GENERATION OF PROCOAGULANT ACTIVITY (PCA) BY MACROPHAGE-LIKE CELLS DERIVED FROM ACUTE AND CHRONIC MYELOID-LEUKEMIA CELLS IN RESPONSE TO PHORBOL ESTERS

Normal human monocytes and macrophages, as well as in vitro human leukaemic promyelocytic cell line (HL-60) transformed into macrophage-like cells by 12-0-tetradecanoylphorbol-13-acetate (TPA) generate potent procoagulant activity (PCA) similar to tissue thromboplastin. In the present study, only mild PCA was detected in primary cultures of cells from the peripheral blood of patients with acute lymphatic leukaemia (ALL), acute myeloid leukaemia (AML) and chronic myeloid leukaemia (CML). After exposure to TPA, AML and CML cells assumed characteristics specific to monocytes and macrophages. Differentiation was associated with the generation of PCA. PCA was not found in ALL cells exposed to TPA. The PCA of TPA-induced macrophages derived from AML and CML cells resembled tissue thromboplastin and normal monocyte and macrophage PCA in several aspects: (a) accelerated clotting via the extrinsic coagulation pathway, (b) inhibition by concanavalin A and protection against lectin inhibition by methyl-alpha-D-mannopyranoside, (c) localization in the cell membrane. The capacity for PCA generation is additional evidence for the similarity between TPA-induced macrophages derived from AML and CML cells and normal human monocytes and macrophages.