Enhanced <i>FOS</i> expression improves tumor clearance and resists exhaustion in NR4A3-deficient CAR T cells under chronic antigen exposure

The dysfunction of chimeric antigen receptor (CAR) T cells in the tumor microenvironment is a major obstacle to their therapeutic efficacy against solid tumors. Through single-cell RNA sequencing analysis of tumor-infiltrating T cells from patients with glioma, NR4A family genes were identified as closely associated with T cell exhaustion and were coexpressed with dysfunctional genes HAVCR2 and TIGIT . Notably, CAR T cells with NR4A3 knockdown exhibited enhanced cytotoxic activity against tumors, leading to improved tumor clearance and prolonged survival in vivo. However, the promoted antiexhausted phenotype diminished with prolonged tumor burden. This decline in T cell function correlates with the compensatory down-regulation of FOS induced by chronic antigen exposure following NR4A3 knockdown. Overexpressing FOS alongside NR4A3 knockdown robustly boosted the antitumor responses of CAR T cells by skewing their phenotypes and transcriptional profiles away from exhaustion and toward increased effector function. These findings offer a promising strategy for the clinical modification of CAR T cell therapy.