Successful chemoimmunotherapy of murine L1210 lymphatic leukemia with cyclophosphamide and mafosfamide-treated leukemia cells.

Balb/c x DBA/2 F1 mice (CD2F1 mice) bearing L1210 lymphatic (10 L1210 cells i.p. injected on day 0) were subjected to chemoimmunotherapy. They received 100 mg/kg of cyclophosphamide i.p. on day +8 and 10(6) or 10(7) immunogenic L1210 cells treated in vitro with mafosfamide - ASTA Z7654 (L1210-Maf cells) i.p. or i.p. + s.c. on days 0, +3, +6, +9, +12 after the leukemia implantation. About 30% of leukemia-bearing mice receiving cyclophosphamide and L1210-Maf cells after L1210 inoculation were able to reject the leukemia (as compared with 0% after injection of L1210-Maf cells only or 5% after cyclophosphamide administration). Better results (54% of cured mice) were obtained if 10(7) L1210-Maf cells were injected i.p. +s.c. beside cyclophosphamide. Biological response modifiers (BRM's): levamisole, BCG, bestatin did not improve these results in the doses used in the experiment. Augmentation of anti-L1210 therapeutic response is dependent on the administration of cyclophosphamide and L1210-Maf cels. Cyclophosphamide not only reduces the tumor burden but probably can potentiate the L1210-Maf dependent antitumor immunity as well.