Hitomi Nakamura1, Hiroshi Aoki, Okio Hino, Mitsuhiko Moriyama. 1. Division of Gastroenterology and Hepatology, Department of Medicine, Nihon University School of Medicine Department of Pathology, Juntendo University School of Medicine, Tokyo, Japan.
Abstract
AIMS: Persistent hepatitis C virus (HCV) infection is a major cause of chronic liver dysfunction and is closely associated with the development of human hepatocellular carcinoma (HCC). Among HCV components, core protein is implicated in cell growth regulation, and we previously demonstrated that HCV core protein interacted with 14-3-3 protein and activated the kinase Raf-1 and mitogen-activated protein kinase (MAPK)/extracellular regulated kinase (ERK) pathway. In the present study, we investigated the expression levels and function of downstream molecules in the MAPK/ERK signaling pathway in cells expressing HCV core protein. METHOD: Heparin-binding EGF-like growth factor (HB-EGF) mRNA, in HepG2 cells stably expressing HCV core protein, was detected by RT-PCR. The soluble HB-EGF in culture media was measured by heparin agarose chromatography/Western blot analysis. Immunodetection of Akt and IKK and IB, in HeLa cells and HepG2 cells expressing HCV core protein, were performed with neutralizing antibody for HB-EGF, phospatidylinositol-3-kinase [PI(3)K] inhibitor and dominant-negative mutant of Ras (DN-Ras). RESULTS: HB-EGF expression was significantly elevated in cells expressing HCV core protein. HCV core protein activated Akt through the Ras/PI(3)K pathway by autocrine secretion of HB-EGF. Also, HCV core protein activated IKK through Ras/PI(3)K/Akt pathway by autocrine secretion of HB-EGF. As the Ras/PI(3)K/Akt pathway is critical in anti-apoptotic HB-EGF signaling, we examined the possible role of this pathway in cells expressing HCV core protein. In addition, we investigated the relationship between IB kinases (IKK) and Akt in cells expressing HCV core protein, since IKKs are known to be activated by HCV core protein and by Akt in the presence of potent mitogen. We showed that HCV core protein promoted autocrine secretion of HB-EGF and activated Akt through the Ras/PI(3)K pathway. This model indicates a new approach to mechanism of proliferation and anti-apoptosis in HCC. CONCLUSION: HCV core protein is a potent activator of mitogenic and anti-apoptotic signaling involved in hepatocarcinogenesis.
AIMS: Persistent hepatitis C virus (HCV) infection is a major cause of chronic liver dysfunction and is closely associated with the development of human hepatocellular carcinoma (HCC). Among HCV components, core protein is implicated in cell growth regulation, and we previously demonstrated that HCV core protein interacted with 14-3-3 protein and activated the kinase Raf-1 and mitogen-activated protein kinase (MAPK)/extracellular regulated kinase (ERK) pathway. In the present study, we investigated the expression levels and function of downstream molecules in the MAPK/ERK signaling pathway in cells expressing HCV core protein. METHOD:Heparin-binding EGF-like growth factor (HB-EGF) mRNA, in HepG2 cells stably expressing HCV core protein, was detected by RT-PCR. The soluble HB-EGF in culture media was measured by heparinagarose chromatography/Western blot analysis. Immunodetection of Akt and IKK and IB, in HeLa cells and HepG2 cells expressing HCV core protein, were performed with neutralizing antibody for HB-EGF, phospatidylinositol-3-kinase [PI(3)K] inhibitor and dominant-negative mutant of Ras (DN-Ras). RESULTS:HB-EGF expression was significantly elevated in cells expressing HCV core protein. HCV core protein activated Akt through the Ras/PI(3)K pathway by autocrine secretion of HB-EGF. Also, HCV core protein activated IKK through Ras/PI(3)K/Akt pathway by autocrine secretion of HB-EGF. As the Ras/PI(3)K/Akt pathway is critical in anti-apoptotic HB-EGF signaling, we examined the possible role of this pathway in cells expressing HCV core protein. In addition, we investigated the relationship between IB kinases (IKK) and Akt in cells expressing HCV core protein, since IKKs are known to be activated by HCV core protein and by Akt in the presence of potent mitogen. We showed that HCV core protein promoted autocrine secretion of HB-EGF and activated Akt through the Ras/PI(3)K pathway. This model indicates a new approach to mechanism of proliferation and anti-apoptosis in HCC. CONCLUSION:HCV core protein is a potent activator of mitogenic and anti-apoptotic signaling involved in hepatocarcinogenesis.
Authors: Maria Victoria Preciado; Pamela Valva; Alejandro Escobar-Gutierrez; Paula Rahal; Karina Ruiz-Tovar; Lilian Yamasaki; Carlos Vazquez-Chacon; Armando Martinez-Guarneros; Juan Carlos Carpio-Pedroza; Salvador Fonseca-Coronado; Mayra Cruz-Rivera Journal: World J Gastroenterol Date: 2014-11-21 Impact factor: 5.742