title: 1,25-Dihydroxyvitamin D3 induces monocytic differentiation of human myeloid leukemia cells by regulating C/EBPβ expression through MEF2C.
abstract: Myogenic enhancer factor2 (Mef2) consists of a family of transcription factors involved in morphogenesis of skeletal, cardiac and smooth muscle cells. Among the four isoforms (Mef2A, 2B, 2C, and 2D), Mef2C was also found to play important roles in hematopoiesis. At myeloid progenitor level, Mef2C expression favors monocytic differentiation. Previous studies from our laboratory demonstrated that ERK5 was activated in 1,25-dihydroxyvitamin D3 (1,25D)-induced monocytic differentiation in AML cells and ERK5 activation was accompanied by increased Mef2C phosphorylation. We therefore examined the role of Mef2C in 1,25D-induced monocytic differentiation in AML cell lines (HL60, U937 and THP1) and found that knockdown of Mef2C with small interfering RNA (siRNA) significantly decreases the expression of the monocytic marker, CD14, without affecting the expression of the general myeloid marker, CD11b. CCAAT/enhancer-binding protein (C/EBP) β, which can bind to CD14 promoter and increase its transcription, has been shown to be the downstream effector of 1,25D-induced monocytic differentiation in AML cells. When Mef2C was knocked down, expression of C/EBPβ was reduced at both mRNA and protein levels. The protein expression levels of cell cycle regulators, p27(Kip1) and cyclin D1, were not affected by Mef2C knockdown, nor the monopoiesis related transcription factor, ATF2 (activating transcription factor 2). Thus, we conclude that 1,25D-induced monocytic differentiation, and CD14 expression in particular, are mediated through activation of ERK5-Mef2C-C/EBPβ signaling pathway, and that Mef2C does not seem to modulate cell cycle progression.
authors.affiliation: UH Cancer Center, Rutgers, New Jersey Medical School, 205 South Orange Ave., Newark, NJ 07103, USA.
authors.forename: Ruifang
authors.initials: R
authors.lastname: Zheng
authors.affiliation: Department of Pathology and Laboratory Medicine, Rutgers, New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103, USA.
authors.forename: Xuening
authors.initials: X
authors.lastname: Wang
authors.affiliation: UH Cancer Center, Rutgers, New Jersey Medical School, 205 South Orange Ave., Newark, NJ 07103, USA; Department of Pathology and Laboratory Medicine, Rutgers, New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103, USA. Electronic address: studzins@njms.rutgers.edu.
authors.forename: George P
authors.initials: GP
authors.lastname: Studzinski
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D064326:MEF2 Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014815:Vitamins / Q000494:pharmacology
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; C530104:CCND1 protein, human; C436291:CDKN1B protein, human; D064326:MEF2 Transcription Factors; C578040:MEF2C protein, human; D012333:RNA, Messenger; D014815:Vitamins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002117:Calcitriol
keywords: AML; C/EBBβ; CD14; Mef2C; Monocytic differentiation; Vitamin D