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Background/Aims: The integration of HBV DNA is thought to be involved in the initial stage of hepatocarcinogenesis, and it has been reported that transactivating factors encoded by the X and preS2/S genes stimulates transcription of multiple viral and cellular genes. We assessed the possible contributions of hepatitis B virus integration to the occurrence of hepatocellular carcinoma in hepatitis C virus-infected as well as in hepatitis B virus-infected patients by identifying the integrated HBV DNA sequence, and the X and preS2/S regions were further investigated in HBV DNA-integrated cases.

Methods: Southern blot hybridization for detecting HBV DNA in tumor tissues from 28 hepatocellular carcinoma patients was carried out with full-length HBV DNA, and then with X and preS2/S regions as probes. We also carried out reverse transcription-polymerase chain reaction for detecting HCV RNA to confirm hepatitis C virus-infection in liver tissues.

Results: Clonally integrated HBV DNA sequences were demonstrated in 16 to 28 patients (57.1%), including five HBsAg seropositive and 11 HBsAg seronegative patients. Of these 11 HBsAg seronegative patients, 10 were also positive for anti-HCV in their sera, and all nine examined cases had HCV RNA in liver. Furthermore, the X region was identified in 14 of 16 HBV DNA integrated cases(87.5%), and the preS2/S region in 6/16 (37.5%).

Conclusions: The present Southern blot analysis demonstrates that clonally integrated HBV DNA sequences were identified even in hepatitis C virus-infected hepatocellular carcinoma patients at a high rate (10/18, 55.6%), and suggests that integrated hepatitis B virus, whose major component is the X gene, may play an important role in hepatocarcinogenesis in hepatitis B virus-integrated cases with and without hepatitis C virus infection.

(C) 1997 Journal of Hepatology