A heat stable serum factor upregulates 5-lipoxygenase activity in HL-60 cells, modulation by TNF alpha or GM-CSF.

5-Lipoxygenase (5-LO) activity in differentiating HL-60 cells was upregulated by a heat stable protein in human serum. Hematopoietic cytokines were evaluated for this effect on 5-lipoxygenase activity, none of the compounds tested could replace serum. However, TNF alpha or GM-CSF were able to augment the effect of heat treated serum, giving 5-LO activities that (per cell) were higher than for granulocytes isolated from peripheral blood. The serum factor primarily upregulated 5-LO activity. The amounts of 5-LO protein, or mRNA for 5-LO or 5-lipoxygenase activating protein (FLAP), were less affected.