title: Synergistic enhancement by 12-O-tetradecanoylphorbol-13-acetate and dibutyryl cAMP of 1alpha,25-dihydroxyvitamin D3 action in human promyelocytic leukemic HL-60 cells.
abstract: We have reported that dibutyryl cAMP (dbcAMP), an activator of cAMP-dependent protein kinase (PKA), potentiated the effects of 1alpha,25-dihydroxyvitamin D3(1,25-(OH)2D3)-induced 24-hydroxylation activity in HL-60 cells by increasing 1,25-(OH)2D3 receptor (VDR). The present study demonstrated that 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent phorbol ester, also potentiated the effect of 1,25-(OH)2D3 on HL-60 cells and that TPA and dbcAMP acted in a synergistic manner to enhance the effect of 1,25-(OH)2D3. It is interesting that TPA induced 24-hydroxylation activity far more efficiently than dbcAMP, in addition to their effects in increasing VDR. TPA increased basal levels of c-fos mRNA to the maximum by 1 h after the treatment, whereas dbcAMP failed to affect c-fos gene expression. Together with the previous data indicating the presence of AP-1-like sequence in the promoter of 24-hydroxylase gene, it was suggested that TPA potentiated the effect of 1,25-(OH)2D3 through an activation of c-fos gene expression. This notion was further supported by the data showing that TPA and dbcAMP also acted in a synergistic manner to activate c-fos gene expression. Neither TPA nor dbcAMP affected c-jun early response gene in the HL-60 clone used in the present study. The present study suggested that the activation of early c-fos response gene by TPA might be another mechanism to enhance the effect of 1,25-(OH)2D3, besides up-regulation of VDR.
authors.affiliation: Second Department of Internal Medicine, Osaka City University Medical School, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hiura
authors.forename: M
authors.initials: M
authors.lastname: Inaba
authors.forename: Y
authors.initials: Y
authors.lastname: Nishizawa
authors.forename: S
authors.initials: S
authors.lastname: Otani
authors.forename: H
authors.initials: H
authors.lastname: Morii
mesh_terms: D003994:Bucladesine / Q000494:pharmacology*; D002117:Calcitriol / Q000378:metabolism; D004357:Drug Synergism; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D016758:Genes, jun; D018922:HL-60 Cells; D006801:Humans; D006900:Hydroxylation; D018167:Receptors, Calcitriol / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D018167:Receptors, Calcitriol; C118756:dihydroxy-vitamin D3; D014807:Vitamin D; D003994:Bucladesine; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate