[The role of TNF-alpha in the growth and differentiation of U937 cells induced by PMA and IFN-gamma].

The effects of PMA and IFN-gamma on regulation of growth and differentiation of human monoblastic leukemic cell U937 were examined. U937 cells were stimulated by different concentrations of PMA and IFN-gamma respectively and NBT reduction assay was used to detect the differentiation of the cells. The results showed that both PMA and IFN-gamma dose-dependently induced differentiation of U937 cells into mature macrophage-like cells. The data also revealed a time-course response in the differentiation induction. Moreover, the U937 cell growth was significantly inhibited by the treatment of PMA and IFN-gamma. These results suggest that PMA and IFN-gamma coupled the regulation of U937 cell growth and differentiation. It was found that tumor necrosis factor-alpha (TNF-alpha) was expressed by the stimulated U937 cells. The specific monoclonal antibody against TNF-alpha diminished the effects of PMA and IFN-gamma on the growth and differentiation of U937 cells. Thus the endogenous TNF-alpha may involved in the mechanism of the effects of PMA and IFN-gamma on the differentiation of U937 cells. The regulatory action of the endogenous TNF-alpha on U937 cells was not due to its cytotoxic effect.