Inhibition by vitamin D3 of erythroid differentiation of human leukemia line cells induced by transforming growth factor beta or erythroid differentiation factor (activin A).

Erythroid differentiation of human leukemic cell lines (HEL, KU812F and K562) was induced by their treatment with transforming growth factor beta (TGF-beta) or erythroid differentiation factor (EDF/Activin A). Their erythroid differentiation was markedly inhibited by vitamin D3, dexamethasone or 12-O-tetradecanoyl-phorbol-13-acetate, which are known to induce monocytic differentiation of leukemic cells. These results suggest that inducers of monocytic differentiation may switch off cellular regulatory mechanisms for induction by TGF-beta and EDF of erythroid differentiation of leukemia cells.