CRISPR-Cas9 screen identifies eIF4G2 as a regulator of CD8+ T cell dysfunction.

CD8+ T cells directly target and kill cancer cells and are required for effective antitumor immunity. However, CD8+ T cells may become dysfunctional when exposed to chronic antigen stimulation during cancer. Dysfunction is characterized by reduced proliferation, increased expression of inhibitory receptors, and impaired effector function, yet the genetic mechanisms controlling dysfunction remain poorly understood. Therefore, we developed a murine ex vivo chronic stimulation model that recapitulates features of CD8+ T cell dysfunction observed within the tumor microenvironment. By coupling this system with genome-wide CRISPR-Cas9 loss-of-function screening, we discovered that the progression of murine CD8+ T cells to a dysfunctional state required eIF4G2, a noncanonical mRNA translation factor. Deletion of eIF4G2 restored CD8+ T cell survival and proliferation during chronic stimulation conditions in vitro. Transcriptomic, proteomic, and flow cytometric analyses revealed that eIF4G2 deletion shifts CD8+ T cell phenotype from a dysfunctional state to a proliferative state. eIF4G2 depletion reduced oxidative stress, lipid peroxidation, and accumulation of misfolded protein aggresomes during chronic in vitro stimulation. Finally, eIF4G2-depleted cells mediated enhanced tumor control in a murine model of melanoma. These data suggest that targeting eIF4G2 may promote CD8+ T cell resilience and improve therapeutic antitumor immunity.