Oxidative stress induced telomere instability/damage drives T cell dysfunction in cancer
The tumor microenvironment imposes immunologic and metabolic stresses sufficient to deviate immune cell differentiation into dysfunctional fates like exhaustion. Our data show that dysfunctional T cells in cancer do not harbor short telomeres indicative of replicative senescence, but rather harbor damaged telomeres, which we hypothesized arose from oxidative stress. Chemo-optogenetic induction of localized mitochondrial or telomeric reactive oxygen species (ROS) using a novel photosensitizer caused DNA damage at telomeres and was sufficient to drive a dysfunctional state in newly activated T cells, with diminished capability for cytokine production. Localizing the ROS scavenger GPX1 directly to telomeres reduced telomere fragility in tumors and improved the function of therapeutic 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.  Overall design: 1. CD8+ T cells from TRF1-FAP-T or Mito-FAP-T mice (3 each) were stimulated overnight with anti-CD3/CD28 antibodies and treated with 660nm light alone or with MG-2I dye for 1 hour. Twenty-four hours later, RNA was isolated for sequencing (samples TRF1FAP_light-1-3, TRF1FAP_lightdye_1-3, MitoFAP_light1-3, MitoFAP_lightdye_1-3). 2. Separately, Pmel-1 CD8 cells were expanded in-vitro and transduced with control (PMIA) or GPX1-TRF1 expression constructs and infused into B16-tumor bearing mice. Ten-days later, CD8+ T cells were sorted from tumors for RNA-sequencing (samples PMIA_1-4 and GPX_1-4). 1. CD8+ T cells from TRF1-FAP-T or Mito-FAP-T mice (3 each) were stimulated overnight with anti-CD3/CD28 antibodies and treated with 660nm light alone or with MG-2I dye for 1 hour. Cells were then passaged in the presence of IL-2. Seven days later, RNA was isolated for sequencing.