T cell suppression by antioxidant proteins released into the tumour microenvironment

Oxidative stress promotes genomic instability and oncogenic signaling in cancer, yet antioxidant therapies have largely failed to improve, and in some cases have worsened cancer outcomes. This necessitates a better understanding of how redox dynamics shape not only the biology of cancer cells but their interactions with the host, including the immune system. Reactive oxygen species (ROS) are essential co-factors in T cell activation but whether cancers exploit this vulnerability to suppress T cell immunity and immunotherapy responses is not known. My preliminary data reveal that peroxiredoxin 1 (PRDX1), a potent ROS-scavenging enzyme primarily expressed and released by tumour cells, profoundly inhibit T cell effector function. Genetic deletion of PRDX1 in cancer cells sensitizes otherwise immunotherapy-resistant tumours to checkpoint blockade. I hypothesize that extracellular PRDX1 disrupts redox-sensitive signaling pathways in CD8+ T cells, weakening their cytotoxic capacity and promoting immune evasion of tumours. This hypothesis challenges the prevailing paradigm that antioxidants are inherently beneficial in oncology and instead posits that tumour-derived antioxidants act as immune suppressors. To test my hypothesis, I will pursue three aims: i). Determine whether genetic ablation of PRDX1 in tumours enhances antigen-specific CD8+ T cell responses and improves outcomes following immune checkpoint blockade. ii). Quantify ROS dynamics in T cells across distinct tumour microenvironments and test whether augmenting intracellular ROS levels can overcome T cell suppression. iii). Define the redox-sensitive signaling networks perturbed by PRDX1 and validate key redox signaling mediators in primary human T cells. By uncovering immunomodulatory roles of extracellular antioxidants, this project opens new avenues for understanding immune evasion and offers a transformative strategy to potentiate cancer immunotherapy by reprogramming the tumour redox environment.