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Persistence of plasmin‐mediated pro‐urokinase activation on the surface of human monocytoid leukemia cells In Vitro
Author(s) -
Tapiovaara Hannele,
Stephens Ross W.,
Vaheri Antti
Publication year - 1993
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910530324
Subject(s) - plasmin , urokinase , cell culture , in vitro , cell , chemistry , microbiology and biotechnology , leukemia , biochemistry , cell growth , fibronectin , biology , enzyme , immunology , genetics
Abstract Human leukemia cell lines, unlike those from adherent tumors, have been shown to continuously activate the prourokinase (pro‐u‐PA) they produce. In the present study we found that, in normal cell‐culture conditions in 10% FCS the plasminogen activation cascade works continuously on monocytoid leukemia cells, which expressed plasmin activity and active u‐PA on their cell surface. This plasmin catalyzed the conversion of the produced pro‐u‐PA to active 2‐chain urokinase (tcu‐PA), and was derived from bovine serum plasminogen the activity of cell‐bound tcu‐PA. Plasmin generation was abolished and pro‐u‐PA accumulated in cell cultures that were grown for several days, either in the presence of serum thoroughly depleted of plasminogen, or in the presence of I mM tranexamic acid. Plasmin generated on the cell surface was found to be present in 2 enzymatically active fragments, of 85,000 and M r 50,000, which were slowly released into the growth medium. These fragments could activate pro‐u‐PA serum‐free growth medium. Most of the bound plasmin could be washed off cells with 10 mM tranexamic acid, but complete removal of plasmin from the cell surface required washing of the cells with acid‐glycine pH 3.0.