title: Inhibitory effects of 1alpha,25-dihydroxyvitamin D(3) on the G(1)-S phase-controlling machinery.
abstract: The nuclear hormone 1alpha,25-dihydroxyvitamin D(3) induces cell cycle arrest, differentiation, or apoptosis depending on target cell type and state. Although the antiproliferative effect of 1alpha,25-dihydroxyvitamin D(3) has been known for years, the molecular basis of the cell cycle blockade by 1alpha,25-dihydroxyvitamin D(3) remains largely unknown. Here we have investigated the mechanisms underlying the G(1) arrest induced upon 1alpha,25-dihydroxyvitamin D(3) treatment of the human breast cancer cell line MCF-7. Twenty-four-hour exposure of exponentially growing MCF-7 cells to 1alpha,25-dihydroxyvitamin D(3) impeded proliferation by preventing S phase entry, an effect that correlated with appearance of the growth-suppressing, hypophosphorylated form of the retinoblastoma protein (pRb), and modulation of cyclin-dependent kinase (cdk) activities of cdk-4, -6, and -2. Time course immunochemical and biochemical analyses of the cellular and molecular effects of 1alpha,25-dihydroxyvitamin D(3) treatment for up to 6 d revealed a dynamic chain of events, preventing activation of cyclin D1/cdk4, and loss of cyclin D3, which collectively lead to repression of the E2F transcription factors and thus negatively affected cyclin A protein expression. While the observed 10-fold inhibition of cyclin D1/cdk 4-associated kinase activity appeared independent of cdk inhibitors, the activity of cdk 2 decreased about 20-fold, reflecting joint effects of the lower abundance of its cyclin partners and a significant increase of the cdk inhibitor p21(CIP1/WAF1), which blocked the remaining cyclin A(E)/cdk 2 complexes. Together with a rapid down-modulation of the c-Myc oncoprotein in response to 1alpha,25-dihydroxyvitamin D(3), these results demonstrate that 1alpha,25-dihydroxyvitamin D(3) inhibits cell proliferation by targeting several key regulators governing the G(1)/S transition.
authors.affiliation: Institute of Cancer Biology, The Danish Cancer Society, DK-2100 Copenhagen, Denmark.
authors.forename: S S
authors.initials: SS
authors.lastname: Jensen
authors.forename: M W
authors.initials: MW
authors.lastname: Madsen
authors.forename: J
authors.initials: J
authors.lastname: Lukas
authors.forename: L
authors.initials: L
authors.lastname: Binderup
authors.forename: J
authors.initials: J
authors.lastname: Bartek
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology; D042846:CDC2-CDC28 Kinases; D002117:Calcitriol / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D016160:Retinoblastoma Protein / Q000378:metabolism; D016196:S Phase / Q000187:drug effects*; D014407:Tumor Cells, Cultured
chemical_list: C493956:CDKN1A protein, human; D019925:Cyclin A; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D002117:Calcitriol