AIM: To investigate the biological impact of hepatitis B virus X- hepatitis C virus core (HBV X-HCV C) fusion gene on hepatoma cells.METHODS: The recombinant adenoviruses AdXC,Ad-X and Ad-C expressing HBV X-HCV C fusion gene,HBVX gene and HCV C gene were constructed,respectively.Hepatoma cells were infected with different recombinant adenoviruses.MTT,colonyforming experiment,FCM,TUNEL assay were performed to observe the biological impact of the HBV X-HCV C fusion gene on liver cells.RESULTS: MTT showed that the Ad-XC group cells grew faster than the other group cells.Colony-forming experiment showed that the colony-forming rate for the Ad-XC group cells was significantly higher than that for the other group cells.FCM analysis showed that Ad-XC/Ad-X/Ad-C infection enhanced the progression of GIS phase in the HepG2 cell cycle.The apoptosis index of the Ad-XC,Ad-X,Ad-C group cells was significantly lower than that of the AdO and control group cells.Semi-quantitative RT-PCR showed that the expression level of c-myc was the highest in AdXC infected cells.Tumor formation was found at the injected site of mice inoculated with Ad-XC-infected LO2 cells,but not in control mice.CONCLUSION: Ad-XC,Ad-X and Ad-C facilitate the proliferation activity of HepG2 cells and inhibit their apoptosis in vitro.The effect of Ad-XC is significantly stronger than that of Ad-X and Ad-C.Up-regulation of c-myc may be one of the mechanisms underlying the synergism of HBVX and HCV C genes on hepatocarcinogenesis in athymic nude mice.