title: Down-regulation of p21WAF1/CIP1 or p27Kip1 abrogates antiestrogen-mediated cell cycle arrest in human breast cancer cells.
abstract: Estrogens and antiestrogens influence the G(1) phase of the cell cycle. In MCF-7 breast cancer cells, estrogen stimulated cell cycle progression through loss of the kinase inhibitor proteins (KIPs) p27 and p21 and through G(1) cyclin-dependent kinase (cdk) activation. Treatment with antiestrogen drugs, Tamoxifen or ICI 182780, caused cell cycle arrest, with up-regulation of both p21 and p27 levels, an increase in their binding to cyclin E-cdk2, and kinase inhibition. The requirement for these KIPs in the arrests induced by estradiol depletion or by antiestrogens was investigated with antisense. Antisense inhibition of p21 or p27 expression in estradiol-depleted or antiestrogenarrested MCF-7 led to abrogation of cell cycle arrest, with loss of cyclin E-associated KIPs, activation of cyclin E-cdk2, and S phase entrance. These data demonstrate that depletion of either p21 or p27 can mimic estrogen-stimulated cell cycle activation and indicate that both of these KIPs are critical mediators of the therapeutic effects of antiestrogens in breast cancer.
authors.affiliation: Division of Cancer Biology Research, Sunnybrook and Women's College Health Science Centre, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5.
authors.forename: S
authors.initials: S
authors.lastname: Cariou
authors.forename: J C
authors.initials: JC
authors.lastname: Donovan
authors.forename: W M
authors.initials: WM
authors.lastname: Flanagan
authors.forename: A
authors.initials: A
authors.lastname: Milic
authors.forename: N
authors.initials: N
authors.lastname: Bhattacharya
authors.forename: J M
authors.initials: JM
authors.lastname: Slingerland
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins; D019927:Cyclin E / Q000037:antagonists & inhibitors; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000378:metabolism*; D017931:DNA Primers; D015536:Down-Regulation; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011960:Receptors, Estrogen / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
chemical_list: C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers; D020847:Estrogen Receptor Modulators; D008869:Microtubule-Associated Proteins; D011960:Receptors, Estrogen; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases