In situ tumor vaccination by combining local radiation and tumor-specific antibody or immunocytokine treatments.

In situ tumor vaccination by combining local radiation and tumor-specific antibody or immunocytokine treatments.

Cancer Res. 2016 May 6;

Authors: Morris ZS, Guy EI, Francis DM, Gressett MM, Werner LR, Carmichael L, Yang RK, Armstrong EA, Huang S, Navid F, Gillies SD, Korman AJ, Hank JA, Rakhmilevich AL, Harari PM, Sondel PM

Abstract
Interest in combining radiotherapy and immune checkpoint therapy is growing rapidly. In this study, we explored a novel combination of this type to augment anti-tumor immune responses in preclinical murine models of melanoma, neuroblastoma, and head and neck squamous cell carcinoma. Cooperative effects were observed with local radiotherapy and intratumoral injection of tumor-specific antibodies, arising in part from enhanced antibody-dependent cell-mediated cytotoxicity (ADCC). We could improve this response by combining radiation with intratumoral injection of an IL-2-linked tumor-specific antibody (termed here an immunocytokine), resulting in complete regression of established tumors in most animals associated with a tumor-specific memory T cell response. Given the T cell response elicited by combined local radiation and intratumoral immunocytokine, we tested the potential benefit of adding this treatment to immune checkpoint blockade. In mice bearing large primary tumors or disseminated metastases, the triple-combination of intratumoral immunocytokine, radiation, and systemic anti-CTLA-4 improved primary tumor response and animal survival compared to combinations of any two of these three interventions. Taken together, our results show how combining radiation and intratumoral immunocytokine in murine tumor models can eradicate large tumors and metastases, eliciting an in situ vaccination effect that can be leveraged further by T cell checkpoint blockade, with immediate implications for clinical evaluation.

PMID: 27197149 [PubMed - as supplied by publisher]

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