Preclinical Use of Focal Radiation and Immune Checkpoint Blockade to Improve Therapeutic Response in an Immunologically Cold Tumor

AACR 2019 -- Radiation therapy (RT) is a highly utilized clinical treatment modality with more than 50% of all cancer patients receiving some type of radiotherapy during the course of their illness. Appropriate systems and models to test preclinical radiation combinations are needed. In mouse models, radiation treatment has been shown to increase the level of tumor antigen presentation and the variety of peptides available for cross-presentation. Current work in the field focuses on using radiation as a tool to bridge the gap from tumor equilibrium to tumor elimination, which could improve the response rate of immuno-oncology agents. 4T1 is a murine breast cancer model known to have a large percentage of myeloid derived suppressor cells (MDSC) making the model resistant to many immunotherapies and is considered an immunologically cold tumor. We hypothesized that treatment with focal radiation would sensitize 4T1 tumors to anti-mCTLA-4 treatment.