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Comparative analysis of T cell receptor and chimeric antigen receptor signaling in primary CD8+ T cells

ABSTRACT: Chimeric antigen receptor-modified (CAR) T cell therapy targeting highly expressed lineage antigens is effective for B cell malignancies. Achieving durable efficacy for hematological malignancies and extending this therapeutic approach to solid tumors will require T cell recognition and elimination of tumor cells that may express lower levels of the CAR target antigen. Realizing this goal is challenging because current approaches to CAR design are largely empiric and detailed information on CAR signaling is only beginning to emerge. Synthetic CARs typically require hundreds of molecules on the target cell to initiate signaling, whereas natural T cell receptors (TCRs) can recognize less than ten peptide-MHC (pMHC) antigen complexes. We reasoned that in depth comparison of TCR and CAR stimulation-induced signaling events in primary T cells might guide rationale adaptations to CAR design that would improve antigen sensitivity. Bi-specific T cells possessing an endogenous TCR and exogenous CAR of defined specificity were formulated from healthy HLA-B8+ Epstein-Barr virus-seropositive donors. Bi-specific T cells were stimulated with magnetic microbeads coated with recombinant TCR or CAR antigen for 10, 45, or 90 minutes. Some bi-specific T cells were also left unstimulated and harvested at each timepoint to serve as controls. Altogether, 9 unique conditions were tested in an experiment and three independent experiments were performed.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): T Cell, Cell Culture

SUBMITTER: Jacob Kennedy

LAB HEAD: Stanley Riddell

PROVIDER: PXD013734 | Pride | 2021-05-20

REPOSITORIES: Pride

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Project description:Adoptive T cell therapies have been transformative in the treatment of a subset of hematological malignancies. However, many patients either fail to respond or relapse, and these therapies still have had much more limited success in solid tumors. A critical challenge for increasing patient response rates and achieving durable efficacy of adoptive T cell therapies is overcoming suppressive signals from both extrinsic factors and intrinsic inhibitory checkpoints. Targeted gene editing has the potential to enhance T cell therapeutic function and improve clinical responses. Here we perform multiple genome-wide CRISPR knock-out screens under different immunosuppressive conditions to nominate genes that could be targeted to prevent T cell dysfunction. These CRISPR screens converged on RASA2 as a target to confer resistance to suppressive conditions found in tumor microenvironments. We identify RASA2 as a signaling checkpoint in human T cells that is downregulated upon acute TCR stimulation but increases gradually with chronic antigen exposure. Antigen titration showed that genetic ablation of RASA2 enhances mitogen activated protein kinase (MAPK) signaling and CAR-T cell cytolytic activity in response to low antigen levels. Repeated tumor antigen stimulation in vitro revealed that RASA2-deficient TCR-T and CAR-T cells have increased activation, cytokine production, and metabolic activity compared to control cells, and show a striking advantage in persistent cancer cell killing. RASA2 KO CAR-T cells showed a competitive fitness advantage over CAR-T control cells in the bone marrow of an in vivo leukemia model. Deletion of RASA2 in multiple preclinical models of TCR- and CAR-T cell therapies prolonged survival in animals xenografted with either liquid or solid tumors. Altogether, our findings from multiple genome-wide screens and preclinical studies highlight RASA2 as a promising new target to enhance both persistence and effector function in TCR-T and CAR-T cell therapies for cancer treatment.

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Comparative analysis of T cell receptor and chimeric antigen receptor signaling in primary CD8+ T cells

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