Combined effects of immunity and antitumor drugs against cancer. I. In vivo studies with cis-diamminedichloroplatinum and cyclophosphamide in mouse models.

Cis-diamminedichloroplatinum (DDP) or cyclophosphamide (Cy) were given to mice bearing L1210 or LSTRA leukemia in H-2 compatible tumor-host combinations. Little anti-tumor activity was afforded by DDP against both leukemias inoculated in entirely histocompatible recipients. However, when the drug was given to mice incompatible for minor histocompatibility loci (MMHL) with the tumor, the efficacy of the treatment was markedly augmented and a substantial number of long-term survivors was found among BALB/c mice inoculated with L1210 cells. On the other hand, no difference in survival times was found between histocompatible or allogeneic mice inoculated with both leukemias, not subjected to chemotherapy. The LSTRA model was much less susceptible to this type of DDP-mediated antineoplastic immuno-chemotherapy synergism. Moreover no synergistic effects with allograft reaction were detected with Cy in both L1210 and LSTRA models, although Cy was markedly more active than DDP against leukemic cells in histocompatible recipients.