Adriamycin-induced antitumor response in lethally irradiated mice.

Lethally irradiated mice pretreated with a wide range of Adriamycin (ADM) doses were tested for their in vivo antitumor response against transplanted lymphoma cells. Tumor growth, as assessed by 125IUdR uptake, was markedly impaired by treatment with ADM by a variety of different administration schedules. This ADM-induced antitumor response was largely dose-dependent, occurred regardless of route of administration, and was detectable as late as 15-30 days following drug treatment. No genetic restriction could be found to regulate the development of this response, since tumor growth inhibition occurred in syngeneic as well as allogeneic tumor-host combinations. ADM-induced antitumor response did not appear to be due to direct antitumor action by the drug, but rather to some interaction with host immune mechanisms. Antimacrophage agents, such as silica or carrageenan, abrogated the response. The possible implication of different cells as effectors of this response is discussed.