Abstract 52: CRISPR-mediated knock-out of A20 lowers the activation threshold and induces metabolic rewiring of CAR-T cells
Authors: Chu Nina Jia , Nava-Barbero Carina , Merlino Ashley , Lee Ping-Hsien , Baker David , Taylor Ben , Moody Gordon , Giardino Letizia 
Published: March 2024

Abstract
Background: Common failures of chimeric antigen receptor (CAR)-T cell therapy regimens stem from immune escape of target antigen low tumors. Strategies to improve CAR-T cell therapy efficacy include enhancing intrinsic effector function while preventing T cell exhaustion. The ubiquitin-modifying enzyme A20, is a key negative regulator of the NF-kB pathway downstream of T cell receptor activation in T cells. Dysfunctional CD8 T cells in tumors have high expression of A20, and deletion of A20 enhances antitumor activity of CD8 T cells in murine tumor models. We tested whether CRISPR-mediated knock-out (KO) of tumor necrosis factor α-induced protein 3 (TNFAIP3), the gene for A20, increases the effector function and alters the metabolic state of CAR-T cells.
Results: A20 deletion led to upregulation of NF-κB target genes and resulted in higher levels of activation marker expression and effector cytokine secretion compared to unarmored CAR-T upon incubation with target cells. In addition, A20 KO CAR-T cells maintained prolonged expression of activation markers upon antigen clearance in the absence of enhanced differentiation, and were more resistant to dysfunction in a repeat challenge serial kill assay. In vivo, A20 deficient CAR-T exhibited increased anti-tumor efficacy against low, medium, and high target expressing tumor models. Consistent with NF-κB upregulation, A20 KO cells significantly upregulated key glycolytic intermediates suggesting that amino acid anabolism was fueled by glycolysis and the pentose phosphate pathway. Moreover, the preferential increase of glycolysis over oxidative phosphorylation confirmed that A20 KO CAR-T cells were skewed towards an effector-like phenotype. Notably, glutathione and its cysteine-glycine bi-products were upregulated upon activation to a higher level in A20 KO CAR-T suggesting enhanced resistance to oxidative stress, in line with their prolonged persistence.
Conclusions: CRISPR-mediated knock-out of A20 lowers the activation threshold of CAR-T cells producing enhanced in vitro and in vivo anti-tumor efficacy particularly against tumors with very low levels of target expression. A20 KO induces metabolic rewiring of CAR-T cells by promoting glycolysis and amino acid anabolism to sustain their superior effector functions. This intrinsic armoring strategy can be applied to any CAR-T in any indication to increase tumor control and reduce immune escape.
Citation Format: Nina Jia Chu, Carina Nava-Barbero, Ashley Merlino, Ping-Hsien Lee, David Baker, Ben Taylor, Gordon Moody, Letizia Giardino. CRISPR-mediated knock-out of A20 lowers the activation threshold and induces metabolic rewiring of CAR-T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 52.