Plasminogen activators in human gastric cancers: Correlation with DNA ploidy and immunohistochemical staining

Plasminogen activator activity was investigated in extracts of 42 surgically removed gastric carcinomas. The mean levels of total plasminogen activator (total‐PA) and urokinase‐type plasminogen activator (u‐PA) activities in the gastric carcinomas were significantly higher than those in the background normal tissues (p < 0.001). On electrophoresis, gastric cancers were found to contain u‐PA as the predominant PA, this being confirmed using zymography by direct inhibition with anti‐urokinase antibody. Assessment of the relationship between PA activity and biological behavior of gastric cancer revealed total‐PA and u‐PA levels to be significantly higher in differentiated than in undifferentiated tumors (p < 0.001), and in aneuploid than in diploid ones (p < 0.01). Immunohistochemical staining showed that the proportion of u‐PA‐positive cancer cells in the carcinoma tissues also correlated with activity as measured by the azocaseinolytic method. These findings suggest that the study of PA contents in gastric cancer, combined with a nuclear DNA ploidy and immunohistochemical analysis, might be useful for understanding the biological characteristics of the tumor.