LOCATION OF PLASMINOGEN-ACTIVATOR (PA) AND PA INHIBITOR IN HUMAN COLORECTAL ADENOCARCINOMAS

Both the coagulation and fibrinolytic cascades generate proteolytic en zymes which appear to be essential for tumor invasion. In the present investigation adenocarcinomas and normal colon from 14 patients with c olorectal cancer were studied by immunohistochemistry. The most striki ng observation was an enrichment of plasminogen activator inhibitor in the tumor tissue, whereas no such immunoreactivity was detected in th e biopsies of normal colon. The tumor-host interface was characterized by a massive accumulation of inflammatory cells, macrophages and T ly mphocytes. In this area fibrin(ogen) immunoreactivity as a sign of loc al activation of the coagulation cascade was also seen. The transition zone between the tumor and normal tissue was furthermore characterize d by a marked enrichment of urokinase plasminogen activator immunoreac tivity. The study strongly indicates that proteases and inhibitors of the fibrinolytic system may be of great importance in tumor invasion.