Antagonistic action of novel 1α,25-dihydroxyvitamin D3-26,23-lactone analogs on differentiation of human leukemia cells (HL-60) induced by 1α,25-dihydroxyvitamin D3

We examined the effects of two novel 1 alpha,25-dihydroxyvitamin D-3-26,23-lactone (1 alpha,25-lactone) analogues on human promyelocytic leukemia cell (HL-60) differentiation using the evaluation system of the vitamin D nuclear receptor (VDR)/vitamin D-responsive element (DRE)-mediated genomic action stimulated by 1 alpha,25-dihydroxyvitamin D-3 (1 alpha,25(OH)(2)D-3) and its analogues. We found that the 1 alpha,25-lactone analogues (23S)-25-dehydro-1 alpha-hydroxyvitamin-D-3-26,23-lactone (TEI-9647), and (23R)-25-dehydro-1 alpha-hydroxyvitamin-D3-26,23-lactone (TEI-9648) bound much more strongly to the VDR than the natural (23S,25R)-1 alpha,25(OH)(2)D-3-26,23-lactone, but did not induce cell differentiation even at high concentrations (10(-6) M). Intriguingly, the differentiation of HL-60 cells induced by 1 alpha,25(OH)(2)D-3 was inhibited by either TEI-9647 or TEI-9648 but not by the natural lactone. In contrast, retinoic acid or 12-O-tetradecanoylphorbol-13- acetate-induced HL-60 cell differentiation was not blocked by TEI-9647 or TEI-9648. In separate studies, TEI-9647 (10(-7) M) was found to be an effective antagonist of both 1 alpha,25(OH)(2)D-3 (10(-8) M) mediated induction of p21(WAF1,CIP1) in HL-60 cells and activation of the luciferase reporter assay in COS-7 cells transfected with cDNA containing the DRE of the rat 25(OH)D-3-24-hydroxylase gene and cDNA of the human VDR. Collectively the results strongly suggest that our novel 1 alpha,25-1actone analogues, TEI-9647 and TEI-9648, are specific antagonists of 1 alpha,25(OH)(2)D-3 action, specifically VDR/DRE-mediated genomic action. As such, they represent the first examples of antagonists, which act on the nuclear VDR.