Abstract 693: The effect of butyrophilin 1A1 blockade in combination with radiation treatment in tumor models

Abstract

Abstract Expression of radiation-induced immune escape molecules, including PD-L1, contributes to the efficacy of cancer immunotherapy. We used an unbiased in vivo gene knockdown screen in naïve T-cells and introduced them into irradiated host tumors to identify novel immunosuppressive genes activated during radiation. From the screen, we found that butyrophilin 1A1 (BTN1A1) knockdown causes T-cell expansion in irradiated tumors. This points to the potential immune checkpoint role of BTN1A1. We validated that BTN1A1 expression is inducible in activated T-cells and that blocking BTN1A1 contributes to T-cell activation. We tested an anti-mouse BTN1A1 antibody (STC109) in mouse colon tumor models (CT26 tumors), we observed partial anti-tumor efficacy using single agent STC109, which was enhanced by the combination of STC109 with radiation. We also got similar result in in mouse lung tumor models (LLC tumors) using anti-mouse BTN1A1 antibody, and the combination treatment showed an improved suppression of tumor growth and lung metastasis compared to single agent. Moreover, our data shown that knockout of BTN1A1 in 4T1 tumor models shown dramatic defect of tumor growth, and the BTN1A1 ko tumors are more sensitive to radiotherapy. These findings indicate the role of BTN1A1 in tumor immune response from radiation stress, and that anti-BTN1A1 has strong potential to enhance efficacy of radiotherapy for cancer treatment. Citation Format: Nan Li, Chen Braun, Young-Seung Kim, Andrew Park, Stephen S Yoo, Steven H. Lin. The effect of butyrophilin 1A1 blockade in combination with radiation treatment in tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 693.