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PubMed1999

[The correlation between integration of HBV X, S, Pre-S, C gene and the expression of oncogenes/tumor suppressor genes in primary hepatocellular carcinoma].

OBJECTIVE: To study the relation between the integration of HBV X, S, Pre-S and C genes and the expression of oncogenes/tumor suppressor genes in hepatocellular carcinoma(HCC). METHODS: To prepare the Dig-HBV probes with random priming method, to detect the existing status of HBV DNA and the integration rates of HBV X, S, Pre-S and C genes by Southern blot and dot blot hybridization, and to examine the expression of oncogenes and tumor suppressor genes by immunohistochemistry in HCC. RESULTS: The integration rates of HBV X, S, Pre-S and C genes in HCC were 87.5%(28/32), 62.5% (20/32), 62.5%(20/32) and 25.0%(8/32), respectively. The expression rates of p62myc, p21ras, p53 and p16 proteins were 81.2%(26/32), 50.0%(16/32), 43.8%(14/32), and 31.3(10/32), respectively. Statistical analysis showed that the expression of p62myc, p21ras and variant p53 proteins was obviously higher in HCC group with X gene than in free-X gene HCC group and that the expression of p62myc protein was obviously higher in HCC group with Pre-S gene than in free-Pre-S HCC group. CONCLUSION: The integration of HBV X or Pre-S gene with cellular chromosome can activate myc, ras oncogenes and inactivate the p53 tumor suppressor gene.

Carcinoma, Hepatocellular↗
PubMed1997

[Viruses and primary hepatocellular carcinoma].

The etiological association between primary hepatocellular carcinoma (PHCC) and chronic viral hepatitis has been proved by now beyond doubt in the hepatitis B virus (HBV) and C virus (HCV). PHCC develops most frequently in cirrhotic livers, sometimes also in the absence of cirrhosis. Extensive epidemiological studies provided convincing evidence of this etiological relationship which is also supported by observations and animal experiments. An important factor in hepatocarcinogenesis due to the influence of HBV is integration of the viral genoma into the liver cell genoma. In the tumourous part of the liver integrated HBV sequences are more frequent than in the non-tumourous part. The integration can produce changes in the genome of the liver cell which may sometimes lead to malignant transformation. The mechanisms of this process are not quite clear so far. Their outcome--the development of carcinoma--can be summarized as the peak effect of factors leading to the disorganization of DNA with participation of chromosomal changes, the action of transactivation of HBs protein, transformation growth factors and the important influence of mutations of the suppressor gene p 53 on the 17th chromosome which is probably the target of HBV. HCV produces chronic live: disease developing into cirrhosis and PHCC, even more frequent than HBV; however its integration into the liver cell does not take place. The genetic variability of this gene is great. Its transformating action is probably implemented rather as a co-carcinogen on the background of cirrhosis of the liver which alone regardless of its cause is an increased risk for the development of PHCC. In clinical practice these findings imply the necessity of optimal prevention of chronic viral hepatic infection (vaccination, so far available for HBV, transfusions) and the necessity to assess the virological status in patients with chronic liver disease and early detection of small tumourous liver lesions where nowadays due to modern therapeutic approaches the prognosis has improved greatly.

Animals↗
PubMed1993

Cytogenetic studies on human liver cancer cell lines.

Karyotyping of human liver cancer cell lines and chromosome in situ hybridization of hepatitis B virus (HBV) DNA was performed in order to elucidate the possible mechanism of hepatocarcinogenesis from evidence of chromosomal changes and HBV integration patterns. HepG2-2 and HepG2-5 cell lines were HepG2 cells experimentally transfected with HBV DNA; the HCC36 cell line was derived from a hepatocellular carcinoma containing integrated HBV DNA from a Taiwanese patient. HepG2 cells, a hepatoblastoma cell line without HBV DNA integration, served as negative control. In HepG2-2, HepG2-5, and HCC36 cells, multiple integrations of HBV DNA were observed by in situ hybridization and hybridization signals occurred preferentially on certain chromosomes: 2, 5, 10, 11, 18; 7, 10, 13, 17, 18; and 4, 6, 11, 12q+, 18; respectively. In addition, a strong correlation between chromosomal changes and HBV integration was noticed in HCC36 cells, especially at chromosome 12q+.

Carcinoma, Hepatocellular↗
PubMed1992

Enhancement of hepatitis-B surface-antigen expression by 5-azacytidine in a hepatitis-B-virus-transfected cell line.

The human hepatoblastoma-derived cell line HB611 secretes hepatitis-B surface antigen (HBsAg) and hepatitis-B e antigen (HBeAg) into the medium. Hepatitis-B-virus (HBV) DNA integrated into the cellular genome was found to be hypermethylated. When the cells were treated with 5-azacytidine for 3 days, the level of HBsAg in the medium increased, while the level of HBeAg remained constant. The level of alpha-fetoprotein (AFP) decreased with the 5-azacytidine treatment. Southern blot analysis of DNA digested with HpaII or MspI showed that 5-azacytidine treatment resulted in hypomethylation of the integrated HBV DNA, suggesting that 5-azacytidine increased HBsAg production in the cells through hypomethylation of the HBV genomic DNA.

Azacitidine↗
PubMed2003

Latent hepatitis B virus (HBV) infection and HBV DNA integration is associated with further transformation of hepatoma cells in vitro.

Hepatitis B virus (HBV) is the major cause of chronic liver disease and hepatocellular carcinoma in the world, with more than 400 million people infected worldwide. To date, there is no reliable model for the study of the many aspects of HBV infection, despite the use of the chimpanzee. Although several alternative methods have been previously developed for the in vitro study of HBV infection, there is still an urgent need for new in vitro infection models, including for the ability of HBV to integrate into the host cell genome. Here we describe a process to improve infection of the human hepatoma cell lines HepG2 and HuH-7 in vitro with HBV originating from human blood. As shown previously for infection of hepatocytes with hepatitis C virus (HCV), the removal of the cell-bound lipoproteins prior to the addition of the viral inoculum to the cells could also be critical for the uptake of HBV via lipoprotein (LDL)-related receptors. Induction by insulin and dexamethasone led to an increase of HBsAg expression at the cell surface in association with the integration of the viral DNA into the host genome and HBx RNA detection. This integration process was also shown to be associated with cytopathic changes and further phenotypic transformations of the cells.

Animal Testing Alternatives↗
PubMed2005

Hepatitis B virus-related insertional mutagenesis in chronic hepatitis B patients as an early drastic genetic change leading to hepatocarcinogenesis.

Growing evidence demonstrates that hepatitis B virus (HBV) integration and resulting insertional mutagenesis play an important role in cell growth or maintenance in hepatocellular carcinomas (HCCs). To determine if HBV integration occurs and affects cellular genes at such a stage of infection, we analysed viral-host junctions in chronic hepatitis tissues without HCC using PCR amplification with primers specific to human Alu-repeat and HBV. We obtained 42 independent viral-host junctions from six patients examined and identified chromosomal locations for 20 of the 42 junctions. In six clones, each integration apparently affected a single gene. These six candidate genes included one known tumor suppressor gene, three human homologs of drosophila genes that are critical for organ development, one putative oncogene and one recently found chemokine. Our data, together with previously reported HBV integrants in HCCs, suggested preferential HBV integration into chromosome 3 (P = 0.022). Our virus-tagging approach provided (a) firm evidence of HBV integration in hepatocytes at an early stage of chronic infection and (b) revealed cellular genes possibly affected by HBV integration and potentially involved in early steps of the process leading to carcinogenesis.

Biopsy↗
PubMed1994

Stability of HBV DNA in cell lines and nude mouse-passaged tissues derived from human hepatocellular carcinoma.

Human hepatitis B virus (HBV) infection has been closely linked to the occurrence of hepatocellular carcinoma (HCC). Hepatoma cell lines and nude mouse-passaged hepatoma tissues were used in this report to study the HBV DNA status in these cells after passage. DNA was extracted from seven hepatoma cell lines and three nude mouse passaged HCC lines. Southern blot hybridization technique was performed with either cloned HBV whole genome or subgenomic DNA fragments as probes to analyze the presence of HBV DNA. Integration of HBV DNA fragments was detected in one mouse passaged tissue, R. Hybridization with HBV subgenomic DNA revealed that there were some DNA rearrangements of the integrated HBV DNA in R. However, the integrated HBV DNA could not be detected in the cell line derived from R after in vitro cultivation for 2 years. Both episomal form and integrated HBV DNA were detected in a cell line NTU-h3. Episomal form HBV DNA ih NTU-h3 changed after several passages. HBV DNA in NTU-h3 was unstable after in vitro cultivation. Therefore, we concluded that the presence of HBV DNA might not be essential for the maintenance of the tumorigenicity of hepatoma and the nude mouse system was more stable for maintaining HBV DNA in HCC.

Animals↗
PubMed1991

Chromosomal sites for hepatitis B virus integration in human hepatocellular carcinoma.

The discovery that hepatitis B virus (HBV) integrates into host chromosomes raises the question of whether such viral DNA integration correlates directly with the activation of specific oncogenes or the inactivation of anti-oncogenes. To obtain insight into this problem, we randomly collected HBV integrant samples from different human hepatocellular carcinomas and identified the site of chromosomal integration by using in situ hybridization and/or linkage analysis with the flanking cellular DNAs as probes. Our findings did not specifically identify particular HBV DNA integration sites in chromosomes, although chromosomes 11 and 17 seemed to have more than the average number of integrants.

Alleles↗
PubMed1986

Detection of hepatitis B virus DNA in hepatocellular carcinoma.

DNA-DNA hybridization was used to examine tissue from 31 patients with hepatocellular carcinoma (HCC) in Taiwan for the presence of the hepatitis B virus genome. Twenty-four of the DNA samples had discrete high molecular weight bands when cut with HindIII and hybridized with a radiolabelled HBV DNA probe, and similar results were obtained with 25 of the samples when cut with EcoRI. Thus integrated HBV DNA was present in almost 80% of the specimens. None of the samples had a similar pattern and most contained HBV DNA integrated at multiple sites. Seventeen out of 19 HBsAg carriers and one out of two patients with anti-HBs were found to have integrated HBV DNA in the tumour tissue, providing further evidence of the strong association between HBV infection and development of hepatocellular carcinoma.

Autoradiography↗
PubMed1987

Multiple integration site of hepatitis B virus DNA in hepatocellular carcinoma and chronic active hepatitis tissues from children.

Attention was directed to hepatitis B virus (HBV) integration in tissues obtained from an hepatocellular carcinoma (HCC) of an 11-year-old boy and from the liver of his 6-year-old brother, who had chronic active hepatitis. Multiple HBV DNA integration sites were demonstrated in both tissues. Cell population(s) in the HCC and liver from the patient with chronic active hepatitis were assumed to be heterogeneous with regard to HBV integration. The integrated forms in the two tissues showed similar genetic organization without gross rearrangement. The location of one of the virus-chromosomal junctions was restricted to the 5'-end region of the minus-strand DNA of HBV. The experimental results support our previous model for the mechanism of HBV integration, in which minus-strand replicative intermediates integrate into chromosomal DNA. The integrated HBV DNAs were conserved in the same region of the viral genome, spanning from the C gene through the S gene to the X gene, which contains intrinsic promoter-enhancer sequences.

Base Sequence↗
PubMed1997

Accumulation of genetic alterations in a human hepatoma cell line transfected with hepatitis B virus.

Chromosome and molecular analyses of the hepatitis B virus (HBV)-transfected HepG2T14.1 variant of the HepG2 cell line was conducted. In HepG2T14.1 cells several genetic alterations such as de novo aberrations of chromosomes 9, 14, 15, and 20 were identified that are not present in the parental HepG2 cell line. Furthermore, HepG2T14.1 cells showed loss of heterozygosity (LOH) in the q region of chromosome 14. The single HBV integration site in HepG2T14.1 cells mapped to the 2q35-36 region of one copy of chromosome 2 by fluorescence in situ hybridization (FISH). No genetic changes were identified at or near the HBV integration site at the level of these analyses. In addition, growth rates in vivo and in vitro were dramatically accelerated in HepG2T14.1 cells. These results document that a HBV-transfected hepatoma cell line has de novo genetic mutations at several sites of the host genome, one HBV integration site in an non-rearranged chromosome and an altered phenotype. These findings support our hypothesis that HBV might play a role in cellular transformation by interfering with cellular processes responsible for the stability of the genome.

Animals↗
PubMed1990

Integrated structures of HBV DNA in chronic hepatitis and hepatoma tissues.

Cellular DNAs of chronically hepatitis B virus (HBV)-infected human livers were analysed by Southern blot hybridization for the presence of integrated HBV DNA. In 15 out of 16 tissue samples, random HBV DNA integration was evident. By molecular cloning and structural analyses of 19 integrants from 3 chronic hepatitis tissues, rearrangement of HBV DNA with inverted duplication or translocation of cellular flanking DNA at the virus-cell junction was noted. Thus, the rearrangement of HBV DNA or cellular flanking DNA not to be a specific incident of HCC formation. Analyses of various integrants bearing HBV DNA rearrangement and their cellular counterpart DNAs failed to indicate any gross structural alteration in cellular DNA except for a small deletion at the integration sites, indicating HBV DNA rearrangement with inverted duplication to possibly occur prior to integration. Based on nucleotide sequencing analyses of virus-virus junctions, a mechanism of this inverted duplication of HBV DNA is proposed, in which an illegitimate recombination may take place by means of a patchy homology on one side of adjoining viral sequences.

Base Sequence↗
PubMed1986

Hepatitis B virus integration site in hepatocellular carcinoma at chromosome 17;18 translocation.

Integrated hepatitis B virus (HBV) DNA is almost invariably found in hepatocellular carcinomas (HCC) which develop in HBV carriers. Integrated HBV DNAs from two single-integration HCCs (C3 and C4) have been cloned, and the cellular integration sites have been analyzed. Integrated HBV DNA of C3 is present in chromosome 6 and contains a nearly complete linear HBV genome. The HBV DNA integration in tumor C3 was not associated with major rearrangements of cellular DNA. In contrast, the integrated HBV DNA in C4 contains a large inverted repeat of HBV DNA, in which each repeat consists of a linear HBV DNA segment similar to that present in C3. The C4 integration was also accompanied by a cellular DNA translocation at the HBV integration site. The translocation occurred between chromosomes 17 and 18, along with a deletion of at least 1.3 kilobases of chromosome 18 DNA at the translocation site. Our data support a model in which postintegration rearrangement of integrated HBV and cellular DNA results in the generation of chromosomal aberrations. These chromosomal aberrations may function in a multistage mechanism leading to fully malignant HCC.

Base Sequence↗
PubMedDate not supplied

Detection of hepatitis B virus DNA in hepatocellular carcinoma: methylation of integrated viral DNA.

In order to determine whether integrated hepatitis B virus DNA sequences in primary liver tumours are methylated we have analysed tumour DNA digested with either MspI or HpaII restriction endonuclease by Southern hybridization. Our results demonstrate methylation in 11 of 17 tumour DNA samples. Where possible, we have examined the tumour tissues for expression of HBsAg and HBcAg using the indirect immunoperoxidase technique. One tumour was positive for both HBsAg and HBcAg and a second was positive for HBsAg alone. Both of these tumours were in the group in which methylation of integrated HBV DNA sequences could not be detected. We postulate that methylation of integrated HBV DNA sequences may influence HBV gene expression in hepatocellular carcinoma.

Carcinoma, Hepatocellular↗
PubMed1987

Hepatitis B virus chronic liver disease and hepatocellular carcinoma.

Numerous studies have shown the presence of a highly significant excess of HBsAg, core and surface antibody in patients with hepatocellular carcinoma (HCC). An important factor in the aetiological association between hepatitis B and HCC may lie in the early age of infection. Although hepatitis B virus (HBV) DNA has been found in HCC tissue, there is no simple correlation between serum markers of hepatitis B infection and viral DNA in the tumour. Nevertheless, it is clear that in the case of HBV-associated HCC, integrated HBV sequences may be present in more than 80% of the tumours. The possible molecular basis for the resulting neoplastic transformation is discussed. Whatever the molecular basis of HBV involvement in the causation of HCC, immunization against HBV is likely to prevent primary liver cancer.

Carcinoma, Hepatocellular↗
PubMed2005

Differential integration rates of hepatitis B virus DNA in the liver of children with chronic hepatitis B virus infection and hepatocellular carcinoma.

BACKGROUND AND AIM: Integration of hepatitis B virus-DNA (HBV-DNA) into the host genome, a phenomenon found frequently in hepatocellular carcinomas (HCC) and causally linked to oncogenesis, has not been well characterized in children. The aim of the present study was to determine the prevalence of HBV integration more accurately and to decide whether the integration rate varies at different stages of chronic HBV infection in children. METHODS: Of 13 children with chronic hepatitis, 14 liver biopsy tissues were analyzed. One liver tissue with pure liver cirrhosis, nine non-tumor, and nine tumor liver tissues from children with HCC were analyzed by a very sensitive method, inverse polymerase chain reaction (IPCR). RESULTS: Thirteen genuine viral-host junctional sequences from 23 patients were successfully isolated and proved that IPCR is a useful method in this context. The results also indicated that the detection rate of HBV-DNA integration increased in parallel with the progress of liver histology towards the neoplastic transformation, with 0% in the liver of chronic hepatitis, 22.2% in non-tumor livers of HCC patients, and 66.7% in tumor liver tissues of HCC patients. CONCLUSION: The present results indicate that integration of HBV-DNA into the host genome was rarely confirmed at the early stage of chronic hepatitis in children until the stage of HCC formation.

Carcinoma, Hepatocellular↗
PubMed2003

Configuration and replication competence of hepatitis B virus DNA in peripheral blood mononuclear cells from chronic hepatitis B patients and patients who have recovered from acute self-limited hepatitis.

Several studies have reported the presence of hepatitis B virus (HBV) DNA in peripheral blood mononuclear cells (PBMCs). However, the mode of existence, infectivity and replication competence of HBV DNA in PBMCs remain unclear. To clarify these questions, we assayed for covalently closed circular DNA (cccDNA) and integrated HBV DNA in PBMCs from ten patients who had recovered from acute self-limited hepatitis B (AHB) and 14 chronic hepatitis B (CHB) patients. HBV DNA was detected in all six CHB patients who were positive for hepatitis B e antigen (eAg), and cccDNA was detected in five. HBV DNA was detected in seven of the eight CHB patients who were negative for eAg, and cccDNA was detected in three. HBV DNA and cccDNA was also detected in five and two of the ten AHB patients, respectively. Integrated HBV was not detected in PBMCs of any patients. HBV DNA presence and replication competence in PBMCs are associated with eAg-positive phenotype. Sequence analysis revealed that the source of HBV DNA differed between PBMCs and serum. Even in patients who have recovered from AHB, replicable HBV may persist in PBMCs.

Journal Article↗