AIM:To investigate the in vitro killing effect of adenovirus-mediated herpes simplex virus thymidine kinase gene(HSV-TK) driven by hypoxic response element(HRE) on hepatoma cell line HepG2.METHODS:Recombinant adenoviral vector Ad-HRE-TK was constructed with HSV-TK under the control of HRE using AdEasy system.Then Ad-HRE-TK was transfected into hepatoma cell line HepG2 and the cells were cultured under normoxic or hypoxic conditions.After treated with GCV for 3 d,the sensitivity to GCV of HepG2 was measured by MTT method.RESULTS:Over 95% HepG2 cells infected with Ad-HRE-TK cultured under hypoxic condition were killed when the MOI was 100 and the concentration of GCV was 50 mg/L.On the contrary,no killing effect of GCV was observed in cells cultured under normoxic condition.CONCLUSION:HRE promotes the expression of HSV-TK specifically under hypoxic condition and induces the specific killing effect of GCV.