T regulatory cells in cancer: recent advances and therapeutic potential

Drug target therapy and emerging clinical relevance of exosomes in meningeal tumors

Meningioma is the most common central nervous system (CNS) tumor. In recent decades, several efforts have been made to eradicate this disease. Surgery and radiotherapy remain the standard treatment options for these tumors. Drug therapy comes to play its role when both surgery and radiotherapy fail to treat the tumor. This mostly happens when the tumors are close to vital brain structures and are nonbenign. Although a wide variety of chemotherapeutic drugs and molecular targeted drugs such as tyrosine kinase inhibitors, alkylating agents, endocrine drugs, interferon, and targeted molecular pathway inhibitors have been studied, the roles of numerous drugs remain unexplored. Recent interest is growing toward studying and engineering exosomes for the treatment of different types of cancer including meningioma. The latest studies have shown the involvement of exosomes in the theragnostic of various cancers such as the lung and pancreas in the form of biomarkers, drug delivery vehicles, and vaccines. Proper attention to this new emerging technology can be a boon in finding the consistent treatment of meningioma.

Deciphering the immune landscape of head and neck squamous cell carcinoma: A single-cell transcriptomic analysis of regulatory T cell responses to PD-1 blockade therapy

Immunotherapy is changing the Head and Neck Squamous Cell Carcinoma (HNSCC) landscape and improving outcomes for patients with recurrent or metastatic HNSCC. A deeper understanding of the tumor microenvironment (TME) is required in light of the limitations of patients' responses to immunotherapy. Here, we aimed to examine how Nivolumab affects infiltrating Tregs in the HNSCC TME. We used single-cell RNA sequencing data from eight tissues isolated from four HNSCC donors before and after Nivolumab treatment. Interestingly, the study found that Treg counts and suppressive activity increased following Nivolumab therapy. We also discovered that changes in the CD44-SSP1 axis, NKG2C/D-HLA-E axis, and KRAS signaling may have contributed to the increase in Treg numbers. Furthermore, our study suggests that decreasing the activity of the KRAS and Notch signaling pathways, and increasing FOXP3, CTLA-4, LAG-3, and GZMA expression, may be mechanisms that enhance the killing and suppressive capacity of Tregs. Additionally, the result of pseudo-temporal analysis of the HNSCC TME indicated that after Nivolumab therapy, the expression of certain inhibitory immune checkpoints including TIGIT, ENTPD1, and CD276 and LY9, were decreased in Tregs, while LAG-3 showed an increased expression level. The study also found that Tregs had a dense communication network with cluster two, and that certain ligand-receptor pairs, including SPP1/CD44, HLA-E/KLRC2, HLA-E/KLRK1, ANXA1/FPR3, and CXCL9/FCGR2A, had notable changes after the therapy. These changes in gene expression and cell interactions may have implications for the role of Tregs in the TME and in response to Nivolumab therapy.

Confirmation of the Prognostic Value of Foxp3+ Cells in Canine Mammary Tumors

Foxp3+ cell counts were evaluated by immunohistochemistry in 59 canine mammary tumors, 20 adenomas, and 39 carcinomas in three different compartments: intratumoral, within the adjacent stroma, and in the distant stroma. Foxp3+ lymphocyte counts were compared with histotype, grading, presence of lymphatic invasion, immunohistochemical expression of estrogen and progesterone receptors, expression of c-erbB-2, and the overall survival (OS). Our findings confirmed that Foxp3+ cells were significantly higher in canine mammary carcinomas compared to adenomas. A significantly higher number of Foxp3+ cells were detected in grade III carcinomas compared to grade II carcinomas, as well as in tumors with lymphatic invasion and loss of ER-expression. Finally, a high number of Foxp3+ cells was associated with poor prognosis. In conclusion, our findings highlighted the association of Foxp3+ lymphocytes with negative clinicopathological features and shorter overall survival (OS), thus confirming the role of Tregs as a negative prognostic marker in canine mammary carcinomas.

CD47 and CD68 expression in breast cancer is associated with tumor-infiltrating lymphocytes, blood vessel invasion, detection mode, and prognosis

CD47 expressed on tumor cells binds to signal regulatory protein alpha on macrophages, initiating inhibition of phagocytosis. We investigated the relationships between tumor expression of CD47 and CD68 macrophage content, subsets of tumor-infiltrating lymphocytes (TILs), and vascular invasion in breast cancer. A population-based series of 282 cases (200 screen detected and 82 interval patients) from the Norwegian Breast Cancer Screening Program was examined. Immunohistochemical staining for CD47 and CD68 was evaluated on tissue microarray (TMA) slides. For CD47 evaluation, a staining index was used. CD68 tumor-associated macrophages were counted and dichotomized. TIL subsets (CD45, CD3, CD4, CD8, and FOXP3) were counted and dichotomized using immunohistochemistry on TMA slides. Vascular invasion (both lymphatic and blood vessel) was determined on whole tissue slides. High CD47 tumor cell expression or high counts of CD68 macrophages were significantly associated with elevated levels of all TIL subsets (p < 0.02), CD163 macrophages (p < 0.001), blood vessel invasion (CD31 positive) (p < 0.01), and high tumor cell Ki67 (p < 0.004). High CD47 expression was associated with ER negativity (p < 0.001), HER2 positive status (p = 0.03), and interval-detected tumors (p = 0.03). Combined high expression of CD47-CD68 was associated with a shorter recurrence-free survival (RFS) by multivariate analysis (hazard ratio [HR]: 2.37, p = 0.018), adjusting for tumor diameter, histologic grade, lymph node status, and molecular subtype. Patients with luminal A tumors showed a shorter RFS for CD47-CD68 high cases by multivariate assessment (HR: 5.73, p = 0.004). This study demonstrates an association of concurrent high CD47 tumor cell expression and high CD68 macrophage counts with various TIL subsets, blood vessel invasion (CD31 positive), other aggressive tumor features, and interval-presenting breast cancer. Our findings suggest a link between CD47, tumor immune response, and blood vessel invasion (CD31 positive). Combined high expression of CD47-CD68 was an independent prognostic factor associated with poor prognosis in all cases, as well as in the luminal A category.

Head and Neck Squamous Cell Carcinoma: Risk Factors, Molecular Alterations, Immunology and Peptide Vaccines

Head and neck squamous cell carcinoma (HNSCC) arises from the epithelial lining of the oral cavity, hypopharynx, oropharynx, and larynx. There are several potential risk factors that cause the generation of HNSCC, including cigarette smoking, alcohol consumption, betel quid chewing, inadequate nutrition, poor oral hygiene, HPV and Epstein–Barr virus, and Candida albicans infections. HNSCC has causative links to both environmental factors and genetic mutations, with the latter playing a more critical role in cancer progression. These molecular changes to epithelial cells include the inactivation of cancer suppressor genes and proto-oncogenes overexpression, resulting in tumour cell proliferation and distant metastasis. HNSCC patients have impaired dendritic cell (DC) and natural killer (NK) cell functions, increased production of higher immune-suppressive molecules, loss of regulatory T cells and co-stimulatory molecules and major histocompatibility complex (MHC) class Ι molecules, lower number of lymphocyte subsets, and a poor response to antigen-presenting cells. At present, the standard treatment modalities for HNSCC patients include surgery, chemotherapy and radiotherapy, and combinatorial therapy. Despite advances in the development of novel treatment modalities over the last few decades, survival rates of HNSCC patients have not increased. To establish effective immunotherapies, a greater understanding of interactions between the immune system and HNSCC is required, and there is a particular need to develop novel therapeutic options. A therapeutic cancer vaccine has been proposed as a promising method to improve outcome by inducing a powerful adaptive immune response that leads to cancer cell elimination. Compared with other vaccines, peptide cancer vaccines are more robust and specific. In the past few years, there have been remarkable achievements in peptide-based vaccines for HNSCC patients. Here, we summarize the latest molecular alterations in HNSCC, explore the immune response to HNSCC, and discuss the latest developments in peptide-based cancer vaccine strategies. This review highlights areas for valuable future research focusing on peptide-based cancer vaccines.

Evaluation of neutrophilia as a prognostic factor in dogs with multicentric lymphoma treated with a cyclophosphamide, doxorubicin, vincristine, and prednisone-based chemotherapy protocol

OBJECTIVE

To determine whether, in dogs with naïve multicentric lymphoma, neutrophilia at the time of initial diagnosis was associated with progression-free survival time (PFST) or overall response rate (ie, percentage of dogs with a complete or partial remission) and whether the initial neutrophil-to-lymphocyte ratio was associated with PFST.

ANIMALS

30 dogs with multicentric lymphoma and neutrophilia (including 16 treated with a cyclophosphamide, doxorubicin, vincristine, and prednisone [CHOP]-based protocol) and 37 historical control dogs without neutrophilia treated with a CHOP-based protocol.

PROCEDURES

Medical records were reviewed, and PFSTs and responses were documented.

RESULTS

Median PFST for the 16 dogs with neutrophilia treated with a CHOP-based protocol (70 days; range, 0 to 296 days) was significantly shorter than that for the 37 control dogs without neutrophilia (184.5 days; range, 23 to 503 days), and the overall response rate for dogs with neutrophilia (12/16 [75%]) was significantly lower than the rate for dogs without neutrophilia (36/37 [97%]). However, when all dogs in the study and control populations were considered together, the neutrophil-to-lymphocyte ratio at the time of diagnosis was not significantly associated with PFST.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that neutrophilia at the time of initial diagnosis may suggest a poorer prognosis in dogs with multicentric lymphoma. Prospective investigation into the role of neutrophils in the peripheral circulation and tumor microenvironment of cancer-bearing patients is warranted.

Association Between FSIP2 Mutation and an Improved Efficacy of Immune Checkpoint Inhibitors in Patients With Skin Cutaneous Melanoma

Background

Immune checkpoint inhibitors (ICIs) have shown remarkable success in treating skin cutaneous melanoma (SKCM); however, the response to treatment varies greatly between patients. Considering that the efficacy of ICI treatment is influenced by many factors, we selected the Fibrosheath interacting protein 2 (FSIP2) gene and systematically analyzed its potential to predict the efficacy of ICI treatment.

Methods

Patient data were collected from an ICI treatment cohort (n = 120) and a The Cancer Genome Atlas (TCGA)-SKCM cohort (n = 467). The data were divided into an FSIP2-mutant (MT) group and FSIP2-wild-type (WT) group according to FSIP2 mutation status. In this study, we analyzed the patients' overall survival rate, tumor mutational burden (TMB), neoantigen load (NAL), copy number variation (CNV), cell infiltration data and immune-related genes. We used gene set enrichment analysis (GSEA) to delineate biological pathways and processes associated with the efficacy of immunotherapy.

Results

The efficacy of ICI treatment of SKCM patients with FSIP2 mutation was significantly better than that of patients without FSIP2 mutation. The patients in the FSIP2-MT group had higher tumor immunogenicity and lower regulatory T cell (Treg) infiltration. Results of GSEA showed that pathways related to tumor progression (MAPK and FGFR), immunomodulation, and IL-2 synthesis inhibition were significantly downregulated in the FSIP2-MT group.

Conclusion

Our research suggests that the FSIP2 gene has the potential to predict the efficacy of ICI treatment. The high tumor immunogenicity and low Treg levels observed may be closely related to the fact that patients with FSIP2-MT can benefit from ICI treatment.

Natural Killer Cell Interactions With Myeloid Derived Suppressor Cells in the Tumor Microenvironment and Implications for Cancer Immunotherapy

The tumor microenvironment (TME) is a complex and heterogeneous environment composed of cancer cells, tumor stroma, a mixture of tissue-resident and infiltrating immune cells, secreted factors, and extracellular matrix proteins. Natural killer (NK) cells play a vital role in fighting tumors, but chronic stimulation and immunosuppression in the TME lead to NK cell exhaustion and limited antitumor functions. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid cells with potent immunosuppressive activity that gradually accumulate in tumor tissues. MDSCs interact with innate and adaptive immune cells and play a crucial role in negatively regulating the immune response to tumors. This review discusses MDSC-mediated NK cell regulation within the TME, focusing on critical cellular and molecular interactions. We review current strategies that target MDSC-mediated immunosuppression to enhance NK cell cytotoxic antitumor activity. We also speculate on how NK cell-based antitumor immunotherapy could be improved.

TLR2 ligation protects effector T cells from regulatory T-cell mediated suppression and repolarizes T helper responses following MVA-based cancer immunotherapy

Cancer immunotherapy is hampered by the immunosuppression maintained by regulatory T cells (Tregs) in tumor-bearing hosts. Stimulation of the Toll-like receptor 2 (TLR2) by Pam3Cys is known to affect Treg-mediated suppression. We found that Pam3Cys increases the proliferation of both CD4⁺ effector T cells (Teffs) and Tregs co-cultured in vitro, but did not induce the proliferation of Tregs alone upon CD3 and CD28 stimulation. In a mouse model of RMA-MUC1 tumors, Pam3Cys was administered either alone or in combination with a modified vaccinia ankara (MVA)-based mucin 1 (MUC1) therapeutic vaccine. The combination of Pam3Cys with MVA-MUC1 (1) diminished splenic Treg/CD4⁺ T-cell ratios to those found in tumor-free mice, (2) stimulated a specific anti-MUC1 interferon γ (IFNγ) response and (3) had a significant therapeutic effect on tumor growth and mouse survival. When CD4⁺ Teffs and Tregs were isolated from Pam3Cys-treated mice, Teffs had become resistant to Treg-mediated suppression while upregulating the expression of BclL-x_L. Tregs from Pam3Cys-treated mice were fully suppressive for Teffs from naïve mice. Bcl-x_L was induced by Pam3Cys with different kinetics in Tregs and Teffs. Teff from Pam3Cys-treated mice produced increased levels of Th1 and Th2-type cytokines and an interleukin (IL)-6-dependent secretion of IL-17 was observed in Teff:Treg co-cultures, suggesting that TLR2 stimulation had skewed the immune response toward a Th17 profile. Our results show for the first time that in a tumor-bearing host, TLR2 stimulation with Pam3Cys affects both Tregs and Teffs, protects Teff from Treg-mediated suppression and has strong therapeutic effects when combined with an MVA-based antitumor vaccine.

Tumor-infiltrating T-regulatory cells adapt to altered metabolism to promote tumor-immune escape

Tumor mass and its microenvironment alter host immune system in various ways to promote tumor growth. One of the modifications is evasion of immune surveillance by augmenting the number of Tregs in tumor vicinity. Elevated levels of Tregs are seen in peripheral circulation and tumor tissue of cancer patients. Cancer cells release several chemokines to attract Tregs in tumor-site. Infiltration of Tregs has clinical significance because being immunosuppressive infiltrating Tregs suppress other immune cells making the tumor microenvironment favorable for tumor growth. On the other hand, infiltrating Tregs show metabolic alteration in tumor microenvironment which allows their selective survival over the others. Persistence of Tregs in the tumor microenvironment and subsequent immunosuppression makes Tregs a potential therapeutic obstacle and the reason behind the failure of immunotherapy. In this review, we emphasize the recent development in the metabolic adaptation of tumor-infiltrating Tregs and the therapeutic approaches to boost immunity against cancer.

Induction of systemic immune responses and reversion of immunosuppression in the tumor microenvironment by a therapeutic vaccine for cervical cancer

Cervical cancer is the most common malignant tumor of the genital tract in females worldwide. Persistent human papillomavirus (HPV) infection is closely associated with the occurrence of cervical cancer. No licensed therapeutic HPV vaccines for cervical cancer are currently available. In our previous study, we demonstrated that the vaccine containing the HPV16 E7 43-77 peptide and the adjuvant unmethylated cytosine-phosphate-guanosine oligodeoxynucleotide elicited significant prophylactic and therapeutic effects on cervical cancer. In the current study, we comprehensively evaluated the effect of the vaccine on systemic immune responses and the tumor microenvironment (TME) in a mouse model of cervical cancer. The results showed that the administration of the vaccine induced a significant increase in splenic IFN-γ-producing CD4 and CD8 T cells as well as tumor infiltrating CD4 and CD8 T cells. Moreover, marked decreases in splenic MDSCs and Tregs as well as intratumoral MDSCs, Tregs and type 2-polarized tumor-associated macrophages were observed in the vaccine group. The profile of cytokines, chemokines and matrix metalloproteinases (MMPs) in the TME revealed significantly increased expression of IL-2, IL-12, TNF-α, IFN-γ, CCL-20, CXCL-9, CXCL-10 and CXCL-14 and decreased expression of IL-6, IL-10, TGF-β, CCL-2, CCL-3, CCL-5, CXCL-8, MMP-2, MMP-9 and VEGF in the vaccine group. The expression of the cell proliferation indicator Ki67, apoptosis regulatory protein p53 and angiogenesis marker CD31 was significantly decreased in the vaccine group. In conclusion, the vaccine reversed tolerogenic systemic and local TME immunosuppression and induced robust antitumor immune responses, which resulted in the inhibition of established implanted tumors.

Nimotuzumab for Patients With Inoperable Cancer of the Head and Neck

EGFR activation induces cell proliferation, neoformation of blood vessels, survival, and metastasis of the cancer cells. Nimotuzumab is an engineered, intermediate affinity anti-EGFR antibody, that apart from other drugs in its class, is very safe and does not cause hypomagnesemia or grade 3–4 cutaneous rash. The antibody inhibits cell proliferation and angiogenesis, activates natural killer cells, stimulates dendritic cell maturation, and induces cytotoxic T cells. Nimotuzumab restores MHC-I expression on tumor cells, hindering one of the EGFR immune-escape ways. The antibody has been extensively studied in 7 clinical trials, concurrently with irradiation or irradiation plus chemotherapy in subjects with inoperable head and neck tumors. Nimotuzumab was safe and efficacious in unfit patients receiving irradiation alone and in subjects treated with cisplatin and radiotherapy. In patients with locally advanced squamous cell carcinomas of the head and neck, nimotuzumab in combination with low dose cisplatin and radiotherapy was superior to cisplatin and radiotherapy in progression free survival, disease free survival, and locoregional tumor control.

Extracellular Vesicles and Tumor-Immune Escape: Biological Functions and Clinical Perspectives

The modulation of the immune system is one of the hallmarks of cancer. It is now widely described that cancer cells are able to evade the immune response and thus establish immune tolerance. The exploration of the mechanisms underlying this ability of cancer cells has always attracted the scientific community and is the basis for the development of new promising cancer therapies. Recent evidence has highlighted how extracellular vesicles (EVs) represent a mechanism by which cancer cells promote immune escape by inducing phenotypic changes on different immune cell populations. In this review, we will discuss the recent findings on the role of tumor-derived extracellular vesicles (TEVs) in regulating immune checkpoints, focusing on the PD-L1/PD-1 axis.

New insight on the correlation of metabolic status on 18F-FDG PET/CT with immune marker expression in patients with non-small cell lung cancer

BACKGROUND

Metabolic information obtained through ¹⁸F-flurodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) is used to evaluate malignancy by calculating the glucose uptake rate, and these parameters play important roles in determining the prognosis of non-small cell lung cancer (NSCLC). The expression of immune-related markers in tumor tissue reflects the immune status in the tumor microenvironment. However, there is lack of reports on the association between metabolic variables and intra-tumor immune markers. Herein, we investigate the correlation between metabolic status on ¹⁸F-FDG PET/CT and intra-tumor immunomarkers' expression in NSCLC patients.

METHODS

From April 2008 to August 2014, 763 patients were enrolled in the analysis to investigate the role of maximum standardized uptake value (SUVmax) in lung cancer. One hundred twenty-two tumor specimens were analyzed by immunohistochemistry (IHC) to intra-tumor immune cells and programmed death protein ligand 1(PD-L1) expression on tumor cells. The correlation between metabolic variables and the expression of tissue immune markers were analyzed.

RESULTS

SUVmax values have significant variations in different epidermal growth factor receptor (EGFR) statuses (wild type vs mutant type), high/low neutrophil-to-lymphocyte ratio (NLR) groups, and high/low platelets-to-lymphocyte ratio (PLR) groups (p < 0.001, p < 0.001, p = 0.003, respectively). SUVmax was an independent prognostic factor in lung cancer patients (p = 0.013). IHC demonstrated a statistically significant correlation between SUVmax and the expression of CD8 tumor-infiltrating lymphocytes (p = 0.015), CD163 tumor-associated macrophages (TAMs) (p = 0.003), and Foxp3-regulatory T cells (Tregs) (p = 0.004), as well as PD-1 and PD-L1 (p = 0.003 and p = 0.012, respectively). With respect to patient outcomes, disease stage, BMI, SUVmax, metabolic tumor volume (MTV), TLG (tumor lesion glycolysis), CD163-TAMs, CD11c-dendritic cells (DCs), PD-L1, and Tregs showed a statistically significant correlation with progression-free survival (PFS) (p < 0.001, 0.023, < 0.001, 0.007, 0.005, 0.004, 0.008, 0.048, and 0.014, respectively), and disease stage, SUVmax, MTV, TLG, CD163-TAMs, CD11c-DCs, and PD-L1 showed a statistically significant correlation with overall survival (OS) (p < 0.001, < 0.001, 0.014, 0.012, < 0.001, 0.001, and < 0.001, respectively).

CONCLUSION

This study revealed an association between metabolic variable and immune cell expression in the tumor microenvironment and suggests that SUVmax on ¹⁸F-FDG PET/CT could be a potential predictor for selecting candidates for immunotherapy.

Analysis of Treg/Th17 cells in patients with tongue squamous cell carcinoma

The aim of the present study was to analyze the percentage of regulatory T cells (Treg) and T helper cell 17 (Th17) cells in the peripheral blood of patients with tongue squamous cell carcinoma (TSCC) to provide novel insight into the development of immune-targeting therapies for TSCC. Peripheral blood samples were collected from 40 patients with TSCC then the peripheral blood mononuclear cells (PBMCs) and plasma were isolated for flow cytometry, cytometric bead array and reverse transcription-quantitative PCR. Results demonstrated that the percentage of cluster of differentiation (CD)4+ T cells in the peripheral blood of patients with TSCC decreased significantly compared with the control. However, the percentage of Treg and Th17 cells increased significantly compared with the control. The levels of interleukin (IL)-10 and IL-17a increased significantly in patients with TSCC. Expression of IL-10 and IL-17 in the advanced stages of cancer (stage III or IV) were significantly higher compared with the early stages (I and II). The mRNA expression levels of the transcription factors forkhead box protein 3 and RAR-related orphan receptor-γ increased significantly with stage of cancer. The percentage of Treg cells and Th17 cells increased significantly in patients with TSCC suggesting that there was an imbalance between Treg and Th17 cells. In conclusion, altered Treg/Th17 balance in TSCC may promote the disease progression and these results provide a theoretical basis for the development of immunomodulators targeting Treg/Th17.

Plasmodium infection inhibits the expansion and activation of MDSCs and Tregs in the tumor microenvironment in a murine Lewis lung cancer model

BACKGROUND

A major challenge in the development of effective cancer immunotherapy is the ability of tumors and their microenvironment to suppress immune cells through immunosuppressive cells such as myeloid -derived suppressor cells and regulatory T cells. We previously demonstrated that Plasmodium infection promotes innate and adaptive immunity against cancer in a murine Lewis lung cancer model but its effects on immunosuppressive cells in the tumor microenvironment are unknown.

METHODS

Whole Tumors and tumor-derived sorted cells from tumor-bearing mice treated with or without plasmodium infected red blood cells were harvested 17 days post tumor implantation and analyzed using QPCR, western blotting, flow cytometry, and functional assays. Differences between groups were analyzed for statistical significance using Student's t-test.

RESULTS

Here we found that Plasmodium infection significantly reduced the proportions of MDSCs and Tregs in the lung tumor tissues of the treated mice by downregulating their recruiting molecules and blocking cellular activation pathways. Importantly, CD8⁺ T cells isolated from the tumors of Plasmodium-treated mice exhibited significantly higher levels of granzyme B and perforin and remarkably lower levels of PD-1.

CONCLUSION

We reveal for the first time, the effects of Plasmodium infection on the expansion and activation of MDSCs and Tregs with a consequent elevation of CD8⁺T cell-mediated cytotoxicity within the tumor microenvironment and hold great promise for the development of effective immunotherapeutic strategies.

CD4+CD25highCD127low/-FoxP3 + Regulatory T-Cell Population in Acute Leukemias: A Review of the Literature

Regulatory T-cells (Tregs) are a very important subtype of lymphocytes when it comes to self-control in the human immunological system. Tregs are decisive not only in the protection against destruction of own tissues by autoimmune immunocompetent cells but also in the immunological answer to developing cancers. On the other hand, Tregs could be responsible for the progression of acute and chronic leukemias. In our study, we review publications available in the PUMED database concerning acute leukemia, with a particular emphasis on child's leukemias. The percentage of regulatory T-lymphocytes in peripheral blood and bone marrow was elevated compared to those in healthy individuals and correlated with progressive disease. Regulatory T-cells taken from children diagnosed with leukemia showed a higher suppressive capability, which was confirmed by detecting elevated levels of secreted IL-10 and TGF-beta. The possibility of pharmacological intervention in the self-control of the immunological system is now under extensive investigation in many human cancers. Presumably, Treg cells could be a vital part of targeted therapies. Routine Treg determination could be used to assess the severity of disease and prognosis in children with acute lymphoblastic leukemia. This proposition results from the fact that in some studies, higher percentage of Treg cells in peripheral blood was demonstrated. However, observations confirming these facts are scarce; thus, extrapolating them to the population of children with hematological malignancies needs to be verified in additional studies.

The PI3K p110δ Isoform Inhibitor Idelalisib Preferentially Inhibits Human Regulatory T Cell Function

In chronic lymphocytic leukemia (CLL), signaling through several prosurvival B cell surface receptors activates the PI3K signaling pathway. Idelalisib is a highly selective PI3K (PI3Kδ) isoform-specific inhibitor effective in relapsed/refractory CLL and follicular lymphoma. However, severe autoimmune adverse effects in association with the use of idelalisib in the treatment of CLL, particularly as a first-line therapy, gave indications that idelalisib may preferentially target the suppressive function of regulatory T cells (Tregs). On this background, we examined the effect of idelalisib on the function of human Tregs ex vivo with respect to proliferation, TCR signaling, phenotype, and suppressive function. Our results show that human Tregs are highly susceptible to PI3Kδ inactivation using idelalisib compared with CD4⁺ and CD8⁺ effector T cells (Teffs) as evident from effects on anti-CD3/CD28/CD2-induced proliferation (order of susceptibility [IC₅₀]: Treg [.5 μM] > CD4⁺ Teff [2.0 μM] > CD8⁺ Teff [6.5 μM]) and acting at the level of AKT and NF-κB phosphorylation. Moreover, idelalisib treatment of Tregs altered their phenotype and reduced their suppressive function against CD4⁺ and CD8⁺ Teffs. Phenotyping Tregs from CLL patients treated with idelalisib supported our in vitro findings. Collectively, our data show that human Tregs are more dependent on PI3Kδ-mediated signaling compared with CD4⁺ and CD8⁺ Teffs. This Treg-preferential effect could explain why idelalisib produces adverse autoimmune effects by breaking Treg-mediated tolerance. However, balancing effects on Treg sensitivity versus CD8⁺ Teff insensitivity to idelalisib could still potentially be exploited to enhance inherent antitumor immune responses in patients.

Nivolumab induced encephalopathy in a man with metastatic renal cell cancer: a case report

Background

Great progress has recently been made in the treatment of metastatic renal cell carcinoma, including the introduction of nivolumab, an immune checkpoint inhibitor. Despite promising results, this treatment brings a completely new spectrum of adverse events, distinct from those experienced with small-molecule kinase inhibitors. Neurologic immune-related adverse events may be serious and potentially life-threatening complications requiring immediate immunosuppressive therapy. Only a few cases of immune-related encephalitis induced by checkpoint inhibitors have been described and the data regarding the management of this serious adverse event are limited.

Case presentation

We report the case of a 63-year-old white man with metastatic renal cancer who developed severe chorea-like dyskinesia during nivolumab therapy. The findings on brain magnetic resonance imaging and flow cytometry of cerebrospinal fluid, and the positivity of anti-paraneoplastic antigen Ma2 immunoglobuline G class autoantibodies were consistent with a diagnosis of immune-related encephalitis. High-dose intravenous corticosteroid therapy was started immediately, with no signs of improvement, even when infliximab was added. Our patient refused further hospitalization and was discharged. Three weeks later, he presented with signs of severe urosepsis. Despite intensive treatment, he died 4 days after admission.

Conclusions

The management of less frequent immune-related adverse events has not been fully established and more information is required to provide uniform recommendations. Immune-related encephalitis is a severe and potentially fatal complication requiring immediate hospital admission and extensive immunosuppressive therapy. The examination of cerebrospinal fluid for paraneoplastic antibodies, such as anti-N-methyl-D-aspartate receptor and anti-Ma2 antibodies, in order to distinguish autoimmune etiology from other possible causes is essential and highly recommended.

Electronic supplementary material

The online version of this article (10.1186/s13256-018-1786-9) contains supplementary material, which is available to authorized users.

Role of Regulatory T Cells in Tumor-Bearing Mice Treated with Allo-Hematopoietic Stem Cell Transplantation Plus Thymus Transplantation

We recently developed a new allogeneic hematopoietic stem cell transplantation method (allo-HSCT) combined with thymus transplantation (TT) from the same donor (allo-HSCT + TT). This method induces elevated T cell function with mild graft-versus-host disease (GVHD) in comparison to conventional HSCT alone and HSCT + donor lymphocyte infusion (DLI). This new method is effective against several intractable diseases, including malignant tumors, for which conventional treatments are ineffective. Regulatory T (T_reg) cells play an important role in the enhanced graft-versus-tumor (GVT) effect and reduction of GVHD, thus leading to longer survival. Replacement and reduction of elevated T_reg cells by donor-derived allo-T_reg cells from the transplanted thymus may play one of crucial roles in the effect. This review discusses the role of T_reg cells in a tumor-bearing mouse model treated with allo-HSCT + TT.

[Immunotherapy - The New Era of Oncology]

In the field of immunotherapy, essential progress was achieved over the past years partially demonstrating long lasting therapeutic responses in different tumor entities. A better understanding of the interactions between the tumor and the immune system as well as the integration of immunotherapeutic approaches into clinical routine were the foundations for this development. The different approaches intervene on multiple levels of the immune response and directly or indirectly mount the patient‘s own immune defense against tumor cells. Immunotherapeutic approaches are represented by cytokine therapies, vaccinations, the use of oncolytic viruses and monoclonal antibody therapies as well as adoptive cell transfer strategies.

T-Cell Immunopeptidomes Reveal Cell Subtype Surface Markers Derived From Intracellular Proteins

Immunopeptidomes promise novel surface markers as ideal immunotherapy targets, but their characterization by mass spectrometry (MS) remains challenging. Until recently, cell numbers exceeding 10⁹ were needed to survey thousands of HLA ligands. Such limited analytical sensitivity has historically constrained the types of clinical specimens that can be evaluated to cell cultures or bulk tissues. Measuring immunopeptidomes from purified cell subpopulations would be preferable for many applications, particularly those evaluating rare, primary hematopoietic cell lineages. Here, we test the feasibility of immunopeptidome profiling from limited numbers of primary purified human regulatory T cells (T_Reg ), conventional T cells (T_conv ), and activated T cells. The combined T cell immunopeptide dataset reported here contains 13 804 unique HLA ligands derived from 5049 proteins. Of these, more than 700 HLA ligands were derived from 82 proteins that we exclusively identified from T_Reg -enriched cells. This study 1) demonstrates that primary, lineage-enriched T cell subpopulations recovered from single donors are compatible with immunopeptidome analysis; 2) presents new T_Reg -biased ligand candidates; and 3) supports immunopeptidome surveys' value for revealing T cell biology that may not be apparent from expression data alone. Taken together, these findings open up new avenues for targeting T_Reg and abrogating their suppressive functions to treat cancer.

Role of regulatory T cells in irinotecan-induced intestinal mucositis

Intestinal mucositis (IM) is a common side effect of irinotecan-based chemotherapy. The involvement of inflammatory mediators, such as TNF-α, IL1-β, IL-18 and IL-33, has been demonstrated. However, the role of adaptive immune system cells, whose activation is partially regulated by these cytokines, is yet unknown. Thus, we investigated the role of regulatory T cells (Tregs) in irinotecan-induced IM. C57BL/6 mice were injected with saline or irinotecan (75mgkg^-1, i.p.), once a day for 4days, and euthanized at day 1, 3, 5 or 7 following the first dose of irinotecan. For Treg depletion, the mice were pretreated with a low single dose of cyclophosphamide (100mgkg^-1, i.p). Intestinal lamina propria lymphocytes were harvested and purified by Percoll gradient. Treg and Th17 cells were identified by flow cytometry. Blood leukocyte count was obtained and ileum samples were collected for histopathological analysis and myeloperoxidase assay. IM caused an accumulation of Tregs and Th17 cells over time. Treg depletion exacerbated intestinal damage, diarrhea, neutrophil infiltration and animal mortality, despite a reduction in Th17 cell number. The frequency of other Th cells increased and was positively correlated with neutrophil infiltration. Tregs showed a negative correlation with neutrophils and the frequency of non-regulatory Th cells. In conclusion, Tregs are important in the control of intestinal damage induced by irinotecan, and their depletion showed a deleterious effect on IM. Activation of these cells appears to be a compensatory mechanism for intestinal inflammation.

FOXP3+ regulatory T cells in normal prostate tissue, postatrophic hyperplasia, prostatic intraepithelial neoplasia, and tumor histological lesions in men with and without prostate cancer

BACKGROUND

The tumor promoting or counteracting effects of the immune response to cancer development are thought to be mediated to some extent by the infiltration of regulatory T cells (T_regs ). In the present study we evaluated the prevalence of T_reg populations in stromal and epithelial compartments of normal, post atrophic hyperplasia (PAH), prostatic intraepithelial neoplasia (PIN), and tumor lesions in men with and without prostate cancer.

METHODS

Study subjects were 102 men consecutively diagnosed with localized prostate cancer undergoing radical prostatectomy and 38 men diagnosed with bladder cancer undergoing cystoprostatectomy without prostate cancer at the pathological examination. Whole mount sections from all patients were evaluated for the epithelial and stromal expression of CD4⁺ T_regs and CD8⁺ T_regs in normal, PAH, PIN, and tumor lesions. A Friedmańs test was used to investigate differences in the mean number of T_regs across histological lesions. Logistic regression was used to estimate crude and adjusted odds ratios (OR) for prostate cancer for each histological area.

RESULTS

In men with prostate cancer, similarly high numbers of stromal CD4⁺ T_regs were identified in PAH and tumor, but CD4⁺ T_regs were less common in PIN. Greater numbers of epithelial CD4+ T_regs in normal prostatic tissue were positively associated with both Gleason score and pT-stage. We observed a fourfold increased risk of prostate cancer in men with epithelial CD4⁺ T_regs in the normal prostatic tissue counterpart.

CONCLUSIONS

Our results may suggest a possible pathway through which PAH develops directly into prostate cancer in the presence of CD4⁺ T_regs and indicate that transformation of the anti-tumor immune response may be initiated even before the primary tumor is established.

Combining FoxP3 and Helios with GARP/LAP markers can identify expanded Treg subsets in cancer patients

Regulatory T cells (Tregs) comprise numerous heterogeneous subsets with distinct phenotypic and functional features. Identifying Treg markers is critical to investigate the role and clinical impact of various Treg subsets in pathological settings, and also for developing more effective immunotherapies. We have recently shown that non-activated FoxP3⁻Helios⁺ and activated FoxP3^+/–Helios⁺ CD4⁺ T cells express GARP/LAP immunosuppressive markers in healthy donors. In this study we report similar observations in the peripheral blood of patients with pancreatic cancer (PC) and liver metastases from colorectal cancer (LICRC). Comparing levels of different Treg subpopulations in cancer patients and controls, we report that in PC patients, and unlike LICRC patients, there was no increase in Treg levels as defined by FoxP3 and Helios. However, defining Tregs based on GARP/LAP expression showed that FoxP3⁻LAP⁺ Tregs in non-activated and activated settings, and FoxP3⁺Helios⁺GARP⁺LAP⁺ activated Tregs were significantly increased in both groups of patients, compared with controls. This work implies that a combination of Treg-specific markers could be used to more accurately determine expanded Treg subsets and to understand their contribution in cancer settings. Additionally, GARP^−/+LAP⁺ CD4⁺ T cells made IL-10, and not IFN-γ, and levels of IL-10-secreting CD4⁺ T cells were elevated in LICRC patients, especially with higher tumor staging. Taken together, our results indicate that investigations of Treg levels in different cancers should consider diverse Treg-related markers such as GARP, LAP, Helios, and others and not only FoxP3 as a sole Treg-specific marker.

Increased cycles of DC/CIK immunotherapy decreases frequency of Tregs in patients with resected NSCLC

Regulatory T cells (Tregs) suppress antitumor immune responses. Cycles of Dendritic cells (DC) vaccination combined with cytokine-induced killer (CIK) cells (DC/CIK) treatment were significantly related with good prognosis. Therefore, we investigated whether increased cycles of immunotherapy could decrease frequency of Tregs in patients with resected non-small cell lung cancer (NSCLC). Previous study from our laboratory has determined that the optimal cutoff point of the cycle count was 3cycles. We examined the levels of Tregs and the related cytokines by flow cytometric and cytokine analysis in these patients after more than (≥) 3cycles or less than (<) 3cycles of DC/CIK cell treatment. Significant reduction of Tregs frequency, Treg-generated cytokines level and recurrence rate were presented in patients received with ≥3cycles of DC/CIK cell treatment compared with patients with <3cycles of treatment. Interestingly, Tregs frequency and the related cytokines level were similar between patients suffered tumor recurrence and patients without recurrence in both groups. Together, our findings reveal that increased cycle count of DC/CIK cell immunotherapy contribute to decline of Tregs frequency and cancer recurrence rate in patients with resected NSCLC.

Daunting but Worthy Goal: Reducing the De Novo Cancer Incidence After Transplantation

Solid-organ transplant recipients are at increased risk of developing de novo malignancies compared with the general population, and malignancies become a major limitation in achieving optimal outcomes. The prevention and the management of posttransplant malignancies must be considered as a main goal in our transplant programs. For these patients, immunosuppression plays a major role in oncogenesis by both impairement of immunosurveillance, enhancement of chronic viral infection, and by direct prooncogenic effects. It is essential to manage the recipient with a long-term adapted screening program beginning before transplantation to use a prophylaxis to decrease infection-related cancer, to propose a viral monitoring, and to modulate the immunosuppression toward lower doses especially for calcineurin inhibitors. Indeed, strategies to induce tolerance or to allow a dramatic reduction of the immunosuppression burden are the more promising approaches for the reduction of the posttransplant malignancies.

Regulatory T Cells in the Tumor Microenvironment and Cancer Progression: Role and Therapeutic Targeting

Recent years have seen significant efforts in understanding and modulating the immune response in cancer. In this context, immunosuppressive cells, including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), have come under intense investigation for their proposed roles in suppressing tumor-specific immune responses and establishing an immunosuppressive tumor microenvironment, thus enabling tumor immune evasion. Additionally, recent evidence indicates that Tregs comprise diverse and heterogeneous subsets; phenotypically and functionally distinct subsets of tumor-infiltrating Tregs could contribute differently to cancer prognosis and clinical outcomes. Understanding Treg biology in the setting of cancer, and specifically the tumor microenvironment, is important for designing effective cancer therapies. In this review, we critically examine the role of Tregs in the tumor microenvironment and in cancer progression focusing on human studies. We also discuss the impact of current therapeutic modalities on Treg biology and the therapeutic opportunities for targeting Tregs to enhance anti-tumor immune responses and clinical benefits.

Regulatory T cells and cancer: an undesired tolerance

The incidence of cancer is markedly increased in organ transplant patients. A better understanding of underlying mechanisms and the identification of biomarkers for diagnosis and prognosis are major challenges. Hope et al. report expansion of regulatory T cells to be associated with the presence and severity of cancer. Although relevant, these results raise several questions.

Analyses of 123 Peripheral Human Immune Cell Subsets: Defining Differences with Age and between Healthy Donors and Cancer Patients Not Detected in Analysis of Standard Immune Cell Types

Recent advances in human immunology have led to the identification of novel immune cell subsets and the biological function of many of these subsets has now been identified. The recent US Food and Drug Administration approval of several immunotherapeutics for the treatment of a variety of cancer types and the results of ongoing immunotherapy clinical studies requires a more thorough interrogation of the immune system. We report here the use of flow cytometry-based analyses to identify 123 immune cell subsets of peripheral blood mononuclear cells. The use of these panels defines multiple differences in younger (< 40 years) vs. older (≥ 40 years) individuals and between aged-matched apparently healthy individuals and metastatic cancer patients, aspects not seen in the analysis of the following standard immune cell types: CD8, CD4, natural killer, natural killer-T, regulatory T, myeloid derived suppressor cells, conventional dendritic cells (DCs), plasmacytoid DCs and B cells. The use of these panels identifying 123 immune cell subsets may aid in the identification of patients who may benefit from immunotherapy, either prior to therapy or early in the immunotherapeutic regimen, for the treatment of cancer or other chronic or infectious diseases.

Immunological factors influencing clinical outcome in lung cancer patients after telomerase peptide vaccination

We have previously reported two trials in non-small cell lung cancer (NSCLC) evaluating vaccine therapy with the telomerase peptide GV1001. The studies demonstrated considerable differences in survival among immune responders, highlighting that an immune response is not necessarily beneficial. In the present study, we conducted long-term clinical follow-up and investigated immunological factors hypothesized to influence clinical efficacy. Peripheral blood mononuclear cells from 33 NSCLC trial patients and 15 healthy donors were analyzed by flow cytometry for T regulatory cells (Tregs, CD4(+)CD25(+)CD127(low/-)FOXP3(+)) and two types of myeloid-derived suppressor cells (MDSCs, HLA-DR (low) CD14 (+) or Lin (-/lo) HLA-DR (-) CD33 (+) CD11b (+)). T cell cultures were analyzed for 17 cytokines. The results demonstrated that immune responders had increased overall survival (OS, p < 0.001) and progression-free survival (p = 0.003), compared to subjects without immunological response. The mean OS advantage was 54 versus 13 months. Six patients were still alive at the last clinical update, all belonging to the immune responders. No serious toxicity had developed (maximum observation 13 years). Most patients developed a polyfunctional cytokine profile, with high IFNγ/IL-4 and IFNγ/IL-10 ratios. Low Treg levels were associated with improved OS (p = 0.037) and a favorable cytokine profile, including higher IFNγ/IL-10 ratios. High CD33(+) MDSC levels were associated with poorer immune response rate (p = 0.005). The levels of CD14(+) MDSC were significantly higher in patients than in healthy controls (p = 0.012). We conclude that a randomized GV1001 trial in NSCLC is warranted. The findings suggest that Tregs and MDSCs are associated with a tolerogenic cytokine milieu and impaired clinical efficacy of vaccine responses.

Immunosuppressive activity of cancer-associated fibroblasts in head and neck squamous cell carcinoma

Cancer-associated fibroblasts (CAFs) have been shown to play an important role in angiogenesis, invasion, and metastasis. In the present study, we determined whether CAFs within the tumor microenvironment (TME) in head and neck squamous cell carcinoma (HNSCC) contributed to promoting immunosuppression and evasion from immune surveillance. Six pairs of CAFs and normal fibroblasts (NFs) were established from the resected tumor tissues of patients with HNSCC. The effects of CAFs and NFs on the functions of T cells were comparatively analyzed. CAFs expressed the co-regulatory molecules, B7H1 and B7DC, whereas NFs did not. The expression levels of cytokine genes, including those for IL6, CXCL8, TNF, TGFB1, and VEGFA, were higher in CAFs. T cell proliferation was suppressed more by CAFs or their supernatants than by NFs. Moreover, PBMCs co-cultured with the supernatants of CAFs preferentially induced T cell apoptosis and regulatory T cells over those co-cultured with the supernatants of NFs. A microarray analysis revealed that the level of genes related to the leukocyte extravasation and paxillin signaling pathways was higher in CAFs than in NFs. These results demonstrated that CAFs collaborated with tumor cells in the TME to establish an immunosuppressive network that facilitated tumor evasion from immunological destruction.

Helios, and not FoxP3, is the marker of activated Tregs expressing GARP/LAP

Regulatory T cells (Tregs) are key players of immune regulation/dysregulation both in physiological and pathophysiological settings. Despite significant advances in understanding Treg function, there is still a pressing need to define reliable and specific markers that can distinguish different Treg subpopulations. Herein we show for the first time that markers of activated Tregs [latency associated peptide (LAP) and glycoprotein A repetitions predominant (GARP, or LRRC32)] are expressed on CD4+FoxP3- T cells expressing Helios (FoxP3-Helios+) in the steady state. Following TCR activation, GARP/LAP are up-regulated on CD4+Helios+ T cells regardless of FoxP3 expression (FoxP3+/-Helios+). We show that CD4+GARP+/-LAP+ Tregs make IL-10 immunosuppressive cytokine but not IFN-γ effector cytokine. Further characterization of FoxP3/Helios subpopulations showed that FoxP3+Helios+ Tregs proliferate in vitro significantly less than FoxP3+Helios- Tregs upon TCR stimulation. Unlike FoxP3+Helios- Tregs, FoxP3+Helios+ Tregs secrete IL-10 but not IFN-γ or IL-2, confirming they are bona fide Tregs with immunosuppressive characteristics. Taken together, Helios, and not FoxP3, is the marker of activated Tregs expressing GARP/LAP, and FoxP3+Helios+ Tregs have more suppressive characteristics, compared with FoxP3+Helios- Tregs. Our work implies that therapeutic modalities for treating autoimmune and inflammatory diseases, allergies and graft rejection should be designed to induce and/or expand FoxP3+Helios+ Tregs, while therapies against cancers or infectious diseases should avoid such expansion/induction.

The role of regulatory T cells in cancer immunology

Regulatory T cells (Treg) are generally considered to be significant contributors to tumor escape from the host immune system. Emerging evidence suggests, however, that in some human cancers, Treg are necessary to control chronic inflammation, prevent tissue damage, and limit inflammation-associated cancer development. The dual role of Treg in cancer and underpinnings of Treg diversity are not well understood. This review attempts to provide insights into the importance of Treg subsets in cancer development and its progression. It also considers the role of Treg as potential biomarkers of clinical outcome in cancer. The strategies for monitoring Treg in cancer patients are discussed as is the need for caution in the use of therapies which indiscriminately ablate Treg. A greater understanding of molecular pathways operating in various tumor microenvironments is necessary for defining the Treg impact on cancer and for selecting immunotherapies targeting Treg.

Antitumor activity of mHSP65-TTL enhanced by administration of low dose cyclophosphamide in pancreatic cancer-bearing mice

Pancreatic cancer remains a lethal malignancy. Despite chemotherapy or/and radiotherapy after the surgery, the improvement on the overall survival of the patients has still been minimal. To develop novel therapeutic approaches, we tried to prepare mHSP65-TTL, a candidate vaccine prepared by mixing the recombinant mycobacterial heat shock protein 65 (mHSP65) with tumor tissue lysate (TTL) of Panc02 pancreatic cancer tissue. The mHSP65-TTL were used to immune the C57BL/6 mice implanted with the Panc02 cancer cells, in combination with or without low dose cyclophosphamide (CY). The results showed that mHSP65-TTL significantly prolonged the survival of the pancreatic cancer bearing mice and low dose CY enhanced the efficacy of the mHSP65-TTL. In addition, we detected mRNA expression of RORγt and IL-17A in spleen cells of mice received mHSP65-TTL or mHSP65-TTL plus CY, and found that mHSP65-TTL up-regulated mRNA expressions of RORγt and IL-17A, CY alone or mHSP65-TTL plus CY up-regulated mRNA expressions of RORγt. The work could provide an insight into a combinational approach for the immunotherapy of pancreatic cancer.

Clinical Impact of Regulatory T cells (Treg) in Cancer and HIV

The role of regulatory T cells, (Treg) in human cancer and HIV-1 infections has been under intense scrutiny. While the lack of a marker specific for human Treg has made it challenging to phenotype these cells, combinations of several markers and functional attributes of Treg have made it possible to assess their contributions to immune homeostasis in health and disease. Treg diversity and their plasticity create a challenge in deciding whether they are beneficial to the host by down-regulating excessive immune activation or are responsible for adverse effects such as suppression of anti-tumor immune responses resulting in promotion of tumor growth. Treg are emerging as active participants in several biochemical pathways involved in immune regulation. This review attempts to integrate current information about human Treg in respect to their activities in cancer and HIV-1. The goal is to evaluate the potential of Treg as targets for future immune or pharmacologic therapies for cancer or HIV-1 infections.

Interleukin-17 facilitates the immune suppressor capacity of high-grade glioma-derived CD4 (+) CD25 (+) Foxp3 (+) T cells via releasing transforming growth factor beta

High-grade glioma is a malignant tumour; the pathogenesis is to be further investigated. Interleukin (IL)-17 is an inflammatory cytokine. Chronic inflammation is a pathological feature of cancer. This study aimed to characterize the glioma-derived IL-17(+) regulatory T cells (Treg). In this study, single cells were isolated from surgically removed high-grade glioma tissue and examined by flow cytometry. The immune suppressor effect of IL-17(+) Tregs on CD8(+) T cells was assessed in vitro. The results showed that abundant IL-17(+) Tregs were found in high-grade glioma tissue. The immune suppressor molecule, transforming growth factor (TGF)-beta, was detected in the IL-17(+) Tregs. The proliferation of CD8(+) T cells was suppressed by culturing with the IL-17(+) Tregs, which was partially abrogated by neutralizing antibodies of either TGF-beta or IL-17 and completely abrogated by neutralizing antibodies against both TGF-beta and IL-17. In conclusion, IL-17(+) Tregs exist in the high-grade glioma tissue; this subset of T cells can suppress CD8(+) T cell activities via releasing TGF-beta and IL-17.