title: Epidermal growth factor receptor-mediated activation of Stat3 during multistage skin carcinogenesis.
abstract: In the present study, we have investigated the possible role of signal transducers and activators of transcription (STATs), particularly Stat3, in mouse skin tumor promotion and multistage carcinogenesis. Stat1, Stat3, and Stat5 were activated in mouse epidermis after treatment with different classes of tumor promoters, including 12-O-tetradecanoylphorbol-13-acetate (TPA), okadaic acid, and chrysarobin. In addition, Stat1, Stat3, and Stat5 were constitutively activated in skin tumors generated by the two-stage carcinogenesis regimen using 7,12-dimethylbenz(a)anthracene as initiator and TPA as promoter. Several approaches were used to examine the possible role of epidermal growth factor receptor (EGFR) in modulating Stat3 activity during tumor promotion. In primary cultures of mouse keratinocytes, addition of exogenous EGF led to activation of Stat3 as shown by an elevation in tyrosine phosphorylation and nuclear translocation. In epidermis of transgenic mice expressing transforming growth factor alpha under control of the keratin 14 promoter, Stat3 was constitutively activated. Abrogation of EGFR function in mouse epidermis using an EGFR kinase inhibitor or by overexpressing a dominant negative form of EGFR led to a reduction in Stat3 activation in response to TPA treatment. Immunoprecipitation analyses using lysates from TPA-treated epidermis and skin papillomas showed enhanced interaction between the EGFR and Stat3. Finally, Stat3 deficiency in mouse epidermis significantly reduced the proliferative response after TPA treatment. Collectively, the current results suggest that Stat3 activation may be a critical event during mouse skin tumor promotion, possibly through regulation of keratinocyte proliferation. In addition, Stat3 activation in tumor promoter-treated epidermis and in skin papillomas may occur, at least in part, via interaction with and phosphorylation by the EGFR. Finally, constitutive activation of Stat3 in both papillomas and squamous cell carcinomas suggest a role in both the development of autonomous growth and the progression of epithelial tumors in mouse skin.
authors.affiliation: Department of Carcinogenesis, The University of Texas, M. D. Anderson Cancer Center, Science Park-Research Division, Smithville, Texas 78957, USA.
authors.forename: Keith Syson
authors.initials: KS
authors.lastname: Chan
authors.forename: Steve
authors.initials: S
authors.lastname: Carbajal
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kiguchi
authors.forename: John
authors.initials: J
authors.lastname: Clifford
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Sano
authors.forename: John
authors.initials: J
authors.lastname: DiGiovanni
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004817:Epidermis / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D066246:ErbB Receptors / Q000502:physiology*; D005260:Female; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018632:Mice, Inbred SENCAR; D008822:Mice, Transgenic; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators / Q000172:deficiency / Q000378:metabolism*
chemical_list: D002273:Carcinogens; D004268:DNA-Binding Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D013755:Tetradecanoylphorbol Acetate