Hypoxia-induced reactive oxygen species contribute to immune checkpoint molecule expression in T cells undergoing rapid clonal proliferation

• Published in: The Journal of immunology (1950) 2018-05, Vol.200 (1_Supplement), p.108-108.18
• Main Authors: OConnor, Roddy, Guo, Lili, Ghassemi, Saba, Snyder, Nathaniel, Worth, Andrew, Weng, Liwei, OBrien, Shaun, Kam, Yoonseok, Philipson, Benjamin, Nunez-Cruz, Selene, Lee, Joyce, Wellen, Kathryn, Busch, Theresa, Moon, Edmund, Blair, Ian, June, Carl H., Milone, Michael
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.200.Supp.108.18

In response to antigen and costimulation, T cells undergo a series of metabolic transitions supporting clonal expansion and differentiation. We recently showed how CD28 and 4-1BB intracellular co-stimulatory domains induce glycolytic vs oxidative metabolic programs, respectively, in the context of a chimeric antigen receptor. Understanding how endogenous co-stimulatory pathways, in particular CD28, supports differentiation and memory cell development despite encountering hostile environments characterized by varying oxygen tension and metabolic checkpoints is of clear importance to cellular immunotherapy. Immune checkpoint molecule (ICM) expression is associated with T cell exhaustion characterized by reduced proliferative capacity and diminished effector function. While studying the role of LCFAO in primary human T cell differentiation, we uncovered that the CPT1a inhibitor, etomoxir (ETO), induces expression of the PD-1, Tim-3, and Lag-3 ICMs. This is mediated by non-specific effects on oxidative metabolism, culminating in reactive oxygen species (ROS) production. The induction of ICM expression by ETO is calcineurin-dependent and reversed by the antioxidant N-acetylcysteine (NAC). We show that Tim-3 is upregulated by T cells in highly hypoxic xenograft tumors independent of TCR signaling. Transition of highly activated T cell cultures from normoxia (21% O2) to hypoxia (1% O2) induces Tim-3, which is reversed by NAC. These results suggest that ICMs, especially Tim-3, are part of a natural regulatory system that responds to oxidative stress and tempers T cell activation and associated metabolism to minimize oxidative damage to T cell clones expanding following antigen receptor activation.