BRD4 Inhibition Enhances the Antitumor Effects of Radiation Therapy in a Murine Breast Cancer Model

Bromodomain-containing protein 4 (BRD4) is an intracellular that regulates expression of various cellular functions. This study investigated whether BRD4 inhibition can alter the immunomodulatory and antitumor effects radiation therapy (RT). A murine breast cancer cell line was implanted into BALB/c mice. The dual-tumor model used to evaluate abscopal RT. total 24 Gy delivered inhibitor injected intravenously. Tumor size measured, in vivo imaging performed tumor growth. Flow cytometry immunohistochemistry were examine immunologic changes upon treatment. combination RT significantly suppressed growth compared alone. reduced unirradiated tumor, indicating it may induce systemic immune responses. HIF-1α PD-L1 downregulated by inhibitor. proportion M1 tumor-associated macrophages (TAMs) increased, M2 TAMs decreased inhibition. expanded CD4+ CD8+ T populations microenvironment. Additionally, splenic monocytic myeloid derived suppressor cells, which increased RT, addition Therefore, enhanced responses local