title: Transcriptional activation of the Cdk inhibitor p21 by vitamin D3 leads to the induced differentiation of the myelomonocytic cell line U937.
abstract: The hormonal form of vitamin D, 1,25-dihydroxyvitamin D3, acting through its cognate nuclear receptor (vitamin D3 receptor, VDR) will induce myeloid leukemic cell lines to terminally differentiate into monocytes/macrophages. Because VDR acts by transcriptionally regulating responsive genes in a ligand-dependent manner, we sought target genes of the receptor that initiate, the differentiation process in response to ligand. We screened a cDNA library prepared from the myelomonocytic U937 cell line with probes generated from either 1,25-dihydroxyvitamin D3-treated or untreated cells. We report here that a candidate clone that hybridized differentially is the Cdk inhibitor p21WAF1, CIP1. Furthermore, we show that p21 is transcriptionally induced by 1,25-dihydroxyvitamin D3 in a VDR-dependent, but not p53-dependent, manner, and we identify a functional vitamin D response element in the p21 promoter. Transient overexpression of p21 and/or the related Cdk inhibitor p27 in U937 cells in the absence of 1,25-dihydroxyvitamin D3 results in the cell-surface expression of monocyte/macrophage-specific markers, suggesting that ligand-modulated transcriptional induction of the p21 gene facilitates the induced differentiation of this monoblastic cell line. We believe that this is the first report demonstrating that the ectopic overexpression of a Cdk inhibitor such as p21 or p27 directly leads to a terminal differentiation program.
authors.affiliation: Cell Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, Cornell University, New York, New York 10021, USA.
authors.forename: M
authors.initials: M
authors.lastname: Liu
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Cohen
authors.forename: M
authors.initials: M
authors.lastname: Bommakanti
authors.forename: L P
authors.initials: LP
authors.lastname: Freedman
mesh_terms: D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins; D002460:Cell Line; D002762:Cholecalciferol / Q000494:pharmacology*; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D006410:Hematopoiesis / Q000235:genetics*; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009000:Monocytes / Q000166:cytology; D018167:Receptors, Calcitriol / Q000378:metabolism; D015533:Transcriptional Activation; D025521:Tumor Suppressor Proteins
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018950:Lipopolysaccharide Receptors; D008869:Microtubule-Associated Proteins; D018167:Receptors, Calcitriol; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002762:Cholecalciferol; D018844:Cyclin-Dependent Kinases