Presence of integrated hepatitis B virus DNA sequences in cellular DNA of human hepatocellular carcinoma

Regulatory T cell-subset imbalance in chronic active hepatitis

Three monoclonal anti-T-cell antibodies, specifically directed against total T cells (OKT3), inducer-helper T cells (OKT4) and suppressor/cytotoxic T cells (OKT8), were used in this study to analyze peripheral T-cell subsets in hepatitis B surface antigen (HBsAg)-positive and -negative chronic active hepatitis (CAH) patients. Results showed that a clear-cut difference exists in the distribution of peripheral T cells of these two groups of subjects. HBsAg-positive CAH patients had a numerical predominance of peripheral T lymphocytes expressing the characteristics of cytotoxic/suppressor T cells. In contrast, patients with "autoimmune" HBsAg-negative CAH exhibit a predominance of OKT4 cells, namely, the helper-inducer T-cell subset. In addition, high numbers of circulating double labeled cells (expressing both the OKT4 and the OKT8 xenoantigens) were detected in some of the HBsAg-positive and HBsAg-negative CAH patients studied.

Integration of HBV-DNA into liver and hepatocellular carcinoma cells during persistent HBV infection

The hepatitis B virus carrier state (persistent HBV infection) is characterized by the presence of viral surface antigen (HBsAg) and virion particles (Dane particles) in the blood. From 1% to 10% of carriers develop chronic liver disease and/or hepatocellular carcinoma. Recent studies have demonstrated integrated HBV-DNA in hepatocellular carcinomas and in several human hepatoma cell lines. In hepatoma patients, integrated HBV-DNA has been found in all HBsAg carriers. Nontumorous liver also revealed integrated HBV-DNA with the same or a different hybridization pattern from that observed in the tumor. To explore when integration occurs, carriers of short-term (less than 2 years) or long-term (greater than 8-10 years) were evaluated. DNA extracts from percutaneous (needle) liver biopsies showed free viral DNA with no specific integration bands in short-term carriers. In long-term carriers, HBV-DNA was integrated into the host genome with either a diffuse or a unique hybridization pattern. HBV-DNA integration correlated with the duration of the carrier state and absence of virions in the serum but did not correlate with histologic evidence of chronic hepatitis. These studies suggest that integration of HBV-DNA occurs during persistent HBV infection irrespective of liver disease and precedes development of hepatocellular carcinoma.

Analysis of hepatitis virus DNA in the liver and serum of HBe antigen positive chimpanzee carriers

Hepatitis B viral DNA present in the liver of HBe antigen positive chimpanzee carriers is in the form of viral molecules (3.2 Kb) and no integration into host DNA was observed. The 3.2 Kb form was not detected in the serum. Other discrete HBV DNA species with faster mobilities than the major 3.2 Kb were consistently detected both in the liver and in the serum and their possible significance is discussed.

Organization and expression of hepatitis B sequences cloned from hepatocellular carcinoma tissue DNA

We have constructed a phage lambda library of liver DNA fragments from West African patient who died of liver failure due to advanced hepatocellular carcinoma. Four hepatitis B virus (HBV) DNA-carrying recombinants have been isolated, one clone (lambda IA22) being analyzed in greatest detail. It contains approximately 3.8 kb of HBV DNA without detectable deletions or rearrangements. One site of integration lies close to the nick in free viral DNA. The restriction map of the HBV sequences is close to those published for the ay subtype. Coconvection of mouse Ltk- cells with lambda IA22 and cloned thymidine kinase gene results in the expression of gene S and the excretion of hepatitis B surface antigen (HBsAg) particles into the culture supernatant.

Primary hepatocellular carcinoma--etiology, pathogenesis, and prevention

Worldwide, primary hepatocellular carcinoma may be the most common cancer in men. Usually it occurs in association with cirrhosis or chronic hepatitis. In this article I present evidence that the majority of these cases are associated with, and probably caused by, persistent infection with hepatitis B virus. I also propose a model that describes the role of the hepatitis B virus in the pathogenesis of primary hepatocellular carcinoma. If persistent infection with hepatitis B virus is required for the development of most cases of primary hepatocellular carcinoma, prevention of such infections should prevent most cases of primary hepatocellular carcinoma. A vaccine against hepatitis B virus, prepared from surface antigen particles (HBsAg) harvested from the blood of hepatitis B virus carriers, has been safe and effective in preventing acute infection with hepatitis B virus in adult homosexual men. If it is equally safe and effective in young children, it will be administered widely to populations living in areas endemic for hepatitis B virus infections. Thereafter it may be possible to learn within five to 10 years whether the vaccine prevents chronic liver disease. If it does, it will be reasonable to conclude that it will also prevent primary hepatocellular carcinoma.

Integration of hepatitis B virus DNA into the genome of liver cells in chronic liver disease and hepatocellular carcinoma. Studies in percutaneous liver biopsies and post-mortem tissue specimens

We used recombinant-DNA technology and gel electrophoresis to find hepatitis B virus DNA (HBV-DNA) in liver and tumor tissue from patients with hepatocellular carcinoma and chronic liver disease, and to study the integration of HBV-DNA into the genome of these tissues' cells. In 12 patients with hepatocellular carcinoma who had hepatitis B surface antigen (HBsAg) in their serum, integrated HBV-DNA was identified in the tumors; it was also found in tumors from three of eight patients who were seronegative for HBsAg but positive for antibody to HBsAg. In some cases, integrated HBV-DNA was also present in nontumorous liver tissue that had the same hybridization pattern or one different from that of the tumor. In five carriers of HBsAg who had evidence of the carrier state and chronic liver disease for less than two years, HBV-DNA was present but not integrated in liver tissue. In the two patients who had carried HBsAg for more than eight years, HBV-DNA was integrated into the host genome. These data suggest that integration of HBV-DNA into hepatocytes occurs during the course of persistent HBV infection and precedes development of gross neoplasm.

Detection of hepatitis B virus DNA in liver and serum: a direct appraisal of the chronic carrier state

The detection of hepatitis B virus (HBV) DNA in the liver and the serum permits direct study of the interaction between the virus and the liver cell. 40 HBV chronic carriers were studied by the blot technique of Southern to detect HBV DNA, and the results were compared with the serological status and histological status of the patients. It was possible to define two different chronic carrier states. The first is characterised by free viral DNA in the liver, with viral DNA and hepatitis B e antigen (HBeAG) in the serum; integrated HBV DNA is also present, at least in some patients. The second carrier state is characterised by the presence of only integrated HBV DNA sequences in the liver: viral DNA and HBeAg are not present in the serum. In one HBeAg-negative patient, however, free HBV DNA was detected in the liver and HBV DNA was present in the serum. The hybridisation technique appears to be a very sensitive test which could reflect viral multiplication better than HBeAg radioimmunoassay. Since a needle biopsy sample provides sufficient tissue for the Southern blot technique, it should be useful in understanding chronic hepatitis, the selection of patients for antiviral therapy, and the estimation of its efficiency.

Biology of hepatitis B virus

Immunochemical investigations of the viral antigens and molecular characterization of the viral DNA have elucidated the nature of the hepatitis B virus infection underlying acute, chronic, and oncogenic disorders of the liver in man. Cloning and sequencing of viral DNA have made possible studies on the structure of the genome and on certain aspects of the biology of the virus, hitherto constrained for a lack of tissue culture systems and laboratory animal models useful in its propagation.

State of hepatitis B virus DNA in hepatocytes of patients with hepatitis B surface antigen-positive and -negative liver diseases

Using the Southern blot technique and cloned hepatitis B virus (HBV) DNA as a probe, we studied the state of HBV DNA in the liver of 13 patients with hepatocellular carcinoma, 17 patients with chronic hepatitis, and 2 patients with acute hepatitis. The hybridization results were compared with the serological and immunohistological data. Integration of HBV DNA in cellular DNA of the liver from patients with hepatocellular carcinoma was demonstrated. In two patients from which tumorous and nontumorous liver tissue samples were available the integration patterns were different. In one patient with hepatitis B e antigen (HBeAg)-positive early hepatocellular carcinoma, free viral DNA was present in the liver. In some patients with HBeAg-negative chronic hepatitis, without tumor, integration of HBV DNA in cellular DNA was also demonstrated. This suggests that HBV is not the only factor involved in the development of a tumor. In patients with HBeAg-positive chronic hepatitis, free viral DNA was detected in the liver. In the two acute hepatitis patients analyzed, the restriction endonuclease patterns strongly suggested HBV DNA integration. Therefore, viral DNA integration seems to occur early in infection. Whatever the form of the disease, discrete bands were observed, suggesting the existence of limited and specific integration sites in host cellular DNA. The presence of integrated or free DNA sequences has implications for antiviral therapy. In addition, detection of HBV DNA in the liver is another sensitive viral marker that could be useful for diagnostic purposes.

Woodchuck hepatitis and hepatocellular carcinoma: correlation of histologic with virologic observations

The livers of 33 captive woodchucks were examined histologically in 30 biopsy and 10 autopsy specimens and the findings were correlated with serum determinations for woodchuck hepatitis virus (WHV), surface antigen (WHsAg) and antibody (anti-WHs), and WHV DNA and DNA polymerase. The liver appeared normal in all 3 serum-negative animals, 7 of 16 with indeterminate WHV status, and 1 of 4 with anti-WHs, but not in 10 animals with WHsAg, WHV DNA, and DNA polymerase. Mild hepatic inflammation was found in 7 woodchucks with indeterminate status, 4 with anti-WHs, and 2 with each marker of WHV infection. Significant inflammation was found in 2 of indeterminate status and 4 with every marker, whereas more severe lesions (2 of chronic active type) occurred, almost always in autopsy specimens, in 8 animals with every marker. Eight of 10 animals with all markers had orcein-positive inclusions (Shikata's technique) and 6 had hepatocellular carcinoma associated with acute and chronic hepatic inflammation and, usually, neoplastic nodules in the noncarcinomatous parenchyma. Features distinguishing the woodchuck lesion from human hepatitis B disease were: association of carcinoma with acute hepatic inflammation (but not with cirrhosis) and DNA polymerase in the serum; transition to carcinoma from neoplastic nodules; conspicuous plasma-cellular reaction of hepatic inflammation, and hematopoietic cells in the tumor. Significant hepatic lesions in the woodchucks were regularly associated with serum WHsAg, WHV DNA, and DNA polymerase. In contrast to man, hepatocellular carcinoma in woodchucks was regularly associated with these markers of active viral replication. The nature of the orcein-positive inclusions requires elucidation, although they may assist in screening for similar viruses in other species. The woodchuck may help in the study of the relation between hepatocellular carcinoma and hepatitis B, including the possibility of cocarcinogenic factors.

The epidemiology and morphology of primary malignant liver tumors

The ubiquitous problem of cirrhosis may be complicated by the development of primary liver cell carcinoma, with rates of incidence so high in certain parts of the world as to make it a candidate for the most common cancer in humans. When cirrhosis reaches the macronodular stage, the risk of developing liver cell carcinoma increases, and at this point liver cell dysplasia may be seen in biopsy. Alcoholics, who classically have a micronodular cirrhosis, may attain the macronodular pattern through better clinical management, abstinence, and longer survival. Hepatitis B-related cirrhosis, on the other hand, is most often macronodular. Recent DNA hybridization studies strongly favor a viral role in oncogenesis, and this possibility is supported by the serologic and epidemiologic evidence complied in the last decade. Liver cell malignant tumors tend to recapitulate the characteristics of normal liver, namely, growth in cords, uniformity of cytologic appearances, and bile production, but also present distinctive histologic and immunohistochemical patterns that are unique to a malignant liver cell population. The other primary malignant tumors of the liver, arising in bile ducts, blood vessels, and mesenchymal elements, all carry their individual epidemiology and morphology, but in general invoke, as does liver cell carcinoma, the concept of a series of step by step cell-carcinogen and cell-carcinogen interactions by which normal cells give rise to malignant populations.

Detection of hepatitis B virus DNA sequences in infected hepatocytes by in situ cytohybridisation

Plasmid pHBV 114 DNA, which contains 73% of the genome of hepatitis B virus (HBV), was radiolabelled with tritium to 1-2 X 10(8) dpm/microgram by nick translation and used as a radioactive probe to detect HBV DNA present in sections of infected liver tissue by in situ hybridisation followed by autoradiography. Factors affecting the sensitivity of the reaction were examined, including different methods of fixation, hybridisation time, temperature, and buffers. The specificity of the reaction for detecting viral DNA was carefully established by the use of unrelated DNA probes, pretreatment of sections with DNAase, and comparing the stability of the binding of DNA probe at different temperatures, with the melting curve of double-stranded DNA in solution. In the one liver studied in detail, cells containing large amounts of viral DNA were distributed in foci corresponding to areas containing morphologically damaged hepatocytes. This observation suggested a relationship between active viral replication and cell damage. Viral DNA was found mainly in the cytoplasm, although a minority of nuclei in these foci were also positive.

Identification of integrated hepatitis B virus DNA sequences in human hepatocellular carcinomas

DNA extracts from hepatocellular carcinomas of 13 patients from South Africa were examined for hepatitis B virus (HBV) DNA sequences by molecular hybridization using [32P]-labeled recombinant, cloned, and purified HBV-DNA. Eight patients were HBV carriers as demonstrated by the presence of hepatitis B surface antigen (HBsAg) in their serum, and each of these patients and HBV-DNA sequences in hepatocellular carcinoma tissue. Five patients who were not HBsAg carriers, did not have HBV-DNA in their tumors. In DNA extracts from all tumors of patients who were HBsAg-positive, the HBV-DNA was integrated into the host genome. The integration pattern was unique for each tumor, but HBV-DNA bands of a given length were present in more than one specimen and in a human hepatocellular carcinoma cell line (PLC/PRF/5). These results suggest that integration of HBV-DNA into the human genome occurs in conjunction with malignant transformation.