Genome-wide fitness gene identification reveals Roquin as a potent suppressor of CD8 T cell expansion and anti-tumor immunity

Robust expansion of adoptively transferred T cells is a prerequisite for effective cancer immunotherapy, but how many genes in the genome modulate T cell expansion remains unknown. Here, we performed in vivo and in vitro CRISPR screens to systematically identify genes influencing CD8 T cell expansion. In the mouse genome, ~ 2,600 and ~ 1,500 genes were required for optimal CD8 T cell expansion in vivo and in vitro, respectively. In vivo-specific CD8 T cell essential genes were enriched in metabolic pathways including mitochondrial metabolism. The strongest repressor of CD8 T cell expansion was Roquin, ablation of which drastically boosted T cell proliferation by enhancing cell cycle progression and upregulation of IRF4. Roquin-deficiency or IRF4 overexpression potently enhanced anti-tumor immunity. These data provide a functional catalog of CD8 T cell fitness genes, and suggest targeting Roquin-IRF4 axis is an effective strategy to enhance efficacy of adoptive transfer therapy for cancer. Overall design: RNA sequencing: mRNA of 2 sgControl samples and 2 sgRc3h1 samples were analysed by NGS.