title: Role of vitamin D3 receptor in the synergistic differentiation of WEHI-3B leukemia cells by vitamin D3 and retinoic acid.
abstract: WEHI-3B D- cells differentiate in response to 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) but not to all-trans-retinoic acid (RA) or other inducing agents. Combinations of RA with 1,25-(OH)2D3 interact to produce synergistic differentiation of WEHI-3B D- cells. To determine factors involved in the synergistic interaction, expression of the 1,25-(OH)2D3 receptor (VDR) and retinoid receptors, RARalpha and RXRalpha, was measured. No VDR was detected in untreated WEHI-3B D- cells; however, RA and 1,25-(OH)2D3 when used as single agents caused a slight induction of the VDR and in combination produced a marked increase in the VDR. In contrast, no changes in RARalpha and RXRalpha were initiated by these compounds. An RAR-selective agonist combined with 1,25-(OH)2D3 produced synergistic differentiation of WEHI-3B D- cells, whereas an RXR-selective agonist did not. To gain information on the role of the VDR in the synergistic interaction, the VDR gene was transferred into WEHI-3B D+ cells, in which no VDR was detected and no synergism was produced. Expression of the VDR conferred differentiation responsiveness to 1,25-(OH)2D3 in WEHI-3B D+ cells. These findings suggest that (a) induction of VDR expression is a key component in the synergistic differentiation induced by 1,25-(OH)2D3 and RA and (b) RAR and not RXR must be activated for enhanced induction of the VDR and for the synergistic differentiation produced by RA and 1, 25-(OH)2D3.
authors.affiliation: Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut, 06520, USA.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: R A
authors.initials: RA
authors.lastname: Finch
authors.forename: A C
authors.initials: AC
authors.lastname: Sartorelli
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D007938:Leukemia / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D018167:Receptors, Calcitriol / Q000502:physiology*; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D004338:Drug Combinations; D018167:Receptors, Calcitriol; D014212:Tretinoin