In vitro studies on selective inhibition of tumor cell growth by seminal ribonuclease

The effect on cell growth of bovine seminal RNase has been tested on cells cultured in vitro. A selective inhibition of growth has been observed on tumor cells as compared to normal cells using several virus-transformed cell lines and a neuroblastoma line. The different cellular response of virus-transformed cells does not appear to depend on a differential permeability to the protein of transformed cells with respect to nontransformed ones. The selective cytotoxic action of seminal RNase on tumor cell growth was also compared with the action of other structurally related RNases and of various RNase derivatives prepared by specific chemical modifications. The results indicate that the protein dimeric structure and its enzymic activity are essential requirements for its action.