Induction of differentiation in chronic myelocytic leukaemia cells by the phorbolester TPA.

The mononuclear peripheral blood cells from eight patients with chronic myelocytic leukaemia (CML) were incubated in cell suspension culture in the presence of the phorbolester 12-O-tetradecanoylphorbol 13-acetate (TPA). TPA caused the treated cells to adhere and to acquire morphological and functional features characteristic of macrophage-like cells. Using isoelectric focusing distinct changes in the isoenzyme profiles of carboxylic esterase, acid phosphatase, hexosaminidase and lactate dehydrogenase were detected in the TPA-exposed cells. Besides an increase in the number and staining intensity of isoenzymes of all enzymes, TPA triggered the new expression of a monocyte-specific esterase isoenzyme isoenzyme and of the tartrate-resistant acid phosphatase isoenzyme. The latter two isoenzymes represent further parameters of the monocyte/macrophage complex. The results indicate that immature leukaemic cells arrested along the granulocytic cell axis retain the ability to transform to macrophages.