In vitro enhancement of radiation-induced apoptosis in human hepatoma cell line HepG2 by a selective inhibitor of cyclooxygenase-2 enzyme NS-398

AIM: To investigate the possible role of NS-398,a selective inhibitor of cyclooxygenase-2 enzyme,in radiation-induced apoptosis of human hepatoma cell line HepG2 in vitro.METHODS: Hepatoma cell line HepG2 was treated with various concentrations(25,50,100,200 μmol/L) of NS-398 before MTT assay was used to evaluate the cytotoxicity of NS-398.Transmission electron microscopy(TEM) was used to observe the changes of apoptosis in morphology.FCM was performed to quantify the apoptotic percentage.Real-time PCR was used to detect the expression of bcl-2,bax and caspase-3 mRNA,Western blotting was used to measure the expression of Bcl-2 and bax protein,and colorimetric method was provided to analyze the change of caspase-3 activity.RESULTS: The cytotoxicity of NS-398 increased in time-dependent and dose-dependent manners.NS-398 significantly enhanced radiation-induced apoptosis(P0.01),increased the expression of bax mRNA,Bax protein,caspase-3 mRNA and enhanced caspase-3 activity,whereas no significant change in Bcl-2 expression was found(P0.05).CONCLUSION: NS-398 enhances radiation-induced apoptosis in hepatoma cell line HepG2.The mechanism may be associated with the up-regulation of the expression of Bax,caspase-3 and enhancement of the activity of caspase-3,which ultimately induce apoptosis in HepG2.