Synergy between low-dose chemotherapy and immunotherapy in mouse L1210 leukemia.

A high dose of 4 mg/kg of daunorubicin (DAU) given in combination with immunostimulation by the P40 immunomodulatory fraction of Corynebacterium granulosum and glutaraldehyde (GA)-treated tumor cells coupled with tetanus toxoid (P40 + GA-L1210-Tet) was more effective than DAU alone for treatment of L1210 mouse leukemia. A combination of low doses of DAU (0.0625-0.25 mg/kg) and P40 + GA-L1210-Tet was more effective than either P40 + GA-L1210-Tet or DAU alone. The cured mice were resistant to challenge with a high tumorigenic dose of L1210 tumor cells. A combination of various doses of mitomycin (1-4 mg/kg) with P40 + GA-L1210-Tet was more effective than mitomycin alone and was at least as effective as P40 + GA-L1210-Tet alone. Administration of DAU (0.5-4 mg/kg) to noninoculated C57BL/6 X DBA/2 mice resulted in increase of stimulation in vitro of collected spleen cells by mitogens.