Glucocorticoid-Induced TNFR family Related gene (GITR) enhances dendritic cell activity

Expression patterns of novel immunotherapy targets in intermediate- and high-grade lung neuroendocrine neoplasms

BACKGROUND

Advancements in immunotherapeutic approaches only had a modest impact on the therapy of lung neuroendocrine neoplasms (LNENs). Our multicenter study aimed to investigate the expression patterns of novel immunotherapy targets in intermediate- and high-grade LNENs.

METHODS

The expressions of V-domain Ig suppressor of T cell activation (VISTA), OX40L, Glucocorticoid-induced TNF receptor (GITR), and T cell immunoglobulin and mucin domain 3 (TIM3) proteins were measured by immunohistochemistry in surgically resected tumor samples of 26 atypical carcinoid (AC), 49 large cell neuroendocrine lung cancer (LCNEC), and 66 small cell lung cancer (SCLC) patients. Tumor and immune cells were separately scored.

RESULTS

Tumor cell TIM3 expression was the highest in ACs (p < 0.001), whereas elevated tumor cell GITR levels were characteristic for both ACs and SCLCs (p < 0.001 and p = 0.011, respectively). OX40L expression of tumor cells was considerably lower in ACs (vs. SCLCs; p < 0.001). Tumor cell VISTA expression was consistently low in LNENs, with no significant differences across histological subtypes. ACs were the least immunogenic tumors concerning immune cell abundance (p < 0.001). Immune cell VISTA and GITR expressions were also significantly lower in these intermediate-grade malignancies than in SCLCs or in LCNECs. Immune cell TIM3 and GITR expressions were associated with borderline prognostic significance in our multivariate model (p = 0.057 and p = 0.071, respectively).

CONCLUSIONS

LNEN subtypes have characteristic and widely divergent VISTA, OX40L, GITR, and TIM3 protein expressions. By shedding light on the different expression patterns of these immunotherapy targets, the current multicenter study provides support for the future implementation of novel immunotherapeutic approaches.

Glucocorticoid induced TNF receptor family-related protein (GITR) - A novel driver of atherosclerosis

Atherosclerosis is a lipid-driven, chronic inflammatory disease. In spite of efficient lipid lowering treatments, such as statins and PCSK9 inhibitors, patients, especially those with elevated inflammatory biomarkers, still have a significant residual cardiovascular disease risk. Novel drugs targeting inflammatory mediators are needed to further reduce this residual risk. Agonistic immune checkpoint proteins, including CD86, CD40L and CD40, have been shown to be drivers of atherosclerosis. Recently, glucocorticoid-induced tumour necrosis factor receptor family-related protein (GITR), a co-stimulatory immune checkpoint protein, was identified to be pivotal in cardiovascular disease. Cardiovascular patients have elevated soluble GITR plasma levels compared to healthy controls. Furthermore, in human carotid endarterectomy plaques, GITR expression was higher in plaques from symptomatic compared to asymptomatic patients and correlated with features of plaque vulnerability. Moreover, depleting GITR reduced atherosclerotic plaque development in mice. GITR-deficient monocytes and macrophages exhibited less inflammatory potential and reduced migratory capacity. In this review, we discuss GITR's effects on various immune cells, mechanisms, signalling pathways and finally GITR's potential as a novel drug target in atherosclerosis.

The Role of GITR/GITRL Interaction in Autoimmune Diseases

Glucocorticoid-induced TNFR-related protein (GITR) is a member of the TNFR superfamily which is expressed in various cells, including T cells, natural killer cells and some myeloid cells. GITR is activated by its ligand, GITRL, mainly expressed on antigen presenting cells and endothelial cells. It has been acknowledged that the engagement of GITR can modulate both innate and adaptive immune responses. Accumulated evidence suggests GITR/GITRL interaction is involved in the pathogenesis of tumor, inflammation and autoimmune diseases. In this review, we describe the effects of GITR/GITRL activation on effector T cells, regulatory T cells (Tregs) and myeloid cells; summarize its role and the underlying mechanisms in modulating autoimmune diseases.

Transcriptomic profiling of bovine blood dendritic cells and monocytes following TLR stimulation

Dendritic cells (DC) and monocytes are vital for the initiation of innate and adaptive immune responses. Recently, we identified bona fide DC subsets in blood of cattle, revealing subset- and species-specific transcription of toll-like receptors (TLR). In the present study, we analyzed phenotypic and transcriptional responses of bovine DC subsets and monocytes to in vitro stimulation with four to six different TLR ligands. Bovine DC subsets, especially plasmacytoid DC (pDC), showed a clear increase of CCR7, CD25, CD40, CD80, CD86, and MHC-II expression both on mRNA and protein level. Flow cytometric detection of p38 MAPK phosphorylation 15 min after stimulation confirmed activation of DC subsets and monocytes in accordance with TLR gene expression. Whole-transcriptome sequencing of sorted and TLR-stimulated subsets revealed potential ligand- and subset-specific regulation of genes associated with inflammation, T-cell co-stimulation, migration, metabolic reprogramming, and antiviral activity. Gardiquimod was found to evoke strong responses both in DC subsets and monocytes, while Poly(I:C) and CpG preferentially triggered responses in cDC1 and pDC, respectively. This in-depth analysis of ligand responsiveness is essential for the rational design of vaccine adjuvants in cattle, and provides a solid basis for comparative studies on DC and monocyte biology across species.

Tolerogenic Transcriptional Signatures of Steady-State and Pathogen-Induced Dendritic Cells

Dendritic cells (DCs) are key directors of tolerogenic and immunogenic immune responses. During the steady state, DCs maintain T cell tolerance to self-antigens by multiple mechanisms including inducing anergy, deletion, and Treg activity. All of these mechanisms help to prevent autoimmune diseases or other hyperreactivities. Different DC subsets contribute to pathogen recognition by expression of different subsets of pattern recognition receptors, including Toll-like receptors or C-type lectins. In addition to the triggering of immune responses in infected hosts, most pathogens have evolved mechanisms for evasion of targeted responses. One such strategy is characterized by adopting the host’s T cell tolerance mechanisms. Understanding these tolerogenic mechanisms is of utmost importance for therapeutic approaches to treat immune pathologies, tumors and infections. Transcriptional profiling has developed into a potent tool for DC subset identification. Here, we review and compile pathogen-induced tolerogenic transcriptional signatures from mRNA profiling data of currently available bacterial- or helminth-induced transcriptional signatures. We compare them with signatures of tolerogenic steady-state DC subtypes to identify common and divergent strategies of pathogen induced immune evasion. Candidate molecules are discussed in detail. Our analysis provides further insights into tolerogenic DC signatures and their exploitation by different pathogens.

Co-stimulatory molecules in and beyond co-stimulation – tipping the balance in atherosclerosis?

A plethora of basic laboratory and clinical studies has uncovered the chronic inflammatory nature of atherosclerosis. The adaptive immune system with its front-runner, the T cell, drives the atherogenic process at all stages. T cell function is dependent on and controlled by a variety of either co-stimulatory or co-inhibitory signals. In addition, many of these proteins enfold T cell-independent pro-atherogenic functions on a variety of cell types. Accordingly they represent potential targets for immune- modulatory and/or anti-inflammatory therapy of atherosclerosis. This review focuses on the diverse role of co-stimulatory molecules of the B7 and tumour necrosis factor (TNF)-superfamily and their downstream signalling effectors in atherosclerosis. In particular, the contribution of CD28/CD80/CD86/CTLA4, ICOS/ICOSL, PD-1/PDL-1/2, TRAF, CD40/CD154, OX40/OX40L, CD137/CD137L, CD70/CD27, GITR/GITRL, and LIGHT to arterial disease is reviewed. Finally, the potential for a therapeutic exploitation of these molecules in the treatment of atherosclerosis is discussed.

Role of Tumor Necrosis Factor Superfamily in Neuroinflammation and Autoimmunity

Tumor necrosis factor superfamily (TNFSF) molecules play an important role in the activation, proliferation, differentiation, and migration of immune cells into the central nervous system (CNS). Several TNF superfamily molecules are known to control alloimmunity, autoimmunity, and immunity. Development of transgenic and gene knockout animals, and monoclonal antibodies against TNFSF molecules have increased our understanding of individual receptor-ligand interactions, and their intracellular signaling during homeostasis and neuroinflammation. A strong clinical association has been observed between TNFSF members and CNS autoimmunity such as multiple sclerosis and also in its animal model experimental autoimmune encephalomyelitis. Therefore, they are promising targets for alternative therapeutic options to control autoimmunity. Although, TNFSF ligands are widely distributed and have diverse functions, we have restricted the discussions in this review to TNFSF receptor-ligand interactions and their role in the pathogenesis of neuroinflammation and CNS autoimmunity.

Amnion-derived multipotent progenitor cells inhibit blood monocyte differentiation into mature dendritic cells

Cells derived from the placenta have become the focus of extensive research concerning their ability to be used for regenerative medicine or cellular therapies. In a previous study, we characterized amnion-derived multipotent progenitor cells, or AMP cells, by in vitro methods and showed they were able to inhibit antigen-specific T-cell proliferation in a cell-to-cell contact-dependent fashion. Here we examine specific mechanisms involved in immunomodulation by AMP cells. We found that AMP cells significantly inhibited monocyte-derived myeloid dendritic cell (DC) maturation when placed in coculture. Cocultured monocytes retained the nondifferentiated macrophage marker CD14 while exhibiting significant reduction in DC maturation markers CD83 and CD1a, indicating an immature DC maturation state that is pivotal in determining its immune stimulatory or regulatory status. This effect was again dependent on cell-to-cell contact interaction. We also found a significant shift in cytokines present in the microenvironment of cocultures, which indicated a regulatory DC function rather than a stimulatory cell type. Here supernatants taken from AMP cell/monocyte cocultures yielded significant levels of regulatory cytokines, such as PGE2, IL-6, IL-10, and MIC-1. The soluble form of HLA-G was also found at higher levels in cocultures. In contrast, supernatants contained significantly less amounts of the T-cell-stimulating factor IL-12, which is normally produced by activated DCs. Interestingly, cocultured monocytes acquired significant expression of HLA-G on their cell surface over time. HLA-G has multifaceted immunological implications and may be a key molecule in influencing these cells to behave as regulatory DCs. Together, the influence of AMP cells on maturing DCs may favor a regulatory pathway that can be useful for therapeutic applications for immune-mediated disorders or transplantation therapies.

Pharmacological modulation of GITRL/GITR system: therapeutic perspectives

Glucocorticoid-induced TNFR-related (gitr) is a gene coding for a member of the TNF receptor superfamily. GITR activation by its ligand (GITRL) influences the activity of effector and regulatory T cells, thus participating in the development of immune response against tumours and infectious agents, as well as in autoimmune and inflammatory diseases. Notably, treating animals with GITR-Fc fusion protein ameliorates autoimmune/inflammatory diseases while GITR triggering, by treatment with anti-GITR mAb, is effective in treating viral, bacterial and parasitic infections, as well in boosting immune response against tumours. GITR modulation has been indicated as one of the top 25 most promising research areas by the American National Cancer Institute, and a clinical trial testing the efficacy of an anti-GITR mAb in melanoma patients has been started. In this review, we summarize results regarding: (i) the mechanisms by which GITRL/GITR system modulates immune response; (ii) the structural and functional studies clearly demonstrating differences between GITRL/GITR systems of mice and humans; (iii) the molecules with pharmacological activities including anti-GITR mAbs, GITR-Fc and GITRL-Fc fusion proteins, GITRL in monomer or multimer conformation; and (iv) the possible risks deriving from GITRL/GITR system pharmacological modulation. In conclusion, GITR triggering and inhibition could be useful in treating tumours, infectious diseases, as well as autoimmune and inflammatory diseases. However, differences between mouse and human GITRL/GITR systems suggest that further preclinical studies are needed to better understand how safe therapeutic results can be obtained and to design appropriate clinical trials.

GITR-expressing regulatory T-cell subsets are increased in tumor-positive lymph nodes from advanced breast cancer patients as compared to tumor-negative lymph nodes

Lymph node (LN) infiltration by neoplastic process involves important changes in lymph node immune microenvironment. In particular, regulatory T cells (Treg) seem to have a key role in altering the immunoediting function of the immune system which leads to the elusion of the tumor from immune surveillance. In this study, we evaluated the expression of T-cell markers in CD4+ and CD8+ subsets from tumor-positive and tumor-negative lymph nodes from the same, advanced stage breast cancer patient. The study was carried out on 3 patients and similar results were obtained. Flow cytometric analysis of CD8+ cells demonstrated a significant difference in the expression of CD25, CD45RA, CD45RO, and GITRL (Glucocorticoid-Induced TNF receptor-Related ligand). Flowcytometric analysis of CD4+ cells demonstrated a significant difference in the expression of GITR (Glucocorticoid-Induced TNF receptor-Related), CD25, FoxP3 (Forkhead box P3), CD28, and CD45RA. Multiple staining allowed the identification of two Treg subpopulations, CD4+ CD25 highGITR+ CD127-/low and CD4+ CD25 low GITR+ CD127+ cells, proving that both are increased in the positive nodes in comparison with the negative nodes from the same patient. We identified for the first time the CD4+ CD25 low GITR+ CD127+ Treg subpopulation in cancer, and the 2.6 fold increase in positive LN suggests that this Treg subpopulation could be a key player in metastasis. We also found GITRL expression in the CD8 lymphocytes, which may also contribute to the changes of metastatic lymph node microenvironment. These findings make both GITR and GITRL good possible co-candidates for future therapeutical intervention against metastasis and perhaps also as disease evolution biomarkers.

CD8+ T cells: GITR matters

As many members of the tumor necrosis factor receptor superfamily, glucocorticoid-induced TNFR-related gene (GITR) plays multiple roles mostly in the cells of immune system. CD8⁺ T cells are key players in the immunity against viruses and tumors, and GITR has been demonstrated to be an essential molecule for these cells to mount an immune response. The aim of this paper is to focus on GITR function in CD8⁺ cells, paying particular attention to numerous and recent studies that suggest its crucial role in mouse disease models.

The glucocorticoid-induced TNF receptor family-related protein (GITR) is critical to the development of acute pancreatitis in mice

BACKGROUND AND PURPOSE

Pancreatitis represents a life-threatening inflammatory condition where leucocytes, cytokines and vascular endothelium contribute to the development of the inflammatory disease. The glucocorticoid-induced tumour necrosis factor (TNF) receptor family-related protein (GITR) is a costimulatory molecule for T lymphocytes, modulates innate and adaptive immune system and has been found to participate in a variety of immune responses and inflammatory processes. Our purpose was to verify whether inhibition of GITR triggering results in a better outcome in experimental pancreatitis.

EXPERIMENTAL APPROACH

In male GITR knock-out (GITR(-/-)) and GITR(+/+) mice on Sv129 background, acute pancreatitis was induced after i.p. administration of cerulein. Other experimental groups of GITR(+/+) mice were also treated with different doses of Fc-GITR fusion protein (up to 6.25 µg·mouse⁻¹), given by implanted mini-osmotic pump. Clinical score and pro-inflammatory parameters were evaluated.

KEY RESULTS

A less acute pancreatitis was found in GITR(-/-) mice than in GITR(+/+) mice, with marked differences in oedema, neutrophil infiltration, pancreatic dysfunction and injury. Co-treatment of GITR(+/+) mice with cerulein and Fc-GITR fusion protein (6.25 µg·mouse⁻¹) decreased the inflammatory response and tissue injury, compared with treatment with cerulein alone. Inhibition of GITR triggering was found to modulate activation of nuclear factor κB as well as the production of TNF-α, interleukin-1β, inducible nitric oxide synthase, nitrotyrosine, poly-ADP-ribose, intercellular adhesion molecule-1 and P-selectin.

CONCLUSIONS AND IMPLICATIONS

The GITR-GITR ligand system is crucial to the development of acute pancreatitis in mice. Our results also suggest that the Fc-GITR fusion protein could be useful in the treatment of acute pancreatitis.