Abstract
Double-stranded RNA-activated protein kinase R (PKR) is known to be upregulated by hepatitis C virus (HCV) and overexpressed in hepatocellular carcinoma (HCC). However, the precise roles of PKR in HCC with HCV infection remain unclear. Two HCV replicating cell lines (JFH-1 and H77s), generated by transfection of Huh7.5.1 cells, were used for experiments reported here. PKR expression was modulated with siRNA and a PKR expression plasmid, and cancer-related genes were assessed by real-time PCR and Western blotting; cell lines were further analyzed using a proliferation assay. Modulation of genes by PKR was also assessed in 34 human HCC specimens. Parallel changes in c-Fos and c-Jun gene expression with PKR were observed. Levels of phosphorylated c-Fos and c-Jun were upregulated by an increase of PKR, and were related to levels of phosphorylated JNK1 and Erk1/2. DNA binding activities of c-Fos and c-Jun also correlated with PKR expression, and cell proliferation was dependent on PKR-modulated c-Fos and c-Jun expression. Coordinate expression of c-Jun and PKR was confirmed in human HCC specimens with HCV infection. PKR upregulated c-Fos and c-Jun activities through activation of Erk1/2 and JNK1, respectively. These modulations resulted in HCC cell proliferation with HCV infection. These findings suggest that PKR-related proliferation pathways could be an attractive therapeutic target.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adult
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Aged
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Aged, 80 and over
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Carcinoma, Hepatocellular / genetics*
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Carcinoma, Hepatocellular / metabolism
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Carcinoma, Hepatocellular / pathology
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Carcinoma, Hepatocellular / virology
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Cell Line, Tumor
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Cell Proliferation
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Female
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Gene Expression Regulation, Neoplastic*
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Hepacivirus / physiology
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Hepatitis C / genetics*
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Hepatitis C / metabolism
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Hepatitis C / pathology
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Hepatitis C / virology
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Host-Pathogen Interactions
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Humans
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Liver Neoplasms / genetics*
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Liver Neoplasms / metabolism
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Liver Neoplasms / pathology
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Liver Neoplasms / virology
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Male
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Middle Aged
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Mitogen-Activated Protein Kinase 1 / genetics
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3 / genetics
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Mitogen-Activated Protein Kinase 3 / metabolism
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Phosphorylation
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Proto-Oncogene Proteins c-fos / genetics*
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Proto-Oncogene Proteins c-fos / metabolism
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Proto-Oncogene Proteins c-jun / genetics*
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Proto-Oncogene Proteins c-jun / metabolism
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Signal Transduction
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eIF-2 Kinase / genetics*
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eIF-2 Kinase / metabolism
Substances
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Proto-Oncogene Proteins c-fos
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Proto-Oncogene Proteins c-jun
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eIF-2 Kinase
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MAPK1 protein, human
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
Grants and funding
This work was supported in part by the following: a Grant-in-Aid for Scientific Research, Japan Society for the Promotion of Science, KAKENHI 24590980 (to Y.H.); the Program for Enhancing Systematic Education in Graduate School from the Ministry of Education, Culture, Sports, Science and Technology, Japan (to T.W.); and by a Grant-in-Aid for Scientific Research and Development from the Japanese Ministry of Health, Labor and Welfare, Japan (to Y.H.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.