RIG-I is an intracellular checkpoint that limits CD8+ T-cell antitumor immunity

RIG-I is a pattern recognition receptor involved in innate immunity, but its role in adaptive immunity remains unclear. Here, we demonstrate that RIG-I is upregulated in tumor infiltrating CD8+ T cells, where it functions as an intracellular checkpoint to negatively regulate CD8+ T cell function and limit antitumor immunity. Mechanically, up-regulation of RIG-I in CD8+ T cells is induced by retinoic acid (RA), a metabolite of vitamin A in TME, and direct inhibits the AKT/glycolysis signaling pathway. In addition, deletion of RIG-I enhances the efficacy of adoptively transferred T cells against solid tumors and inhibition of RIG-I enhances the response to PD-1 blockade. Our findings identify RIG-I as an intracellular checkpoint and a potential target for alleviating inhibitory constraints on T cells in cancer immunotherapy, either alone or in combination with immune checkpoint blockade. Comparative gene expression profiling analysis of RNA-seq data for WT and KO.