Regnase-1 suppresses TCF-1+ precursor exhausted T cell formation to limit CAR T cell responses against ALL.

Abstract

Chimeric antigen receptor T cell (CAR-T cell) therapeutic efficacy is associated with long-term T cell persistence and acquisition of memory. Memory subset formation requires TCF-1, a master transcription factor for which few regulators have been identified. Here, we demonstrate using an immune-competent mouse model of B cell acute lymphoblastic leukemia (B-ALL) that Regnase-1 deficiency promotes TCF-1 expression to enhance CAR-T cell expansion and memory-like cell formation. This leads to improved CAR-T-mediated tumor clearance, sustained remissions, and protection against secondary tumor challenge. Phenotypic, transcriptional, and epigenetic profiling identified increased tumor-dependent programming of Regnase-1-deficient CAR-T cells into TCF-1+ precursor exhausted (TPEX) cells characterized by upregulation of both memory and exhaustion markers. Regnase-1 directly targets Tcf7 mRNA; its deficiency augments TCF-1 expression leading to the formation of TPEX that support long-term CAR-T cell persistence and function. Regnase-1 deficiency also reduces exhaustion and enhances the activity of TCF-1- CAR-T cells. We further validate these findings in human CAR-T cells, where Regnase-1 deficiency mediates enhanced tumor clearance in a xenograft B-ALL model. This is associated with increased persistence and expansion of a TCF-1+ CAR-T cell population. Our findings demonstrate pivotal roles of TPEX, Regnase-1, and TCF-1 in mediating CAR-T cell persistence and recall responses, and identify Regnase-1 as a modulator of human CAR-T cell longevity and potency that may be manipulated for improved therapeutic efficacy.