High frequency of plasminogen activator secretion by malignant human lymphoid cell lines of T‐cell type origin

Diffuse defibrination is rarely observed in acute lymphoblastic leukemia (ALL). Clinical and immunologic data suggest that it is more likely to occur in T cell derived ALL. The current investigation involved the secretion of plasminogen activators (PA) of tissue type (t‐PA) or urokinase type (U‐PA) by testing su‐pernatants of 21 permanent human leukemic cell lines originating from various hematopoietic lineages and one induced lymphoblastoid cell line. (LCL) the amount of PA in each supernatant was determined by biologic and immunoenzymologic assays. The correspondance with the expected molecular weight (MW) according to the PA type was checked by zymography. PA secretion of U‐PA type was observed in the three myeloid cell lines. Except for the normal LCL, no B‐lymphoid lineage related cell lines of various levels of differentiation displayed PA secretion, whereas PA activity was observed in the supernatant of six of nine malignant T‐cell lines. The T‐leukemic cell lines CCRF CEM, KE 37, HUT 78, and HUT 102 released U‐PA‐like activity. Peer released t‐PA‐like activity and CCRF‐HSB2 supernatant showed both types of PA activity. These findings are discussed in view of the natural history of these diseases and the stage of differentiation of the cell lines.