Expression of TRX1 optimizes the antitumor functions of human CAR T cells and confers resistance to a pro-oxidative tumor microenvironment
Emre Balta, Nina Janzen, Henning Kirchgessner, Vasiliki Toufaki, Christian Orlik, Jie Liang, Divya Lairikyengbam, Hinrich Abken, Beate Niesler, Karin Müller‐Decker, Thomas Ruppert, Yvonne Samstag
Abstract
Use of chimeric antigen receptor (CAR) T cells to treat B cell lymphoma and leukemia has been remarkably successful. Unfortunately, the therapeutic efficacy of CAR T cells against solid tumors is very limited, with immunosuppression by the pro-oxidative tumor microenvironment (TME) a major contributing factor. High levels of reactive oxygen species are well-tolerated by tumor cells due to their elevated expression of antioxidant proteins; however, this is not the case for T cells, which consequently become hypo-responsive. The aim of this study was to improve CAR T cell efficacy in solid tumors by empowering the antioxidant capacity of CAR T cells against the pro-oxidative TME. To this end, HER2-specific human CAR T cells stably expressing two antioxidant systems: thioredoxin-1 (TRX1), and glutaredoxin-1 (GRX1) were generated and characterized. Thereafter, antitumor functions of CAR T cells were evaluated under control or pro-oxidative conditions. To provide insights into the role of antioxidant systems, gene expression profiles as well as global protein oxidation were analyzed. Our results highlight that TRX1 is pivotal for T cell redox homeostasis. TRX1 expression allows CAR T cells to retain their cytolytic immune synapse formation, cytokine release, proliferation, and tumor cell-killing properties under pro-oxidative conditions. Evaluation of differentially expressed genes and the first comprehensive redoxosome analysis of T cells by mass spectrometry further clarified the underlying mechanisms. Taken together, enhancement of the key antioxidant TRX1 in human T cells opens possibilities to increase the efficacy of CAR T cell treatment against solid tumors.