Interferon (IFN)-cx 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-a stimulation. Thus, it is very important to examine the IFN-ca signal pathway in primary human hepatocytes.

The IFN-α-activated signals and genes in primary human hepatocytes and hepatoma cells were examined by Western blotting and microarray analyses. BARRESULTS:: Primary human hepatocytes respond very well to IFN-α 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-a stimulation in primary human and mouse hepatocytes may be caused by expression of predominant functional IFN-a 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-α 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-α suppression of the c-Met promoter through down-regulation of Sp1 binding and results in attenuation of HGF-induced signals and cell proliferation.

IFN-α 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-α in human liver.