In an earlier study, we found that hepatitis C virus core protein, HCV-C, participated in the malignant transformation of HCV-C transfected normal human biliary epithelial (hBE) cells by activating telomerase. Here we further investigated the signaling of the malignant transformation.
Methods: Reverse transcription-polymerase chain reaction (RT-PCR), western blotting and immunoprecipitation were used to analyze the expression of HCV-C, human telomerase reverse transcriptase (hTERT), nuclear factor-kappaB (NF-kappaB) and NF-kappaB inhibitor alpha (IkappaBalpha) genes and the phosphorylation level of IkappaBalpha protein. Electrophoretic mobility shift assays (EMSA) and NF-kappaB-linked luciferase reporter assays were carried out to measure NF-kappaB activity.
Results: The expression of HCV-C and hTERT was detected only in HCV-C-transfected hBE (hBE-HCV-C) cells but not in vector-transfected or parental hBE cells. More NF-kappaB protein accumulated in nuclear extracts of hBE-HCV-C cells rather than in those of control cells, though total NF-kappaB protein level showed no difference among these cells. DNA binding activity of NF-kappaB and the NF-kappaB-linked luciferase activity were much higher in HCV-C-transfected hBE cells than those in vector- or non-transfected hBE cells. In addition, the IkappaBalpha phosphorylation level, but not the IkappaBalpha mRNA or protein levels, was increased after HCV-C transfection.
Conclusions: 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.