This paper reports on the antitumor activity of
BS RNase on human
melanoma and mouse
seminoma. Human
melanoma cells established in culture were extremely susceptible to
BS RNase, administered in concentrations ranging from 1-100 microg/ml. Concentrations of
BS RNase over 10 microg/ml caused complete inhibition of cell growth. Bovine
pancreatic ribonuclease (
RNase A), a prototype of the
ribonuclease superfamily, did not exert any effect under these conditions. Based on our previous results, athymic mice bearing human
melanoma or mouse
seminoma were treated with intratumoral administration of
BS RNase (12.5 mg/kg b.w.). This dose was injected for five consecutive days excluding weekends. The intratumoral administration of
BS RNase to nude mice bearing human
melanoma showed a significant antitumor effect. There were no
tumors seen in eighty percent of mice treated for three weeks, and
tumors in the other mice diminished significantly. After some delay the
tumors started to regrow. Prolonging of the treatment to five weeks had a similar effect. The effect of
BS RNase on mouse
seminoma was well pronounced. Five to seven doses of
BS RNase were sufficient to eliminate
tumors in all treated mice. However, as in the previous experiment, the growth of
tumor tissue later reappeared.