Abstract 1362: Metabolic engineering of CAR-T cells overcomes suppressive adenosine signaling and enhances functionality
Authors: Klysz Dorota , Malipatlolla Meena , Freitas Katherine , Bashti Malek , Labanieh Louai , Xu Peng , Ramello Cecilia , Lerust Amaury , Want Hyatt Balke , Pacheco Kaithlen Zen , Weber Evan W. , Patel Shabnum , Feldman Steven , Sotillo Elena , Mackall Crystal L. 
Published: June 2022

Abstract
Chimeric Antigen Receptor (CAR) T cell therapy has resulted in remarkable clinical outcomes in the context of acute and chronic lymphoblastic leukemia, but remains unsuccessful in the treatment of solid tumors. One reason for this failure is thought to be T cell dysfunction or exhaustion promoted by suppressive soluble factors within the tumor microenvironment (TME). High extracellular levels of the immunosuppressive factor adenosine (Ado) are generated in the TME via breakdown of ATP by ecto-enzymes CD39 and CD73 expressed on tumor-infiltrating immune cells. Binding of extracellular Ado to its receptor A2a on T cells results in inhibition of proliferation and effector function. Interestingly, CD39 has recently been described as a surrogate marker of exhaustion on human CAR-T cells and non-engineered T cells. Therefore, we hypothesized that CD39 expression on exhausted CAR-T cells promotes dysfunction through generation of extracellular adenosine.
Using an in vitro model of T cell exhaustion, whereby human T cells express a CAR that tonically signals in an antigen-independent manner (HA CAR), we demonstrate that exhausted HA CAR T cells actively hydrolyze extracellular ATP via their elevated expression of CD39 and CD73. Moreover, exhausted CD39+ CAR T cells upregulate several genes associated with a Treg phenotype at the mRNA and protein levels, suggesting that this cell population might be suppressive. To assess whether CD39+/CD73+ CAR T cells exhibit suppressive functions, we co-cultured them with non-exhausted CD19-CAR T cells. Indeed, proliferation and secretion of IL-2 by CD19 CAR T cells were diminished when they were co-cultured with exhausted CD39+ CAR T cells, and that this suppression is dependent on the A2a receptor. Using this knowledge, we used gene-editing and overexpression approaches to engineer CAR-T cells with resistance to suppressive adenosine signaling. In contrast to genetic deletion of CD39 or CD73, which did not alleviate CAR T cell dysfunction, genetic deletion of adenosine receptor A2aR in exhausted CAR T cells resulted in phenotypic changes and a modest improvement in tumor-specific killing. Further, ectopic overexpression of adenosine deaminase (ADA) in CAR T cells led to decreased exhaustion marker expression and significantly enhanced effector function. These data indicate that ADA overexpression is an innovative approach to increase the functionality of CAR T cells through avoidance of suppressive adenosine signaling, and provides proof-of-concept that metabolic engineering of CAR-T cells can pave the way for responses in patients with solid tumors.
Citation Format: Dorota Klysz, Meena Malipatlolla, Katherine Freitas, Malek Bashti, Louai Labanieh, Peng Xu, Cecilia Ramello, Amaury Lerust, Hyatt Balke Want, Kaithlen Zen Pacheco, Evan W. Weber, Shabnum Patel, Steven Feldman, Elena Sotillo, Crystal L. Mackall. Metabolic engineering of CAR-T cells overcomes suppressive adenosine signaling and enhances functionality [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1362.