TISSUE FACTOR AND PLASMINOGEN-ACTIVATOR INHIBITOR EXPRESSION IN THE DIFFERENTIATION OF MYELOID LEUKEMIC-CELLS

Disturbances in the regulation of the balance between the fibrinolytic and procoagulant properties of leukemic cells may contribute to the coagulopathy of acute leukemia. The coagulant response to a number of stimuli is regulated by the expression of tissue factor, but the role of the plasminogen activator inhibitors, PAI-1 and PAI-2, in contributing to the net coagulant response is not known. In this study, we have examined the production of these proteins by cultured myeloid leukemic cells arrested at different stages of differentiation. Northern blot analysis showed time-dependent and differential production of mRNA for PAI-2 and tissue factor, and to a much lesser extent, PAI-1, in response to the differentiating agent, 12-phorbol-13-myristate acetate. The capacity to synthesize PAI-2 appeared to be related to the stage of myeloid cell differentiation. Examination of the gene products by immunoblot analysis demonstrated multiple forms of PAI-2 in all myeloid cells examined. In addition, a common characteristic of all the myeloid cells was the production of a high molecular weight species of tissue factor which may be a secreted form unique to leukemic cells. Taken together, the findings demonstrate that myeloid leukemic cells are capable of generating a multicomponent coagulant response.