Dominant negative signal transducer and activator of transcription 2 (STAT2) protein: stable expression blocks interferon alpha action in skin squamous cell carcinoma cells.
We have demonstrated previously that suppression of some or all of the IFN-stimulated gene factor 3 (ISGF-3) proteins in skin squamous cell carcinomas is an early event in squamous skin carcinogenesis. This finding led to the hypothesis that suppressed expression of ISGF-3 proteins may lead to reduced IFN responsiveness, which in turn may contribute to skin malignancy by conferring a growth and/or survival advantage. To test this hypothesis, we have developed a skin cell-based model for inhibiting the IFN-alpha signaling pathway through the forced expression of a dominant negative-acting signal transducer and activator of transcription 2 (dnSTAT2) protein. Expression of dnSTAT2 suppressed cell growth inhibition with a pharmacologically achievable concentration (100 IU/ml) of IFN-alpha in the IFN-alpha-sensitive skin squamous cell carcinoma cell line SRB12-p9. dnSTAT2 also suppressed the IFN-alpha-induced phosphorylation of signal transducer and activator of transcription (STAT) 1 and STAT2, which are early events following IFN-alpha treatment, but did not suppress the IFN-gamma-induced phosphorylation of STAT1. Finally, the dnSTAT2 protein suppressed the up-regulation of several IFN-alpha-inducible genes that were identified in this system by cDNA microarray screening. We conclude that the cell growth-inhibitory effect of IFN-alpha in skin cells requires an intact STAT2 protein and is therefore mediated by the ISGF-3 complex. These results support STAT2 as an important molecular target for skin cancer chemoprevention. Furthermore, we propose that these dnSTAT2-expressing cells provide a novel in vitro model for the study of type I IFN action in human skin cells.
Clifford
John L
JL
Department of Clinical Cancer Prevention, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA. jclifford@mdanderson.org
Yang
Xiulan
X
Walch
Eugene
E
Wang
Michael
M
Lippman
Scott M
SM
D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology; D005799:Genes, Dominant; D006801:Humans; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
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; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D015534:Trans-Activators; D014157:Transcription Factors