Phenotypic alterations, clinical impact and therapeutic potential of regulatory T cells in cancer

GRAMD1A Is a Biomarker of Kidney Renal Clear Cell Carcinoma and Is Associated with Immune Infiltration in the Tumour Microenvironment

Background

GRAM structural domain-containing protein 1A (GRAMD1A) is upregulated in a variety of human cancer tissues and is closely associated with tumourigenesis and progression.

Methods

Patient RNA-sequencing data and clinicopathological information were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets. The expression of GRAMD1A in kidney cancer cell lines and KIRC patients was analysed by quantitative polymerase chain reaction (qPCR). Receiver Operator Characteristic (ROC) curves, nomograms, Kaplan-Meier analysis, forest plots, and COX analysis were used to assess the diagnostic and prognostic value of GRAMD1A in KIRC, and gene set enrichment analysis (GSEA) was used to explore its potential signalling pathways. In addition, the Sangerbox website, Kaplan-Meier plotter database, and TISIDB and TIMER databases were used to further analyse the correlation of GRAMD1A with microsatellite instability (MSI), tumour mutational burden (TMB), immune checkpoint genes, and tumour-infiltrating lymphocytes (TILs).

Results

GRAMD1A was significantly highly expressed in KIRC and associated with shorter overall survival and relapse-free survival (P < 0.05). The AUC value of the ROC curve to identify KIRC and normal renal tissues was 0.942. Forest plot and COX analysis visualized that GRAMD1A could be an independent prognostic factor in KIRC patients (P < 0.01), and nomograms to determine the overall survival (OS) of KIRC patients also showed good efficacy (C-index: 0.776). Moreover, Spearman correlation analysis showed a positive correlation between GRAMD1A and MSI, TMB (P < 0.01). On the other hand, GRAMD1A was also found to be closely associated with immune checkpoint genes. Meanwhile, patients with KIRC with high GRAMD1A expression had a relatively low hazard ratio (HR) of death when B lymphocytes, natural killer T cells, CD4+ T lymphocytes, CD8+ T lymphocytes, and macrophages were enriched in the tumour microenvironment (TME), and a greater HR of death when regulatory T lymphocytes with tumour-specific immunosuppressive effects were significantly enriched. Last, GSEA shows that GRAMD1A is closely associated with the regulation of energy metabolism in KIRC.

Conclusions

GRAMD1A is a promising diagnostic and prognostic biomarker for patients with KIRC, and its biological function correlates to some extent with immune infiltration in TME.

Circulating and Tumor-Infiltrating Immune Checkpoint-Expressing CD8+ Treg/T Cell Subsets and Their Associations with Disease-Free Survival in Colorectal Cancer Patients

Simple Summary

Colorectal cancer is one of the leading causes of global cancer-related mortality. Tumor-infiltrating effector immune cells play critical roles in tumor control, and their activity can dictate disease outcomes. In this study, we provide evidence of the associations between different CD8⁺ T cell subpopulations with disease-free survival (DFS) in CRC patients. We report associations between higher levels of certain circulating and tumor-infiltrating CD8⁺ T cell subsets and improved clinical outcomes in CRC patients.

Abstract

T cells in the tumor microenvironment (TME) have diverse roles in anti-tumor immunity, including orchestration of immune responses and anti-tumor cytotoxic attack. However, different T cell subsets may have opposing roles in tumor progression, especially in inflammation-related cancers such as colorectal cancer (CRC). In this study, we phenotypically characterized CD3⁺CD4^- (CD8⁺) T cells in colorectal tumor tissues (TT), normal colon tissues (NT) and in circulation of CRC patients. We investigated the expression levels of key immune checkpoints (ICs) and Treg-related markers in CD8⁺ T cells. Importantly, we investigated associations between different tumor-infiltrating CD8⁺ T cell subpopulations and disease-free survival (DFS) in CRC patients. We found that FoxP3 expression and ICs including PD-1, CTLA-4, TIM-3, and LAG-3 were significantly increased in tumor-infiltrating CD8⁺ T cells compared with NT and peripheral blood. In the TME, we found that TIM-3 expression was significantly increased in patients with early stages and absent lymphovascular invasion (LVI) compared to patients with advanced stages and LVI. Importantly, we report that high levels of certain circulating CD8⁺ T cell subsets (TIM-3-expressing, FoxP3⁻Helios⁻TIM-3⁺ and FoxP3⁻Helios⁺TIM-3⁺ cells) in CRC patients were associated with better DFS. Moreover, in the TME, we report that elevated levels of CD25⁺ and TIM-3⁺ T cells, and FoxP3⁺Helios⁻TIM-3⁺ Tregs were associated with better DFS.

Pushing Past the Blockade: Advancements in T Cell-Based Cancer Immunotherapies

Successful cancer immunotherapies rely on a replete and functional immune compartment. Within the immune compartment, T cells are often the effector arm of immune-based strategies due to their potent cytotoxic capabilities. However, many tumors have evolved a variety of mechanisms to evade T cell-mediated killing. Thus, while many T cell-based immunotherapies, such as immune checkpoint inhibition (ICI) and chimeric antigen receptor (CAR) T cells, have achieved considerable success in some solid cancers and hematological malignancies, these therapies often fail in solid tumors due to tumor-imposed T cell dysfunctions. These dysfunctional mechanisms broadly include reduced T cell access into and identification of tumors, as well as an overall immunosuppressive tumor microenvironment that elicits T cell exhaustion. Therefore, novel, rational approaches are necessary to overcome the barriers to T cell function elicited by solid tumors. In this review, we will provide an overview of conventional immunotherapeutic strategies and the various barriers to T cell anti-tumor function encountered in solid tumors that lead to resistance. We will also explore a sampling of emerging strategies specifically aimed to bypass these tumor-imposed boundaries to T cell-based immunotherapies.

Are Changes in the Percentage of Specific Leukocyte Subpopulations Associated with Endogenous DNA Damage Levels in Testicular Cancer Patients?

Chemoresistance of germ cell tumors (GCTs) represents an intensively studied property of GCTs that is the result of a complicated multifactorial process. One of the driving factors in this process is the tumor microenvironment (TME). Intensive crosstalk between the DNA damage/DNA repair pathways and the TME has already been reported. This study aimed at evaluating the interplay between the immune TME and endogenous DNA damage levels in GCT patients. A cocultivation system consisting of peripheral blood mononuclear cells (PBMCs) from healthy donors and GCT cell lines was used in an in vitro study. The patient cohort included 74 chemotherapy-naïve GCT patients. Endogenous DNA damage levels were measured by comet assay. Immunophenotyping of leukocyte subpopulations was performed using flow cytometry. Statistical analysis included data assessing immunophenotypes, DNA damage levels and clinicopathological characteristics of enrolled patients. The DNA damage level in PBMCs cocultivated with cisplatin (CDDP)-resistant GCT cell lines was significantly higher than in PBMCs cocultivated with their sensitive counterparts. In GCT patients, endogenous DNA damage levels above the cutoff value were independently associated with increased percentages of natural killer cells, CD16-positive dendritic cells and regulatory T cells. The crosstalk between the endogenous DNA damage level and specific changes in the immune TME reflected in the blood of GCT patients was revealed. The obtained data contribute to a deeper understanding of ongoing interactions in the TME of GCTs.

Thymic Function Associated With Cancer Development, Relapse, and Antitumor Immunity - A Mini-Review

The thymus is the central lymphoid organ for T cell development, a cradle of T cells, and for central tolerance establishment, an educator of T cells, maintaining homeostatic cellular immunity. T cell immunity is critical to control cancer occurrence, relapse, and antitumor immunity. Evidence on how aberrant thymic function influences cancer remains largely insufficient, however, there has been recent progress. For example, the involuted thymus results in reduced output of naïve T cells and a restricted T cell receptor (TCR) repertoire, inducing immunosenescence and potentially dampening immune surveillance of neoplasia. In addition, the involuted thymus relatively enhances regulatory T (Treg) cell generation. This coupled with age-related accumulation of Treg cells in the periphery, potentially provides a supportive microenvironment for tumors to escape T cell-mediated antitumor responses. Furthermore, acute thymic involution from chemotherapy can create a tumor reservoir, resulting from an inflammatory microenvironment in the thymus, which is suitable for disseminated tumor cells to hide, survive chemotherapy, and become dormant. This may eventually result in cancer metastatic relapse. On the other hand, if thymic involution is wisely taken advantage of, it may be potentially beneficial to antitumor immunity, since the involuted thymus increases output of self-reactive T cells, which may recognize certain tumor-associated self-antigens and enhance antitumor immunity, as demonstrated through depletion of autoimmune regulator (AIRE) gene in the thymus. Herein, we briefly review recent research progression regarding how altered thymic function modifies T cell immunity against tumors.

[Metformin inhibits proliferation and functions of regulatory T cells in acidic environment]

OBJECTIVE

To investigate the regulatory effect of metformin on regulatory T cells (Treg) in acidic environment.

METHODS

CD4⁺ CD25⁺ Treg cells were obtained by magnetic bead sorting. Treg and conventional T cells (Tcon) cells were cultured for 24-72 h in pH 7.4 or pH 6.7 medium, and the cell proliferation, apoptosis and Foxp3 expression were detected by flow cytometry. Real-time PCR was used to detect the expression levels of the genes related with glucose metabolism. Thirty-two C57BL/6 male mouse models bearing subcutaneous prostate cancer xenograft derived from RM-1 cells were randomized into 4 equal groups for treatment with PBS, metformin, tumor vaccine, or both metformin and the vaccine. The treatment started on the 4th day following tumor cell injection, and metformin (100 mg/kg) or PBS was administered by intraperitoneal injection on a daily basis; the vaccine was intramuscularly injected every 4 days. The tumor size was continuously monitored, and the mice were euthanized on day 25 after tumor implantation to obtain tumor and blood samples. Flow cytometry was used to detect the changes in CD4⁺, CD8⁺, CD4⁺Foxp3⁺ cell subsets in the tumor tissue and peripheral blood.

RESULTS

Treg cells showed significantly enhanced proliferation (P < 0.05) while the proliferation of Tcon cells was suppressed in acidic medium (P < 0.001). Treg cells cultured in acidic medium showed significantly increased expressions of OXPHOS-related genes pgc1a (P < 0.001) and cox5b (P < 0.01), which did not vary significantly in Tcon cells in acidic medium. Treg cells exhibited significantly decreased apoptosis in acidic medium (P < 0.01) with increased Foxp3⁺ cells (P < 0.001) and intracellular alkaline levels (P < 0.01). Metformin obviously reversed the acid tolerance of Treg cells without producing significant effect on Tcon cells. In the animal experiment, both metformin (P < 0.05) and vaccine (P < 0.01) alone reduced the tumor volume, but their combined treatment more potently reduced the tumor volume (P < 0.001). Metformin alone did not obviously affect CD4⁺ cells or CD8⁺ cells but significantly decreased the percentage of CD4⁺Foxp3⁺ (P < 0.05); the vaccine alone significantly increased CD4⁺ cells and CD8⁺ cells (P < 0.001) and also the percentage of CD4⁺Foxp3⁺ cells (P < 0.05). The combined treatment, while reducing the percentage of CD4⁺Foxp3⁺cells to a level lower than that in the vaccine group (P < 0.01), produced the strongest effect to increase CD4⁺ cells and CD8⁺ cells (P < 0.01).

CONCLUSIONS

Metformin can inhibit the proliferation and function of regulatory T cells in an acidic environment and enhance the effect of tumor vaccine by reducing the proportion of Treg cells in vivo to achieve the anti-tumor effect.

Tumor Microenvironment: A Metabolic Player that Shapes the Immune Response

Immune cells survey and patrol throughout the body and sometimes take residence in niche environments with distinct cellular subtypes and nutrients that may fluctuate from those in which they matured. Rooted in immune cell physiology are metabolic pathways and metabolites that not only deliver substrates and energy for growth and survival, but also instruct effector functions and cell differentiation. Unlike cancer cells, immune cells are not subject to a "Darwinian evolutionary pressure" that would allow them to adapt to developing tumors but are often irrevocably affected to local nutrient deprivation. Thus, immune cells must metabolically adapt to these changing conditions in order to perform their necessary functions. On the other hand, there is now a growing appreciation that metabolic changes occurring in cancer cells can impact on immune cell functionality and contribute to tumor immune evasion, and as such, there is a considerable and growing interest in developing techniques that target metabolism for immunotherapy. In this review, we discuss the metabolic plasticity displayed by innate and adaptive immune cells and highlight how tumor-derived lactate and tumor acidity restrict immunity. To our knowledge, this review outlines the most recent insights on how tumor microenvironment metabolically instructs immune responsiveness.

The Role of Natural Killer Cells and Regulatory T Cells While Aging with Human Immunodeficiency Virus

Combined antiretroviral therapy (cART) has increased the quality of life of people living with HIV (PLHIV). Consequently, the number of PLHIV >50 years is increasing worldwide. Patients on cART are known to remain in a proinflammatory state. The latter is linked to the development of non-AIDS-related chronic conditions. Although the number of aging PLHIV is increasing, the effect of HIV infection on the process of aging is not fully understood. Understanding the complexity of aging with HIV by investigating the effect of the latter on different components of the innate and adaptive immune systems is important to reduce the impact of these comorbid conditions and improve the quality of life of PLHIV. The role of killer immunoglobulin receptors (KIRs), expressed on the surface of natural killer (NK) cells, and their human leukocyte antigen (HLA) ligands in the clearance, susceptibility to or disease progression following HIV infection is well established. However, data on the effect of KIR-HLA interaction in aging HIV-infected population and the development of non-AIDS-related comorbid conditions are lacking. Moreover, conflicting data exist on the role of regulatory T cells (Tregs) during HIV infection. The purpose of this review is to advance the current knowledge on the role of NK cells and Tregs while aging with HIV infection.

Natural killer cell cytotoxicity is a predictor of outcome for patients with high risk myelodysplastic syndrome and oligoblastic acute myeloid leukemia treated with azacytidine

The aim of the present study was to identify biomarkers predictive of the outcome of patients with high-risk myelodysplastic syndrome and oligoblastic acute myeloid leukemia (AML) treated with 5-azacytidine (AZA). We prospectively examined the association between NK-cytotoxic activity, myeloid-derived suppressor cells (MDSCs), and T-regulatory cells (Tregs) on the overall survival (OS) of patients. Patients with NK-cytotoxicity above a critical threshold had a longer duration of response and survived longer than patients with severe impairment of NK-cytotoxicity. The numbers of MDSCs, and Tregs in the PB of patients after a short exposure to AZA were not different from normal donors. In conclusion, the results of our study suggest that the therapeutic activity of AZA is at least partly mediated by an immunomodulatory effect. To our knowledge, this is the first study reported so far, that shows a positive correlation between NK cytotoxicity and OS of AZA-treated patients.

Regulation of T cell immunity by cellular metabolism

T cells are an important adaptive immune response arm that mediates cell-mediated immunity. T cell metabolism plays a central role in T cell activation, proliferation, differentiation, and effector function. Specific metabolic programs are tightly controlled to mediate T cell immune responses, and alterations in T cell metabolism may result in many immunological disorders. In this review, we will summarize the main T cell metabolic pathways and the important factors participating in T cell metabolic programming during T cell homeostasis, differentiation, and function.

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.

γδ cells and tumor microenvironment: A helpful or a dangerous liason?

γδ T cells are a subset of T lymphocytes that have been implicated in immunosurveillance against infections and tumors. γδ T cells are endowed with antitumor activities, and hence several γδ T cell-based small-scale clinical trials have been conducted either by in vivo activation by intravenous administration of aminobiphosphonates or by adoptive transfer of in vitro expanded γδ T cells. Although both these strategies have yielded promising results, there are a number of limitations associated with each of them which, if overcome may help to further improve efficacy. One of the most important limits is the possible polarization of tumor-infiltrating γδ T cells toward different γδ T cells population with functional activities that help the progression and spread of the tumor. Here, we review the modalities and the possible mechanisms involved in the polarization of tumor-infiltrating γδ T cells upon interaction with several components of the tumor microenvironment and discuss their implications for the manipulation of γδ T cells in cancer immunotherapy.

The Effects of Intestinal Nematode L4 Stage on Mouse Experimental Autoimmune Encephalomyelitis

Helminths use various immunomodulatory and anti-inflammatory strategies to evade immune attack by the host. During pathological conditions, these strategies alter the course of disease by reducing immune-mediated pathology. The study examines the therapeutic effect of the nematode L4 stage based on an in vivo model of multiple sclerosis, monophasic encephalomyelitis (EAE), induced by sensitization with MOG_35-55 peptide in C57BL/6 female mice infected with the intestinal nematode Heligmosomoides polygyrus. The EAE remission was correlated with altered leukocyte number identified in the central nervous system (CNS), and temporary permeability of the blood-brain barrier at the histotrophic phase of infection. At 6 days post-infection, when the L4 stage had almost completely attenuated the clinical severity and pathological signs of EAE, CD25⁺ cell numbers expanded significantly, with parallel growth of CD8⁺ and CD4⁺, both CD25⁺Foxp3⁺ and CD25⁺Foxp3^- subsets and alternatively activated macrophages. The phenotypic changes in distinct subsets of cerebrospinal fluid cells were correlated with an inhibited proliferative response of encephalitogenic T cells and elevated levels of nerve growth factor and TGF-β. These results enhance our understanding of mechanisms involved in the inhibition of immune responses in the CNS during nematode infection.

The immunosuppressive effect of the tick protein, Salp15, is long-lasting and persists in a murine model of hematopoietic transplant

Salp15, a salivary protein of Ixodes ticks, inhibits the activation of naïve CD4 T cells. Treatment with Salp15 results in the inhibition of early signaling events and the production of the autocrine growth factor, interleukin-2. The fate of the CD4 T cells activated in the presence of Salp15 or its long-term effects are, however, unknown. We now show that Salp15 binding to CD4 is persistent and induces a long-lasting immunomodulatory effect. The activity of Salp15 results in sustained diminished cross-antigenic antibody production even after interruption of the treatment with the protein. Transcriptionally, the salivary protein provokes an acute effect that includes known activation markers, such as Il2 or Cd44, and that fades over time. The long-term effects exerted by Salp15 do not involve the induction of either anergy traits nor increased populations of regulatory T cells. Similarly, the treatment with Salp15 does not result in B cell anergy or the generation of myeloid suppressor cells. However, Salp15 induces the increased expression of the ectoenzyme, CD73, in regulatory T cells and increased production of adenosine. Our study provides a profound characterization of the immunomodulatory activity of Salp15 and suggests that its long-term effects are due to the specific regulation of CD73.

Impact of Metabolism on T-Cell Differentiation and Function and Cross Talk with Tumor Microenvironment

The immune system and metabolism are highly integrated and multilevel interactions between metabolic system and T lymphocyte signaling and fate exist. Accumulating evidence indicates that the regulation of nutrient uptake and utilization in T cells is critically important for the control of their differentiation and manipulating metabolic pathways in these cells can shape their function and survival. This review will discuss some potential cell metabolism pathways involved in shaping T lymphocyte function and differentiation. It will also describe show subsets of T cells have specific metabolic requirements and signaling pathways that contribute to their respective function. Examples showing the apparent similarity between cancer cell metabolism and T cells during activation are illustrated and finally some mechanisms being used by tumor microenvironment to orchestrate T-cell metabolic dysregulation and the subsequent emergence of immune suppression are discussed. We believe that targeting T-cell metabolism may provide an additional opportunity to manipulate T-cell function in the development of novel therapeutics.

Myeloid cells in circulation and tumor microenvironment of breast cancer patients

Pathological conditions including cancers lead to accumulation of a morphological mixture of highly immunosuppressive cells termed as myeloid-derived suppressor cells (MDSC). The lack of conclusive markers to identify human MDSC, due to their heterogeneous nature and close phenotypical and functional proximity with other cell subsets, made it challenging to identify these cells. Nevertheless, expansion of MDSC has been reported in periphery and tumor microenvironment of various cancers. The majority of studies on breast cancers were performed on murine models and hence limited literature is available on the relation of MDSC accumulation with clinical settings in breast cancer patients. The aim of this study was to investigate levels and phenotypes of myeloid cells in peripheral blood (n = 23) and tumor microenvironment of primary breast cancer patients (n = 7), compared with blood from healthy donors (n = 21) and paired non-tumor normal breast tissues from the same patients (n = 7). Using multicolor flow cytometric assays, we found that breast cancer patients had significantly higher levels of tumor-infiltrating myeloid cells, which comprised of granulocytes (P = 0.022) and immature cells that lack the expression of markers for fully differentiated monocytes or granulocytes (P = 0.016). Importantly, this expansion was not reflected in the peripheral blood. The immunosuppressive potential of these cells was confirmed by expression of Arginase 1 (ARG1), which is pivotal for T-cell suppression. These findings are important for developing therapeutic modalities to target mechanisms employed by immunosuppressive cells that generate an immune-permissive environment for the progression of cancer.

Increased Levels of Circulating and Tumor-Infiltrating Granulocytic Myeloid Cells in Colorectal Cancer Patients

Increased levels of myeloid cells, especially myeloid-derived suppressor cells (MDSCs), have been reported to correlate with bad prognosis and reduced survival in cancer patients. However, limited data are available on their conclusive phenotypes and their correlation with clinical settings. The aim of this study was to investigate levels and phenotype of myeloid cells in peripheral blood and tumor microenvironment (TME) of colorectal cancer (CRC) patients, compared to blood from healthy donors (HDs) and paired, adjacent non-tumor colon tissue. Flow cytometric analysis was performed to examine the expression of different myeloid markers in fresh peripheral blood samples from CRC patients and HDs, and tissue-infiltrating immune cells from CRC patients. We found significantly higher levels of cells expressing myeloid markers and lacking the expression of major histocompatibility complex class II molecule HLA-DR in blood and tumor of CRC patients. Further analysis revealed that these cells were granulocytic and expressed Arginase 1 indicative of their suppressive phenotype. These expanded cells could be neutrophils or granulocytic MDSCs, and we refer to them as granulocytic myeloid cells (GMCs) due to the phenotypical and functional overlap between these cell subsets. Interestingly, the expansion of peripheral GMCs correlated with higher stage and histological grade of cancer, thereby suggesting their role in cancer progression. Furthermore, an increase in CD33+CD11b+HLA-DR-CD14-CD15- immature myeloid cells was also observed in CRC tumor tissue. Our work shows that GMCs are expanded in circulation and TME of CRC patients, which provides further insights for developing immunotherapeutic approaches targeting these cell subsets to enhance antitumor immune and clinical responses.

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.

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.

Emerging roles of regulatory T cells in tumour progression and metastasis

The metastasis of cancer is a complex and life-threatening process that is only partially understood. Immune suppressive cells are recognized as important contributors to tumour progression and may also promote the development and growth of tumour metastases. Specifically, regulatory T cells (Tregs) have been found to promote primary tumour progression, and emerging pre-clinical data suggests that Tregs may promote metastasis and metastatic tumour growth. While the precise role that Tregs play in metastatic progression is understudied, recent findings have indicated that by suppressing innate and adaptive anti-tumour immunity, Tregs may shield tumour cells from immune detection, and thereby allow tumour cells to survive, proliferate and acquire characteristics that facilitate dissemination. This review will highlight our current understanding of Tregs in metastasis, including an overview of pre-clinical findings and discussion of clinical data regarding Tregs and therapeutic outcome. Evolving strategies to directly ablate Tregs or to inhibit their function will also be discussed. Improving our understanding of how Tregs may influence tumour metastasis may lead to novel treatments for metastatic cancer.

The prognostic value of histopathological grading systems in oral squamous cell carcinomas

OBJECTIVE

This study evaluated the association of four histopathological grading systems (WHO grading system, malignancy grading of the deep invasive margins (MG), histological risk (HR) model, and tumor budding and depth of invasion (BD) model) with clinicopathological parameters and outcome of 113 oral squamous cell carcinomas to identify their roles in prognosis.

METHODS

Demographic and clinical features were obtained from patients' records. Sections from all paraffin-embedded blocks were evaluated according to the four grading systems. Demographic and clinical associations were analyzed using chi-square test, and correlations between the grading systems were established with the Spearman's rank correlation test. Survival curves were performed with Kaplan-Meier method, and multivariate analysis based on Cox proportional hazard model was calculated.

RESULTS

Significant associations with survival were observed for WHO grading system and BD model in the univariate analysis, but only the BD model was significantly associated with disease outcome as an independent prognostic marker. Age, tumor size, and presence of regional metastasis were also independent markers of reduced survival.

CONCLUSION

A significant association between the BD model and outcome of OSCC patients was observed, indicating this new histopathological grading system as a possible prognostic tool.

Novel expression of Neuropilin 1 on human tumor-infiltrating lymphocytes in colorectal cancer liver metastases

OBJECTIVES

Neuropilin 1 (NRP1) is a transmembrane protein with diverse roles in physiological and pathological settings. NRP1 expression has been reported on T cells in inflammatory microenvironments and in secondary lymphoid tissue. Tumor-infiltrating lymphocytes (TILs) play an important role in cancer prognosis. In this study, we investigated NRP1 expression on TILs and peripheral blood mononuclear cells (PBMCs) from colorectal cancer liver metastases (LI/CRC).

METHODS

TILs from LI/CRC and PBMCs from healthy donors and patients were analyzed for expression of NRP1, in addition to other Treg-related markers. PBMCs were co-cultured in vitro with tumor tissue and analyzed for NRP1 expression.

RESULTS

We report for the first time that NRP1 is highly expressed on CD3(+)CD4(+) TILs compared to PBMCs. NRP1 expression correlated closely with CD25 expression in TILs. NRP1 was expressed on both Helios(+) and Helios(-) FoxP3-expressing Tregs and on a FoxP3(-)Helios(-) T cell subset. It was also induced on PBMCs following in vitro co-culture with tumor tissue.

CONCLUSIONS

NRP1 is upregulated on TILs and can be induced on PBMCs by tumor tissue. Further studies are warranted to define the function of NRP1 on human TILs. As a therapeutic target, NRP1 may allow selective targeting of TIL subsets including suppressive Tregs.