Antitumoral action of bovine seminal ribonuclease

The antitumor action of bovine seminal RNAase is studied as a function of the enzyme concentration and of the number of plated cells. With polyoma transformed hamster kidney cells, a 50% inhibition of cell growth is obtained with a 10 micrograms/ml of enzyme, while at this concentration growth of normal cells is very little affected. On the other hand the higher the number of plated cells, the lesser is the effect. The enzyme is found to be very effective also on tumor cells derived from a spontaneous tumor (neuroblastoma) and on cells derived from a chemically induced tumor (glioma). Amphoterycin B which is known to alter the permeability of eukariotic cells, does not affect the resistance of normal cells to the cytotoxic action of the enzyme.