Interferon-alpha activates multiple STAT signals and down-regulates c-Met in primary human hepatocytes.
OBJECTIVE
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-alpha 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-alpha 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 down-regulation of Sp1 binding and results in attenuation of HGF-induced signals and cell proliferation.


CONCLUSIONS
IFN-alpha 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.
Radaeva
Svetlana
S
Section on Liver Biology, Laboratory of Physiologic Studies, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892, USA.
Jaruga
Barbara
B
Hong
Feng
F
Kim
Won-Ho
WH
Fan
Saijun
S
Cai
Hongbo
H
Strom
Stephen
S
Liu
Youhua
Y
El-Assal
Osama
O
Gao
Bin
B
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D002455:Cell Division / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology*; D016898:Interferon-alpha / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D008113:Liver Neoplasms; D008297:Male; D008565:Membrane Proteins; D008894:Milk Proteins; D020411:Oligonucleotide Array Sequence Analysis; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000235:genetics; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects*; D012995:Solubility; D016329:Sp1 Transcription Factor / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects
D000998:Antiviral Agents; D004268:DNA-Binding Proteins; D007155:Immunologic Factors; D016898:Interferon-alpha; D008565:Membrane Proteins; D008894:Milk Proteins; D017471:Receptors, Interferon; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D016329:Sp1 Transcription Factor; C494081:Stat1 protein, rat; C494088:Stat3 protein, rat; D015534:Trans-Activators; D053633:Receptor, Interferon alpha-beta; D007371:Interferon-gamma; D019859:Proto-Oncogene Proteins c-met