AIM In this study we investigated therelationship of the X protein of HBV and nuclearfactor-KB (NF-κB) and the expression of NF-KB inhuman hepatocellular carcinoma tissues.METHODS Immunohistochemistry SP methodwas used to detect the expression of NF-κB and the X protein of HBV in human hepatocellularcarcinoma tissues of 52 cases. Gene transfectionmediated by lipofectamine was used to transfectthe eukaryotic expression vector pCDNA3. 1-HBXof HBV x gene into human hepatocellularcarcinoma cell line HCC-9204 and NF-κB wasdetected.RESULTS NF-κB was widely expressed inhuman hepatocellular carcinoma tissues in atotal of 52 cases and its expression was relatedto the X protein of HBV. NF-KB was localizedboth in the cytoplasm and . The nuclei ofhepatocellular carcinoma cells in 11 cases whichwere positive for the X protein of HBV while in 41cases negative for the X protein of HBV, NF-Kbwas only localized in the cytoplasm ofhepatocellular carcinoma cells but translocatedto the nuclei of hepatocellular carcinoma cellsafter the eukaryotic expression vectorpCDNA3.1-HBX was transfected into HCC-9204cells.CONCLUSION This study strongly suggeststhat the nuclear factor NF-KB is widely expressedin hepatocellular carcinoma tissues in differentstyles according to the expression of the Xprotein of HBV. NF-κB is abnormally activated inhepatocellular carcinoma, which is probablyrelated to the X protein of HBV. The X protein ofHBV can activate NF-κB to translocate into nucleiof hepatocellular carcinoma cells.