LC3-dependent intercellular transfer of phosphorylated STAT1/2 elicits CXCL9+ macrophages and enhances radiation-induced antitumor immunity.

The efficacy of anticancer treatments, including radiotherapy, depends on the activation of type I IFN signaling. However, its regulatory networks and mechanisms remain to be elucidated. Here, we report that tumor cell-intrinsic type I IFN signaling can be transferred to macrophages via secretory autophagy, inducing CXCL9hi macrophages and enhancing CD8+ T cell-mediated antitumor immunity. Mechanistically, K63-linked ubiquitination at the K167 site of phosphorylated STAT2 (p-STAT2) facilitates its binding to LC3B, promoting the loading of p-STAT1 and p-STAT2 into extracellular vesicles and intercellular transference from tumor cells to macrophages, which, however, is suppressed by USP5-mediated STAT2 deubiquitination. Genetic depletion or pharmacological inhibition of USP5 promotes autophagy-dependent unconventional protein secretion of p-STAT1 and p-STAT2, leading to the induction of CXCL9+ macrophages. This process promotes the expression of T cell chemokines and upregulates the antigen presentation machinery, thereby enhancing radiation-induced CD8+ T cell antitumor immunity and radiotherapy efficacy. Our findings reveal a critical role of USP5 in type I IFN-induced antitumor immunity, providing potential targets for improving the efficacy of radiotherapy.