[ ABSTRACT] AIM:To investigate the effects of tanshinone IIA ( Tan IIA) on proliferation, apoptosis and its mo-lecular mechanism in human hepatoma HepG2 cells under hypoxic condition.METHODS:Hypoxia model was established by treatment with cobalt chloride ( CoCl2 ) .The cells were divided into normoxia control group, hypoxia control group and hypoxia combined at different concentrations of Tan IIA groups.After HepG2 cells were incubated with different concentra-tions of Tan IIA (0.5, 1.0, 2.0, 5.0 and 10.0 mg/L) for 24 h, 48 h and 72 h under hypoxic condition, the cell prolifer-ation was determined by MTT assay.After Tan IIA was added to the media at different concentrations for 24 h and 48 h, the apoptotic cells were observed by Hoechst 33258 staining.The protein levels of hypoxia-inducible factor 1 alpha (HIF-1α) , vascular endothelial growth factor ( VEGF) and wild-type P53 were detected by Western blotting after cultured with different concentrations of Tan IIA for 48 h.RESULTS:Tan IIA inhibited the proliferation of HepG2 cells in a dose-and time-dependent manner.Tan IIA induced the typical morphology of apoptotic cells and increased the apoptotic rate in a dose-and time-dependent manner after treatment with 1.0 mg/L~5.0 mg/L for 24 h and 48 h under hypoxic condition. The protein levels of HIF-1αand VEGF were weakly expressed in HepG2 cells under normoxia but up-regulated after incu-bated under hypoxia for 48 h.The protein expression of HIF-1αand VEGF were decreased with the increase in the concen-tration of Tan IIA under hypoxia.The protein expression of wild-type P53 was increased with the increase in the concentra-tions of Tan IIA under hypoxia.CONCLUSION:Tan IIA significantly inhibits the proliferation and induces the apoptosis of human hepatoma HepG2 cells under hypoxia, which may be related to the down-regulation of HIF-1αand VEGF and up-regulation of wild-type P53.