Study of the effects of interferon a on several human hepatoma cell lines: analysis of the signalling pathway of the cytokine and of its effects on apoptosis and cell proliferation.
BACKGROUND
Interferon alpha (IFNalpha), currently used for the treatment of chronic viral hepatitis, is also known to prevent the development of hepatocellular carcinoma (HCC), the mechanism of this action being still debatable.


OBJECTIVE
To study thoroughly in human hepatoma cell lines (HHL)--Hep3B, HepG2, HuH7, SKHep1, and Chang-Liver--submitted to rhIFNalpha, the signalling pathway of IFNalpha, the binding activity of the cytokine on specific gamma-activated sequence (GAS) and interferon-stimulated regulatory element (ISRE) nuclear sequences, and its effects on apoptosis and cell proliferation.


METHODS
The behaviour of signal transducer and activator of transcription (STAT)1, STAT2, p48(IRF9) and the binding of nuclear proteins were investigated by immunoblot and electro-mobility shift assay. Expression of some IFNalpha-dependent proteins--p21/(WAF1), inducible nitric oxide synthase, IRF1 and 2--were studied by immunoblot. Apoptosis and the cell cycle were studied by morphological and biochemical methods.


RESULTS
Transduction of INFalpha was unaltered, although there were some variations in the different HHL. Nuclear protein binding to GAS or ISRE showed that ISRE was mainly involved. Apoptosis did not occur. The cell cycle was slightly modified in HuH7. Three GAS- and/or ISRE-dependent proteins increased, suggesting that IFNalpha may have some biological effects on HHL.


CONCLUSIONS
The IFNalpha signalling pathway is functional in several HHL, but the cytokine has no apoptotic effect and a moderate anti-proliferative effect. This suggests that the preventive role of IFNalpha on HCC cannot be explained by an apoptotic and/or an anti-proliferative effect, but possibly by its action on several specific nuclear sequences that protect liver cells from transformation.
Legrand
A
A
Laboratoire de Biologie Cellulaire, Unité 481 INSERM, Faculté de Médecine Xavier Bichat, Université Paris 7, France.
Vadrot
N
N
Lardeux
B
B
Bringuier
A F
AF
Guillot
R
R
Feldmann
G
G
D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha / Q000378:metabolism* / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; C494227:IRF9 protein, human; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D015534:Trans-Activators; D014157:Transcription Factors