Cloning and analysis of integrated hepatitis B virus DNA of the adr subtype derived from a human primary liver cell carcinoma.l gen

A 10 kb genomic DNA fragment derived from a human primary liver cell carcinoma (PLC) and containing integrated hepatitis B virus (HBV) DNA was cloned and analysed. Physical mapping showed the viral DNA to comprise alinear sequence of at least 2.8 kb (87~) of the HBV genome and to be of the adr subtype. Integration appeared to have occurred in the region of the viral genome spanning the cohesive ends. The cellular flanking DNA sequences to one side of the integrated viral DNA contained repeats of the Alu family. The finding of no apparent rearrangements of the integrated HBV DNA sequences in this clone is in contrast to the situation in the huSP and PLC/PRF/5 PLC cell lines in which the integrated viral DNA sequences are greatly rearranged and suggests that such rearrangements may be atypical of solid PLCs. The epidemiological evidence linking hepatitis B virus (HBV) with the development of primary liver cell carcinoma (PLC) is strong (Beasley, 1982). This association has recently been further strengthened by the finding of HBV DNA sequences integrated into the genomes of many PLCs (Brechot et al., 1981; Shafritz & Kew, 1981; Shafritz et al., 1981; Chen et al., 1982; Hino et al., 1984; Fowler et al., 1984) and has led to the hypothesis that integration of the viral DNA may be directly involved in the development of PLC (Shafritz, 1982). In order to investigate the possible molecular mechanisms by which integration may lead to the development of the transformed phenotype, several groups have cloned integrated HBV DNA sequences derived from two HBV surface antigen (HBsAg)-positive PLC cell lines (PLC/PRF/