Analysis of integrated hepatitis B virus DNA and flanking cellular sequences in a childhood hepatocellular carcinoma

Abstract

The DNA of tumor tissue K1 obtained at autopsy from a case of hepatocellular carcinoma (HCC) in a 9-year-old boy contained integrated hepatitis B virus (HBV) DNA at a single site in the chromosome (case 2, Chang et al.: Hepatology 13:316-320, 1991). To characterize further the integrated viral DNA sequences, a genomic library of the K1 DNA was constructed in the lambda L47.1 vector. One phage clone, designated KTM-1, containing integrated HBV DNA and cellular flanking sequences was obtained from this library. The restriction map and DNA sequence of this clone showed that the integrated HBV DNA was partially deleted and rearranged. The most conserved viral DNA sequences were surface and X genes and arranged in the opposite orientation. The viral core gene was not present. Using chloramphenicol acetyltransferase (CAT) assay, the C-terminal truncated X open reading frame was demonstrated to retain its trans-activating ability. The result suggested that the functional integrated X gene may play a role in hepatocarcinogenesis. The study also showed that the right cellular flanking sequences were human alphoid repetitive sequences.

The carboxy‐terminus of the hepatitis B virus X protein is necessary and sufficient for the activation of hypoxia‐inducible factor‐1α

“…The X gene is the most frequently integrated portion of HBV DNA found in hepatocyte chromosomes during the development of HCC [33]. It has been shown that most, if not all, HBx isolated from integrated HBV DNA in HCC patients was in a truncated form [15–22]. Interestingly enough, Lee et al demonstrated that hypoxia stimulated the expression of HBx gene in HBV‐integrated liver cancer cells obtained from HCC patients [34].…”

“…Mutations and deletions in the HBx open reading frame are frequently found in naturally occurring human HCC [15–22], which may indicate differential functions of structural domains of HBx that contribute to the development of HCC. In the present investigation, therefore, we analyzed the functional domain of the HBx that induces transcriptional activity of HIF‐1α to provide further insights on the role of HBx in the HBV‐associated hepatocarcinogensis.…”

HBV Integration Induces Complex Interactions between Host and Viral Genomic Functions at the Insertion Site

“…1 ; Gene Annotation), contributing to phenotype changes of affected cells. The integration site can be either only hundreds of base pairs (e.g., 257 bp upstream of hTERT 54 ) or over 100 kb (e.g., 2,582 kb upstream of CCNE1 55 ) from the genes in the vicinity along the human genome. In the first large-scale screening for HBV integrations in HCC, Sun et al .…”

“…1; Gene Annotation), contributing to phenotype changes of affected cells. The integration site can be either only hundreds of base pairs (e.g., 257 bp upstream of hTERT 54 ) or over 100 kb (e.g., 2,582 kb upstream of CCNE1 55 ) from the genes in the vicinity along the human genome. In the first large-scale screening for HBV integrations in HCC, Sun et al 18 explored integrations in the promoter region which were from 0 to −5 kb relative to the transcriptional start site (commonly referred to as TSS), while Fujimoto et al 49 enlarged this region up to 10 kb upstream, which has become widely adopted.…”

Characterization of integration patterns and flanking cellular sequences of hepatitis B virus in childhood hepatocellular carcinomas

“…Analyses of viral junction sequences indicate that the 11-bp direct repeats (DR 1 and 2) are preferred sites of integration in the HBV genome [Shih et al, 1987;Robinson, 1992]. Cellular sequences flanking HBV DNA display weak preference for regions that contain repeating sequences [Shaul et al, 1986;Berger and Shaul, 1987;Tsuei et al, 1994a], but no specific integration sites have been identified. The complexity of the genomic rearrangements found in each HCC tissue and the lack of specific integrations and translocations make the interpretation of the function of HBV DNA in HCC development quite difficult.…”