Tumor-associated proteolysis and prognosis: new functional risk factors in gastric cancer defined by the urokinase-type plasminogen activator system

The significance of tumor-associated proteolysis as reflected by parameters of the urokinase-type plasminogen activator (uPA) system for prognosis in cancer patients has been proposed because of evidence for its central role in basic mechanisms of invasion and metastasis. The aim of the present study was to evaluate whether the expression of the uPA parameters might be of clinical value in gastric cancer as a tumor/biologically defined risk factor. In a consecutive series of 203 patients resected for primary gastric cancer, the expression of uPA, uPA-receptor (uPA-R), plasminogen activator inhibitor (PAI)-1, and PAI-2 was determined immunohistochemically. The results were classified semiquantitatively (0 to 3). Patients were followed-up prospectively for a median of 31 months (range, 9 to 56 months). Disease-free and overall survival were analyzed according to Kaplan-Meier and with univariate and multivariate Cox analyses in relation to conventional prognostic factors. Univariate analyses revealed a highly significant inverse correlation of uPA, uPA-R, and PAI-1 expression with survival time (P = .0008, P = .0002, and P = .0002, respectively), whereas PAI-2 demonstrated only a weak correlation. In multivariate analyses, PAI-1 was an independent and strong prognostic factor (P = .005; relative risk, 1.47 per staining degree; 95% confidence interval [CI], 1.31 to 1.64). In pT1/2 tumors and in Laurén's diffuse and mixed types, uPA, uPA-R, and PAI-1 added significant prognostic information. PAI-1 was also associated with survival in the subgroup of lymph node-positive patients. PAI-1, uPA, and uPA-R are new functional risk factors reflecting clinical prognosis. In particular, PAI-1 is a new independent variable for the identification of patients at high risk after tumor resection. Our results support the hypothesis that the uPA system probably is of general importance for prognosis of patients with malignant disease, indicating an individual tumor's capacity for invasion and metastasis.