Differentiation of human myeloid leukemia cell line ML-1 induced by retinoic acid and 1,25-dihydroxyvitamin D3.

Human myeloblastic leukemia cell line ML-1 was induced to differentiate by 1 mumol/l all-trans-retinoic acid (RA) or by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). After 4-6 days of the induction several differentiation-associated characteristics were observed: (1) Ability to stimulate respiration burst in the ML-1 induced cells as detected by nitroblue tetrazolium (NBT) test or by chemiluminescence (CL). (The percentage of the NBT-positive cells was up to 99% in the RA-induced cells and up to 85% in the 1,25(OH)2D3-induced cells.) (2) Substantially higher phagocytosis of colloid iron, latex or Staphylococcus particles was found in the induced cells. (3) The 1,25(OH)2D3-induced ML-1 cells expressed the monocytic enzyme NaF-inhibitable alpha-naphthyl butyrate esterase and the surface monocytic antigen CD-14. (4) A majority of the induced cells lost the morphological features of blast cells; while the 1,25(OH)2D3-treated cells acquired certain features of monocyte-macrophage differentiation, the RA-treated cells displayed several granulocytic characteristics. (5) Cytofluorometric DNA assay after treatment of the cells with colcemid showed that the decline observed in the growth rate of the induced cells was connected with their arrest in G1/G0 phase of the cell cycle. The obtained results indicate granulocytic differentiation of the RA-induced ML-1 cells and monocyto/macrophage differentiation of the 1,25-(OH)2-D3 induced cells.