High level expression of hepatitis C virus core protein (HCV-C) was detected in hilar cholangiocarcinoma tissues in our previous studies. This protein played an important role in the process of cancer cell inversion and proliferation, by some direct and indirect effects on certain genes. Based on this observation, we investigated the effect of HCV-C on human normal biliary epithelial (hBE) cell transformation and tumor development. Plasmid pHCV-C encoding the gene of HCV core protein was constructed and transfected into hBE cells. The expression and the biological effect of HCV-C in HCV-C gene-modified hBE cells were determined in vitro and in vivo. The clone formation rates of hBE cells transfected with pHCV-C, pcDNA3.1 and mocktransfected cells were 36, 2.5 and 1.5%, respectively. Tumor developed in 7 of 7 nude mice after incubated with pHCV-C transfected hBE cells, while no tumor appeared in mice injected with pcDNA3.1-and mock-transfected hBE cells. To investigate the possible mechanism of malignant transformation, we further studied the telomerase activity and human telomerase reverse transcriptase (hTERT) expression in pHCV-C transfected hBE cells. The elevated expression of hTERT was confirmed by RT-PCR, immunocytochemistry (ICC) and Western blot analysis, which in turn elevated the telomerase activity, confirmed by TRAP-ELISA. These results indicated that HCV-C protein could participate in malignant transformation of human normal biliary epithelial cells and induce cholangiocarcinoma tumorigenesis, and the activation of telomerase was one of the possible mechanisms.

Hepatitis C virus core protein activates NF-kappaB pathway in hBE cells by increasing the phosphorylation of IkappaBalpha. The pathway may be responsible for HCV-C-induced malignant transformation of hBE cells.

Previous studies showed that transient transfection of HCVc improved hTERT expression in hepatoma cell lines and it was noteworthy that phosphorylated signal transducer and activator of transcription 3 (pSTAT3) and DNA methyltransferases (DNMTs) were up regulated simultaneously. This study was designed to investigate the role of epigenetic regulation in the process of hTERT up regulation after HCVc transfection. Q-PCR and Western blot were used to analyze the expression of pSTAT3, DNMT1, and hTERT after the transfection of HCVc in hepatoma cell line Huh7. Proliferation and hTERT activity of Huh7 after HCVc transfection were examined by CCK8 and ELISA, respectively. Then, we blocked the JAK/STAT3 pathway or inhibited DNMT1 expression to investigate the regulation of pSTAT3, DNMT1, and hTERT. Methylation status of the promoter of hTERT gene was monitored by MS-PCR. Cell proliferation, hTERT expression level and activity of hTERT were promoted after HCVc transfection. The expression of pSTAT3 and DNMT1 were up-regulated simultaneously. DNMT1 and hTERT were down-regulated after blocking JAK/STAT3 pathway and the expression of hTERT weakened with DNMT1 inhibition. MS-PCR showed HCVc transfection increased the methylation level of hTERT promoter, and this effect was weakened after blocking the JAK/STAT3 pathway or with the treatment with DNMT1 inhibitor. HCVc transfection improved hTERT expression via epigenetic regulation. JAK/STAT3 pathway could be one of the essential factors in regulating DNMT1 expression during this process.