Immunological analysis of plasminogen activators from cultured human cancer cells

Immunological similarities or differences between urokinase and plasminogen activators from 9 lines of cultured human cancer cells with varying degrees of fibrinolytic activity were examined with antibodies against human urokinase. The antibodies completely inhibited the fibrinolytic activity of 4 lines of gastric cancer, 2 lines of lung cancer, 1 line of urinary bladder cancer and 1 line of renal cancer, indicating that the plasminogen activators from these cell lines were immunologically identical to urokinase. In 5 out of these cell lines, immunological identity was also confirmed by double diffusion analysis. The plasminogen activator from 1 line of lung cancer was found to be immunologically dissimilar to urokinase by a neutralization experiment and double diffusion analysis. These findings indicate that there are at least two immunologically distinguishable forms of plasminogen activators from human cancer cells.