title: 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) modulates lactogenic hormone-mediated differentiation and gene expression in HC11 mouse mammary epithelial cells.
abstract: 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mammary gland carcinogen in cooked meat. Using the HC11 mouse mammary epithelial cell line, a well-characterized model for hormone-mediated differentiation, we examined whether PhIP altered the expression of genes regulated by lactogenic hormones dexamethasone, insulin, and prolactin (DIP). When HC11-Lux cells (stably transfected with a beta-casein promoter luciferase construct) were cultured in DIP-containing medium, PhIP (100 microM) enhanced luciferase activity 11-fold over that observed in DIP medium alone. The effect of PhIP on augmenting luciferase activity was observed only when lactogenic hormones were included in the medium. Expression of the endogenous beta-casein gene was also higher in HC11 cells treated with PhIP in hormone-enriched medium. With the increased expression of beta-casein gene, the level of phospho-signal transducer and activator of transcription 5A (phospho-STAT5A), the transcription factor regulating beta-casein gene expression, was elevated in PhIP-exposed HC11 cells. AG490, a Janus kinase 2 (JAK2)-specific inhibitor, blocked the effect of PhIP on beta-casein gene expression. PhIP-treated cells also showed higher expression of Bcl-2 and lower expression of Bax, consistent with a possible antiapoptotic action of PhIP. The findings indicate that PhIP modulates lactogenic hormone-mediated gene expression in mammary epithelial cells, apparently via enhanced phosphorylation of STAT5A. The findings have implications for a novel mechanism of action of the mammary gland carcinogen PhIP.
authors.affiliation: Chemical Carcinogenesis Section, Laboratory of Experimental Carcinogenesis, Division of Basic Sciences, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
authors.forename: L
authors.initials: L
authors.lastname: Shan
authors.forename: S A
authors.initials: SA
authors.lastname: Rouhani
authors.forename: H A
authors.initials: HA
authors.lastname: Schut
authors.forename: E G
authors.initials: EG
authors.lastname: Snyderwine
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002273:Carcinogens; D002364:Caseins / Q000378:metabolism; D018736:DNA Adducts / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D007093:Imidazoles; D007150:Immunohistochemistry; D053614:Janus Kinase 2; D008156:Luciferases / Q000378:metabolism; D015674:Mammary Neoplasms, Animal / Q000378:metabolism*; D051379:Mice; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D011388:Prolactin / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D020032:Tyrphostins / Q000494:pharmacology; D051028:bcl-2-Associated X Protein
chemical_list: C494827:Bax protein, mouse; D002273:Carcinogens; D002364:Caseins; D018736:DNA Adducts; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050799:STAT5 Transcription Factor; C494093:Stat5a protein, mouse; D015534:Trans-Activators; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D051028:bcl-2-Associated X Protein; D011388:Prolactin; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D020928:Mitogen-Activated Protein Kinases