title: Modulation of cell cycle control by vitamin D3 and its analogue, EB1089, in human breast cancer cells.
abstract: Examination of a panel of ER positive breast cancer cell lines showed that they were differentially growth inhibited by vitamin D3 and its analogue EB1089. EB1089 treatment of the breast cancer cell lines MCF-7 E, BT20, T47D, and ZR75 demonstrated a correlation between a reduction in Cdk2 kinase activity towards phosphorylation of histone H1 and a decrease in DNA synthesis, while no modulation of Cdk2 activity was observed in the vitamin D3 and EB1089 resistant cell line MCF-7 L. This was accompanied by a time dependent decrease in the percentage of S phase cells in the responsive lines. Characterization of the expression levels of Cdk2 and its related cell cycle proteins in MCF-7 E cells showed that after EB1089 treatment, there was a concentration and time dependent up-regulation of p21 as well as a decrease in cyclin A proteins. Paradoxically, cyclin E levels were increased as a function of treatment. Analysis of cyclin-Cdk2-Cdki complex formation showed that in EB1089 treated MCF-7 E cells, Cdk2, cyclin A and cyclin E immunoprecipitates contained an increased abundance of p21. In contrast to MCF-7 E cells, increases in both p21 and p27 as well as their complex formation with Cdk2 were observed in BT20 and ZR75 cells. These findings indicate that up-regulation of p21 as well as p27 in some cell types may account for the inactivation of Cdk2 activity and a G1 block of the cell cycle following EB1089 treatment.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Ohio, Toledo 43699-0008, USA.
authors.forename: G
authors.initials: G
authors.lastname: Wu
authors.forename: R S
authors.initials: RS
authors.lastname: Fan
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: T C
authors.initials: TC
authors.lastname: Ko
authors.forename: M G
authors.initials: MG
authors.lastname: Brattain
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms; D042846:CDC2-CDC28 Kinases; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002762:Cholecalciferol / Q000494:pharmacology*; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004273:DNA, Neoplasm / Q000096:biosynthesis; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation
chemical_list: D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004273:DNA, Neoplasm; D008869:Microtubule-Associated Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002762:Cholecalciferol; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D002117:Calcitriol; C078903:seocalcitol