radiosensitivity of pre-treated cells. But the G2 phase fraction of cells after treating both genisten and X-ray irradiation whatever pre-treated or co-treated were not enhanced.