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Hepatitis C virus core protein activates the MAPK/ERK cascade synergistically with tumor promoter TPA, but not with epidermal growth factor or transforming growth factor α

Authors

  • Junpei Hayashi,

    1. Department of Experimental Pathology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
    2. Third Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
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  • Hiroshi Aoki,

    1. Department of Experimental Pathology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
    2. Third Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
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  • Kazunori Kajino,

    1. Department of Experimental Pathology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
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  • Mitsuhiko Moriyama,

    1. Third Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
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  • Yasuyuki Arakawa,

    1. Third Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
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  • Okio Hino

    Corresponding author
    1. Department of Experimental Pathology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
    • Chief, Department of Experimental Pathology, Cancer Institute, Japanese Foundation for Cancer Research, 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo 170-8455, Japan. fax: (81) 3-5394-3815
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Abstract

Persistent hepatitis C virus (HCV) infection is associated with the development of human hepatocellular carcinoma (HCC), although the mechanism of HCV-related hepatocarcinogenesis remains unclear. Recently, however, the close relationships between the development of HCC and the mitogen-activated protein kinase (MAPK)/extracellular signal–regulated protein kinase (ERK) cascade have been described. In the present study, we investigated the effects of HCV core protein on this MAPK/ERK cascade. HCV core protein significantly activated the MAPK/ERK cascade, including Elk1. We also examined whether HCV core protein acted synergistically along with hepatocyte mitogen-mediated MAPK/ERK activation. Interestingly, Elk-1 activities were further enhanced by the tumor promoter, 12-O-tetradecanoyl phorbol 13-acetate (TPA), but not by hepatocyte mitogens (epidermal growth factor [EGF] and transforming growth factor α [TGF-α]) in NIH3T3 cells and HepG2 cells expressing HCV core protein. Moreover, the MAPK/ERK activation by HCV core protein was blocked in the presence of the specific MEK1 inhibitor, PD98059. These results indicate that ERK activation by HCV core protein may be independent of hepatocyte mitogen-mediated signaling but synergistic with TPA, and HCV core protein may function at MEK1 or farther upstream of that component.

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