title: Role of estrogen receptor (ER) alpha in insulin-like growth factor (IGF)-I-induced responses in MCF-7 breast cancer cells.
abstract: Insulin-like growth factor-I (IGF-I) is a mitogenic polypeptide that induces proliferation of MCF-7 breast cancer cells, and cotreatment with the phosphoinositide 3-kinase (PI3-K) inhibitor LY294002 and the antiestrogen ICI 182780 inhibits IGF-I-induced growth. The role of estrogen receptor alpha (ERalpha) in mediating responses induced by IGF-I was investigated in cells transfected with small inhibitory RNA for ERalpha (iERalpha). The results showed that IGF-I-dependent phosphorylation of Akt and mitogen-activated protein kinase, induction of G(1)-S-phase progression and enhanced expression of cyclin D1 and cyclin E were dependent on ERalpha. Moreover, these same IGF-I-induced responses were also inhibited by the antiestrogen ICI 182780 and this was in contrast to a previous report suggesting that ICI 182780 did not affect IGF-I-dependent activation of PI3-K or induction of cyclin D1 expression. ICI 182780 exhibits antimitogenic activity and iERalpha inhibits G(1)-S-phase progression and proliferation of MCF-7 cells treated with IGF-I, suggesting that the effects of the antiestrogen are primarily related to downregulation of ERalpha.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, 77843, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: R
authors.initials: R
authors.lastname: Burghardt
authors.forename: R
authors.initials: R
authors.lastname: Smith
authors.forename: S H
authors.initials: SH
authors.lastname: Safe
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016213:Cyclins / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008934:Mitogens / Q000494:pharmacology; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection
chemical_list: D016213:Cyclins; D020847:Estrogen Receptor Modulators; D047628:Estrogen Receptor alpha; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D008934:Mitogens; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D000077267:Fulvestrant; D004958:Estradiol; D007334:Insulin-Like Growth Factor I