Decrease in CuZn‐superoxide dismutase mRNA level during differentiation of human monocytic and promyelotic leukemia cells

Abstract
Change in the level of CuZn‐superoxide dismutase (SOD) mRNA was examined using a molecular probe during differentiation of human monocytic leukemia U937 cells or promyelotic leukemia HL‐60 cells induced by either 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA) or dimethylsulfoxide (DMSO). CuZn‐SOD mRNA levels were found to decrease during the course of differentiation, and this response is specific for differentiation, since the treatment of human B cell leukemia cells or normal diploid fibroblasts with TPA failed to have any effect on the level of CuZn‐SOD mRNA. The activity of CuZn‐SOD in U937 cells also decreased during differentiation, but following that of the CuZn‐SOD mRNA level. The expression of the CuZn‐SOD gene is thus concluded to diminish during the differentiation of HL‐60 and U937 cells.