RETINOIC ACID-INDUCED HL-60 CELL-DIFFERENTIATION IS AUGMENTED BY COPPER SUPPLEMENTATION

The objective of this study was to determine how copper influences the ability of HL-60 cells to differentiate into cells of the granulocyti c lineage. We hypothesized that granulopoiesis requires copper because copper-deficient humans become neutropenic. Differentiation of HL-60 cells along the granulocytic lineage with retinoic acid was enhanced b y copper. The results showed a greater number of cells were more diffe rentiated when copper was added to the medium for 96 h. The respirator y burst activity of retinoic acid-induced cells was increased by coppe r supplementation, but intracellular superoxide anion generation was n ot affected. Supplementation with copper resulted in more cell-associa ted copper in both noninduced and induced cells; however, the induced cells accumulated three times more copper than the noninduced cells. E ven though the amount of copper associated with retinoic acid-treated cells was greater than in untreated cells, the activity of a copper-re quiring enzyme, copper/zinc superoxide dismutase, was significantly lo wer. Copper supplementation increased the activity of this enzyme in b oth retinoic acid-treated and untreated cells. Cytochrome c oxidase ac tivity was not affected by retinoic acid treatment or by copper supple mentation. Copper seems to play a specific role during the early stage s of granulocyte differentiation.