Abstract
Transplantable Yoshida ascites sarcoma cells of Donryu rat were treated with plasmin, and changes in the lysosomal enzyme activities of tumor cells were investigated. Both total and free activities of three lysosomal hydrolases, acid deoxyribonuclease, β-glucuronidase, and acid phosphatase, increased in the sedimentable fraction of tumor cells at 2 hours after plasmin treatment, while the total activities of acid deoxyribonuclease and acid phosphatase increased in the unsedimentable fraction at 1 hour after Mitomycin-C treatment. When treated with plasmin and Mitomycin-C, not only the total activity in the unsedimentable fraction, but also both free and total activities in the sedimentable fraction increased as compared to those obtained by treatment with Mitomycin-C alone. In the survival experiments, survival period of tumor-bearing rats following plasmin treatment was almost the same with the control group. The survival curve of the Mitomycin-C treated group was much better than that of the control group, and the combined treatment with plasmin and Mitomycin-C brought much longer survival periods than treatment with Mitomycin-C alone. From these results it was concluded that plasmin labilized the lysosomes of tumor cells in vivo, and that the cytocidal effect of Mitomycin-C was enhanced through the increased release of lysosomal enzymes by concomitant treatment with plasmin.
