title: Induction of monocytic differentiation of HL-60 cells by 1,25-dihydroxyvitamin D analogs.
abstract: 1,25-Dihydroxyvitamin D3, the hormonal form of vitamin D, induces differentiation of HL-60 human promyelocytes into monocyte-like cells in vitro. We assessed the relative activity of 30 analogs of 1,25-dihydroxyvitamin D3 in inducing development of monocytic markers in HL-60 cells. The three differentiation markers assayed were nonspecific acid esterase activity, nitro blue tetrazolium reducing activity, and phagocytic capacity. Of the known metabolites of vitamin D, 1,25-dihydroxyvitamin D3 is the most active; 50% of the cells exhibit the mature phenotype following a 4-day treatment with 10(-8) M 1,25-dihydroxyvitamin D3. Removal of either the C-1 or C-25-hydroxyl group reduces activity by 2 orders of magnitude, while epimerization of the 1 alpha- to 1 beta-hydroxyl group virtually abolishes activity. Elongation of the steroidal side chain of 1,25-dihydroxyvitamin D3 by addition of one carbon at C-24 or C-26 improves the potency by an order of magnitude. Truncation of the steroidal side chain leads to a 10-fold reduction in activity for each carbon removed. Elimination of the C-26 and C-27 methyl groups reduces activity 100-fold. Analogs with short aliphatic side chains as 1 alpha-hydroxyhomo- and bishomopregnacholecalciferol have surprisingly high activity, being only 20-fold less potent than the natural hormone. The activity of most analogs in the HL-60 system parallels their known relative affinities for the well characterized 1,25-dihydroxyvitamin D3 receptor in chick intestine, providing further evidence that this function of 1,25-dihydroxyvitamin D3 is receptor mediated.
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D043182:Carboxylesterase; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D006801:Humans; D015470:Leukemia, Myeloid, Acute; D009000:Monocytes / Q000166:cytology; D010587:Phagocytosis / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D002265:Carboxylic Ester Hydrolases; D043182:Carboxylesterase; D002117:Calcitriol