OBJECTIVESTo study the phenomena of hepatitis B virus (HBV) integration into the tissues of hilar cholangiocarcinoma (HCCA) and to identify the integration sites in the host genome.

METHODSTen fresh HCCA samples were collected from the tissues by surgical ablation, 1 normal hilar bile duct sample selected as control. Cellular DNA were extracted by Wizard SV Genomic DNA Purification System. PCR-derived assay (HBV-Alu-PCR) was employed to amplify the viral-host junctions which contain the HBV sequence and the adjacent cellular flanking sequences. The PCR products were purified and subjected to sequencing by ABI-3730XL Auto DNA Analyzer. The sequence analysis of viral-host junctions was performed by DNASIS MAX 3.0 bioinformatics software. The insertion sites between viral and cellular sequences were identified through homology comparison using NCBI BLAST and MapViewer search.

RESULTSIn 10 HCCA samples, 5 were demonstrated to have HBV integration fragments with total 6 inserted sites identified. Sequence analysis from viral-host junction showed that HBV X gene inserted into host genome at random distribution with truncated fragments. HBV integration recurrently targeted the unknown region in upstream of CXXC finger protein-1 (CpG-binding protein) gene (4 cases). p53 tumor suppressor gene was also found at the integration site.

CONCLUSIONSThere is high integration rate of HBV DNA into cellular genome of HCCA. HBV integration is found frequently into or close to cancer-related genes. The findings demonstrate that HBV infection might have association with the pathogenesis of HCCA.