Engineering Next-Generation CAR-T Cells: Overcoming Tumor Hypoxia and Metabolism

Abstract

T cells engineered to express chimeric antigen receptors (CARs) have shown remarkable success in treating B-cell malignancies, reflected by multiple US Food and Drug Administration–approved CAR-T cell products currently on the market. However, various obstacles have thus far limited the use of approved products and constrained the efficacy of CAR-T cell therapy against solid tumors. Overcoming these obstacles will necessitate multidimensional CAR-T cell engineering approaches and better understanding of the intricate tumor microenvironment (TME). Key challenges include treatment-related toxicity, antigen escape and heterogeneity, and the highly immunosuppressive profile of the TME. Notably, the hypoxic and nutrient-deprived nature of the TME severely attenuates CAR-T cell fitness and efficacy, highlighting the need for more sophisticated engineering strategies. In this review, we examine recent advances in protein- and cell-engineering strategies to improve CAR-T cell safety and efficacy, with an emphasis on overcoming immunosuppression induced by tumor metabolism and hypoxia.

Pairing of single-cell RNA analysis and T cell antigen receptor profiling indicates breakdown of T cell tolerance checkpoints in atherosclerosis

“…This observation indicates that atherosclerosis/hyperlipidemia-related autoantigens may give rise to proatherogenic autoreactive CD8 + T cells and that atherosclerosis autoimmune responses involve the generation of autoreactive T reg cells and CD4 + T cells. These data lead us to propose that next-generation antigen-specific T reg cells including chimeric antigen-receptor T cells to treat atherosclerosis should be considered in future experimental studies 42,43 . Many T cells recognizing self-antigens are T reg cells 10 T reg cells become unstable and may switch sides from immunosuppressive to immunostimulatory T cells during T reg /TH 17 cell conversion: (1) they acquire additional transcription factors in addition to the hallmark transcription factor FoxP3 (plasticity); and (2) they lose FoxP3 and CD25, the high-affinity IL-2 receptor (T reg cell instability) generating cells termed exT reg cells 32,44 .…”

Successes and challenges in clinical gene therapy

“…For example, the SWI/SNF family complex member ARID1A and the RAS GTPase-activating protein RASA2 have been identified through library screens and subsequently individually validated as knockout candidates to minimize T-cell exhaustion and improve T-cell function [13,79]. Finally, numerous strategies are now under evaluation to "armor" tumor-targeting immune cells with chemokines, cytokines, and genetic circuitry designed to enhance anti-tumor efficacy, particularly against solid tumors that are otherwise protected by highly immunosuppressive tumor microenvironments [80,81].…”

Paving the road to make chimeric antigen receptor‐T‐cell therapy effective against solid tumors

“…Those immune checkpoint molecules induce poor expansion and short‐term persistence of CAR‐T cells in TME, disturb the exertion of CAR‐T‐cell functions, and eventually render CAR‐T cells irreversibly exhausted 1,46–48 . Metabolism in TME also affects the anti‐tumor functions of effector T cells 49–51 . Effector T cells, including CAR‐T cells, could compete with tumor cells and other cell types in TME for several nutrients including glutamate and fatty acids.…”

“… 1 , 46 , 47 , 48 Metabolism in TME also affects the anti‐tumor functions of effector T cells. 49 , 50 , 51 Effector T cells, including CAR‐T cells, could compete with tumor cells and other cell types in TME for several nutrients including glutamate and fatty acids. For example, cancer cells, unlike normal cells, produce ATP in the glycolytic system rather than through mitochondrial oxidative phosphorylation, even under aerobic conditions, which is known as the Warburg effect.…”

“…In addition, high oxygen consumption due to rapid proliferation and poor vascularity due to continuous increase in the mass size render the TME hypoxic. 49 , 50 , 51 Hypoxia inhibits the differentiation, proliferation, and cytokine production of effector T cells. 52 …”