Inhibitory Action of Transforming Growth Factor‐β on Induction of Differentiation of Myeloid Leukemia Cells

The effect of transforming growth factor‐β (TGF‐β) on induction of differentiation of mouse myeloid leukemia M1 cells was investigated. TGF‐β1 induced adherence of M1 cells to plastic dishes and inhibited their proliferation. However, it did not induce differentiation‐associated properties, such as phagocytic activity, lysozyme activity or morphological maturation. TGF‐β1 also caused dosedependent inhibition of dexamethasone‐induced differentiation of M1 cells. The inhibitory activity of TGF‐β1 was 20 times that of TGF‐β2 on M1 cells. These results suggest that TGF‐β1 inhibits proliferation and dexamethasone‐induced differentiation of M1 cells by interacting with receptors that can distinguish between TGF‐β1 and TGF‐β2. TGF‐β1 had a much lower inhibitory effect on the growth of a variant M1 cell clone, which was resistant to differentiation inducers, and it did not induce adherence of the resistant M1 cells.