5-Lipoxygenase inhibitors potentiate effects of TGF-beta 1 on the differentiation of human leukemia HL-60 cells.

It was clearly demonstrated that two structurally different inhibitors of 5-lipoxygenase (5-LPO) metabolism (leukotriene synthesis), i.e. MK-886 and esculetin, when combined with transforming growth factor-beta 1 (TGF-beta 1), significantly enhanced the differentiation but did not change proliferation (i.e. cell number and cell cycle parameters) of human leukemia HL-60 cells in vitro. Although cell morphology and measurement of cell surface antigens (CD11b, CD14, and CD66b) after 48 h of combined treatment with MK-886 and TGF-beta 1 suggested a shift of the HL-60 cell population into more differentiated stages of myelopoiesis, cells with a fully mature phenotype were not observed. The effects on differentiation were better distinguished in the functional parameters of differentiation, i.e. oxidative burst of cells as detected by chemiluminescence and the nitroblue tetrazolium reduction test. Detailed statistical analysis of these data proved a significant synergistic interaction between TGF-beta 1 and inhibitors of 5-LPO metabolism. The differentiation effects of TGF-beta 1 alone and especially of its combination with MK-886 were most pronounced when the cells were pretreated with dimethyl sulfoxide or all-trans-retinoic acid. The results imply that either the lack of 5-LPO metabolites or a certain type of mis-balance in arachidonic acid metabolism can modulate the TGF-beta 1 effect on myeloid differentiation.