1,25-dihydroxyvitamin D3 inhibits proliferation of human promyelocytic leukaemia (HL60) cells and induces monocyte-macrophage differentiation in HL60 and normal human bone marrow cells.

1,25-dihydroxyvitamin D3 induces monocyte-macrophage differentiation and inhibits proliferation of cells from the human promyelocytic leukaemia cell line HL60. Similarly human bone marrow progenitor cells differentiate preferentially along the monocyte-macrophage pathway when incubated in the presence of 1,25-dihydroxyvitamin D3. We suggest that the inhibition of growth which occurs after addition of the vitamin to HL60 might be paralleled in vivo by inhibition of proliferation of leukaemic cells; also we speculate that the vitamin may be involved in the control of both monocyte-macrophage and osteoclast production in vivo.