A STUB1-CHIC2 complex decreases IL-27Rα expression on CD8+ T cells to restrain tumor immunity

CRISPR screens in CD8+ T cells have uncovered novel immunotherapy targets for cancer; however, these screens used activated CD8+ T cells, precluding identification of genes regulating CD8+ T cell priming in the tumor-draining lymph (tdLN). Here we present an 899-gene in vivo CRISPR screen in naive CD8+ T cells, which identifies novel regulators of CD8+ T cell responses in the tdLN and tumor. We find that STUB1, an E3 ubiquitin ligase, significantly regulates CD8+ T cell accumulation in both tissues and Stub1 knockout (KO) CD8+ T cells improve tumor growth control. Mechanistically, STUB1 interacts with the adapter protein, CHIC2, to regulate IL-27Rα, which is required for the increased anti-tumor responses of Stub1 and Chic2 KO CD8+ T cells. Overall, these findings demonstrate that the STUB1-CHIC2 complex is a novel regulator of cytokine receptor expression in CD8+ T cells and provide the rationale for inhibiting this pathway to improve CD8+ T cell-mediated anti-tumor immunity.