Subgenomic studies on hepatitis B virus DNA integrated into the genome of hepatocellular carcinoma.

Integration of hepatitis B virus (HBV) DNA into the chromosomal DNA of hepatocellular carcinoma (HCC) tissue was studied by the Southern blot analysis using probes for subgenomic regions C, PreS, S and X. Eighteen Hind III-fragments prepared from DNA of the tumor regions of six patients with HCC, and hybridized with a full genomic HBV probe were analyzed. Lack of region S or PreS was concurrently accompanied by deletion of their 3'-end region of the HBV minus strand DNA. Region C was missing in 11 out of 18 fragments while regions X, S and PreS were deleted in 5/18, 3/18 and 5/18 respectively. Therefore, in some sequences integrated by subgenomic HBV DNA, the integration of replicative intermediate of the HBV minus strand DNA into the chromosomal DNA may take place and one of the viral integration sites seems to be in the region X.