The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate inhibits or enhances induction of differentiation of mouse myeloid leukemia cells depending on the type of serum in the medium.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibited the induction of both functional and morphological differentiation of mouse myeloid leukemia cells (Ml) cultured in medium containing 10% calf serum, but enhanced these inductions in medium containing 10% fetal calf serum and several inducers. These results suggest that some factor(s) in sera modifies the differentiation-inducing action of TPA on leukemia Ml cells.