Abstract A020: Neutralizing oxidative damage at telomeres prevents T cell dysfunction and improves adoptive cell therapy
Authors: Rivadeneira Dayana , Thosar Sanjana , Dean Victoria , Gunn William , Lontos Konstantinos , Bruchez Marcel , Opresko Patricia , Delgoffe Greg 
Published: December 2023

Abstract
Background: Failure of adoptive cell therapies (ACTs) is associated with insufficient persistence within the patient, inability to infiltrate tumor sites, and cell-intrinsic loss of functionality. One of the key factors responsible for T cell dysfunction are metabolic barriers such as nutrient competition, low oxygen tension and damaging byproducts in the tumor microenvironment. This leads to a T cell metabolic deregulation affecting their ability to find and kill cancer cell targets properly and effectively. Therefore, elucidating the metabolic pressures experienced in the TME could provide new therapeutic targets to improve ACTs. Reactive Oxidative Species (ROS) accumulation in the TME have detrimental effects on T cell function and anti-tumor response, although the precise targets of ROS are unclear. There are accumulating data showing that mitochondrial ROS can have profound effects on the telomere status of cells. However, there is little evidence describing the role or oxidative stress on telomere health, or the importance of telomere function in immune cells. Our current study demonstrates that tumor infiltrating lymphocytes (TIL) accumulate DNA damage at telomeres, most prominently in terminally exhausted T cells. Furthermore, inducing ROS accumulation at telomeres alone drives T cell dysfunction. Importantly we discovered that alleviating ROS specifically at telomeres improves the response to adoptive cell therapies in a mouse tumor model.
Methods: In this study we perform telomeric and centromeric FISH assays to analyze TIL for DNA damage accumulation. We used a chemo-optogenetic FAPS-TAPS to generate singlet oxygen and consequent 8-oxo-guanine lesions specifically at telomeres.1 We tethered the antioxidant protein GPX1 to TRF1, subunit of the Shelterin Complex at telomeres, to generate a telomere-guided ROS scavenger.
Results: Telo-FISH analysis demonstrates an accumulation of telomeric DNA damage in TIL from B16 mouse tumors shown by the presence of 53BP1 and ƔH2AX at telomeres. Our data show that mitochondria and telomeric ROS cause the accumulation of DNA damage at telomeres, as well as the development of telomere fragility. These cells ultimately become dysfunctional showing a diminished capability for cytokine production. Importantly, localizing the ROS scavenger GPX1 directly to telomeres reduced telomere fragility and improved the function of therapeutic T cells in the B16 melanoma.
Conclusions: Our data suggest that dysfunctional T cells in cancer are not classically senescent, bearing short telomeres, but rather harbor damaged telomeres due to exposure to oxidative stress. Telomeric damage is sufficient to drive a dysfunctional state in newly activated T cells. Protecting telomeres through expression of a telomere-targeted antioxidant protein may preserve T cell function in the tumor microenvironment and drive superior responses to adoptive cell therapies.
Citation Format: Dayana Rivadeneira, Sanjana Thosar, Victoria Dean, William Gunn, Konstantinos Lontos, Marcel Bruchez, Patricia Opresko, Greg Delgoffe. Neutralizing oxidative damage at telomeres prevents T cell dysfunction and improves adoptive cell therapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A020.