Biological activity of 24,24-difluoro-1 alpha, 25-dihydroxyvitamin D3 and 1 alpha, 25-dihydroxyvitamin D3-26,23-lactone in inducing differentiation of human myeloid leukemia cells.
Vitamin D compounds added to the culture medium induce differentiation of human myeloid leukemia cells (HL-60 cells) by binding to a specific cytosol receptor protein. This system provides a biologically relevant and technically simple assay to examine the relationship between molecular structure and biological activity of vitamin D compounds. Using this culture system, the biological activity of 24,24-F2-1 alpha,25(OH)2D3 and 1 alpha,25(OH)2D3-26,23-lactone was assayed. 24,24-F2-1 alpha,25(OH)2D3 was four to seven times more potent than 1 alpha,25(OH)2D3 in inducing phagocytosis and C3 rosette formation of HL-60 cells, though both compounds bound equally well to the cytosol receptor, suggesting that the defuorination at the 24-carbon position may stimulate membrane permeability of the compound. 1 alpha,25(OH)2D3-26,23-lactone, on the other hand, was only 1/200th as active as 1 alpha,25(OH)2D3. The binding affinity of the lactone for the cytosol receptor was identical with that of 1 alpha (OH)D3, suggesting that the lactone formation between the 26 and 23 positions masks the function of the 25-hydroxyl group. The binding affinity of vitamin D3 derivatives to the specific cytosol receptor of HL-60 cells was well correlated with that of intestinal cytosol protein specifically bound to 1 alpha,25(OH)2D3.
D002117:Calcitriol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007951:Leukemia, Myeloid / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects; D011485:Protein Binding; D013329:Structure-Activity Relationship
C023370:24,24-difluoro-1,25-dihydroxyvitamin D3; C026947:1,25-dihydroxyvitamin D3-26,23-lactone; D002117:Calcitriol