In vitro and in vivo cytotoxicity of adriamycin and daunomycin for murine macrophages.

In virto exposure of murine lymphoma cells to adriamycin and daunomycin (DM) for 24 hr resulted in comparable cytotoxicity as assessed by viable cell counts and inhibition of DNA synthesis. The spontaneous DNA synthesis of spleen lymphocytes in vitro was also equally affected by the two agents. However, when the in vitro effects of the two drugs on macrophage monolayers were investigated, DM was found to be at least four times more toxic than AM. In vivo-administered DM was more suppressive than AM of Corynebacterium parvum-induced spleen macrophage cytotoxicity. The fact that DM is less effective than AM as a cancer chemotherapeutic agent in vivo may actually be due to the greater destruction of macrophages by DM and a resultant reduction in the contribution of host immunity to the anti-tumor action.