Acute undifferentiated leukemia: induction of partial differentiation by phorbol ester.

Expression of lineage-associated surface antigens, was studied in 7 patients with acute undifferentiated leukemia (AUL), 3 patients with acute myeloid leukemia (AML), 4 patients with acute lymphoid leukemia (ALL) and bone marrow from 2 healthy donors, before and after exposure to the differentiating agent 12-O-tetradecanoylphorbol-13-acetate (TPA). The surface antigens were identified by monoclonal antibodies (My4, My8, My9, MO1, B1, CALLA, T11) and formation of EA and EAC rosettes. Adherence to plastic was also assessed. Cells from the AML patients responded to TPA with an increase in myeloid antigen positive cells and other markers of differentiation. Four of the AUL patients showed, also, a large increase in the fraction of cells expressing one or more myeloid markers, in correlation with formation of EAC rosettes. In contrast, the percentage of cells expressing myeloid antigens, did not increase in the 4 ALL patients, or in the normal donors. These findings confirm the heterogeneity of undifferentiated leukemias, and suggest the hypothesis that some AUL's can be induced to express markers of early myeloid cells.