The effect of 1,25-dihydroxyvitamin D3 on the relationship between growth and differentiation in HL-60 cells.

Cells of the human promyelocytic leukaemia line HL-60 may be induced to differentiate along the monocytic lineage by the seco-steroid hormone 1,25-dihydroxyvitamin D3. We used fluorescence-activated cell sorting to show that, in addition to inducing differentiation, the hormone caused HL-60 cells to accumulate in G1/G0 phases of the cell cycle. We also labelled differentiating cells with both a monocyte-specific antibody and a DNA stain simultaneously. Analysis of these cell populations showed that, although cells acquired the differentiated phenotype irrespective of their position in the cell cycle, they eventually became arrested in G1/G0 as a consequence of differentiation. The normal relationship between differentiation and growth which is lost on malignant transformation is therefore restored by treatment of HL-60 cells with 1,25-dihydroxyvitamin D3.