Interferon inducer, polyriboguanylic.polyribocytidylic acid, inhibits experimental hepatic metastases in mice

The antitumour activity of an interferon inducer, the double-stranded complex of polyriboguanylic.polyribocytidylic acid was studied on murine lymphosarcoma LS/BL. The antitumour effect was determined with the aid of an experimental liver-colony model and compared to that exhibited by another synthetic RNA, polyriboinosinic.polyribocytidylic acid. We found that both polynucleotide complexes decreased the number of liver colonies and prolonged the survival of the tumour-bearing mice. This effect was only observed if the complexes were applied in an appropriate dose schedule which included the administration of the drug prior to tumour cell inoculation and subsequent continuous treatment. We have also verified that the polynucleotide complexes did not exert their antitumour effect by a direct action on tumour cells.