Metabolism of 1alpha,25(OH)2D3 and its 20-epi analog integrates clonal expansion, maturation and apoptosis during HL-60 cell differentiation.
Induction of growth arrest and monocyte differentiation of HL-60 leukemia cells by 1alpha,25 dihydroxyvitamin D3 (1alpha,25(OH)2D3) is well established. By contrast, we have observed, that 1alpha,25(OH)2D3 and its metabolites play separate roles in clonal expansion and survival of differentiating HL-60 cells. Cells that had differentiated by 48 h (CD14 positive) grew slower than control cells, whereas CD14 negative cells were growing faster at this time point. Inhibiting 1alpha,25(OH)2D3 or 1alpha,25(OH)2-20-epi-D3 metabolism, by the 25(OH)D3-24-hydroxylase inhibitor ketoconazole, abolished hyperproliferation of CD14 negative cells. Instead, both the onset of differentiation and subsequent apoptosis were enhanced. These events were associated with immediate up-regulation of the cyclin-dependent kinase inhibitor p21(waf1) and a lack of sustained expression, respectively. Stimulation and inhibition of growth by vitamin D3-related compounds was observed to be concentration and metabolite specific. Low amounts of 1alpha,25(OH)2-20-epi-D3 and 1alpha,24,25(OH)3-20-epi-D3 stimulated HL-60 cell growth. At higher concentrations, 1alpha,25(OH)2-20-epi-D3 was a more potent inducer than 1alpha,24,25(OH)3-20-epi-D3 of HL-60 differentiation; 1alpha,25(OH)2-20-epi-24-oxo-D3 was exclusively pro-differentiative at all concentrations. 1alpha,25(OH)2-20-epi-D3 and 1alpha,24,25(OH)3-20-epi-D3 stimulated proliferation of KG-1a leukemia cells, but neither of these compounds nor 1alpha,25(OH)3-20-epi-24-oxo-D3 exerted pro-differentiative effects on these cells. These findings shed new light on the pro- and anti-proliferative effects of 1alpha,25(OH)2D3 and lead to the postulate that metabolism of 1alpha,25(OH)2D3 and its 20-epi analog regulates different subsets of genes so as to co-ordinate population expansion and the differentiation process. Furthermore, 1alpha,25(OH)2D3 metabolism and/or sensitivity to the effects of metabolites may be altered in transformed cells to derive a clonal advantage.
Campbell
M J
MJ
Department of Immunology, University of Birmingham Medical School, Edgbaston, UK. m.j.campbell@bham.ac.uk
Drayson
M T
MT
Durham
J
J
Wallington
L
L
Siu-Caldera
M L
ML
Reddy
G S
GS
Brown
G
G
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D007654:Ketoconazole / Q000494:pharmacology; D008954:Models, Biological; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors; D065668:Vitamin D3 24-Hydroxylase
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D002117:Calcitriol; D007654:Ketoconazole