Objective   To investigate the apoptosis in gastric cancer cells induced by soybean isoflavone, and the relation between this apoptosis and expression of bcl-2 and bax.

  Methods   In vitro experiments, MTT assay was used to determine the cell growth inhibitory rate.Transmission electron microscope and TUNEL staining method were used to quantitatively and qualitively detect the apoptosis status of gastric cancer cell line SGC-7901 before and after the soybean isoflavone treatment.Immunohistochemical staining and RT-PCR were used to detect the expression of apoptosis-regulated gene bcl-2 and bax.

  Results   Soybean isoflavone inhibited the growth of gastric cancer cell line SGC-7901 in a dose-and time-dependent manner.Soybean isoflavone induced SGC-7901 cells to undergo apoptosis with typically apoptotic characteristics, including morphological changes of chromatin condensation, chromatin crescent formation, nucleus fragmentation and apoptotic body formation by transmission electron microscope and staining positive cells by TUNEL assay.Soybean isoflavone can reduce the expression of apoptosis-regulated gene bcl-2, and improve the expression of apoptosis-regulated gene bax.

  Conclusion   Soybean isoflavone was able to induce the apoptosis in gastric cancer.This apoptosis may be mediated by down-expression of apoptosis-regulated gene bcl-2 and up-expression of apoptosis-regulated gene bax.