Effects of 1,25-dihydroxyvitamin D3 analogue 1,24(OH)2-22-ene-24-cyclopropyl D3 on proliferation and differentiation of a human megakaryoblastic leukemia cell line.

The novel analogue of 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3), 1,24(OH)2-22-ene-24-cyclopropyl D3 (calcipotriol, MC903), exhibits similar effects on cell proliferation and cell differentiation in a newly established human megakaryoblastic leukemia cell line (HIMeg). MC903 was found to inhibit cell proliferation and induce cell differentiation in a liquid culture system at concentrations comparable to those of 1,25(OH)2 D3. Colony formation assay showed that MC903 or 1,25(OH)2 D3 markedly diminished the colony-forming ability of HIMeg cells at concentrations of 10(-6) M to 10(-10) M. Cell cycle analysis demonstrated that, as seen with 1,25(OH)2 D3, MC903 also altered the cell cycle distribution; the fraction of cells in G0 + G1 increased while those in S and G2 + M decreased. It can be concluded from these findings that 1,25(OH)2 D3 and its analogue MC903 have approximately equipotent effects on cells of megakaryoblastic lineage and are potentially useful in studying the cellular processes that are responsible for megakaryocytopoiesis.