Systematic identification of immunotherapy targets using genome-scale in vivo CRISPR screens in CD8+ cytotoxic T cells

CD8+ cytotoxic T cells play essential roles in anti-tumor immune responses. Here, weperformed in vivo screens in CD8+ T cells and identified regulators of tumor infiltrationand killing, which are directly relevant to cancer immunotherapy. Unlike in vitroscreens, the in vivo screen robustly re-identified canonical immunotherapy targets PD-1 and Tim-3, along with genes that have not been characterized in T cells. Infiltrationand degranulation screens converged on an RNA helicase Dhx37. Dhx37 knockoutenhanced the efficacy of antigen-specific CD8+ T cells against cancer in vivo.Immunological characterization in mouse and human CD8+ T cells revealed thatDHX37 suppresses effector function, cytokine production, and T cell activation.Transcriptomic profiling and biochemical interrogation revealed a role for DHX37 inmodulating the NF-KB pathway. These data demonstrated the power of high-throughputin vivo genetic screens for immunotherapy target discovery, and uncovered DHX37 asa functional regulator of CD8+ T cells.