Fibrinolysis associated with oncogenic transformation. Partial purification and characterization of the cell factor, a plasminogen activator

The cell factor that is involved in tumor associated fibrinolysis was partially purified from the supernatant fluid of transformed chicken embryo fibroblast cultures. It is an arginine specific protease that acts as a plasminogen activator. The molecular weight is approximately 39,000, and the irreversible inhibitory effect of diisopropyl fluorophosphate suggests it is a serine enzyme. The cell factor that is detected in the supernatant culture fluid also occurs in a cell associated form in transformed but not in normal cells. This form is tightly bound in a postnuclear cellular particulate fraction and can be solubilized by sodium dodecyl sulfate or Triton X 100. The cell factor activates plasminogen by proteolytic cleavage, and it acts preferentially on one of two electrophoretic classes of plasminogen molecules found in chicken plasma.