ABSTRACT
Live regulatory T cells (Treg cells) suppress antitumor immunity, but how Treg cells behave in the metabolically abnormal tumor microenvironment remains unknown. Here we show that tumor Treg cells undergo apoptosis, and such apoptotic Treg cells abolish spontaneous and PD-L1-blockade-mediated antitumor T cell immunity. Biochemical and functional analyses show that adenosine, but not typical suppressive factors such as PD-L1, CTLA-4, TGF-ß, IL-35, and IL-10, contributes to apoptotic Treg-cell-mediated immunosuppression. Mechanistically, apoptotic Treg cells release and convert a large amount of ATP to adenosine via CD39 and CD73, and mediate immunosuppression via the adenosine and A2A pathways. Apoptosis in Treg cells is attributed to their weak NRF2-associated antioxidant system and high vulnerability to free oxygen species in the tumor microenvironment. Thus, the data support a model wherein tumor Treg cells sustain and amplify their suppressor capacity through inadvertent death via oxidative stress. This work highlights the oxidative pathway as a metabolic checkpoint that controls Treg cell behavior and affects the efficacy of therapeutics targeting cancer checkpoints.
Subject(s)
Apoptosis/immunology , B7-H1 Antigen/metabolism , Immune Tolerance/immunology , Ovarian Neoplasms/immunology , Oxidative Stress/physiology , T-Lymphocytes, Regulatory/immunology , 5'-Nucleotidase/genetics , 5'-Nucleotidase/metabolism , Adenosine/metabolism , Animals , Antigens, CD/metabolism , Apyrase/metabolism , CTLA-4 Antigen/metabolism , Female , GPI-Linked Proteins/genetics , Humans , Interleukin-10/metabolism , Interleukins/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , NF-E2-Related Factor 2/metabolism , Oxygen/metabolism , Receptor, Adenosine A2A/metabolism , Transforming Growth Factor beta/metabolism , Tumor Cells, Cultured , Tumor Microenvironment/immunologyABSTRACT
Aerobic glycolysis regulates T cell function. However, whether and how primary cancer alters T cell glycolytic metabolism and affects tumor immunity in cancer patients remains a question. Here we found that ovarian cancers imposed glucose restriction on T cells and dampened their function via maintaining high expression of microRNAs miR-101 and miR-26a, which constrained expression of the methyltransferase EZH2. EZH2 activated the Notch pathway by suppressing Notch repressors Numb and Fbxw7 via trimethylation of histone H3 at Lys27 and, consequently, stimulated T cell polyfunctional cytokine expression and promoted their survival via Bcl-2 signaling. Moreover, small hairpin RNA-mediated knockdown of human EZH2 in T cells elicited poor antitumor immunity. EZH2(+)CD8(+) T cells were associated with improved survival in patients. Together, these data unveil a metabolic target and mechanism of cancer immune evasion.