Inhibition of a mouse hepatoma by the alkylating agent Trenimon linked to immunoglobulins

Trenimon was conjugated in active alkylating form to rabbit anti-mouse H6 hepatoma globulin (AHG) with retention of antibody activity. H6 hepatoma-inoculated mice were given various combinations of conjugates, free Trenimon, and unconjugated immunoglobulins in daily injections for 5 days. Linkage of Trenimon to immunoglobulins reduced systemic toxicity of the drug, with comparative retention of its antitumor activity. The antitumor action of Trenimon was potentiated by AHG irrespective of whether the drug was directly linked to AHG or free AHG was administered along with Trenimon linked to normal rabbit globulin (NRG). In vitro, Trenimon bound to AHG was less inhibitory to hepatoma cells than free Trenimon, but more inhibitory than Trenimon-NRG conjugates. There was no significant endocytosis of conjugates by the hepatoma cells. This suggests that unlike free Trenimon, the target molecules of Trenimon-immunoglobulin conjugates are not intracellular DNA but are located on the surface of the hepatoma cells.