Studies of the effect of 1,25-dihydroxycholecalciferol on the proliferation and differentiation of the human promyelocytic leukaemia cell line HL-60.

Abstract

Treatment of the human promyelocytic leukaemia cell line HL-60 with 1,25(OH)2D3, the active metabolite of vitamin D3, led to a dose- and time-dependent inhibition of growth and 3H-TdR incorporation at the population level. A similar effect was noted at the single cell level in clonogenic assays and autoradiographic experiments. Flow cytometry indicated that there was an arrest of cells in the G0/G1 phase of the cell cycle. Parallel to the loss of proliferative capacity 1,25(OH)2D3 induced differentiation of HL-60 into monocyte/macrophages as measured by the enzyme NSE and the macrophage membrane antigen recognised by the monoclonal antibody EB11 as well as by morphological changes. These findings reinforce the concept of concordant induction of differentiation and loss of proliferative capacity and demonstrate that the latter occurs not only at the population level but also at the single cell level in this system. In limiting dilution assays in liquid culture there was evidence for positive interactions between HL-60 cells as untreated cells gave less colonies at low dilutions than would have been expected by Poisson statistical analysis. In the presence of 10(-8) M 1,25(OH)2D3 more complex growth parameters were noted indicating the involvement of both positive and negative cellular interactions.