Interferon-α activates multiple STAT signals and downregulates c-Met in primary human hepatocytes

Background & Aims: Interferon (IFN)-alpha therapy is currently the primary choice for viral hepatitis and a promising treatment for hepatocellular carcinoma (HCC). Primary mouse and rat hepatocytes respond poorly to IFN-alpha stimulation. Thus, it is very important to examine the IFN-a signal pathway in primary human hepatocytes. Methods: The IFN-alpha-activated signals and genes in primary human hepatocytes and hepatoma cells were examined by Western blotting and microarray analyses. Results: Primary human hepatocytes respond very well to IFN-alpha stimulation as shown by activation of multiple signal transducer and activator of transcription factor (STAT) :1, 2, 3, 5, and multiple genes. The differential response to IFN-alpha stimulation in primary human and mouse hepatocytes may be caused by expression of predominant functional IFN-alpha receptor 2c (IFNAR2c) in primary human hepatocytes vs. expression of predominant inhibitory IFNAR2a in mouse hepatocytes. Microarray analyses of primary human hepatocytes show that IFN-a up-regulates about 44 genes by over 2-fold and down-regulates about 9 genes by 50%. The up-regulated genes include a variety of antiviral and tumor suppressors/proapoptotic genes. The down-regulated genes include c-myc and c-Met, the hepatocyte growth factor (HGF) receptor. Down-regulation of c-Met is caused by IFN-alpha suppression of the c-Met promoter through downregulation of Sp1 binding and results in attenuation of HGF-induced signals and cell proliferation. Conclusions: IFN-a directly targets human hepatocytes, followed by activation of multiple STATs and regulation of a wide variety of genes, which may contribute to the antiviral and antitumor activities of IFN-alpha in human liver.