Detection and analysis of replicating hepatitis C virus RNA in hepatocellular carcinoma tissues

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.

Hepatocellular carcinoma: an overview

Hepatocellular carcinoma remains widely prevalent in tropical Africa and south-east Asia and is largely related to chronic hepatitis B virus (HBV) infection. Primary prevention by vaccination of infants at or near birth is effective but any reduction in tumour incidence cannot be expected for decades to come yet, even in those countries in which the necessary resources exist, as millions of adults remain chronically infected. Meanwhile, the incidence is rising in Japan, Mediterranean countries of Europe, Middle East and North Africa and in the USA, largely due to chronic hepatitis C virus (HCV) infection introduced by the indiscriminate use of unscreened blood and blood products in the recent past. Much has been learned from molecular biological studies on hepatocarcinogenesis incriminating the HBX gene of HBV, the core protein of HCV and a unique guanine to thymine transversion at codon 249 has been observed in cases due to aflatoxin exposure. The subject of precancerous lesions, notably adenomatous/dysplastic nodules and large-cell/small-cell change continues to be a source of much debate and the distinction of nodular lesions in cirrhosis from early carcinoma remains uncertain. Spontaneous regression of hepatocellular carcinoma is rare but it is probably immunologically mediated and treatment by activated T-lymphocytes may reduce recurrence rates after surgery. The positive identification of hepatocellular carcinoma by a liver-specific antibody has greatly facilitated the diagnosis in difficult cases.

Difference in quasispecies of the hypervariable region 1 of hepatitis C virus between alcoholic and non-alcoholic patients

BACKGROUND

Habitual alcohol intake is known to aggravate the clinical outcome of hepatitis C virus (HCV)-related chronic liver diseases and to increase the risk of hepatocellular carcinoma.

METHODS

To investigate the possible mechanism of these effects by alcohol, we examined 31 cases of HCV-related chronic liver diseases of which 17 cases were drinking just before admission and the remaining 14 cases were non-drinkers. The studied cases included 18 patients with chronic hepatitis, six with liver cirrhosis and seven with hepatocellular carcinoma. The quasispecies of the hypervariable region 1 of the HCV genome were analyzed by using polymerase chain reaction single strand conformation polymorphism (PCR-SSCP). Hepatitis C virus viral load was quantitated by using multicyclic PCR after reverse transcription of the 5' non-coding region of the genome.

RESULTS

The mean PCR-SSCP band number that reflected the quasispecies complexity in hypervariable region 1 was more significantly increased in alcoholics than in non-alcoholics (5.5 +/- 1.4 vs 3.9 +/- 1.1, P< 0.01). The significant increase in alcoholics remained, even if the cases were restricted to males (P < 0.01), to HCV genotype 1b (P < 0.05) or to chronic hepatitis (P < 0.05). The HCV viral load was not statistically different between alcoholic and non-alcoholic HCV-related chronic liver diseases (5.02 x 10(6) +/- 5.16 x 10(6) copies/mL vs 9.00 x 10(7) +/- 2.75 x 10(8) copies/mL, P = 0.28). Mutation events seemed to occur randomly when amino acid sequences of hypervariable region 1 were compared between four drinkers and four non-drinkers.

CONCLUSIONS

The enhanced quasispecies complexity in hypervariable region 1 of HCV in alcoholics may be the main cause of more progressive HCV-related chronic liver diseases, and may provide the disease the resistance against any therapeutic modalities including interferon.

Effects of continuous hepatitis with persistent hepatitis C viremia on outcome after resection of hepatocellular carcinoma

The effect of persistent hepatitis C viremia on the outcome after resection of hepatocellular carcinoma (HCC) was investigated in 59 consecutive patients with a single small HCC (< or = 3.0 cm in diameter). The presence of serum hepatitis C virus (HCV) RNA was evaluated using a reverse transcription polymerase chain reaction method as well as a branched DNA probe method. Clinicopathologic findings were compared between patients with and without viremia and the risk factors for poor outcome were evaluated. Hepatitis C virus (HCV) RNA was not detected in the sera from 7 patients (group 1), but was detected in the sera from the other 52 patients (group 2). Alanine aminotransferase (ALT) activity was significantly higher in group 2 than in group 1. The proportion of patients with active hepatitis was significantly higher in group 2. In group 2, new HCC often developed after the operation and four patients died of liver dysfunction. HCV viremia, high ALT activity, high concentration of total bilirubin, and liver cirrhosis were related to recurrence after the operation. Multivariate analysis indicated that HCV viremia and high ALT activity were independent risk factors for recurrence of HCC. Continuous hepatitis with persistent HCV viremia worsened the outcome after the resection of HCC by causing new development of HCC and deterioration of liver function. In patients with HCV-related HCC, but without HCV viremia, satisfactory results can be expected after liver resection.

Comparison of serum and liver hepatitis C virus quasispecies in HCV-related hepatocellular carcinoma

BACKGROUND/AIMS

The hepatitis C virus (HCV) genome consists of quasispecies populations of heterogeneous variants, especially in the hypervariable region. To assess the profiles of viral quasispecies in HCV-related hepatocellular carcinoma, we studied the viral population patterns in serum and liver tissues of 13 HCV-positive patients with hepatocellular carcinoma developed on cirrhotic and non-cirrhotic livers (5 and 8 cases, respectively).

METHODS

HCV genome heterogeneity was analyzed by polymerase chain reaction-mediated single-strand conformation polymorphism analysis, which showed multiple DNA bands representing different hypervariable region sequences.

RESULTS

The HCV populations were different between tumorous and nontumorous tissues in 3/5 hepatocellular carcinomas with cirrhosis and in 6/8 without cirrhosis. At least one or more than one common band was detected in both compartments in all but one case. No significant differences in the complexity of HCV quasispecies were found in hepatocellular carcinoma with or without underlying cirrhosis. Comparison of the HCV quasispecies profiles in serum and liver tissues showed a different distribution of HCV variants between these two compartments in 6/7 patients. In four cases, both common and compartmentalized sequences were detected, whereas in two cases, both without cirrhosis, the HCV population in serum was completely different from that found in the liver.

CONCLUSIONS

These results suggest that the complexity of HCV populations is influenced by the presence of hepatocellular carcinoma rather than by the severity of the underlying chronic liver disease. The different quasispecies patterns found in serum and liver may reflect different biological properties of circulating and intrahepatic HCV particles or the existence of extrahepatic sites of replication.

Selection of hepatitis C virus quasispecies during interferon treatment

Preliminary studies have shown that hepatitis C virus (HCV) quasispecies populations after interferon therapy are different from those before interferon, suggesting that selection of HCV quasispecies occurs during IFN treatment. To confirm this, fluctuations of HCV quasispecies populations were investigated by single strand conformation polymorphism analysis in eight patients who remained viremic during interferon treatment. In all patients, HCV quasispecies populations changed in 1 to 4 months after the start of interferon therapy. In seven patients, a minor population of HCV quasispecies that was present before the interferon therapy was selected and became predominant during the therapy, whereas the abundance of the other quasispecies was reduced. In the other patients, new HCV quasispecies that had not been detected before interferon therapy appeared and replaced the pretreatment HCV. In contrast, no significant changes were observed during the pretreatment period in these patients. In two patients, deduced amino acid sequences of the hypervariable region were identical despite the difference in nucleotide sequences between interferon-sensitive and interferon-resistant HCV. Thus, selection of HCV quasispecies occurs during interferon treatment and immune responses to the hypervariable region may not be the determining factor of the selection.

Hepatitis B and C viruses and primary liver cancer

The data presented indicate that viral agents (namely, HBV and HCV) are major environmental aetiological factors for human primary liver cancer. It is important to elucidate the molecular mechanisms further because HCC is one of the few examples of virus-related human cancers. In addition, the available evidence points to the possibility of at least partial prevention of the tumour by large-scale vaccination.

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.

Clinical relevance of hepatitis C virus quasispecies

It has been shown that hepatitis C virus (HCV) populations in infected individuals are composed of quasispecies with diverse mutations. The analysis of these variants may reveal mechanisms of the persistence of HCV infection, carcinogenesis and resistance to antiviral therapy. Recently, genetic features of interferon-resistant HCV have been elucidated through the analysis of interferon-resistant quasispecies, making it possible to predict interferon efficacy by detecting interferon-resistant strains.