Effects of Retinoids on Induction of Differentiation of Cultured Mouse Myeloid Leukemia Cells1

Retinoic acid, retinol, metinylacetate, and retinal induced activities of lysosomal enzymes, such as lysozyme, acid pro tease, and acid phosphatase, in mouse myeloid leukemia cells (Ml ), while the pynidyl analog of metinoicacid had no effect. Retinoic acid was the most potent inducer of lysosomal enzyme activities. The induction of lysozyme activity by retinoic acid was inhibited by treatment with pumomycin.The retinoids did not induce phagocytic and locomotive activities or morpholog ical changes in Ml cells, and they inhibited the induction of these differentiation-associated pnoperties by various inducems without inhibiting cell growth. Retinoic acid was the most potent inhibitor of induction of these differentiation-associated prop erties. The inhibitory effect of metinoicacid was found to be reversible. These results suggest that distinct mechanisms exist for control of induction of lysosomal enzyme activities and of other differentiation-associated properties of Ml cells, such as phagocytosis, morphological changes, and migration.