Inhibition of cell-surface neutral protease of Ehrlich ascites tumor cells by potassium p-(3,3-dimethyl-1-triazeno) benzoate

Ehrlich ascites tumour (EAT) cells possess a trypsin-like neutral protease on the cell surface. The antimetastatic triazene drug potassium p-(3,3-dimethyl-1-triazeno) benzoate (DM-COOK) inhibits this neutral protease, and also trypsin. Incubation of EAT cells with human erythrocytes (ratio of 1 to 5) at 37 degrees C for 18 h caused haemolysis of 28.8% of the erythrocytes. Addition of millimolar concentrations of DM-COOK to a fixed quantity (2.5 X 10(8)) of EAT cells caused a dose-related inhibition of haemolysis. DM-COOK was strongly bound to EAT cells and could not be removed by repeated washing.