title: Enhancement of antiproliferative activity of 1alpha,25-dihydroxyvitamin D3 (analogs) by cytochrome P450 enzyme inhibitors is compound- and cell-type specific.
abstract: Ketoconazole (keto) or liarozole (liaro), inhibitors of the cytochrome P450 enzymes that mediate vitamin D and A hydroxylations, could potentiate the antiproliferative effects of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and its analogs. Proliferation of MCF-7 and T47-D human breast cancer cells, MG-63 human osteosarcoma cells and HL-60 human promyeloid leukemia cells was concentration dependently inhibited by 1alpha,25(OH)2D3. The vitamin D analogs KH 1060 [20-epi-22-oxa-24,26,27-trihomo-1alpha,25(OH)2D3], RO 23-6010 [16-ene-23-yne-26-trifluoro-1,25(OH)2D2D3], ZXY 835 [20-epi-23-yne-25,26-epoxy-1alpha(OH)D3], and CD 99 [11alpha-methyl-1alpha,25(OH)2D3] were 150-,58-,16- and 7-fold more potent than 1alpha,25(OH)2D3 in inhibiting the proliferation of MCF-7 cells, respectively. A similar rank order of potency was observed in other cell lines. The antiproliferative effects of the vitamin D hormone and analogs was enhanced in MCF-7 cells when coincubated with 1 microM keto (7-, 10-, 5-, 25- and 1.3-fold more potent than in the absence of keto), respectively. The antiproliferative effect was less enhanced when 1alpha,25(OH)2D3 or its analogs KH 1060, ZXY 835 and RO 23-6010 were combined with liaro (3-, 7-, 2- and 3-fold, respectively). Keto and liaro did not markedly potentiate the activity of 1alpha,25(OH)2D3 or its analogs in MG-63 or HL-60 cells. These results suggest that differences in cellular metabolism can at least partially explain the different potency of vitamin D analogs. Moreover, the metabolism of vitamin D analogs is cell-type specific.
authors.affiliation: Laboratory of Experimental Medicine and Endocrinology, Gasthuisberg, Catholic University of Leuven, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: B K
authors.initials: BK
authors.lastname: Tan
authors.forename: S
authors.initials: S
authors.lastname: Marcelis
authors.forename: A
authors.initials: A
authors.lastname: Verstuyf
authors.forename: R
authors.initials: R
authors.lastname: Bouillon
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects*; D065607:Cytochrome P-450 Enzyme Inhibitors; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007654:Ketoconazole / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D007093:Imidazoles; D002117:Calcitriol; C061121:liarozole; D007654:Ketoconazole