Tomasz Maj

Cancer mediates effector T cell dysfunction by targeting microRNAs and EZH2 via glycolysis restriction

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.

Inhibition of Fatty Acid Oxidation Modulates Immunosuppressive Functions of Myeloid-Derived Suppressor Cells and Enhances Cancer Therapies

Myeloid-derived suppressor cells in tumors, but not in the spleen, activated fatty acid uptake and oxidation (FAO) and increased their immunosuppressive pathways. Blocking FAO with inhibitors induced T-cell–mediated antitumor activity, which provides a novel approach for treatment. Myeloid-derived suppressor cells (MDSC) promote tumor growth by inhibiting T-cell immunity and promoting malignant cell proliferation and migration. The therapeutic potential of blocking MDSC in tumors has been limited by their heterogeneity, plasticity, and resistance to various chemotherapy agents. Recent studies have highlighted the role of energy metabolic pathways in the differentiation and function of immune cells; however, the metabolic characteristics regulating MDSC remain unclear. We aimed to determine the energy metabolic pathway(s) used by MDSC, establish its impact on their immunosuppressive function, and test whether its inhibition blocks MDSC and enhances antitumor therapies. Using several murine tumor models, we found that tumor-infiltrating MDSC (T-MDSC) increased fatty acid uptake and activated fatty acid oxidation (FAO). This was accompanied by an increased mitochondrial mass, upregulation of key FAO enzymes, and increased oxygen consumption rate. Pharmacologic inhibition of FAO blocked immune inhibitory pathways and functions in T-MDSC and decreased their production of inhibitory cytokines. FAO inhibition alone significantly delayed tumor growth in a T-cell–dependent manner and enhanced the antitumor effect of adoptive T-cell therapy. Furthermore, FAO inhibition combined with low-dose chemotherapy completely inhibited T-MDSC immunosuppressive effects and induced a significant antitumor effect. Interestingly, a similar increase in fatty acid uptake and expression of FAO-related enzymes was found in human MDSC in peripheral blood and tumors. These results support the possibility of testing FAO inhibition as a novel approach to block MDSC and enhance various cancer therapies. Cancer Immunol Res; 3(11); 1236–47. ©2015 AACR.

Oxidative stress controls regulatory T cell apoptosis and suppressor activity and PD-L1-blockade resistance in tumor

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-β, 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.

T cells and costimulation in cancer

Abstract Optimal T cell response is dependent not only on T cell receptor activation, but also on additional signaling from coreceptors. The main coreceptors include B7 and tumor necrosis factor family members. They exert costimulatory or coinhibitory effects, and their balance determines the fate of T cell response. In normal conditions, costimulators facilitate the development of protective immune response, whereas coinhibitors dampen inflammation to avoid organ/tissue damage from excessive immune reaction. In the tumor microenvironment, the balance is garbled: inhibitory pathways predominate, and T cell response is impaired. The importance of cosignaling in the tumor immune response has been experimentally and clinically demonstrated. New therapeutic strategies targeting T cell cosignaling, especially coinhibitory molecules, are under active experimental and clinical investigation. This review summarizes the functions of main T cell cosignaling axes and discusses their clinical application.

Suppression of FIP200 and autophagy by tumor-derived lactate promotes naïve T cell apoptosis and affects tumor immunity

Tumor-derived lactate induced naïve T cell apoptosis via suppressing FIP200 expression and autophagy formation, resulting in mitochondria activation and imbalance of Bcl-2 family members in T cells. Tumor immunity flounders without FIP200 The tumor microenvironment impairs the function of effector and memory T cells, but its effect on naïve T cells is not well understood. Xia et al. show that the autophagy component FAK family–interacting protein of 200 kDa (FIP200) is critical for promoting antitumor responses mediated by T cells. Ovarian cancer patients and mouse tumor models had significantly higher rates of apoptosis and impaired autophagy in naïve T cells, as well as the selective loss of FIP200, which disrupted the balance of pro- and antiapoptotic factors. Tumor-derived lactate was shown to suppress FIP200 expression, thus causing enhanced apoptosis and attenuated antitumor responses. Naïve T cells are poorly studied in cancer patients. We report that naïve T cells are prone to undergo apoptosis due to a selective loss of FAK family–interacting protein of 200 kDa (FIP200) in ovarian cancer patients and tumor-bearing mice. This results in poor antitumor immunity via autophagy deficiency, mitochondria overactivation, and high reactive oxygen species production in T cells. Mechanistically, loss of FIP200 disables the balance between proapoptotic and antiapoptotic Bcl-2 family members via enhanced argonaute 2 (Ago2) degradation, reduced Ago2 and microRNA1198-5p complex formation, less microRNA1198-5p maturation, and consequently abolished microRNA1198-5p–mediated repression on apoptotic gene Bak1. Bcl-2 overexpression and mitochondria complex I inhibition rescue T cell apoptosis and promoted tumor immunity. Tumor-derived lactate translationally inhibits FIP200 expression by down-regulating the nicotinamide adenine dinucleotide level while potentially up-regulating the inhibitory effect of adenylate-uridylate–rich elements within the 3′ untranslated region of Fip200 mRNA. Thus, tumors metabolically target naïve T cells to evade immunity.

Dendritic cells are stressed out in tumor

A recently paper published in Cell reports that dendritic cells (DCs) are dysfunctional in the tumor environment. Tumor impairs DC function through induction of endoplasmic reticulum stress response and subsequent disruption of lipid metabolic homeostasis.

Human Naive T Cells Express Functional CXCL8 and Promote Tumorigenesis

Naive T cells are thought to be functionally quiescent. In this study, we studied and compared the phenotype, cytokine profile, and potential function of human naive CD4+ T cells in umbilical cord and peripheral blood. We found that naive CD4+ T cells, but not memory T cells, expressed high levels of chemokine CXCL8. CXCL8+ naive T cells were preferentially enriched CD31+ T cells and did not express T cell activation markers or typical Th effector cytokines, including IFN-γ, IL-4, IL-17, and IL-22. In addition, upon activation, naive T cells retained high levels of CXCL8 expression. Furthermore, we showed that naive T cell–derived CXCL8 mediated neutrophil migration in the in vitro migration assay, supported tumor sphere formation, and promoted tumor growth in an in vivo human xenograft model. Thus, human naive T cells are phenotypically and functionally heterogeneous and can carry out active functions in immune responses.

Phenotype and tissue distribution of CD28H+ immune cell subsets

ABSTRACT CD28H is a newly discovered co-receptor of the human B7 family. CD28H interacts with its ligand B7-H5 and regulates T cell response. Here we showed that CD28H was not expressed on granulocytes, monocytes, myeloid dendritic cells (MDCs), and B cells, but constitutively expressed with moderate levels on memory T cells and with high levels on naïve T cells, innate lymphoid cells (ILCs), natural killer (NK) cells, and plasmacytoid dendritic cells (PDCs) in human peripheral blood. Similar CD28H+ cell profile existed in secondary lymphoid organs and pathological tissues including multiple types of cancers. Further analysis demonstrated that CD28H+ naïve and CD28H+ memory T cells were characterized with increased naïve feature and less effector functional phenotype, respectively. High levels of constitutive CD28H expression on naïve T cells and innate immune cells suggest a potential role of CD28H in innate and adaptive immunity.

Abstract 4078: EZH2 marks polyfunctional memory T cells and controls tumor immunity

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Polyfunctional T cells mediate potent anti-viral immunity. However, the nature and molecular mechanisms controlling their functional signature remain poorly understood. Here we report that polyfunctional T cells are characterized by high proliferative capacity and apoptotic resistance. Enhancer of zeste homolog 2 (EZH2) phenotypically marks them and functionally controls their survival and expansion. Notch signaling regulates effector T cell function. We show that EZH2 represses Numb and Fbxw7, two Notch repressors, activates Notch signaling, and Notch subsequently stimulates Bcl-2 expression and protects EZH2+ T cells from apoptosis via trimethylating histone H3 on lysine 27. Moreover, EZH2 targets T cell cycling repressors and promotes their expansion. EZH2+CD8+ T cells mediate anti-tumor immunity and are associated with improved long-term cancer survival. Together, the data reveal a novel role and mechanism for EZH2 in controlling polyfunctional T cells. Thus, manipulation of EZH2 signaling in T cells may have therapeutic potential in treating cancer patients. Citation Format: Ende Zhao, Tomasz Maj, Ilona Kryczek, Lili Zhao, Shuang Wei, Shanshan Wan, Joel Crespo, Wojciech Szeliga, Linda Vatan, Ke Wu, Arul M. Chinnaiyan, Theodore H. Welling, Victor E. Marquez, Jan Kotarski, Yi Zhang, Rebecca Liu, Kaixiong Tao, Guobin Wang, Weiping Zou. EZH2 marks polyfunctional memory T cells and controls tumor immunity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4078. doi:10.1158/1538-7445.AM2014-4078