Hepatitis B virus Xprotein ( HBx) plays a role in the development of hepatocellular carcinoma ( HCC) . Studies on t he relationshi p bet ween HBx and HCC development can provide an important basis for the mechanism of tumorigenesis of HBV. Amongits various activities , HBx can regulate cell apoptosis and proliferation . However , whether HBx is anti-apoptotic or pro-apoptotic is still debatable . In this study , Huh7 and 293Tcells were transiently transfected with HBx-expressing plasmid at different concentrations . The results showed that HBx could exhibit anti- or pro-apoptotic activity depending on the transfection concentration. At a low transfection concentration, HBx appeared to inhibit apoptosis while it promoted apoptosis at a higher transfection concentration. Furt her more , preli mi nary results suggested that different HBx expression levels could cause different cellular localizations of nuclear fact or κB( NF-κB) .