CRISPR Screening of CAR T Cells and Cancer Stem Cells Reveals Critical Dependencies for Cell-Based Therapies [GSC]

Glioblastoma (GBM) is the most prevalent primary malignant brain tumor, containing self-renewing stem-like GBM stem cells (GSCs) that have been a focus of immunotherapies. Chimeric antigen receptor (CAR) T cell therapy has shown evidence of clinical activity, but overall limited responses in patients with GBMs. Here, we interrogated molecular determinants of CAR T cell-mediated GBM killing through whole-genome CRISPR screens in both CAR T cells and patient-derived GSCs. CRISPR screening of CAR T cells identified dependencies for their effector functions, including TLE4 and IKZF2. Targeted knockout of these genes in CAR T cells robustly enhanced antitumor efficacy against GBM patient-derived xenografts (PDXs). Bulk and single cell-RNA sequencing of edited CAR T cells revealed transcriptional profiles of superior effector function and inhibited exhaustion responses. Reciprocal screening of GSCs identified genes essential for their susceptibility to CAR-mediated killing, including RELA and NPLOC4, the knockout of which altered the tumor-immune signaling axis and increased responsiveness of CAR therapy. Overall, CRISPR screening of CAR T cells and GSCs are promising strategies to discover avenues and inform potential combinatorial approaches for enhancing CAR T cell therapeutic efficacy against GBM, and can be extended to reveal key mediators of immunotherapy responses across solid tumors.