Expression of hepatitis C virus in hepatocellular carcinoma

Hepatocellular carcinoma after direct-acting antivirals for hepatitis C is associated with KIR-HLA types predicting weak NK cell-mediated immunity

BACKGROUND AND AIMS

Second-generation direct-acting antivirals (2G DAA) to cure HCV have led to dramatic clinical improvements. HCV-associated hepatocellular carcinoma (HCC), however, remains common. Impaired immune tumor surveillance may play a role in HCC development. Our cohort evaluated the effects of innate immune types and clinical variables on outcomes including HCC.

METHODS

Participants underwent full HLA class I/KIR typing and long-term HCV follow-up.

RESULTS

A total of 353 HCV+ participants were followed for a mean of 7 years. Cirrhosis: 25% at baseline, developed in 12% during follow-up. 158 participants received 2G DAA therapy. HCC developed without HCV therapy in 20 subjects, 24 HCC after HCV therapy, and 10 of these after 2G DAA. Two predictors of HCC among 2G DAA-treated patients: cirrhosis (OR, 10.0, p = 0.002) and HLA/KIR profiles predicting weak natural killer (NK) cell-mediated immunity (NK cell complementation groups 6, 9, 11, 12, OR of 5.1, p = 0.02). Without 2G DAA therapy: cirrhosis was the main clinical predictor of HCC (OR, 30.8, p < 0.0001), and weak NK-cell-mediated immunity did not predict HCC.

CONCLUSION

Cirrhosis is the main risk state predisposing to HCC, but weak NK-cell-mediated immunity may predispose to post-2G DAA HCC more than intermediate or strong NK-cell-mediated immunity.

Hepatitis C Virus-Associated Cancers

Most hepatitis C virus (HCV) infection results in persistent infection. Significant portion of chronic HCV-infected patients develop hepatocellular carcinoma (HCC). Chronic hepatitis C is also associated with extrahepatic manifestations, including cryoglobulinemia, lymphoma, insulin resistance, type 2 diabetes, and neurological disorders. The molecular mechanisms of how HCV infection causes liver cancer are largely unknown. HCV replication or viral proteins may perturb cellular hemostasis and induce the generation of reactive oxygen species (ROS); viral components or viral replication products act as agonist to trigger innate immune response and cause chronic inflammation. Within the liver, non-hepatocytes such as hepatic stellate cell (HSC) are activated upon HCV infection to provide the major source of extracellular proteins and play important roles in fibrogenesis. With the great achievements of HCV treatment, especially the direct-acting antivirals (DAAs) against HCV, HCV eradication is possible. However, until now there are only very limited data on the effect of DAA-based anti-HCV treatment on HCC patients.

Diminished viral replication and compartmentalization of hepatitis C virus in hepatocellular carcinoma tissue

Analysis of hepatitis C virus (HCV) replication and quasispecies distribution within the tumor of patients with HCV-associated hepatocellular carcinoma (HCC) can provide insight into the role of HCV in hepatocarcinogenesis and, conversely, the effect of HCC on the HCV lifecycle. In a comprehensive study of serum and multiple liver specimens from patients with HCC who underwent liver transplantation, we found a sharp and significant decrease in HCV RNA in the tumor compared with surrounding nontumorous tissues, but found no differences in multiple areas of control non-HCC cirrhotic livers. Diminished HCV replication was not associated with changes in miR-122 expression. HCV genetic diversity was significantly higher in livers containing HCC compared with control non-HCC cirrhotic livers. Tracking of individual variants demonstrated changes in the viral population between tumorous and nontumorous areas, the extent of which correlated with the decline in HCV RNA, suggesting HCV compartmentalization within the tumor. In contrast, compartmentalization was not observed between nontumorous areas and serum, or in controls between different areas of the cirrhotic liver or between liver and serum. Our findings indicate that HCV replication within the tumor is restricted and compartmentalized, suggesting segregation of specific viral variants in malignant hepatocytes.

HCV-hepatocellular carcinoma: new findings and hope for effective treatment

We present here a comprehensive review of the current literature plus our own findings about in vivo and in vitro analysis of hepatitis C virus (HCV) infection, viral pathogenesis, mechanisms of interferon action, interferon resistance, and development of new therapeutics. Chronic HCV infection is a major risk factor for the development of human hepatocellular carcinoma. Standard therapy for chronic HCV infection is the combination of interferon alpha and ribavirin. A significant number of chronic HCV patients who cannot get rid of the virus infection by interferon therapy experience long-term inflammation of the liver and scarring of liver tissue. Patients who develop cirrhosis usually have increased risk of developing liver cancer. The molecular details of why some patients do not respond to standard interferon therapy are not known. Availability of HCV cell culture model has increased our understanding on the antiviral action of interferon alpha and mechanisms of interferon resistance. Interferons alpha, beta, and gamma each inhibit replication of HCV, and the antiviral action of interferon is targeted to the highly conserved 5'UTR used by the virus to translate protein by internal ribosome entry site mechanism. Studies from different laboratories including ours suggest that HCV replication in selected clones of cells can escape interferon action. Both viral and host factors appear to be involved in the mechanisms of interferon resistance against HCV. Since interferon therapy is not effective in all chronic hepatitis C patients, alternative therapeutic strategies are needed to treat chronic hepatitis C patients not responding to interferon therapy. We also reviewed the recent development of new alternative therapeutic strategies for chronic hepatitis C, which may be available in clinical use within the next decade. There is hope that these new agents along with interferon will prevent the occurrence of hepatocellular carcinoma due to chronic persistent hepatitis C virus infection. This review is not inclusive of all important scientific publications due to space limitation.

Mutations in the E2-PePHD region of hepatitis C virus type 1b in patients with hepatocellular carcinoma

An interaction between the protein kinase (PKR)-eIF2-alpha phosphorylation homology domain (PePHD) within the E2 protein of hepatitis C virus (HCV) and cell protein kinase (PKR) may affect the control of protein synthesis and cell growth. In an attempt to investigate the genetic variability of the E2-PePHD domain in hepatocellular carcinoma (HCC), we studied sera and liver tissues from HCC patients. The partial E2-PePHD region was analysed by direct sequencing of the sera of 47 HCCs in cirrhotic livers and 31 cases of chronic active hepatitis (CAH), and tumoral and non-tumoral liver tissues from 13 HCC patients. A similar number of mutations was detected within the E2 domain in the HCC and CAH cases, but nine of the 47 HCCs (19%) showed an amino acid (aa) mutation at position 660, eight of which involved a change in the same aa (alanine instead of serine; A/S). No such mutation was detected in any of the PePHD sequences from the CAH patients: this difference was statistically significant (P = 0.008). The aa change at position 660 was also found in two sequences from tumoral but not non-tumoral tissue from the same liver. The analysis of 461 sequences obtained from GenBank supports the conclusion that the observed aa change is an infrequent event in HCV-infected patients, thus suggesting that it could be associated with HCC.

The Oncogenic Potential of Hepatitis C Virus NS5A Sequence Variants Is Associated with PKR Regulation

The NS5A protein of hepatitis C virus (HCV) confers cell growth regulation and has been implicated in viral oncogenesis. Here, we investigated whether highly divergent NS5A proteins obtained from HCV-infected patients presented an oncogenic potential when expressed in mammalian cells. In general, NS5A expression was associated with increased rates of cell growth and culture proliferation. Immortalized primary hepatocyte and immortalized fibroblast cell lines expressing a subset of these sequences exhibited a significant increase in protein synthetic rate, culture saturation density, and a transformed cellular phenotype, as shown by anchorage-independent cell growth and colony formation in soft agar assays. Oncogenic transformation correlated with inhibition of protein kinase R (PKR) activity and concomitant reduction of eukaryotic initiation factor 2alpha (elF2alpha) phosphorylation levels that caused stimulation of mRNA translation. The extent of sequence variation throughout NS5A or within the previously characterized PKR-binding domain was not a predictive indicator of this cellular phenotype, suggesting that sequences outside this region contribute to PKR regulation. Our data indicate that NS5A oncogenic potential is conditional through viral sequence variation. These results provide further evidence to define the PKR pathway as a mediator of cell growth control and suggest that viral regulation of PKR may contribute to hepatocyte growth deregulation during chronic HCV infection.

Naturally Acquired MAGE-A10- and SSX-2-Specific CD8+ T Cell Responses in Patients with Hepatocellular Carcinoma

Immunotherapy is being proposed to treat patients with hepatocellular carcinoma (HCC). However, more detailed knowledge on tumor Ag expression and specific immune cells is required for the preparation of highly targeted vaccines. HCC express a variety of tumor-specific Ags, raising the question whether CTL specific for such Ags exist in HCC patients. Indeed, a recent study revealed CTLs specific for two cancer-testis (CT) Ags (MAGE-A1 and MAGE-A3) in tumor infiltrating lymphocytes of HCC patients. Here we assessed the presence of T cells specific for additional CT Ags: MAGE-A10, SSX-2, NY-ESO-1, and LAGE-1, which are naturally immunogenic as demonstrated in HLA-A2(+) melanoma patients. In two of six HLA-A2(+) HCC patients, we found that MAGE-A10- and/or SSX-2-specific CD8(+) T cells naturally responded to the disease, because they were enriched in tumor lesions but not in nontumoral liver. Isolated T cells specifically and strongly killed tumor cells in vitro, providing evidence that these CTL were selected in vivo for high avidity Ag recognition. Therefore, besides melanoma, HCC is the second solid human tumor with clear evidence for in vivo tumor recognition by T cells, providing the rational for specific immunotherapy, based on immunization with CT Ags such as MAGE-A10 and SSX-2.

Epstein-Barr virus and human hepatocellular carcinoma

Recent studies suggest that Epstein-Barr virus (EBV) may act as a helper virus for the development of hepatocellular carcinoma by promoting replication of the hepatitis C virus (HCV) in the infected liver. Detection of EBV DNA in a high percentage of HCV-positive human hepatocellular carcinomas (HCC) from Japanese patients has supported this concept. In order to determine whether EBV infection is associated with HCC, we examined paraffin-embedded tissues from 31 cases of non-cirrhotic livers with hepatocellular carcinoma for the presence of EBV, HCV and hepatitis B virus (HBV) infection. RNA prepared from tumor samples were used as a template for reverse transcription followed by double-nested PCR with primers for the 5' untranslated region (NT) of HCV. DNA extracts of tumor samples were tested by single polymerase chain reaction for the detection of EBV and HBV (X- and/or S-gene) DNA sequences. To control for nucleic acid integrity, all tumor samples were amplified for human beta-globin DNA by polymerase chain reaction and subjected to Southern blot hybridization. None of the cases was found to be positive for EBV. Ten HCC cases (32%) tested positive for HCV and 12 HCC cases (38%) tested positive for HBV. Six of the surveyed patients had nucleic acids of both HCV and HBV in their tumor tissue. All HCC tumor samples were positive for beta-globin. Our study shows that HCV and HBV infections, but not EBV infection, are associated with hepatocarcinogenesis in non-cirrhotic livers. Other unknown risk factors seem to be in effect in the development of hepatocellular carcinoma in non-cirrhotic livers.

Variation of hepatitis C virus load, hypervariable region 1 quasispecies and CD81 hepatocyte expression in hepatocellular carcinoma and adjacent non-cancerous liver

Hepatitis C virus (HCV) infection is etiologically associated with the development of hepatocellular carcinoma (HCC) worldwide. HCV has been reported to exist and replicate in both HCC and adjacent non-cancerous liver tissue, but limited information was available on HCV viral load and quasispecies composition in HCC relative to adjacent non-cancerous hepatocytes. Previous study has also suggested CD81, a surface hepatocyte protein, as a receptor for HCV. To clarify the above, HCV-RNA and CD81-RNA titers in 20 paired hepatectomized liver and serum were quantitatively measured by chemiluminescent RT-cPCR. Hypervariable region 1 (HVR-1) variations of parallel specimens were analyzed after subcloning in 6 patients. HCV-RNA levels in serum and non-cancerous liver were markedly higher for HCV genotype 1 than genotype non-1. HCV levels were markedly higher in non-cancerous liver than in HCC (P = 0.001) in a genotype-independent manner, with a mean ratio of 56:1 for non-cancerous tissue to HCC. Both non-cancerous and HCC tissues had the same level of CD81-RNA expression, which was not linked to HCV load. HCV-RNA quantity in both HCC and non-cancerous liver correlated with the number of HVR-1 quasispecies in the tissue, and distinct HVR-1 subclones existed.

Prevalence of wild-type in NS5A-PKR protein kinase binding domain in HCV-related hepatocellular carcinoma

BACKGROUND/AIMS

Experimental studies have demonstrated that the wild-type PKR-NS5A strain of hepatitis C virus (HCV) may have oncogenic potential through the binding and functional repression of PKR protein kinase. To assess whether the NS5A-PKR-binding domain may be involved in HCV-related liver carcinogenesis, its sequence was analyzed in the sera of 85 patients with hepatocellular carcinoma (HCC) and in 51 patients with chronic active hepatitis (CAH). In 13 HCC cases sequence analysis was also performed in tumor and nontumor liver tissues.

METHODS

The nucleotide sequences of the PKR-binding domain were inferred by direct sequencing of the amplified HCV products and deduced amino acids were compared with the sequence of HCV-J.

RESULTS

A wild-type or single mutated strain which retains PKR-binding activity was found in 88% of HCC and 69% of CAH cases (P=0.0096). All but three HCC cases showed no divergences in amino acid changes between serum and liver tissues. The wild-type strains were equally distributed between the HCC with or without cirrhosis.

CONCLUSIONS

The prevalance of the wild-type NS5A-PKR strain is significantly higher in HCC than in CAH. These data suggest that inhibition of PKR activity by HCV might represent a potential mechanism of HCV-related carcinogenesis.

Immunohistochemical detection of hcv in cirrhosis, dysplastic nodules, and hepatocellular carcinomas with parallel-tissue quantitative RT-PCR

Hepatitis C virus is a major risk factor for hepatocarcinogenesis in humans. In situ detection of the virus in early sequential lesions of hepatocarcinogenesis could provide information about the role of the virus in the transformation and promotion process. Parallel in situ detection of HCV proteins and RNA in human tissues were performed in 55 posthepatitis C cirrhosis, 17 dysplastic nodules (DN), and 25 hepatocellular carcinomas (HCC), using immunohistochemistry and tissue quantitative RT-PCR. A consistent cytoplasmic hepatocellular staining was obtained in 73% of cirrhosis cases (with or without HCC) and in 55% DN cases. A few tumoral hepatocytes were unambiguously stained in 28% HCC. The percentage of positive cells and the intensity of immunostaining significantly decreased from cirrhosis to HCC through DN, whereas there was no difference in the prevalence of positivity or the number of viral copies between cirrhosis and HCC using tissue-quantitative RT-PCR. Finally, RT-PCR levels were found parallel with the immunostaining in cirrhosis but not in HCC. These results suggest that HCV protein synthesis may persist but be down-regulated during sequential hepatocarcinogenesis. A putative role of HCV proteins on cell proliferation and differentiation during the early steps of carcinogenesis cannot therefore be excluded.

Co-occurrence of hepatocellular carcinoma and lymphoma in patients with hepatitis C virus cirrhosis

The association of hepatitis C virus (HCV) with neoplasia is not completely understood. Hepatitis C virus is hepatolymphotrophic. It is considered an inducing factor of hepatocellular carcinoma (HCC) and is associated with various types of lymphomas. We describe a patient with HCV cirrhosis who developed gastric lymphoma and HCC, and we review the current data and theories about the oncogenesis of HCV.

Pathomorphological Characteristics and Pathogenesis of Viral Hepatitis

Viral hepatitis (VH) is an inflammatory reaction of the liver to hepatotropic viruses. Acute VH can be classified according to the virus and type of necrosis. Chronic hepatitis (CH) might be active, persistent or lobular based on previous classification. More recently the grade (necroinflammatory activity) and stage (fibrosis and architectural distorsion) of CH have been distinguished and scored. Apoptosis and necrosis probably coexist in VH and contribute to hepatocyte death. Several "death factors", such as transforming growth factor b, Apo1/Fas and tumor necrosis factor play a role in the execution of cell death. Injury of hepatocytes during viral infection can occur as a direct effect of the virus or as a result of the host immune response. Expression of different viral antigens can be detected during VH and might be visualized. Phenotyping of the portal inflammatory cell infiltrate in CH has shown a T-cell zone comprised of CD4+ helper T cells and CD8+ supressor/cytotoxic T cells at the periphery of the lobules. The pathogenetic mechanisms responsible for the final outcome of viral infection depend on viral factors (such as genotype, mutation etc.), virus-host interaction, expression of viral protein, several cytokines etc. which finally lead to the well known histological alterations of viral hepatitis.

Detection of hepatitis C virus RNA sequences in B-cell non-Hodgkin lymphoma

Serologic testing shows that hepatitis C virus (HCV) may have a role in the pathogenesis of B-cell non-Hodgkin lymphomas (B-cell NHLs). We tried to demonstrate HCV RNA sequences in paraffin-embedded tissue from B-cell NHLs by reverse-transcription double polymerase chain reaction (RT-PCR) and Southern blotting. We studied 31 consecutive cases of B-cell NHLs; lymph nodes from 32 patients with diseases other than B-cell NHL were negative controls. Positive-strand HCV RNA was tested with primers for the 5' untranslated region. Replicative negative strand HCV RNA was tested with strand-specific RT-PCR for the 5' untranslated region. Immunohistochemical staining for HCV was done using an antibody to HCV core protein. Positive-strand HCV RNA was detected in 8 patients with B-cell NHL; negative-strand HCV RNA was detected in 6 of these cases, indicating viral replication. All control cases were negative for HCV RNA. Immunohistochemistry showed no staining of lymphoma cells for HCV core proteins in any case. HCV and B-cell NHLs may be associated. RT-PCR on paraffin-embedded lymphoma tissue is an alternative method of testing for HCV. The value of immunohistochemistry could not be ascertained. The exact role of HCV in the pathogenesis of B-cell NHL needs to be studied further.

Primary hepatic leiomyosarcoma in a patient with hepatitis C virus-related liver cirrhosis

We describe an autopsy case of primary hepatic leiomyosarcoma in a 68-year-old man with hepatitis C virus-related liver cirrhosis. The patient, who had a history of acute hepatitis 20 years previously, died of a ruptured hepatic tumor. At autopsy, a well-circumscribed 14 x 16 x 15 cm tumor replaced the medial site of the right hepatic lobe with multiple intrahepatic and distant metastases. Histologically the tumor, which had extensive central necrosis, consisted predominantly of well or moderately differentiated spindle-shaped cells, which were positive for smooth muscle actin and vimentin on immunohistochemical staining. In addition, clusters of markedly atypical cells and myxoid change of the matrix were discretely found in the focal and small areas of the tumor. These findings indicated that many sections were necessary for the histologically accurate estimation of primary hepatic smooth muscle tumor. The histological examination of a non-tumorous lesion showed liver cirrhosis. Hepatitis C virus was detected in the cytoplasm of cirrhotic hepatocytes by immunohistochemistry and reverse transcriptase-polymerase chain reaction, but not in the tumor cells. This suggested that the virus was not directly involved in the development of primary hepatic leiomyosarcoma.

Antiapoptotic and oncogenic potentials of hepatitis C virus are linked to interferon resistance by viral repression of the PKR protein kinase

Hepatitis C virus (HCV) is prevalent worldwide and has become a major cause of liver dysfunction and hepatocellular carcinoma. The high prevalence of HCV reflects the persistent nature of infection and the large frequency of cases that resist the current interferon (IFN)-based anti-HCV therapeutic regimens. HCV resistance to IFN has been attributed, in part, to the function of the viral nonstructural 5A (NS5A) protein. NS5A from IFN-resistant strains of HCV can repress the PKR protein kinase, a mediator of the IFN-induced antiviral and apoptotic responses of the host cell and a tumor suppressor. Here we examined the relationship between HCV persistence and resistance to IFN therapy. When expressed in mammalian cells, NS5A from IFN-resistant HCV conferred IFN resistance to vesicular stomatitis virus (VSV), which normally is sensitive to the antiviral actions of IFN. NS5A blocked viral double-stranded RNA (dsRNA)-induced PKR activation and phosphorylation of eIF-2alpha in IFN-treated cells, resulting in high levels of VSV mRNA translation. Mutations within the PKR-binding domain of NS5A restored PKR function and the IFN-induced block to viral mRNA translation. The effects due to NS5A inhibition of PKR were not limited to the rescue of viral mRNA translation but also included a block in PKR-dependent host signaling pathways. Cells expressing NS5A exhibited defective PKR signaling and were refractory to apoptosis induced by exogenous dsRNA. Resistance to apoptosis was attributed to an NS5A-mediated block in eIF-2alpha phosphorylation. Moreover, cells expressing NS5A exhibited a transformed phenotype and formed solid tumors in vivo. Disruption of apoptosis and tumorogenesis required the PKR-binding function of NS5A, demonstrating that these properties may be linked to the IFN-resistant phenotype of HCV.

Possible contribution to hepatocarcinogenesis of X transcript of hepatitis B virus in Japanese patients with hepatitis C virus

Serological research suggests that hepatitis B virus (HBV) and hepatitis C virus (HCV) are associated with the development of hepatocellular carcinoma (HCC). It is unclear how genes of hepatitis viruses participate in hepatocarcinogenesis in patients infected with HCV. We investigated the expression of hepatitis virus-related RNAs in resected liver from 51 patients with HCV antibodies (Ab) and without hepatitis B surface antigen (HBsAg). mRNA transcripts of the genes HBx, HBc, HBs, nonstructural (NS) region 3 of HCV, the 5'-untranslated region (UTR) of HCV, and the 5'-UTR of hepatitis G virus (HGV) were amplified by reverse-transcription polymerase chain reaction (RT-PCR) with specific primers for each gene. The HBx transcript was detected in 19 (37%) tumors and in 8 (16%) specimens of noncancerous tissues (P =.014). The NS3 gene of HCV was detected in 35 (69%) tumors and 41 (80%) noncancerous tissues. HGV RNA was detected in 3 tumors (6%). Patients with HBx transcripts were younger than patients without HBx transcripts (P =.012). HBx transcripts were detected in 3 (33%) of 9 well-differentiated HCCs, in 8 (31%) of 26 moderately differentiated HCCs, and in 8 (50%) of 16 poorly differentiated HCCs. Codon 130 (AAG) and codon 131 (GTC) of HBx were changed to ATG and ATC, respectively, in all HCCs with HBx transcripts. In conclusion, we found that the HBx gene was expressed in many HCCs; the gene might promote hepatocarcinogenesis in patients with HCVAb and without HBsAg, but HGV is not closely related to hepatocarcinogenesis in such patients.

Detection of hepatitis-C virus and hepatitis-C virus replication in hepatocellular carcinoma by in situ hybridization

BACKGROUND

Although hepatitis C virus (HCV) is a major causative agent of hepatocellular carcinoma (HCC), the role of this virus in carcinogenesis is not fully understood.

METHODS

We studied HCV infection and replication by detecting plus- and minus-strand HCV RNA by in situ hybridization (ISH) in surgically resected HCCs and adjacent non-cancerous tissue obtained from 15 anti-HCV antibody-positive patients with HCC.

RESULTS

Plus-strand HCV RNA was found in 9 of 15 HCCs. Both plus- and minus-strand HCV RNA were detected in four of these nine patients. In non-cancerous tissues obtained adjacent to the HCC, plus-strand HCV RNA was found in 10 of 15 patients, whereas both plus- and minus-strand HCV RNA were detected in 7 of these 10 patients. The degree of staining by ISH did not correlate with the differentiation of the HCC, histologic classification of the non-cancerous tissue, serum HCV RNA levels, or serum transaminase levels.

CONCLUSIONS

HCV can be found in and replicates in both hepatoma cells and in non-cancerous hepatocytes in anti-HCV antibody-positive patients with HCC. The direct effects of HCV viral gene products on normal hepatocytes in the development of HCC require additional study.

Hepatitis C virus infection, mixed cryoglobulinemia, and non-Hodgkin's lymphoma: an emerging picture

Hepatitis C virus (HCV) is a single-stranded RNA agent which expresses its genetic informations in the form of a single, large polyprotein encoded by an open reading frame (ORF) that extends through most of its genomic RNA. Proteolytic cleavage of the ORF product is essential for the virogenesis and the production of viral progeny. HCV is responsible for chronic liver disease, cirrhosis and possibly hepatocellular carcinoma. Viral persistence is considered the greatest problem in the management of HCV infection. It may result from several mechanisms, two of which are established. In the first, the high rate of genetic variations during viral replication results in the production of mutants capable of escaping the immune attack. In the second, the virus infects cells of the immune system itself, which represent a privileged site that cannot be reached by virus-specific T cell response. Involvement of lymphoid cells in the early stages of HCV infection may provide insight into the pathobiologic patterns of extrahepatic dissemination (lymph nodes, major salivary glands, kidneys, blood vessels). Dissemination of HCV-infected lymphoid cells throughout the organism is likely to maintain a mobile and extensive reservoir of the virus. In this respect, extrahepatic sites may act as a source of continuous reinfection of hepatocytes. Studies of intrahepatic B lymphocytes indicate that they are infected with HCV, clonally expanded and activated to secrete IgM molecules with rheumatoid factor activity. This strongly suggests that HCV directly stimulates B cell expansion, which may result in an indolent stage of lymphoproliferation (i.e., mixed cryoglobulinemia) or in frank B cell non-Hodgkin's lymphoma (NHL). The frequency of NHL, however, is much lower than that of HCV infection, suggesting that HCV alone is not able to induce tumors and that cellular events, in addition to the presence of virus and virus-encoded products, are necessary in order to obtain a malignant B cell phenotype. The demonstration of HCV productive infection in bone marrow-recruited and circulating pluripotent hematopoietic CD34+ stem cells indicates that HCV replication occurs in the early differentiation stages of hematopoietic progenitors. These are stable cell populations and are likely to represent the initial site of infection and a continuous source of virus production.

Pathogenesis of hepatitis B and C-induced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is estimated to have an annual worldwide incidence of 0.25 to 1.2 million new cases per year. Both the prevalence and incidence of HCC vary markedly as a function of geography and the local prevalence of chronic viral hepatitis. Both chronic hepatitis B and chronic hepatitis C are recognized as risk factors for HCC. The prevalence of cirrhosis in individuals with HCC and chronic hepatitis B or C is reported to be 80.9% and 75.8%, respectively. HCC occurs at a lower rate in chronic viral hepatitis in the absence of cirrhosis. Moreover, hepatitis C virus (HCV) rather than hepatitis B virus (HBV) is associated with the majority of non-cirrhotic cases of HCC. It is probable that the ongoing process of hepatocyte necrosis and liver cell renewal coupled with inflammation, which is characteristic of chronic viral hepatitis, causes not only nodular regeneration and cirrhosis but also progressive genomic errors in hepatocytes as well as unregulated growth and repair mechanisms leading to hepatocyte dysplasia and, in some cases, hepatic carcinoma. Current concepts concerning virus-induced HCC are reported and discussed in the following review.

Histopathology of HCV infection

The basic morphologic features of acute and chronic viral hepatitis C are similar to those of other hepatitides; however, hepatitis C is characterized by the histologic triad of lymphoid aggregates in portal tracts, epithelial damage of small bile ducts and microvesicular and macrovesicular steatosis of hepatocytes. Significant progress has been made in the demonstration of HCV in infected liver tissues by immunohistochemical and in situ hybridization techniques. The new classification of chronic hepatitis, based on etiology, grading (extent of necroinflammatory activity) and staging (extent of fibrosis) has been widely accepted and will lead to a better understanding of the variable course and response to therapy of this enigmatic disease.

Hepatitis C virus core protein shows a cytoplasmic localization and associates to cellular lipid storage droplets

There is now abundant evidence to substantiate an important role of hepatitis C virus (HCV) core protein in cellular gene expression as well as in the viral cycle. Thus the subcellular localization of this protein has important implications. However, several studies have shown controversial results: the HCV core has been, indeed, described as cytoplasmic or nuclear depending on the size of the protein or on the genotype analyzed. We have studied the localization of the HCV core protein in two different cell lines, one nonhepatic (CHO) and the other hepatic (HepG2). Double immunofluorescence staining using a nuclear membrane marker and confocal analysis showed the core protein pattern to be cytoplasmic and globular. This pattern is not cell cycle-regulated. Electron microscopy analysis revealed the nature of the globular staining observed in immunofluorescence. The HCV core protein accumulated at the surface of lipid droplets that were also the unique morphological feature of nonhepatic core transfected cells. The lipid droplets were isolated by sequential ultracentrifugation on the basis of their density; biochemical analysis revealed a prevalence of triglycerides. In addition the core protein colocalized with apolipoprotein AII at the surface of the lipid droplets as revealed by confocal microscopy. Moreover analysis of liver biopsies from chronically HCV-infected chimpanzees revealed that HCV core is cytoplasmic and localized on the endoplasmic reticulum and on lipid droplets. These results clearly define the subcellular localization of the HCV core protein and suggest a relationship between the expression of the HCV core protein and cellular lipid metabolism.

HCV cDNA transfection to HepG2 cells

The establishment of an in vitro system for hepatitis C virus (HCV) propagation is essential to characterize virus replication, virus persistence and viral pathogenicity. The aim was to establish HCV replication in HepG2 cells by gene transfer of infectious HCV cDNA. First, several gene transfer methods were evaluated that employed cationic liposomes (lipofectin, lipofectamine. DOTAP), DEAE-dextran and replication-deficient adenovirus for transfection to HepG2 cells using a lacZ reporter gene. Highest transfection efficiency (20%) of cultured HepG2 cells was obtained by the combined use of lipofectamine and adenovirus. This method was used for transfection of HepG2 cells with HCV cDNA in a mammalian expression plasmid (pRC/CMV). The success and efficacy of HCV transfection to HepG2 cells was evaluated by testing for the presence of genomic and replicative (negative) strands of HCV RNA by strand-specific reverse transcription (RT) followed by nested PCR. Expression of structural and non-structural proteins of hepatitis C virus was detected using polyclonal antibodies to core, NS3, NS4 and NS5. Positive-strand HCV RNA was detected by RT-PCR for over 6 weeks in the HCV cDNA-transfected HepG2 cells. Presence of HCV replication in these cells was confirmed by detecting HCV negative-strand RNA by strand-specific RT-PCR and was observed to continue for over 4 weeks. HCV proteins (core, NS3, NS4 and NS5) were detected in the cytoplasm of the transfected cells by immunostaining. In summary, these findings suggest that replication and translation of HCV were achieved for a prolonged time in HepG2 cells after transfection with HCV cDNA and may provide an in vitro system for HCV studies.

Hepatitis and cancer: genetic aspects

Hepatocellular carcinoma (HCC) is one of the most common tumours in the world. It is the seventh most common cancer in men and the ninth in women with an estimated 500,000 to 1,000,000 new HHC cases per year. However, there are considerable variations in the incidence of HCC throughout the world, related to geographical areas, socioeconomic factors, sex and age-specific incidence rates, suggesting genetic differences in susceptibility to HCC.

Detection of hepatitis C virus RNA in hepatocellular carcinoma by in situ hybridization

BACKGROUND

Hepatocellular carcinoma frequently is associated with chronic hepatitis C virus (HCV) infection. The presence of HCV in hepatocellular carcinoma has been detected by reverse-transcription polymerase chain reaction of antigenomic HCV RNA, a tissue-specific replicative form of the virus. Now, however, this method of detecting the presence of HCV has been invalidated by reports of antigenomic RNA in the blood or in peripheral blood mononuclear cells.

METHODS

In situ hybridization of HCV RNA was conducted with digoxigenin-labeled cDNA from the core region on surgical specimens of noncancerous and cancerous areas from 12 patients with chronic hepatitis C with or without cirrhosis associated with hepatocellular carcinoma. Several control experiments were also performed, including RNase digestion before hybridization, hybridization with the use of a negative control, and immunohistochemical staining of HCV-core protein.

RESULTS

The in situ hybridization showed positive signals both in noncancerous and cancerous areas of the liver tissue in eight cases. Positive signals were confined to neoplastic cells and nonneoplastic hepatocytes. There were fewer HCV-positive cells in the cancerous area than in the surrounding noncancerous area.

CONCLUSIONS

In situ detection of HCV presents direct evidence of HCV infection in the neoplastic cells of hepatocellular carcinoma and suggests that neoplastic cells may lose their affinity for HCV in the course of malignant transformation.