Inhibition of radiation-induced transformation of C3H/10T1/2 cells by chymotrypsin inhibitor 1 from potatoes

In this report, we have investigated whether a protease inhibitorobtained from potatoes (chymotrypsin inhibitor 1; CI-1) willinhibit carcinogen-induced transformation of C3H/10T cells.CI-1 was as effective as the soybean-derived Bowman Birk inhibitorat suppressing radiation-induced transformation of C3H/10T cells,at a concentration of 10 µg/ml. The inhibitor was nottoxic to the cells at concentrations of 0.1 –10 µg7sol;ml,the concentrations of CI-1 employed in the transformation experiments.To investigate the interaction of this inhibitor with the targetcells, binding studies were carried out. ¹²⁵I-labelled CI-1could not be displaced from C3H7sol;10T cells by co-incubationof the cells with a 5000-fold excess of unlabelled inhibitor.These results suggest that this inhibitor does not reversiblybind to specific receptor proteins on the surface of these cells.