Glucocorticoid-induced TNFR-related Protein Research Articles

Exploring the Role of GITR/GITRL Signaling: From Liver Disease to Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and presents a continuously growing incidence and high mortality rates worldwide. Besides advances in diagnosis and promising results of pre-clinical studies, established curative therapeutic options for HCC are not currently available. Recent progress in understanding the tumor microenvironment (TME) interactions has turned the scientific interest to immunotherapy, revolutionizing the treatment of patients with advanced HCC. However, the limited number of HCC patients who benefit from current immunotherapeutic options creates the need to explore novel targets associated with improved patient response rates and potentially establish them as a part of novel combinatorial treatment options. Glucocorticoid-induced TNFR-related protein (GITR) belongs to the TNFR superfamily (TNFRSF) and promotes CD8+ and CD4+ effector T-cell function with simultaneous inhibition of Tregs function, when activated by its ligand, GITRL. GITR is currently considered a potential immunotherapy target in various kinds of neoplasms, especially with the concomitant use of programmed cell-death protein-1 (PD-1) blockade. Regarding liver disease, a high GITR expression in liver progenitor cells has been observed, associated with impaired hepatocyte differentiation, and decreased progenitor cell-mediated liver regeneration. Considering real-world data proving its anti-tumor effect and recently published evidence in pre-clinical models proving its involvement in pre-cancerous liver disease, the idea of its inclusion in HCC therapeutic options theoretically arises. In this review, we aim to summarize the current evidence supporting targeting GITR/GITRL signaling as a potential treatment strategy for advanced HCC.

Abstract 4034: Lag3 blockade enhances the anti-tumor effect of dual GITR agonism and PD-1 blockade in a preclinical melanoma model

Abstract Immune checkpoint blockade (ICB) therapies, specifically anti PD-1 and anti CTLA-4, have resulted in tremendous success in the clinic. However, a substantial number of patients still relapse due to either inherent or acquired resistance to ICB therapies. In this scenario, activation of T cell co-stimulation pathways along with ICB emerges as a promising strategy to improve anti-tumor responses. Engagement of Glucocorticoid induced TNFR Related protein (GITR) costimulatory molecule, leads to enhanced activation of cytotoxic T cells while destabilizing suppressive T regulatory cells in the tumor microenvironment. Additionally, combining GITR agonism with PD-1 blockade improves the anti-tumor response in a murine model of advanced melanoma resistant to ICB, positioning GITR as an attractive immunotherapeutic target. In this study, we evaluated the therapeutic efficacy of combining blockade of the immune checkpoint LAG3 with GITR agonism for treating ICB-resistant advanced melanoma, using the B16 model. The combination of LAG3 blockade with GITR agonism was well tolerated, leading to better tumor control and improved survival. Our data revealed increased B cell infiltration and activation within tumors and draining lymph nodes (LNs) of treated mice. B cell depletion diminished the anti-tumor effect of the combination therapy, suggesting that B cells play an active role in controlling tumor growth. Spleens from treated mice exhibited increased lymphocytic hyperplasia, along with more and larger germinal centers. B cell receptor sequencing revealed an increased clonality and reduced entropy. Treating B cells with GITR agonism and LAG3 blockade in vitro led to increased activation and proliferation, suggesting a direct effect of these therapies on B cells. Furthermore, adding LAG3 blockade to the dual combination of GITR agonism and PD-1 blockade resulted in superior tumor control and increased B cell activity in the draining LNs. Collectively, our findings suggest that the humoral response significantly contributes to the anti-tumor responses elicited by ICB when combined with GITR agonism. This triple combination therapy (LAG3 blockade + PD1 blockade + GITR agonism) holds promise as a safe and potent therapeutic strategy to overcome ICB resistance. Further investigation into the mechanism of action by which GITR agonism leads to enhanced B cell responses when combined with ICB is warranted in order to design more effective therapies for cancer treatment. Citation Format: Rachana R. Maniyar, Yuval Elhanati, Levi Mangarin, Yacine Marouf, Ashley Ahmed, Benjamin Greenbaum, Jedd Wolchok, Taha Merghoub. Lag3 blockade enhances the anti-tumor effect of dual GITR agonism and PD-1 blockade in a preclinical melanoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4034.

Intravenous injection of tumor extracellular vesicles suppresses tumor growth by reducing the regulatory T cell phenotype.

Colorectal cancer is a disease of unmet medical need. Although extracellular vesicles (EVs) have been implicated in anti-tumor responses, discrepancies were observed among studies. We analyzed the role of tumor-derived EVs (TEVs) in tumor progression in vivo by focusing on regulatory T (Treg) cells, which play essential roles in tumor development and progression. A mouse model of colorectal cancer lung metastasis was generated using BALB/c mice by tail vein injection of the BALB/c colon adenocarcinoma cell line Colon-26. TEVs derived from Colon-26 and BALB/c lung squamous cell carcinoma ASB-XIV were retrieved from the culture media supernatants. A TEV equivalent to 10µg protein was injected every other day for 2weeks. Histology and immunohistochemistry studies revealed that lung tumors reduced in the Colon-26-EV group when compared to the phosphate-buffered saline (PBS) group. The population of CD4 + FoxP3 + cells in the lung was upregulated in the PBS group mice when compared to the healthy mice (P < 0.001), but was significantly downregulated in the Colon-26-EV group mice when compared to the PBS group mice (P < 0.01). Programmed cell death protein 1, glucocorticoid-induced TNFR-related protein, and CD69 expression in lung Treg cells were markedly upregulated in the PBS group when compared to the healthy mice, but downregulated in the Colon-26-EV group when compared to the PBS group. The changes in expression were dose-dependent for Colon-26-EVs. ASB-EVs also led to significantly downregulated Treg cell expression, although non-cancer line 3T3-derived EVs did not. Our study suggests that TEVs possess components for tumor suppression.

CD103 Regulates Dermal Regulatory T Cell Motility and Interactions with CD11c-Expressing Leukocytes to Control Skin Inflammation.

Dermal regulatory T cells (Tregs) are essential for maintenance of skin homeostasis and control of skin inflammatory responses. In mice, Tregs in the skin are characterized by high expression of CD103, the αE integrin. Evidence indicates that CD103 promotes Treg retention within the skin, although the mechanism underlying this effect is unknown. The main ligand of CD103, E-cadherin, is predominantly expressed by cells in the epidermis. However, because Tregs are predominantly located within the dermis, the nature of the interactions between E-cadherin and CD103-expressing Tregs is unclear. In this study, we used multiphoton intravital microscopy to examine the contribution of CD103 to Treg behavior in resting and inflamed skin of mice undergoing oxazolone-induced contact hypersensitivity. Inhibition of CD103 in uninflamed skin did not alter Treg behavior, whereas 48 h after inducing contact hypersensitivity by oxazolone challenge, CD103 inhibition increased Treg migration. This coincided with E-cadherin upregulation on infiltrating myeloid leukocytes in the dermis. Using CD11c-enhanced yellow fluorescent protein (EYFP) × Foxp3-GFP dual-reporter mice, inhibition of CD103 was found to reduce Treg interactions with dermal dendritic cells. CD103 inhibition also resulted in increased recruitment of effector CD4+ T cells and IFN-γ expression in challenged skin and resulted in reduced glucocorticoid-induced TNFR-related protein expression on Tregs. These results demonstrate that CD103 controls intradermal Treg migration, but only at later stages in the inflammatory response, when E-cadherin expression in the dermis is increased, and provide evidence that CD103-mediated interactions between Tregs and dermal dendritic cells support regulation of skin inflammation.

Targeting GITR in cancer immunotherapy - there is no perfect knowledge.

Glucocorticoid-induced TNFR-related protein (GITR) belongs to the TNFR superfamily (TNFRSF) and stimulates both the acquired and innate immunity. GITR is broadly expressed on immune cells, particularly regulatory T cells (Tregs) and natural killer (NK) cells. Given its potential to promote T effector function and impede Treg immune suppression, GITR is an attractive target for cancer immunotherapy. Preclinically, GITR agonists have demonstrated potent anti-tumor efficacy singly and in combination with a variety of agents, including PD-1 blockade. Multiple GITR agonists have been advanced into the clinic, although the experience with these agents has been disappointing. Recent mechanistic insights into the roles of antibody structure, valency, and Fc functionality in mediating anti-tumor efficacy may explain some of the apparent inconsistency or discordance between preclinical data and observed clinical efficacy.

Implications of GITR expression profile for precision immunotherapeutics.

e14561 Background: Glucocorticoid-induced TNFR-related protein (GITR) is a type I transmembrane protein expressed mostly on CD25+CD4+ T-regs and upregulated on all T-cells upon activation. It serves as a T-cell co-stimulatory receptor and its role in cancer treatment is being explored. While pre-clinical data using combination therapies involving GITR agonism showed promise, early clinical trials have not shown improved outcomes to date. Methods: RNA expression levels of 397 genes in 514 patients with a variety of cancer types were assessed and analyzed at OmniSeq. Transcript levels were normalized to internal housekeeping gene profiles and ranked as percentiles using a reference population. High expression was defined as ≥ 75th percentile, and low-moderate as &lt;75th percentile. Univariate p-values were calculated using Welch t-test or Fischer’s exact test. Multivariate p-values were calculated using logistical regression. Results: A total of 99 patients (19.3%) had GITR high expression. Cancers with the highest proportion of GITR high expression were lung (7/20, 35%) and breast (19/49, 39%), and both these cancers showed a statistically significant association with GITR high expression on multivariate analysis (lung: OR 3.5, p = 0.04, 95% confidence interval (CI) 1.06 – 10.06 CI and breast: OR 4.59, p &lt;0.001, 95% CI: 2.11 – 9.85). 30% of lung and 30.6% of breast cancer patients had a GITR high with ligand low-moderate expression profile; these cancers had the highest proportion of patients with this profile. GITR high expression showed significant association with high RNA expression of multiple known immune checkpoint proteins (PD-1, PD-L1, CTLA4, LAG3, OX40, ICOS and CD137, but not TIM3) as well as PD-L1 IHC ≥1 on univariate analysis, but statistically significant association was only seen with PD-L1 IHC ≥1 (p = 0.007) and OX40 high expression (p = 0.001) on multivariate analysis. Conclusions: While clinical trials with GITR agonism are ongoing, our data suggests selection of certain types of malignancies depending on GITR status may be required. Moreover, there is a correlation between high GITR and high OX40 RNA expression, which could imply increased efficacy using this targeted combination. Further clinical development based on this immune-profiling is warranted. [Table: see text]

Regulatory T cells infiltrate the tumor-induced tertiary lymphoïd structures and are associated with poor clinical outcome in NSCLC

On one hand, regulatory T cells (Tregs) play an immunosuppressive activity in most solid tumors but not all. On the other hand, the organization of tumor-infiltrating immune cells into tertiary lymphoid structures (TLS) is associated with long-term survival in most cancers. Here, we investigated the role of Tregs in the context of Non-Small Cell Lung Cancer (NSCLC)-associated TLS. We observed that Tregs show a similar immune profile in TLS and non-TLS areas. Autologous tumor-infiltrating Tregs inhibit the proliferation and cytokine secretion of CD4+ conventional T cells, a capacity which is recovered by antibodies against Cytotoxic T-Lymphocyte-Associated protein-4 (CTLA-4) and Glucocorticoid-Induced TNFR-Related protein (GITR) but not against other immune checkpoint (ICP) molecules. Tregs in the whole tumor, including in TLS, are associated with a poor outcome of NSCLC patients, and combination with TLS-dendritic cells (DCs) and CD8+ T cells allows higher overall survival discrimination. Thus, Targeting Tregs especially in TLS may represent a major challenge in order to boost anti-tumor immune responses initiated in TLS.

High-level of intratumoral GITR+ CD4 Tcells associate with poor prognosis in gastric cancer.

Immunotherapy targeting glucocorticoid-induced TNFR-related protein (GITR) exhibited strong anti-tumor capacity in mouse model but poor efficacy in clinical trials. This may be attributed to the different GITR expression mode between human and mouse. In this study, we analyzed single-cell RNA sequencing (scRNA-seq) data of human gastric cancer (GC) and used flow to explore the GITR expression across Tcell subsets and tissue types in GC patients. We revealed that GITR+ CD4 Tcells, including regulatory CD4T (Treg) cells and conventional CD4T (Tconv) cells, might contribute to the immunosuppressive microenvironment in GC. The enrichment of these cells was associated with a worse prognosis. Moreover, we found the cellular distribution of GITR protein in Treg cells was microenvironment dependent. In conclusion, GITR is still an important immune checkpoint need to be studied.

218P A symbiotic relationship between persistent and emerging resistant oligo-clones dictates resistance to immunotherapy in pancreatic cancer

Immunotherapy has had a limited clinical benefit in pancreatic ductal adenocarcinoma (PDAC). In a pre-clinical mouse model of PDAC treated with glucocorticoid-induced TNFR-related protein (GITR) agonist, the tumours showed nondurable and heterogeneous responses to the GITR agonist. We hypothesised that resistance to GITR agonist is associated with a unique symbiotic interaction between persistent and emergent tumour clones resistant to therapy response.

GITR agonistic stimulation enhances the anti-tumor immune response in a mouse model of ESCC.

Esophageal cancer is a significant health burden in the United States and worldwide and is the 8th leading cause of cancer-related death. Over 90% of esophageal cancers are squamous cell cancers (ESCC). Despite the development of new therapies, the overall 5-year survival rate remains lower than 20%. Recent clinical trials of immunotherapy approaches in ESCC have shown that blocking PD-1/PD-L1 interactions can reduce tumor burden and increase survival, but this only occurs in a fraction of patients. This emphasizes the need for additional therapeutic options to improve overall response rates, duration of response, and overall survival. Glucocorticoid-induced TNFR-related protein (GITR) stimulation has emerged as a promising immunotherapy target, as its stimulation appears to promote tumor regression. In this study, we evaluated the consequences of GITR agonistic stimulation with the DTA-1 antibody (anti-GITR agonist) on esophageal squamous cell carcinoma (ESCC) progression. Increased expression of GITR was observed in esophageal tumors from ESCC patients in comparison to normal adjacent tissue and in a mouse model of ESCC. 100% of mice treated with 4-NQO/IgG control antibody developed invasive squamous cell carcinoma. Less advanced esophageal tumors were seen in mice treated with 4-NQO/anti-GITR agonist compared to 4-NQO/IgG treatment. 4-NQO/anti-GITR agonist-treated mice demonstrated a significant increase in mucosal CTL/Treg ratios as well as decreased gene expression profiles of pathways related to esophageal squamous cell carcinogenesis. Thus, GITR agonism merits further study as a treatment strategy for ESCC patients.

Abstract 5622: Preclinical evaluation of humanized PD1/GITR combination therapy using double humanized mouse

Abstract GITR (glucocorticoid-induced TNFR-related protein) is a member of tumor necrosis factor receptor superfamily, expressed on many kinds of cells including T cells, attracting attention as a co-stimulatory immune checkpoint molecule. GITRL, the ligand of GITR is mainly expressed on antigen presenting cells. GITR/GITRL interaction plays an important role on the development of immune response, which can serve as promising anti-tumor target. While more than twenty anti-GITR antibodies are at clinical stages, combination treatments of GITR agonist and PD-1 inhibitor may be a better choice. Thus, there is a need for pre-clinical mouse model to evaluate the anti-tumor effect of humanized PD1/GITR antibodies. Gempharmatech established PD1/GITR double humanized mouse line on a BALB/c background, in which the extracellular domain of mGITR was replaced with its human counterparts while the trans-membrane and cytoplasmic domain kept intact, as well as the same strategy of PD1. BALB/c-hPD1/hGITR mouse could successfully express similar levels of hGITR and hPD1 compared with BALB/c wild type mice. Moreover, no immune or developmental abnormalities were observed in the humanized mouse. Anti-GITR combination with anti-PD1 presented greater tumor growth inhibition than anti-PD1 or anti-GITR monotherapies in PD1/GITR double humanized mouse bearing CT26 tumors. In summary, BALB/c-hPD1/hGITR are valuable models for the pre-cilincal evaluation of candidate humanized PD1/GITR combination treatment or bispecific antibody therapies. Citation Format: Dongdong Yuan, Dongdong zhang, Hongyan Sun, Mingkun Zhang, Liyou Dong, Cunxiang Ju, Shuai Li, Huiyi Wang, Jing Zhao, Xiang Gao. Preclinical evaluation of humanized PD1/GITR combination therapy using double humanized mouse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5622.

Antibody-mediated blockade of the IL23 receptor destabilizes intratumoral regulatory T cells and enhances immunotherapy

Regulatory T cells (Treg) can impede antitumor immunity and currently represent a major obstacle to effective cancer immunotherapy. Targeting tumor-infiltrating regulatory Treg while sparing systemic Treg represents an optimal approach to this problem. Here, we provide evidence that the interleukin 23 receptor (IL23R) expressed by tumor-infiltrating Treg promotes suppressive activity. Disruption of the IL23R results in increased responsiveness of destabilized Treg to the IL12 cytokine, the production of γ-interferon, and the recruitment of CD8 T cells that inhibit tumor growth. Since the Treg destabilization pathway that is initiated by IL23R blockade is distinct and independent from the destabilization pathway coupled to glucocorticoid-induced TNFR-related protein (GITR) activation, we examined the impact of the coordinate induction of the two destabilization pathways on antitumor immune responses. Combined GITR and IL23R antibody treatment of mice inoculated with MC38 tumors resulted in robust and synergistic antitumor responses. These findings indicate that the delineation of independent Treg destabilization pathways may allow improved approaches to the development of combination immunotherapy for cancers.

Activated but functionally impaired memory Tregs are expanded in slow progressors to type 1 diabetes

Aims/hypothesisSlow progressors to type 1 diabetes are individuals positive for multiple pancreatic islet autoantibodies who have remained diabetes-free for at least 10 years; regulation of the autoimmune response is understudied in this group. Here, we profile CD4+ regulatory T cells (Tregs) in a small but well-characterised cohort of extreme slow progressors with a median age 43 (range 31–72 years), followed up for 18–32 years.MethodsPeripheral blood samples were obtained from slow progressors (n = 8), age- and sex-matched to healthy donors. One participant in this study was identified with a raised HbA1c at the time of assessment and subsequently diagnosed with diabetes; this donor was individually evaluated in the analysis of the data. Peripheral blood mononuclear cells (PBMCs) were isolated, and to assess frequency, phenotype and function of Tregs in donors, multi-parameter flow cytometry and T cell suppression assays were performed. Unsupervised clustering analysis, using FlowSOM and CITRUS (cluster identification, characterization, and regression), was used to evaluate Treg phenotypes.ResultsUnsupervised clustering on memory CD4+ T cells from slow progressors showed an increased frequency of activated memory CD4+ Tregs, associated with increased expression of glucocorticoid-induced TNFR-related protein (GITR), compared with matched healthy donors. One participant with a raised HbA1c at the time of assessment had a different Treg profile compared with both slow progressors and matched controls. Functional assays demonstrated that Treg-mediated suppression of CD4+ effector T cells from slow progressors was significantly impaired, compared with healthy donors. However, effector CD4+ T cells from slow progressors were more responsive to Treg suppression compared with healthy donors, demonstrated by increased suppression of CD25 and CD134 expression on effector CD4+ T cells.Conclusions/interpretationsWe conclude that activated memory CD4+ Tregs from slow progressors are expanded and enriched for GITR expression, highlighting the need for further study of Treg heterogeneity in individuals at risk of developing type 1 diabetes.Graphical abstract

Soluble type immune checkpoint regulators using multiplex luminex immunoassay in chronic hepatitis B patients

AimsSoluble immune checkpoint regulators (sICs) were reported to have clinical impact on the diagnosis and progress of various diseases. This study compared the serum levels of 16 sICs in patients...

Phosphoproteomics reveals GITR agonism differentially regulates inflammatory vs. regulatory T cell subsets.

Abstract Triggering the co-stimulatory receptor glucocorticoid-induced TNFR-related protein (GITR) on T cells has been identified as a promising cancer immunotherapeutic strategy, yet the signaling events by which GITR agonism induces antitumor immunity are not well understood. GITR is expressed on activated CD4+ and CD8+ T cells, and is constitutively expressed on regulatory T cells (Tregs). While GITR appears to act as a conventional co-stimulatory receptor in effector CD4+ and CD8+ T cells, the role of GITR on Tregs remains controversial. The goal of this research was to utilize a phosphoproteomics approach to identify and compare GITR-mediated intracellular signaling events in induced-Tregs (iTregs), CD4+ T cells, and CD8+ cytotoxic T cells. We used the GITR agonist monoclonal antibody DTA-1 to stimulate the T cell subsets and confirmed GITR signaling via NFκB pathway activation and phospho-JNK induction. The phosphoproteomics data revealed different protein phosphorylation patterns among T cell subsets. For example, we observed phospho-p38 MAPK induction in the iTreg subset but not in the CD4+ T cells or CD8+ cytotoxic T cells. We also observed additional phospho-proteins induced by GITR triggering in the p38 pathway in the iTreg subset including phospho-MKK3, phospho-MKK6, phospho-MAPKAPK-2, and phospho-ATF-2. Induction of p38 MAPK signaling is functionally important as inhibition of p38 abrogated GITR-induced proliferation of iTregs. These data demonstrate that GITR agonism induces distinct phospho-proteome profiles between T cell subsets, and this differential signaling leads to unique responses that will need to be considered when targeting GITR with immunotherapeutic strategies.

In Vitro Treg Immunosuppression Assay of GITR Proteins Could Elucidate the Autoimmune-mediated Mechanism Underlying Type 1 Narcolepsy

Abstract: Type 1 narcolepsy is a hypersomnia sleep disorder characterized by excessive daytime sleep and shallow NREM nighttime sleep. Deficiency of hypocretin-1 secreting neurons in the lateral hypothalamus is the primary cause of the disorder and studies demonstrated that these neurons were solely diminished in a brain region of remarkable heterogeneous neuronal population. Specific destruction of targeted neurons could be achieved via antigen presentation to immune cells, a characteristic of cell-mediated response in the adaptive immune system. Given that hypocretin-1 neurons were exclusively targeted, this cultivated significant interest in searching for an autoimmune-mediated mechanism but studies currently lack adequate knowledge and consistent results. In this research proposal, it is hypothesized that enhanced glucocorticoid-induced TNFR-related (GITR) protein expression in T regulatory (Treg) cells results in defective suppression capacity of CD4+CD25+ T helper cells and defective self-tolerance thereby promoting destruction of hypocretin-1 secreting-neurons in the lateral hypothalamus of narcoleptics. The proposal devises a correlational study to measure cerebrospinal fluid (CSF) hypocretin-1 levels that were inversely proportional to GITR expression levels in Treg cells to assess the autoimmune nature of the disorder. This study is aimed at investigating how defective T regulatory cells respond in type 1 narcolepsy patients via CSF hypocretin-1 measurement and in vitro human T regulatory cell suppression assay.

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.

29 Poster Discussion - GITR agonist sensitizes MC38/OVA tumor to CTLA4 treatment by attenuating Tregs in GITR HuGEMM

Background: GITR (glucocorticoid-induced TNFR-related protein), a member of the TNF receptor superfamily, is highly expressed on the activated T cells, including CD4+ T cells, CD8+ T cells and Tregs. Upon binding to its ligand, GITR serves as a co-stimulating molecule, playing a vital role in T cell proliferation and anti-tumor activity by converting immunesuppressive Tregs into antitumor effector T cells. Activating GITR by agonistic antibodies, in combination of immune checkpoint inhibitors (ICIs), has been thought to be a highly plausible combo strategy which is now been tested in a few clinical studies. However, we are lacking preclinical models to evaluate efficacy of therapeutic GITR agonistic antibodies, which usually don’t cross-bind to mouse targets. To fill this gap, we developed a human GITR knock-in model (GITR HuGEMM).

Tumor-infiltrating regulatory T cells, CD8/Treg ratio, and cancer stem cells are correlated with lymph node metastasis in patients with early breast cancer.

Tumor-infiltrating lymphocytes are an important component of the tumor microenvironment (TME) in breast cancer. They have been linked with tumor pathogenesis in advanced stages. However, little is known about their contribution in early phases. In this study, we analyzed the infiltration of leukocytes and cancer stem cells (CSC) in tumors from patients with early breast cancer. Samples of blood and tumor tissue from 30 patients with breast cancer were collected, and the number of dendritic cells (DC), T cells, and CSC were analyzed by flow cytometry. Tumor-infiltrating CD4 and CD8 T cells expressed higher levels of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) compared with peripheral T cells. Regulatory T cells (Treg) were enriched in tumors and overexpressed glucocorticoid-induced TNFR-related protein and CTLA-4. Tumor Treg had a positive correlation with the amount of myeloid DC (mDC) and disease progression. The CD8/Treg ratio was associated with lymph node metastasis and tumor stages. The main subset of DC in early breast tumors was mDC, while plasmacytoid DC were almost absent. CSC were present in most tumors with higher frequencies in patients with lymph node metastasis. CSC were also associated with the amount of tumor-infiltrating Treg. Early breast cancer has an inflammatory milieu characterized by mDC, Treg, and CSC infiltration. The frequencies of Treg, CSC and CD8/Treg ratio were associated with disease progression. The composition of leukocytes and the presence of CSC in early breast tumors should be considered for the development of new therapeutic approaches.

GITR differentially affects lung effector T cell subpopulations during influenza virus infection.

Tissue resident memory T cells (Trm) are critical for local protection against reinfection. The accumulation of T cells in the tissues requires a post-priming signal from TNFR superfamily members, referred to as signal 4. Glucocorticoid-induced TNFR-related protein (GITR; TNFRSF18) signaling is important for this post-priming signal and for Trm formation during respiratory infection with influenza virus. As GITR signaling impacts both effector T cell accumulation and Trm formation, we asked if GITR differentially affects subsets of effector cells with different memory potential. Effector CD4+ T cells can be subdivided into 2 populations based on expression of lymphocyte antigen 6C (Ly6C), whereas effector CD8+ cells can be divided into 3 populations based on Ly6C and CX3CR1. The Ly6Chi and CX3CR1hi T cell populations represent the most differentiated effector T cells. Upon transfer, the Ly6Clo CD4+ effector T cells preferentially enter the lung parenchyma, compared to the Ly6Chi CD4+ T cells. We show that GITR had a similar effect on the accumulation of both the Ly6Chi and Ly6Clo CD4+ T cell subsets. In contrast, whereas GITR increased the accumulation of all three CD8+ T cell subsets defined by CX3CR1 and Ly6C expression, it had a more substantial effect on the least differentiated Ly6Clo CX3CR1lo subset. Moreover, GITR selectively up-regulated CXCR6 on the less differentiated CX3CR1lo CD8+ T cell subsets and induced a small but significant increase in CD127 selectively on the Ly6Clo CD4+ T cell subset. Thus, GITR contributes to accumulation of both differentiated effector cells as well as memory precursors, but with some differences between subsets.