Combinations of Recombinant Human Interferons and Retinoic Acid Synergistically Induce Differentiation of the Human Promyelocytic Leukemia

The human acute promyelocytic leukemia cell line HL-6O is induced to differentiate into morphologically and functionally mature monocytelike cells by incubation with a combination of 10 nmol/L retinoic acid (RA) and various concentrations of recombinant immune interferon (rIFN-”y). These induced cells show marked increases in antibody-dependent cellular cytotoxicity (ADCC). antibody-coated erythrocyte (EA) rosettes, nonspecific esterase. and 5’-nucleotidase activity. rIFN-’y alone at concentrations of 1 0 to 1.000 U/mi has essentially no effect on morphological maturation. nitroblue tetrazolium reduction, and immunophagocytosis. However, rIFN-’y at these concentrations increases EA rosetting in a concentration-dependent manner that is not affected by 10 nmol/i RA. At a concentration of 1,000