Abstract 3230: Tumor microenvironment modulation by immunotherapy sensitizes solid tumors to radiation

Abstract Radiation therapy (RT) has been prevalently implemented to treat cancer in clinical settings by inducing DNA damage in tumor cells. However, tumor microenvironmental factors such as severe hypoxic conditions and vascular anomalies attenuate the therapeutic efficacy of RT, thus resulting in unsatisfactory outcomes in solid tumors. Recently, Immune checkpoint blockade (ICB) has improved immune recognition to tumor cells and normalized tumor vasculature to diminish hypoxia in solid tumors. Herein, we suggest that RT combined with ICB synergistically alters tumor microenvironments, thus facilitating the recruitment of cytotoxic immune cells into tumors as well as sensitizing radiation effectiveness. RT in combination with ICB not only normalized tumor vasculature to reduce hypoxia, but also increased anti-tumor effects from immune-mediated toxicity and DNA damage-mediated apoptosis in several solid tumor-bearing mouse models to a greater extent than did either monotreatment of RT or ICB. This study will provide mechanistic insight into synergistic effects conferred by RT and ICB as well as a strong preclinical rationale for combining the two therapeutic modalities in human cancers. Citation Format: Minjeong Kang, DaeYong Lee, Yifan Wang, Betty Kim, Wen Jiang. Tumor microenvironment modulation by immunotherapy sensitizes solid tumors to radiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3230.