title: EGF modulates expression of STAT5 in mammary epithelial cells.
abstract: HC11 mouse mammary epithelial cells are capable of differentiating in vitro. By growing cells in EGF-containing medium, and upon confluence withdrawing EGF, these cells become competent at responding to lactogenic hormone treatment and expressing milk proteins. We found that during proliferation and at confluence STAT5A and STAT5B proteins were expressed at equal levels or with STAT5B being predominant. In competent cells, expression levels of STAT5A and STAT5B increased markedly with STAT5A now being the predominant form, an expression pattern resembling the expression patterns of STAT5 proteins seen during mammary gland differentiation in vivo. This suggests that EGF has a suppressive effect on STAT5 expression, in particular, STAT5A, which we conclude to be mediated through ras/raf/MEK/MAPK pathway and to a lesser extent through a PI3-kinase-mediated pathway. Furthermore, we also found that EGF regulated a nuclear phosphatase capable of dephosphorylating tyrosine-phosphorylated STAT5. Our data show that HC11 cells have retained the expression patterns of STAT5 proteins seen in vivo. This makes HC11 cells useful for studying molecular mechanisms regulating expression of STAT factors and their participation in differentiation processes of mammary gland.
authors.affiliation: Department of Medical Nutrition, Karolinska Institute, NOVUM, Hudddinge, S-141 86, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Petersen
authors.forename: L A
authors.initials: LA
authors.lastname: Haldosén
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division; D002457:Cell Extracts; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006728:Hormones / Q000378:metabolism / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D008894:Milk Proteins; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism
chemical_list: D002457:Cell Extracts; D004268:DNA-Binding Proteins; D006728:Hormones; D008894:Milk Proteins; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; C494080:Stat1 protein, mouse; C494087:Stat3 protein, mouse; C494093:Stat5a protein, mouse; C494096:Stat5b protein, mouse; D015534:Trans-Activators; D004815:Epidermal Growth Factor; D004247:DNA