Radiation-Enhanced CD24 Membrane Trafficking via GPI Anchoring Mediates Antitumor Immune Evasion

Radiotherapy plays a central role in cancer treatment, and the immunostimulatory effects of radiotherapy have been increasingly recognized. A better understanding of the mechanisms underlying postradiation immune escape is needed to help overcome radioresistance. In this study, we identified that irradiated tumor cells exploit the ANAPC5/GPAA1 axis to elevate surface expression of the "do not eat me" signal CD24, inducing phagocytosis resistance and immune evasion. Mechanistically, radiation inhibited the APC/C complex, reducing ANAPC5-mediated ubiquitination of GPAA1, a catalytic subunit of glycosylphosphatidylinositol (GPI) transamidase. The subsequent accumulation of GPAA1 facilitated GPI anchoring, thereby enhancing CD24 membrane localization. Accordingly, ablation of GPAA1 or CD24 significantly potentiated the local antitumor effects of radiotherapy across multiple preclinical models, dependent on T cells and macrophages. Notably, CD24 deficiency also stimulated abscopal effects, suppressing the growth of nonirradiated tumors. Overall, this study elucidates a mechanism of radiotherapy-mediated upregulation of the innate immune checkpoint CD24, offering perspectives on radiation-induced immune escape and presenting a strategy to improve radiotherapy efficacy. SIGNIFICANCE: Radiation enhances CD24 membrane trafficking by regulating ANAPC5/GPAA1-mediated GPI anchoring to drive cancer immune evasion, which can be circumvented by targeting CD24 to potentiate the local and abscopal antitumor effects of radiotherapy.