Interferon for preventing and treating hepatocellular carcinoma associated with the hepatitis B and C viruses

Interferon-alpha enhances TRAIL-mediated apoptosis by up-regulating caspase-8 transcription in human hepatoma cells

BACKGROUND/AIMS

IFNalpha is an approved treatment option for patients chronically infected with the hepatitis B and C viruses. Additionally, there is an indication for tumor therapy. The exact mechanisms underlying the antiviral and antitumor effects of IFNalpha are not completely understood. In this study, we investigated if the pro-apoptotic factor caspase-8 is a target gene of IFNalpha signalling.

METHODS

Huh7 hepatoma cells were used for measuring caspase-8 promoter activity in luciferase reporter assays after IFNalpha stimulation. Caspase-8 expression was monitored by RT-PCR, immunoblotting and measurement of enzymatic activity. Functional caspase-8 promoter elements were identified in gelshift assays and by site directed mutagenesis. Caspase-8 was inhibited using siRNA.

RESULTS

IFNalpha treatment induced caspase-8 promoter activity and mRNA expression. We identified a unique promoter element mediating the IFNalpha-dependent increase in caspase-8 transcription. Up-regulation of caspase-8 expression by IFNalpha had no impact on the rate of apoptosis per se. However, co-stimulation with IFNalpha doubled TRAIL-mediated apoptosis and enzymatic caspase-8 activity. The synergistic effect of TRAIL and IFNalpha could be blocked by inhibiting caspase-8 expression.

CONCLUSIONS

We demonstrate that caspase-8 is a target gene of IFNalpha and provide evidence showing that IFNalpha treatment sensitizes cells for apoptosis via enhanced caspase-8 transcription.

Safe use of pegylated interferon/ribavirin in hepatitis C virus cirrhotic patients with hypersplenism after partial splenic embolization

BACKGROUND AND AIMS

Partial splenic embolization (PSE) is a non-surgical alternative for the treatment of hypersplenism. Thrombocytopenia precludes the use of pegylated interferon (peg-IFN) and ribavirin in cirrhotic patients with hepatitis C virus (HCV). We aimed to evaluate the role of PSE as a procedure allowing combined HCV therapy in this setting.

METHODS

A retrospective analysis of the safety and rate of sustained virological response (SVR) after a full-dose course of peg-IFN plus ribavirin in eight HCV cirrhotic patients with severe hypersplenism undergoing PSE at a tertiary centre in Madrid, Spain, from May 2002 to August 2004.

RESULTS

Six patients (75%) were in Child-Pugh class B (median score 7). PSE significantly improved the mean platelet (P = 0.012), leucocyte (P = 0.017) and haemoglobin (P = 0.035) levels, and prothrombin activity (P = 0.012). After a mean of 20 weeks after PSE all patients started weight-adjusted ribavirin plus peg-IFN-alpha2b (n = 6) or 180 microg/week of peg-IFN-alpha2a (n = 2). Six subjects (75%) completed therapy with no peg-IFN dose reductions; the dose of ribavirin was reduced in two patients reaching haemoglobin levels of less than 10 g/dl (one also received erythropoietin and granulocyte colony-stimulating factor because of neutrophil counts < 300 cells/microl). Three patients (38%) achieved SVR. Portal vein thrombosis was observed in 50% of patients, but did not preclude antiviral therapy. The pathogenic mechanism was multifactorial. It was successfully managed with anticoagulant therapy in two cases.

CONCLUSIONS

PSE allowed the safe use of peg-IFN plus ribavirin in HCV cirrhotic patients with severe cytopenias who otherwise would never have been treated. The rate of SVR was 38%.

Similarities and differences in hepatitis B and C virus induced hepatocarcinogenesis

Hepatocellular carcinoma (HCC), the major manifestation of primary liver cancer, is one of the most frequent and malignant diseases worldwide. Among other environmental factors, hepatitis viruses, as the hepatitis B (HBV) and hepatitis C (HCV) viruses, are to be listed in the etiology of HCC. Both of these viruses cause a wide spectrum of clinical manifestations, ranging from healthy carrier state to acute and chronic hepatitis, cirrhosis and HCC. HBV and HCV are different viruses in structure: HBV contains a DNA genome which replicates through an RNA intermediate and requires an active viral reverse transcriptase (RT) polymerase enzyme, while HCV is an RNA virus which has no RT activity and replicates on the cellular membrane by RNA replication. In this review we discuss how these two biologically diverse viruses use common pathways to induce hepatocarcinogenesis despite their significant structural and viral cycle differences. A summary is also given of several observable common and different features. Direct integration of HBV viral sequences into the host genome increases the genomic instability, which does not occur in HCV infection. However, viral proteins may directly play a significant role in the induction of carcinogenesis by both viruses.