Plasminogen activator activity in bone metastases of prostatic carcinomas as compared to primary tumors.

The plasminogen activator content of extracts of 14 prostatic carcinomas and the respective bone metastases was determined and found to be at an average 1.5 times higher in the extracts from bone metastases than in the primary tumors. Furthermore, the relative contribution of the two known types of plasminogen activators, urokinase-type (u-PA) and tissue-type (t-PA), was evaluated using specific antibodies. About 70% of the plasminogen activator activity in the primary tumors was inhibited by anti-urokinase IgG, whereas the same antibody nearly completely inhibited the plasminogen activator activity in extracts from bone metastases. Using antibodies against t-PA about 30% of the plasminogen activator activity could be quenched in extracts of primary tumors but less than 10% in extracts of bone metastases. Further studies revealed that the increased amount of u-PA in extracts of bone metastases is not caused by different extractability but is also reflected by a relative increase in the amount of u-PA demonstrable by immune histochemical techniques using anti-urokinase IgG. Upon purification, the predominant plasminogen activator from extracts of bone metastases could also be identified physicochemically as urokinase.