CD8A and neoplasm: In summary, butyrate exhibits a “double-edged sword” effect in radiotherapy: on the one hand, it enhances histone acetylation and activates the FOXO3A pathway to block S-phase cells, thereby increasing local tumor radiosensitivity; on the other hand, it impairs the antigen-presenting function of (DCs), weakening CD8+ T cell activation and IFN secretion, thereby antagonizing radiotherapy-induced systemic antitumor immunity.