Terminal differentiation of human leukemic blasts in response to 12-0-tetradecanoyl-13-phorbol acetate (TPA).

Phorbol ester, 12-0-Tetradecanoyl-13-Phorbol-Acetate (TPA), induces a terminal macrophage-like differentiation of cells from human acute myelogenous leukemia cell lines. We report here that blastoid cells obtained from acute nonlymphocytic leukemia (M1-M2) undergo differentiation-related changes characteristic of macrophage lineage after exposure to TPA. Blast cells from a patient with ANLL-M1-M2 underwent morphological, functional and histochemical changes after treatment with 1 x 10(-7) and 1 x 10(-8) M TPA. The changes included adhesion to the plastic substrate, 2-4 fold increase in the number of NBT positive cells and an increase in the number of alpha-naphthyl-acetate esterase (alpha-NAE) positive cells. These differentiation changes after treatment with TPA were followed by decrease in proliferative index and G1 cells containing high RNA as estimated by flow cytometry. Of the thirteen cases of undifferentiated or unclassified leukemias studied, two failed to respond to TPA. These data suggest that leukemic blasts retain their ability to express a variety of differentiated functions on induction by TPA. Our data gives evidence suggesting that the "switch" into the differentiation pathways occurred after inhibition of proliferation and reduction in the percentage of G1 high RNA containing cells.