Radiation enhances the efficacy of antitumor immunotherapy with an immunocomplex of interleukin-2 and its monoclonal antibody

Abstract

Aim: An immunocomplex of interleukin-2 (IL-2) and its monoclonal antibody, S4B6 (IL-2/S4B6), contributes to antitumor immune systems. We investigated the antitumor efficacy of radiation (IR) combined with IL-2/S4B6 for osteosarcoma. Materials and Methods: LM8 mouse osteosarcoma cells were inoculated into both legs of C3H mice. For groups treated with IL-2/S4B6 alone, and those treated with IR combined with IL-2/S4B6 (COMB), IL-2/S4B6 was intraperitoneally administered on days 12 and 16 after tumor cell inoculation. For groups treated with IR alone or COMB, one side leg was irradiated at 10 Gy on day 12. Results: Although monotherapy with IL-2/S4B6 provided no significant tumor growth inhibition, combined therapy significantly reduced tumor volume in both irradiated and unirradiated tumors by 99% and 58%, respectively, compared to the no-treatment group, with significant induction of CD8+ T-cells in unirradiated tumors. Moreover, the combination therapy significantly prolonged overall survival. Conclusion: Radiation combined with IL-2/S4B6 may be a potential therapeutic option for therapy of osteosarcoma.