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.     

Molecular mechanisms of viral hepatitis induced hepatocellular carcinoma

Chronic infection with viral hepatitis affects half a billion individuals worldwide and can lead to cirrhosis, cancer, and liver failure. Liver cancer is the third leading cause of cancer-associated mortality, of which hepatocellular carcinoma (HCC)represents 90%of all primary liver cancers. Solid tumors like HCC are complex and have heterogeneous tumor genomic profiles contributing to complexity in diagnosis and management. Chronic infection with hepatitis B virus (HBV),hepatitis delta virus (HDV), and hepatitis C virus (HCV) are the greatest etiological risk factors for HCC. Due to the significant role of chronic viral infection in HCC development, it is important to investigate direct (viral associated) and indirect (immune-associated) mechanisms involved in the pathogenesis of HCC. Common mechanisms used by HBV, HCV, and HDV that drive hepatocarcinogenesis include persistent liver inflammation with an impaired antiviral immune response, immune and viral protein-mediated oxidative stress, and deregulation of cellular signaling pathways by viral proteins.DNA integration to promote genome instability is a feature of HBV infection, and metabolic reprogramming leading to steatosis is driven by HCV infection. The current review aims to provide a brief overview of HBV, HCV and HDV molecular biology, and highlight specific viral-associated oncogenic mechanisms and common molecular pathways deregulated in HCC, and current as well as emerging treatments for HCC.     

Primary hepatocellular carcinoma following nonspecific non-B hepatitis with tumor DNA negative for HBV DNA

Summary An association between non-A, non-B hepatitis and hepatocellular carcinoma has been made on the basis of negative serological markers for hepatitis B virus (HBV); however, hepatocellular carcinomas have been found to contain hepatitis B virus deoxyribonucleic acid (HBV DNA) in individuals who lack serological markers of HBV infection. Therefore, reports which ascribed a hepatocellular carcinoma to non-A, non-B hepatitis but did not examine the tumor for HBV DNA are open to question. We describe a case of chronic active hepatitis with primary hepatocellular carcinoma that lacked HBV DNA in the tumor, the nontumorous liver tissue, and serum. The individual lacked all serological markers for HBV infection. This report more fairly supports the association between hepatocellular carcinoma, and chronic hepatitis not due to hepatitis B. Whether this is related specifically to a non-A, non-B hepatitis agent requires identification of the viral agents that cause non-A, non-B hepatitis.     

Hepatocellular carcinoma and hepatitis B virus

Chronic hepatitis B is the most common cause of hepatocellular carcinoma (HCC) in Asia. Integration of hepatitis B virus (HBV) genome is likely an early event of carcinogenesis. The integrated HBV genome may activate neighboring cellular genes directly to offer a selective growth advantage to the liver cells. Production of hepatitis B X protein can act as a transactivator on various cellular genes for tumor development. Hepatic inflammation and cirrhosis also favors the process of carcinogenesis. Various viral factors associated with hepatocellular carcinoma development include HBV genotype, basal core promoter mutations, and high viral load. Polymorphisms at the androgen receptor-regulating genes and cytokine genes are possible host factors associated with HCC. This review article summarizes the pathogenesis of HBV-related carcinogenesis and the viral and host factors that may increase the risk of HCC development.     

Extensive oxidative DNA damage in hepatocytes of transgenic mice with chronic active hepatitis destined to develop hepatocellular carcinoma.

A transgenic mouse strain that expresses the hepatitis B virus (HBV) large envelope protein in the liver was used to determine the extent of oxidative DNA damage that occurs during chronic HBV infection. This mouse strain develops a chronic necroinflammatory liver disease that mimics the inflammation, cellular hyperplasia, and increased risk for cancer that is evident in human chronic active hepatitis. When perfused in situ with nitroblue tetrazolium, an indicator for superoxide formation, the liver of transgenic mice displayed intense formazan deposition in Kupffer cells, indicating oxygen radical production, and S-phase hepatocytes were commonly seen adjacent to the stained Kupffer cells. Similar changes were not observed in nontransgenic control livers. To determine whether these events were associated with oxidative DNA damage, genomic DNA from the livers of transgenic mice and nontransgenic controls was isolated and examined for 8-oxo-2'-deoxyguanosine, an oxidatively modified adduct of deoxyguanosine. Results showed a significant, sustained accumulation in steady-state 8-oxo-2'-deoxyguanosine that started early in life exclusively in the transgenic mice and increased progressively with advancing disease. The most pronounced increase occurred in livers exhibiting microscopic nodular hyperplasia, adenomas, and hepatocellular carcinoma. Thus, HBV transgenic mice with chronic active hepatitis display greatly increased hepatic oxidative DNA damage. Moreover, the DNA damage occurs in the presence of heightened hepatocellular proliferation, increasing the probability of fixation of the attendant genetic and chromosomal abnormalities and the development of hepatocellular carcinoma.     

Roles of micrornas in the Hepatitis B Virus Infection and Related Diseases

The hepatitis B virus (HBV) is a small enveloped DNA virus that belongs to the Hepadnaviridae family. HBV can cause acute and persistent infection which can lead to hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) play a crucial role in the main cellular events. The dysregulation of their expression has been linked to the development of the cancer as well as to viral interference. This chapter will describe the involvement of miRNAs in the case of HBV infection and their implication in the development of the HBV-related diseases.     

Liver cell transformation in chronic HBV infection

Epidemiological studies have provided overwhelming evidence for a causal role of chronic HBV infection in the development of hepatocellular carcinoma (HCC), but the molecular mechanisms underlying virally-induced tumorigenesis remain largely debated. In the absence of a dominant oncogene encoded by the HBV genome, indirect roles have been proposed, including insertional activation of cellular oncogenes by HBV DNA integration, induction of genetic instability by viral integration or by the regulatory protein HBx, and long term effects of viral proteins in enhancing immune-mediated liver disease. In this chapter, we discuss different models of HBV-mediated liver cell transformation based on animal systems of hepadnavirus infection as well as functional studies in hepatocyte and hepatoma cell lines. These studies might help identifying the cellular effectors connecting HBV infection and liver cell transformation.     

State of hepatitis B viral DNA in the liver of patients with hepatocellular carcinoma and chronic liver disease

In order to clarify the relationship between the integration of hepatitis B virus (HBV) DNA and human hepatocellular carcinoma (HCC), the states of HBV DNA in liver tissues were examined by the Southern blot hybridization procedure. Integration of HBV DNA was found in 12 of 25 HCC cases and 5 of 12 cirrhotic cases. Of these 17 cases, 11 were positive for serum hepatitis B virus surface antigen (HBsAg) and the remaining six were positive for more than one of the serum HBV-related antibodies. In all three cases of chronic hepatitis and 18 controls, integration of HBV DNA could not be detected. Free viral DNA was found in 12 of 15 cases with serum HBsAg. One patient without serum HBsAg also had free viral DNA in the liver. Integration of HBV DNA could be observed in HCC cases positive for serum HBsAg at the highest frequency. However, there was one HCC case from an HBsAg carrier in whom integration of HBV DNA might not have a causal effect on malignant transformation, because integrated HBV DNA could be detected only in a non-tumor region. Since integrated HBV DNA could not be detected in 13 of 25 HCC cases, other etiologic factors than the integration of HBV DNA must also be taken into consideration for HCC.     

Hepatitis B viral DNA in infected human liver and in hepatocellular carcinoma

Blot-hybridization analysis of DNA forms from hepatitis B virus (HBV) in the liver of chronic carriers of hepatitis B surface antigen (HBsAg) has revealed the presence of both relaxed and closed circular viral DNA and of novel viral DNA-RNA hybrid molecules in patients with complete virions, with the hepatitis B e antigen (HBeAg), or with both, in serum. One carrier of HBsAg with no detectable virus or HBeAg in his serum had small amounts of free viral DNA in his liver sample, a finding suggesting the potential for production of complete virus; another such carrier had only HBV DNA integrated in cellular DNA and, thus, may have lost the ability to replicate virus. The liver sample of one of eight patients with antibodies to HBsAg in his serum, but no HBsAg, contained small amounts of free viral DNA. Analysis of tissue from hepatocellular carcinoma revealed evidence for integrated viral DNA sequences in multiple-cellular DNA sites, and stoichiometric analysis suggested that the tumors were monoclonal in origin. These results demonstrate the presence of a new form of HBV in infected human liver and reveal that serological profiles are not always a reliable guide in determining the presence of potentially infectious forms of HBV in the liver.     

Hepatitis B virus DNA in mononuclear blood cells. A frequent event in hepatitis B surface antigen-positive and -negative patients with acute and chronic liver disease

We have investigated 38 hepatitis B surface antigen (HBsAg)-positive and 34-negative patients with acute and chronic liver disease for the presence of hepatitis B virus (HBV) DNA in peripheral mononuclear blood cells. Among the HBsAg-positive subjects HBV DNA was detected in the mononuclear cells of asymptomatic HBV carriers (2/6), patients with acute hepatitis (8/8), chronic active hepatitis (18/21), and with hepatocellular carcinoma (2/3); the viral DNA sequences were also identified in the mononuclear cells of patients with HBsAg-negative acute hepatitis (2/3), chronic active hepatitis (5/15) and hepatocellular carcinoma (5/16), some of these showing no evidence of HBV by conventional serological markers. By contrast HBV DNA was not detected after resolution of the acute viral infection. For 7 patients different mononuclear cell-enriched subpopulations were assayed and the viral DNA was observed in T lymphocytes (both OKT4+ and OKT8+ enriched subsets) and/or in B enriched lymphocytes; the restriction DNA patterns showed in some patients a genetic organisation of the viral DNA similar to those observed in the liver (including free monomeric and oligomeric HBV DNA and results consistent with integrated viral sequences); however, no HBV DNA replicative forms were detected. These results show that the hepatitis B virus infection of mononuclear blood cells (including lymphoid cells) is a frequent event at all stages of the viral infection which might be related to immunological abnormalities observed in HBV carriers; in addition the mononuclear blood cells analysis may provide an insight to the liver cells status.     

Deletion of integrated hepatitis B virus genome and cellular flanking sequences in hepatocellular carcinoma cells in BALB/c mice

We have previously reported the establishment of well-differentiated BALB/c mouse liver (ML) cell lines. Transfection of these cell lines with hepatitis B virus (HBV) DNA led to the expression of HBV-specific antigens and integration of HBV sequences in the cellular genome. Two cloned HBV-transfected ML cell lines, ML2(HBV) and ML-3(HBV), expressed viral antigens and were highly tumorigenic in nude mice. However, the tumorigenicity of the two cell lines was significantly reduced in BALB/c mice. Southern blot analyses showed that the integrated HBV sequences were retained in tumors growing in nude mice but deleted in tumors growing in BALB/c mice. Furthermore, the deletion of HBV DNA was accompanied by deletion of chromosomal sequences flanking the HBV integration sites. In ML-2(HBV) cells, a significant reduction in chromosomal number was also observed. These results suggest that the immune response of BALB/c mice selected against hepatocellular carcinoma (HCC) cells expressing viral antigens and led to the proliferation of cells with deleted HBV sequences and concomitant chromosome aberrations. By using this mechanism, HCC cells escape the immune surveillance and gain the advantage of cell growth.     

Hepatocellular carcinoma in noncirrhotic young adult patients with chronic hepatitis B viral infection

Background The aims of this study were to define the clinical characteristics of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) in young adult patients without cirrhosis and to evaluate the efficacy of interferon (IFN) therapy on HCC recurrence.Methods Of 187 patients with HBV-related HCC treated at our hospital, 4 had no liver cirrhosis and were less than 30 years of age (10, 22, 23, and 26 years).Results At the time of diagnosis of HCC, all cases had antibody to hepatitis B e antigen (anti-HBe) and histological staging of nontumorous liver was F0 or F1, i.e., low-grade hepatitis. The mothers of all 4 young adult patients with HCC had HBV-related liver disease. Three cases developed recurrence of HCC. In these patients, long-term intermittent IFN therapy after reresection of HCC resulted in long-term survival without recurrence for more than 3 years of follow-up.Conclusions (1) Young adult patients with HCC are positive for anti-HBe, lack cirrhosis, and the route of infection seems to be mother-to-infant transmission. Transplacental transmission of HBV and HBV DNA integration into the cellular genomic DNA during fetal life is a possible explanation of HBV-related hepatocarcinogenesis in young adults; and (2) long-term IFN therapy seems to be useful for prevention of tumor recurrence after radical operation for HBV-related HCC.     

Analysis of serum pre-S antigens in chronic hepatitis B virus infection in relation to the expression pattern of hepatitis B virus DNA in the liver.

Pre-S antigens have been analyzed in the serum of patients with chronic hepatitis B virus (HBV) infection according to the expression pattern of HBV DNA in the liver. Pre-S1 and pre-S2 have been identified (1) in all viremic cases with free replicative forms of viral DNA irrespective of the simultaneous detection of integrated sequences; (2) in 2 out of 3 patients with only integrated HBV DNA, and (3) in 19 patients who lacked viral DNA sequences detectable in the host genome. The amounts of hepatitis B surface and pre-S antigens were significantly higher in high-viremic versus low-viremic patients and correlated with the hepatocellular expression of HBV DNA. Conversely, the pre-S-to-hepatitis B surface antigen ratios were lower in the presence of viral DNA sequences in the liver. In summary, detection and level of pre-S antigens are closely related to the hepatocellular expression of viral DNA and seem to reflect reliably different stages of the virus life cycle during the course of HBV infection.     

Subgenomic studies on hepatitis B virus DNA integrated into the genome of hepatocellular carcinoma

Integration of hepatitis B virus (HBV) DNA into the chromosomal DNA of hepatocellular carcinoma (HCC) tissue was studied by the Southern blot analysis using probes for subgenomic regions C, PreS, S and X. Eighteen Hind III-fragments prepared from DNA of the tumor regions of six patients with HCC, and hybridized with a full genomic HBV probe were analyzed. Lack of region S or PreS was concurrently accompanied by deletion of their 3'-end region of the HBV minus strand DNA. Region C was missing in 11 out of 18 fragments while regions X, S and PreS were deleted in 5/18, 3/18 and 5/18 respectively. Therefore, in some sequences integrated by subgenomic HBV DNA, the integration of replicative intermediate of the HBV minus strand DNA into the chromosomal DNA may take place and one of the viral integration sites seems to be in the region X.     

Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) is DNA-based virus, member of the Hepadnaviridae family, which can cause liver disease and increased risk of hepatocellular carcinoma (HCC) in infected individuals, replicating within the hepatocytes and interacting with several cellular proteins. Chronic hepatitis B can progressively lead to liver cirrhosis, which is an independent risk factor for HCC. Complications as liver decompensation or HCC impact the survival of HBV patients and concurrent HDV infection worsens the disease. The available data provide evidence that HBV infection is associated with the risk of developing HCC with or without an underlying liver cirrhosis, due to various direct and indirect mechanisms promoting hepatocarcinogenesis. The molecular profile of HBV-HCC is extensively and continuously under study, and it is the result of altered molecular pathways, which modify the microenvironment and lead to DNA damage. HBV produces the protein HBx, which has a central role in the oncogenetic process. Furthermore, the molecular profile of HBV-HCC was recently discerned from that of HDV-HCC, despite the obligatory dependence of HDV on HBV. Proper management of the underlying HBV-related liver disease is fundamental, including HCC surveillance, viral suppression, and application of adequate predictive models. When HBV-HCC occurs, liver function and HCC characteristics guide the physician among treatment strategies but always considering the viral etiology in the treatment choice.     

Hepatocellular carcinoma and hepatitis B virus infection: molecular evidence for monoclonal origin and expansion of malignantly transformed hepatocytes

Summary The clonality of tumor cells was studied in a patient with metastasizing hepatocellular carcinoma (HCC). Using hepatitis B virus (HBV) DNA as a genetic marker, the pattern of integration of viral DNA into the tumor cell genome was determined by Southern blot analyses of DNAs extracted from different HCC lesions in the liver and both lungs. All tumor tissues examined were found to have viral DNA integrated into the same site(s) of the cellular genome. This finding provides direct molecular evidence for a monoclonal origin and expansion of malignantly transformed hepatocytes during tumor growth and metastasis. This characteristic is similar to other human cancers associated with viral infections, such as adult T-cell leukemia, Burkitt's lymphoma, or cervical cancer, and is important für our understanding of viral oncogenesis in man.     

Hepatitis B virus DNA in children's liver diseases: detection by blot hybridisation in liver and serum.

Molecular hybridisation using cloned hepatitis B virus DNA (HBV DNA) was applied to liver and serum samples from 46 children (39 with liver diseases and seven controls) for detection of HBV DNA sequences, free and integrated into the liver cell genome. HBV DNA integration was observed in 10 children. The young age of some of these cases indicates that such integration can occur early in liver disease and is not related to the duration of viral infection. Thirteen children exhibited serological evidence of active viral multiplication. All but one had free HBV DNA in liver tissue and integrated HBV DNA sequences were found in four cases. Integrated HBV DNA sequences alone were also detected in three children with neither HBV-antigens nor HBV DNA in serum. One had inactive cirrhosis, and the two others, chronic active hepatitis. Consequently DNA hybridisation may be useful for diagnosis, in the absence of serological signs of HBV infection; its specificity was enhanced in the present investigation by negative results in six children with autoimmune chronic active hepatitis. Taken together, the above results imply that HBV-DNA integration can occur in both active and inactive liver disease. Integrated HBV DNA was also observed in the liver of three children with fatal hepatic failure who presented with antibodies to HBsAg and/or to hepatitis B core antigen in the serum. This finding raises the question of the relationship between the host immune factors and the state of HBV DNA.     

How did hepatitis B virus effect the host genome in the last decade?

The principal reason of chronic liver disease, cirrhosis and hepatocellular carcinoma is chronic viral hepatitis all over the world. Hepatitis B virus (HBV) has some mutagenic effects on the host genome. HBV may be exhibiting these mutagenic effects through integrating into the host genome, through its viral proteins or through some epigenetic mechanisms related with HBV proteins. This review aims to summarize the molecular mechanisms used by HBV for effecting host genome determined in the last decade. The focus will be on the effects of integration, HBV proteins, especially HBV X protein and epigenetic mechanisms on the host genome. These interactions between HBV and the host genome also forms the underlying mechanisms of the evolution of hepatocellular carcinoma.