TGF-beta1 maintains suppressor function and Foxp3 expression in CD4+CD25+ regulatory T cells

Ouabain Decreases Regulatory T Cell Number in Mice by Reducing IL-2 Secretion

BACKGROUND

Ouabain (OUA) is a cardiotonic glycoside originally extracted from African plants. It has also been described as an endogenous component in mammals, being released in stress situations mainly by the adrenal gland. OUA has been reported to be capable of inhibiting mitogen-induced lymphocyte proliferation and also affects B and T lymphocytes.

OBJECTIVES

The aim of this work is to show the effects of OUA in peripheral T lymphocytes.

METHODS

In the in vivo experiments, mice were injected intraperitoneally for 3 consecutive days with RPMI medium (control group) or 0.56 mg/kg of OUA diluted in RPMI medium (OUA group). On the fourth day, spleen or mesenteric lymph nodes were removed.

RESULTS

OUA significantly reduced the number of CD4+ T lymphocytes in the spleen, especially regulatory T cells (Tregs). In vitro OUA did not inhibit the proliferation of CD4+T lymphocytes stimulated with anti-CD3 neither was able to induce the apoptosis of CD4+ nor Tregs. There was no increase in the number or percentage of T lymphocytes in the mesenteric lymph nodes, suggesting that there was no preferential accumulation of these cells in this organ. Secretion of IL-2 by activated T lymphocytes was decreased by the OUA, explaining at least in part the reduction of Tregs, since this cytokine is involved in the peripheral conversion and maintenance of Tregs.

CONCLUSION

The impact of this reduction in autoimmune diseases, allergy and cancer as well as the potential use of OUA as a therapeutic approach in tumor treatment still needs more investigation.

Emerging roles of transforming growth factor β signaling in wet age-related macular degeneration

Age-related macular degeneration (AMD) is one of the major causes of irreversible blindness among aging populations in developed countries and can be classified as dry or wet according to its progression. Wet AMD, which is characterized by angiogenesis on the choroidal membrane, is uncommonly seen but more severe. Controlling or completely inhibiting the factors that contribute to the progression of events that lead to angiogenesis may be an effective strategy for treating wet AMD. Emerging evidence has shown that transforming growth factor-β (TGF-β) signaling plays a significant role in the progression of wet AMD. In this review, we described the roles of and changes in TGF-β signaling in the development of AMD and discussed the mechanisms of the TGF-β superfamily in choroidal neovascularization (CNV) and wet AMD, including the modulation of angiogenesis-related factors, inflammation, vascular fibrosis, and immune responses, as well as cross-talk with other signaling pathways. These remarkable findings indicate that TGF-β signaling is a potential target for wet AMD treatment.

Regulatory T Cells for More Targeted Immunosuppressive Therapies

There has been a prolific amount of research dedicated to the T-regulatory cells (Tregs) and their role in achieving immune homeostasis. Here, the authors briefly discuss the known biology, utilization, and potential of Tregs, for current trials and future immunotherapy. Most current trials of Treg therapies include either ex vivo expanded Tregs transferred into the peripheral blood of patients with diseases of immunologic origin or interleukin 2 injected to stimulate Tregs directly. Ongoing trials designed to measure the clinical efficacy and safety profile of these novel therapeutic approaches have resulted in largely favorable outcomes in a variety of autoimmune and alloimmune diseases.

The Transcriptome of Human Endometrial Mesenchymal Stem Cells Under TGFβR Inhibition Reveals Improved Potential for Cell-Based Therapies

Mesenchymal stem/stromal cells (MSCs) are multipotent cells with favorable properties for cell therapies and regenerative medicine. Human endometrium harbors a small population of perivascular, clonogenic MSCs (eMSCs) identified by the SUSD2 marker. As for other MSCs, eMSCs require extensive in vitro expansion to generate clinically relevant numbers of cells, resulting in spontaneous differentiation, replicative senescence and cell death, decreasing therapeutic potency. We previously demonstrated that A83-01, a TGF-β receptor inhibitor, maintained eMSC clonogenicity, promoted proliferation, prevented apoptosis and maintained MSC function in vitro. Here we compare the transcriptome of passaged eMSCs from six women cultured with and without A83-01 for 7 days. We identified 1206 differentially expressed genes (DEG) using a false discovery rate cut-off at 0.01 and fold change >2. Significant enrichment of genes involved in anti-inflammatory responses, angiogenesis, cell migration and proliferation, and collagen fibril and extracellular matrix organization were revealed. TGF-β, Wnt and Akt signaling pathways were decreased. Anti-fibrotic and anti-apoptotic genes were induced, and fibroblast proliferation and myofibroblast related genes were downregulated. We found increased MSC potency genes (TWIST1, TWIST2, JAG1, LIFR, and SLIT2) validating the enhanced potency of A83-01-treated eMSCs, and importantly no pluripotency gene expression. We also identified eMSCs’ potential for secreting exosomes, possibly explaining their paracrine properties. Angiogenic and cytokine protein arrays confirmed the angiogenic, anti-fibrotic and immunomodulatory phenotype of A83-01-treated eMSCs, and increased angiogenic activity was functionally demonstrated in vitro. eMSCs culture expanded with A83-01 have enhanced clinically relevant properties, suggesting their potential for cell-therapies and regenerative medicine applications.

Impact of activated invariant natural killer T cells on the expansion of regulatory T cell precursors in murine thymocytes in vitro

Tolerance induction is a goal of clinical transplantation to prevent graft rejection without the lifelong use of immunosuppressive drugs. In a series of mouse studies, we previously reported that the establishment of mixed chimerism by treatment with a ligand for invariant natural killer T (iNKT) cells with CD40 signal blockade makes it possible to prevent allograft rejection without immunosuppressants, and this approach fails in thymectomized recipient mice. In this study, we showed that iNKT cells in murine thymocyte cultures are indispensable for the expansion of CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells as well as CD4⁺CD25⁺Foxp3^- cells, which contained precursor Tregs (preTregs). After the culture of BALB/c mouse-derived thymocytes in the presence of α-galactosylceramide (α-GalCer), a representative ligand for iNKT cells, the ratio of CD4⁺CD25⁺Foxp3^- preTregs to total CD4⁺CD8^- T cells was much higher than that of CD4⁺CD25⁺Foxp3⁺ Treg cells, regardless of anti-CD40 L mAb treatment. The proliferation of CD4⁺CD25⁺Foxp3^- cells, but not Treg cells, was significantly augmented, and the stability of Treg cells was not affected by α-GalCer. The expansion of thymocyte-derived Tregs was not inhibited by cytokine neutralization. However, in vitro thymus-derived CD4⁺CD25⁺Foxp3^- cells expressed Foxp3 after IL-2 stimulation in a dose-dependent manner. These results collectively suggest that in vitro thymus-derived Treg cell expansion by α-GalCer treatment was caused by the proliferation of CD4⁺CD25⁺Foxp3^- preTregs but not existing Treg cells.

Factors Produced by Macrophages Eliminating Apoptotic Cells Demonstrate Pro-Resolutive Properties and Terminate Ongoing Inflammation

Unresolved inflammation is a common feature in the pathogenesis of chronic inflammatory/autoimmune diseases. The factors produced by macrophages eliminating apoptotic cells during resolution are crucial to terminate inflammation, and for subsequent tissue healing. We demonstrated here that the factors produced by macrophages eliminating apoptotic cells were sufficient to reboot the resolution of inflammation in vivo, and thus definitively terminated ongoing chronic inflammation. These factors were called SuperMApo and revealed pro-resolutive properties and accelerated acute inflammation resolution, as attested by both increased phagocytic capacities of macrophages and enhanced thioglycollate-induced peritonitis resolution. Activated antigen-presenting cells exposed to SuperMApo accelerated their return to homeostasis and demonstrated pro-regulatory T cell properties. In mice with ongoing collagen-induced arthritis, SuperMApo injection resolved and definitively terminated chronic inflammation. The same pro-resolving properties were observed in human settings in addition to xenogeneic colitis and graft-vs.-host disease modulation, highlighting SuperMApo as a new therapeutic opportunity to circumvent inflammatory diseases.

Development and Functional Modulation of Regulatory T Cells by Transcription Factors and Epigenetics

Regulatory T cells (Tregs) are essential for the maintenance of immune homeostasis. Studies of Treg are not only necessary for understanding the mechanism of immune homeostasis but also extremely useful for the development of treatments of various immune diseases. Forkhead box P3 (Foxp3) was identified as the master gene responsible for the immune-suppressing activity of Tregs. The promoter region and several intronic enhancers, designated conserved noncoding sequence (CNS) 0, 1, 2, and 3, at the Foxp3 gene locus have important roles in Foxp3 expression and Treg development. We demonstrated that transcription factors Nr4a and Smad2/3 are required for development of thymic Tregs and induced Tregs, respectively. In addition to transcription factors, Treg-specific DNA demethylation has been shown to be important for Treg stability. In particular, DNA demethylation of CNS2 was implicated in Treg stability, and members of the ten-eleven translocation family of demethylation factors were recently demonstrated to have important roles in 5'-C-phosphate-G-3' demethylation at CNS2. This article summarizes recent findings regarding the roles of transcription factors and epigenetic modifications in the differentiation, maintenance, and function of Tregs. This review will facilitate clinical application of Tregs to diseases in the field of ophthalmology, including uveitis and age-related macular degeneration.

Promoting remyelination through cell transplantation therapies in a model of viral-induced neurodegenerative disease

Multiple sclerosis (MS) is a central nervous system (CNS) disease characterized by chronic neuroinflammation, demyelination, and axonal damage. Infiltration of activated lymphocytes and myeloid cells are thought to be primarily responsible for white matter damage and axonopathy. Several United States Food and Drug Administration-approved therapies exist that impede activated lymphocytes from entering the CNS thereby limiting new lesion formation in patients with relapse-remitting forms of MS. However, a significant challenge within the field of MS research is to develop effective and sustained therapies that allow for axonal protection and remyelination. In recent years, there has been increasing evidence that some kinds of stem cells and their derivatives seem to be able to mute neuroinflammation as well as promote remyelination and axonal integrity. Intracranial infection of mice with the neurotropic JHM strain of mouse hepatitis virus (JHMV) results in immune-mediated demyelination and axonopathy, making this an excellent model to interrogate the therapeutic potential of stem cell derivatives in evoking remyelination. This review provides a succinct overview of our recent findings using intraspinal injection of mouse CNS neural progenitor cells and human neural precursors into JHMV-infected mice. JHMV-infected mice receiving these cells display extensive remyelination associated with axonal sparing. In addition, we discuss possible mechanisms associated with sustained clinical recovery. Developmental Dynamics 248:43-52, 2019. © 2018 Wiley Periodicals, Inc.

TGF-β-mediated enhancement of TH17 cell generation is inhibited by bone morphogenetic protein receptor 1α signaling

The cytokines of the transforming growth factor-β (TGF-β) family promote the growth and differentiation of multiple tissues, but the role of only the founding member, TGF-β, in regulating the immune responses has been extensively studied. TGF-β is critical to prevent the spontaneous activation of self-reactive T cells and sustain immune homeostasis. In contrast, in the presence of proinflammatory cytokines, TGF-β promotes the differentiation of effector T helper 17 (TH17) cells. Abrogating TGF-β receptor signaling prevents the development of interleukin-17 (IL-17)-secreting cells and protects mice from TH17 cell-mediated autoimmunity. We found that the receptor of another member of TGF-β family, bone morphogenetic protein receptor 1α (BMPR1α), regulates T helper cell activation. We found that the differentiation of TH17 cells from naive CD4+ T cells was inhibited in the presence of BMPs. Abrogation of BMPR1α signaling during CD4+ T cell activation induced a developmental program that led to the generation of inflammatory effector cells expressing large amounts of IL-17, IFN-γ, and TNF family cytokines and transcription factors defining the TH17 cell lineage. We found that TGF-β and BMPs cooperated to establish effector cell functions and the cytokine profile of activated CD4+ T cells. Together, our data provide insight into the immunoregulatory function of BMPs.

TGF-β Signaling in Lung Health and Disease

Transforming growth factor (TGF)-β is an evolutionarily conserved pleiotropic factor that regulates a myriad of biological processes including development, tissue regeneration, immune responses, and tumorigenesis. TGF-β is necessary for lung organogenesis and homeostasis as evidenced by genetically engineered mouse models. TGF-β is crucial for epithelial-mesenchymal interactions during lung branching morphogenesis and alveolarization. Expression and activation of the three TGF-β ligand isoforms in the lungs are temporally and spatially regulated by multiple mechanisms. The lungs are structurally exposed to extrinsic stimuli and pathogens, and are susceptible to inflammation, allergic reactions, and carcinogenesis. Upregulation of TGF-β ligands is observed in major pulmonary diseases, including pulmonary fibrosis, emphysema, bronchial asthma, and lung cancer. TGF-β regulates multiple cellular processes such as growth suppression of epithelial cells, alveolar epithelial cell differentiation, fibroblast activation, and extracellular matrix organization. These effects are closely associated with tissue remodeling in pulmonary fibrosis and emphysema. TGF-β is also central to T cell homeostasis and is deeply involved in asthmatic airway inflammation. TGF-β is the most potent inducer of epithelial-mesenchymal transition in non-small cell lung cancer cells and is pivotal to the development of tumor-promoting microenvironment in the lung cancer tissue. This review summarizes and integrates the current knowledge of TGF-β signaling relevant to lung health and disease.

Stem cells for lupus nephritis: a concise review of current knowledge

Lupus nephritis (LN), a common manifestation of systemic lupus erythematosus (SLE), accounts for significant morbidity and mortality in SLE patients. Since the available standard therapies and biologic agents for LN are yet to achieve the desired response and have considerable secondary effects, stem cell therapy has now emerged as a new approach. This therapy involves the transplantation of hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Our current review will highlight the progress of stem cell therapy for LN, along with the challenges encountered and the future direction of this approach.

Protective Regulatory T Cell Immune Response Induced by Intranasal Immunization With the Live-Attenuated Pneumococcal Vaccine SPY1 via the Transforming Growth Factor-β1-Smad2/3 Pathway

Vaccine effectiveness is mainly determined by the mechanism mediating protection, emphasizing the importance of unraveling the protective mechanism for novel pneumococcal vaccine development. We previously demonstrated that the regulatory T cell (Treg) immune response has a protective effect against pneumococcal infection elicited by the live-attenuated pneumococcal vaccine SPY1. However, the mechanism underlying this protective effect remains unclear. In this study, a short synthetic peptide (P17) was used to downregulate Tregs during immunization and subsequent challenges in a mouse model. In immunized mice, increase in immune cytokines (IL-12p70, IL-4, IL-5, and IL-17A) induced by SPY1 were further upregulated by P17 treatment, whereas the decrease in the infection-associated inflammatory cytokine TNF-α by SPY1 was reversed. P17 also inhibited the increase in the immunosuppressive cytokine IL-10 and inflammatory mediator IL-6 in immunized mice. More severe pulmonary injuries and more dramatic inflammatory responses with worse survival in P17-treated immunized mice indicated the indispensable role of the Treg immune response in protection against pneumococcal infection by maintaining a balance among acquired immune responses stimulated by SPY1. Further studies revealed that the significant elevation of active transforming growth factor β (TGF-β)1 by SPY1 vaccination activated FOXP3, leading to increased frequencies of CD4+CD25+Foxp3+ T cells. Moreover, SPY1 vaccination elevated the levels of Smad2/3 and phosphor-Smad2/3 and downregulated the negative regulatory factor Smad7 in a time-dependent manner during pneumococcal infection, and these changes were reversed by P17 treatment. These results illustrate that SPY1-stimulated TGF-β1 induced the generation of SPY1-specific Tregs via the Smad2/3 signaling pathway. In addition, SPY1-specific Tregs may participate in protection via the enhanced expression of PD-1 and CTLA-4. The data presented here extend our understanding of how the SPY1-induced acquired Treg immune response contributes to protection elicited by live-attenuated vaccines and may be helpful for the evaluation of live vaccines and other mucosal vaccine candidates.

Transforming growth factor-β1 gene promoter -509C/T polymorphism in association with expression affects colorectal cancer development and depends on gender

It is widely known that sporadic colorectal cancer (CRC) is age-related diseases with higher incidence rate among men. Transforming growth factor-β1 (TGF-β1) is a major immune regulatory cytokine with a great impact and dual role in gastrointestinal carcinogenesis. In this context, the aim of the study was to explore the role of circulating TGF-β1 and the -509C/T functional promoter polymorphism (rs1800469) within the TGF-β1 gene (TGFB1) in the susceptibility, progression, and prognosis of CRC among Bulgarian male and female patients. Patients with sporadic CRC and healthy controls were genotyped by polymerase-chain reaction–restriction fragment length polymorphism. Serum TGF-β1 levels before and after curative surgery were determined by ELISA. Total RNA was extracted from paired tumor, normal mucosa and distant metastasis samples and was used for quantitative detection of TGFB1 mRNA by TaqMan qPCR.We observed that TGF-β1 serum levels depend on the -509C/T genotype in combination with gender. TGF-β1 serum levels in CRC patients were decreased compared to controls, but statistical significance was reached only for men. In the stratified analysis by gender and genotype, a significant association was found for the CC genotype. Overall, our results indicate that the -509C allele increased the cancer risk, particularly for advanced stages (OR = 1.477; p = 0.029). The results from the relative mRNA quantification showed a significant upregulation of TGFB1 in distant metastases compared to primary tumor tissues and higher TGFB1 mRNA levels in men (RQ = 4.959; p = 0.022). In conclusion, we present data that diminished circulating TGF-β1 due to the CC genotype could be a possible risk factor for tumor susceptibility and progression. This association is more pronounced in males than in females. Colorectal cancer tissue expression of TGFB1 gene mRNA correlates with tumor progression and metastasis.

Contact-independent suppressive activity of regulatory T cells is associated with telomerase inhibition, telomere shortening and target lymphocyte apoptosis

Regulatory T cells (Tregs) play a fundamental role in the maintenance of immunological tolerance by suppressing effector target T, B and NK lymphocytes. Contact-dependent suppression mechanisms have been well-studied, though contact-independent Treg activity is not fully understood. In the present study, we showed that human native Tregs, as well as induced ex vivo Tregs, can cause in vitro telomere-dependent senescence in target T, B and NK cells in a contact-independent manner. The co-cultivation of target cells with Tregs separated through porous membranes induced alternative splicing of the telomerase catalytic subunit hTERT (human Telomerase Reverse Transcriptase), which suppressed telomerase activity. Induction of the hTERT splicing variant was associated with increased expression of the apoptotic endonuclease EndoG, a splicing regulator. Inhibited telomerase in target cells co-cultivated with Tregs for a long period of time led to a decrease in their telomere lengths, cell cycle arrest, conversion of the target cells to replicative senescence and apoptotic death. Induced Tregs showed the ability to up-regulate EndoG expression, TERT alternative splicing and telomerase inhibition in mouse T, B and NK cells after in vivo administration. The results of the present study describe a novel mechanism of contact-independent Treg cell suppression that induces telomerase inhibition through the EndoG-provoked alternative splicing of hTERT and converts cells to senescence and apoptosis phenotypes.

Transforming Growth Factor-β1/Smad7 in Intestinal Immunity, Inflammation, and Cancer

In physiological conditions, the activity of the intestinal immune system is tightly regulated to prevent tissue-damaging reactions directed against components of the luminal flora. Various factors contribute to maintain immune homeostasis and diminished production and/or function of such molecules trigger and/or propagate detrimental signals, which can eventually lead to chronic colitis and colon cancer. One such a molecule is transforming growth factor-β1 (TGF-β1), a cytokine produced by many inflammatory and non-inflammatory cells and targeting virtually all the intestinal mucosal cell types, with the down-stream effect of activating intracellular Smad2/3 proteins and suppressing immune reactions. In patients with inflammatory bowel diseases (IBD), there is defective TGF-β1/Smad signaling due to high Smad7, an inhibitor of TGF-β1 activity. Indeed, knockdown of Smad7 with a specific antisense oligonucleotide restores endogenous TGF-β1 activity, thereby inhibiting inflammatory pathways in patients with IBD and colitic mice. Consistently, mice over-expressing Smad7 in T cells develop severe intestinal inflammation in various experimental models. Smad7 expression is also upregulated in colon cancer cells, in which such a protein controls positively intracellular pathways that sustain neoplastic cell growth and survival. We here review the role of TGF-β1 and Smad7 in intestinal immunity, inflammation, and cancer.

Murine regulatory T cells induce death of effector T, B, and NK lymphocytes through a contact-independent mechanism involving telomerase suppression and telomere-associated senescence

Regulatory T cells (Tregs) suppress the activity of effector T, B and NK lymphocytes and sustain immunological tolerance, but the proliferative activity of suppressed cells remains unexplored. In the present study, we report that mouse Tregs can induce replicative senescence and the death of responder mouse CD4⁺CD25^- T cells, CD8⁺ T cells, B cells and NK cells in vitro and in vivo. Contact-independent in vitro co-cultivation with Tregs up-regulated endonuclease G (EndoG) expression and its translocation to the nucleus in responder cells. EndoG localization in the nucleus induced alternative mRNA splicing of the telomerase catalytic subunit Tert and telomerase inhibition. The lack of telomerase activity in proliferating cells led to telomere loss followed by the development of senescence and cell death. Injection of Tregs into mice resulted in EndoG-associated alternative splicing of Tert, telomerase inhibition, telomere loss, senescence development and increased cell death in vivo. The present study describes a novel contact-independent mechanism by which Tregs specify effector cell fate and provides new insights into cellular crosstalk related to immune suppression.

YAP Is Essential for Treg-Mediated Suppression of Antitumor Immunity

Regulatory T cells (Treg) are critical for maintaining self-tolerance and immune homeostasis, but their suppressive function can impede effective antitumor immune responses. FOXP3 is a transcription factor expressed in Tregs that is required for their function. However, the pathways and microenvironmental cues governing FOXP3 expression and Treg function are not completely understood. Herein, we report that YAP, a coactivator of the Hippo pathway, is highly expressed in Tregs and bolsters FOXP3 expression and Treg function in vitro and in vivo. This potentiation stemmed from YAP-dependent upregulation of activin signaling, which amplifies TGFβ/SMAD activation in Tregs. YAP deficiency resulted in dysfunctional Tregs unable to suppress antitumor immunity or promote tumor growth in mice. Chemical YAP antagonism and knockout or blockade of the YAP-regulated activin receptor similarly improved antitumor immunity. Thus, we identify YAP as an unexpected amplifier of a Treg-reinforcing pathway with significant potential as an anticancer immunotherapeutic target.Significance: Tregs suppress antitumor immunity, and pathways supporting their function can be novel immunotherapy targets. Here, the selective expression of YAP by Tregs, its importance for their function, and its unexpected enhancement of pro-Treg Activin/SMAD signaling are reported, as are validations of potential cancer-fighting antagonists of YAP and its regulatory targets. Cancer Discov; 8(8); 1026-43. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 899.

Targeting the TGFβ pathway with galunisertib, a TGFβRI small molecule inhibitor, promotes anti-tumor immunity leading to durable, complete responses, as monotherapy and in combination with checkpoint blockade

Background

TGFβ signaling plays a pleotropic role in tumor biology, promoting tumor proliferation, invasion and metastasis, and escape from immune surveillance. Inhibiting TGFβ’s immune suppressive effects has become of particular interest as a way to increase the benefit of cancer immunotherapy. Here we utilized preclinical models to explore the impact of the clinical stage TGFβ pathway inhibitor, galunisertib, on anti-tumor immunity at clinically relevant doses.

Results

In vitro treatment with galunisertib reversed TGFβ and regulatory T cell mediated suppression of human T cell proliferation. In vivo treatment of mice with established 4T1-LP tumors resulted in strong dose-dependent anti-tumor activity with close to 100% inhibition of tumor growth and complete regressions upon cessation of treatment in 50% of animals. This effect was CD8+ T cell dependent, and led to increased T cell numbers in treated tumors. Mice with durable regressions rejected tumor rechallenge, demonstrating the establishment of immunological memory. Consequently, mice that rejected immunogenic 4T1-LP tumors were able to resist rechallenge with poorly immunogenic 4 T1 parental cells, suggesting the development of a secondary immune response via antigen spreading as a consequence of effective tumor targeting. Combination of galunisertib with PD-L1 blockade resulted in improved tumor growth inhibition and complete regressions in colon carcinoma models, demonstrating the potential synergy when cotargeting TGFβ and PD-1/PD-L1 pathways. Combination therapy was associated with enhanced anti-tumor immune related gene expression profile that was accelerated compared to anti-PD-L1 monotherapy.

Conclusions

Together these data highlight the ability of galunisertib to modulate T cell immunity and the therapeutic potential of combining galunisertib with current PD-1/L1 immunotherapy.

Recent advances in the development of vaccines for chronic inflammatory autoimmune diseases

Chronic inflammatory autoimmune diseases leading to target tissue destruction and disability are not only causing increase in patients' suffering but also contribute to huge economic burden for the society. General increase in life expectancy and high prevalence of these diseases both in elderly and younger population emphasize the importance of developing safe and effective vaccines. In this review, at first the possible mechanisms and risk factors associated with chronic inflammatory autoimmune diseases, such as rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE) and type 1 diabetes (T1D) are discussed. Current advances in the development of vaccines for such autoimmune diseases, particularly those based on DNA, altered peptide ligands and peptide loaded MHC II complexes are discussed in detail. Finally, strategies for improving the efficacy of potential vaccines are explored.

Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development

This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.

IL-2 and IL-15 dependent thymic development of Foxp3-expressing regulatory T lymphocytes

Immunosuppressive regulatory T lymphocytes (Treg) expressing the transcription factor Foxp3 play a vital role in the maintenance of tolerance of the immune-system to self and innocuous non-self. Most Treg that are critical for the maintenance of tolerance to self, develop as an independent T-cell lineage from common T cell precursors in the thymus. In this organ, their differentiation requires signals from the T cell receptor for antigen, from co-stimulatory molecules, as well as from cytokine-receptors. Here we focus on the cytokines implicated in thymic development of Treg, with a particular emphasis on the roles of interleukin-2 (IL-2) and IL-15. The more recently appreciated involvement of TGF-β in thymic Treg development is also briefly discussed. Finally, we discuss how cytokine-dependence of Treg development allows for temporal, quantitative, and potentially qualitative modulation of this process.

TGFβ1 transduction enhances immunomodulatory capacity of neural stem cells in experimental autoimmune encephalomyelitis

Bone marrow-derived neural stem cells (BM-NSCs) have therapeutic effect on EAE, an animal model of multiple sclerosis. However, the beneficial effect is suboptimal due to the limited immunomodulatory capacity of these cells. In this study, we engineered BM-NSCs with inducible TGFβ1, a potent immunosuppressive cytokine, to enhance their anti-inflammatory capacity. We found that i.v. injected TGFβ1-BM-NSCs more effectively suppressed clinical severity, inflammation and demyelination of the central nervous system of EAE mice. Transduction of TGFβ1 resulted in a higher percentage of Tregs and lower percentage of Th1 and Th17 cells in the periphery, with increased production of IL-10, and reduced production of IFN-γ, IL-17 and GM-CSF. Moreover, myelin-specific splenic proliferation was also inhibited more profoundly by TGFβ1-BM-NSCs. We also found that TGFβ1-BM-NSCs have the capacity to switch microglia from M1 to M2 phenotype. On the other hand, transduction of TGFβ1 did not affect proliferative ability and differentiating potential of BM-NSCs in vitro and in vivo. Together, these findings demonstrate that transduction of TGFβ1 significantly enhanced the immunomodulatory capacity of BM-NSCs for EAE treatment, through inducing Tregs and an M2 phenotype of macrophages/microglia, while retaining their capacity for neural cell differentiation. Thus, our study provides an easily accessible, inducible and effective therapy for CNS inflammatory demyelination.

Cytokine Signaling in the Development and Homeostasis of Regulatory T cells

Cytokine signaling is indispensable for regulatory T-cell (Treg) development in the thymus, and also influences the homeostasis, phenotypic diversity, and function of Tregs in the periphery. Because Tregs are required for establishment and maintenance of immunological self-tolerance, investigating the role of cytokines in Treg biology carries therapeutic potential in the context of autoimmune disease. This review discusses the potent and diverse influences of interleukin (IL)-2 signaling on the Treg compartment, an area of knowledge that has led to the use of low-dose IL-2 as a therapy to reregulate autoaggressive immune responses. Evidence suggesting Treg-specific impacts of the cytokines transforming growth factor β (TGF-β), IL-7, thymic stromal lymphopoietin (TSLP), IL-15, and IL-33 is also presented. Finally, we consider the technical challenges and knowledge limitations that must be overcome to bring other cytokine-based, Treg-targeted therapies into clinical use.

Bifunctional immune checkpoint-targeted antibody-ligand traps that simultaneously disable TGFβ enhance the efficacy of cancer immunotherapy

A majority of cancers fail to respond to immunotherapy with antibodies targeting immune checkpoints, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) or programmed death-1 (PD-1)/PD-1 ligand (PD-L1). Cancers frequently express transforming growth factor-β (TGFβ), which drives immune dysfunction in the tumor microenvironment by inducing regulatory T cells (Tregs) and inhibiting CD8⁺ and T_H1 cells. To address this therapeutic challenge, we invent bifunctional antibody-ligand traps (Y-traps) comprising an antibody targeting CTLA-4 or PD-L1 fused to a TGFβ receptor II ectodomain sequence that simultaneously disables autocrine/paracrine TGFβ in the target cell microenvironment (a-CTLA4-TGFβRIIecd and a-PDL1-TGFβRIIecd). a-CTLA4-TGFβRIIecd is more effective in reducing tumor-infiltrating Tregs and inhibiting tumor progression compared with CTLA-4 antibody (Ipilimumab). Likewise, a-PDL1-TGFβRIIecd exhibits superior antitumor efficacy compared with PD-L1 antibodies (Atezolizumab or Avelumab). Our data demonstrate that Y-traps counteract TGFβ-mediated differentiation of Tregs and immune tolerance, thereby providing a potentially more effective immunotherapeutic strategy against cancers that are resistant to current immune checkpoint inhibitors.

Bifunctional immune checkpoint-targeted antibody-ligand traps that simultaneously disable TGFβ enhance the efficacy of cancer immunotherapy

A majority of cancers fail to respond to immunotherapy with antibodies targeting immune checkpoints, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) or programmed death-1 (PD-1)/PD-1 ligand (PD-L1). Cancers frequently express transforming growth factor-β (TGFβ), which drives immune dysfunction in the tumor microenvironment by inducing regulatory T cells (Tregs) and inhibiting CD8+ and TH1 cells. To address this therapeutic challenge, we invent bifunctional antibody-ligand traps (Y-traps) comprising an antibody targeting CTLA-4 or PD-L1 fused to a TGFβ receptor II ectodomain sequence that simultaneously disables autocrine/paracrine TGFβ in the target cell microenvironment (a-CTLA4-TGFβRIIecd and a-PDL1-TGFβRIIecd). a-CTLA4-TGFβRIIecd is more effective in reducing tumor-infiltrating Tregs and inhibiting tumor progression compared with CTLA-4 antibody (Ipilimumab). Likewise, a-PDL1-TGFβRIIecd exhibits superior antitumor efficacy compared with PD-L1 antibodies (Atezolizumab or Avelumab). Our data demonstrate that Y-traps counteract TGFβ-mediated differentiation of Tregs and immune tolerance, thereby providing a potentially more effective immunotherapeutic strategy against cancers that are resistant to current immune checkpoint inhibitors.

The effect of foxp3-overexpressing Treg cells on non-small cell lung cancer cells

The aim of the present study was to investigate the novel mechanisms of forkhead box protein P3 (foxp3) in T regulatory (Treg) cells in lung cancer behavior. Treg cells were isolated from the peripheral blood of healthy volunteers and then co-cultured with 95D cells. A plasmid overexpressing foxp3 was constructed and transfected into Treg cells and an MTS assay was performed to assess cell viability. Flow cytometry was performed to evaluate cell apoptosis and reverse transcription-quantitative polymerase chain reaction was used to measure mRNA expression. A Transwell assay was used to assess cell invasion. Treg cells were successfully isolated from peripheral blood with purity of 94.26%. Foxp3 expression in Treg cells was significantly increased following co-culture with 95D cells, while matrix metalloproteinase-9 expression was upregulated in 95D cells co-cultured with Treg cells. The apoptosis, invasion and migration abilities of 95D cells were suppressed by co-culture with Treg cells, whereas the adhesive ability was enhanced. Foxp3 overexpression in Treg cells enhanced the viability and invasiveness of 95D cells, whereas cell adhesion and migration were decreased. The results of the present study demonstrate that the viability and invasiveness of 95D cells are enhanced by foxp3 overexpression in Treg cells, indicating that increased levels of foxp3 in the tumor microenvironment may promote tumor cell growth.

Immunosuppressive Mesenchymal Stromal Cells Derived from Human-Induced Pluripotent Stem Cells Induce Human Regulatory T Cells In Vitro and In Vivo

Despite mesenchymal stromal cells (MSCs) are considered as a promising source of cells to modulate immune functions on cells from innate and adaptive immune systems, their clinical use remains restricted (few number, limited in vitro expansion, absence of a full phenotypic characterization, few insights on their in vivo fate). Standardized MSCs derived in vitro from human-induced pluripotent stem (huIPS) cells, remediating part of these issues, are considered as well as a valuable tool for therapeutic approaches, but their functions remained to be fully characterized. We generated multipotent MSCs derived from huiPS cells (huiPS-MSCs), and focusing on their immunosuppressive activity, we showed that human T-cell activation in coculture with huiPS-MSCs was significantly reduced. We also observed the generation of functional CD4⁺ FoxP3⁺ regulatory T (Treg) cells. Further tested in vivo in a model of human T-cell expansion in immune-deficient NSG mice, huiPS-MSCs immunosuppressive activity prevented the circulation and the accumulation of activated human T cells. Intracytoplasmic labeling of cytokines produced by the recovered T cells showed reduced percentages of human-differentiated T cells producing Th1 inflammatory cytokines. By contrast, T cells producing IL-10 and FoxP3⁺-Treg cells, absent in non-treated animals, were detected in huiPS-MSCs treated mice. For the first time, these results highlight the immunosuppressive activity of the huiPS-MSCs on human T-cell stimulation with a concomitant generation of human Treg cells in vivo. They may favor the development of new tools and strategies based on the use of huiPS cells and their derivatives for the induction of immune tolerance.

The PI3K/AKT signaling pathway in regulatory T-cell development, stability, and function

The PI3K/AKT signaling pathway is an essential node in mammalian cells that controls cell growth, migration, proliferation, and metabolism. During the last decade, a number of works have demonstrated an important role for the PI3K/AKT pathway in regulatory T cell development, function, and stability. This review summarizes our current knowledge of how the PI3K/AKT pathway regulates thymic and peripheral Treg generation and function, with an emphasis on translation of these observations to therapies targeting Tregs in several pathologies.

Lymphatic endothelial cells attenuate inflammation via suppression of dendritic cell maturation

Vascular endothelial growth factor-C (VEGF-C)-induced lymphangiogenesis and increased tissue drainage have been reported to inhibit acute and chronic inflammation, and an activated lymphatic endothelium might mediate peripheral tolerance. Using transgenic mice overexpressing VEGF-C in the skin, we found that under inflammatory conditions, VEGF-C-mediated expansion of the cutaneous lymphatic network establishes an immune-inhibitory microenvironment characterised by increased regulatory T (Treg) cells, immature CD11c+CD11b+ dendritic cells (DCs) and CD8+ cells exhibiting decreased effector function. Strikingly, lymphatic endothelial cell (LEC)-conditioned media (CM) potently suppress DC maturation with reduced expression of MHCII, CD40, and IL-6, and increased IL-10 and CCL2 expression. We identify an imbalance in prostaglandin synthase expression after LEC activation, favoring anti-inflammatory prostacyclin synthesis. Importantly, blockade of LEC prostaglandin synthesis partially restores DC maturity. LECs also produce TGF-ß1, contributing to the immune-inhibitory microenvironment. This study identifies novel mechanisms by which the lymphatic endothelium modulates cellular immune responses to limit inflammation.

Basic Aspects of T Helper Cell Differentiation

CD4+ T helper cells orchestrate the immune response and play a pivotal role during infection, chronic inflammatory, autoimmune diseases, and carcinogenesis. CD4+ T helper cells can be subdivided into different subsets, which are characterized by a specific network of transcriptional regulators and unique cytokine profiles: Th17 cells express RORγt that in turn promotes the transcription of Il17a, Il17f; Th1 cells, expresses T-bet and produces IFN-γ, IL-2, and TNF-α; Th2 cells express GATA-3 and secrete IL-4, IL-5, and IL-13. The two most studied regulatory T cell subtypes are Foxp3+ regulatory T cells, which can be generated either in the thymus (tTreg) or induced in peripheral lymphoid organs (pTregs) and type 1 regulatory T cells (Tr1), which are induced in the periphery. These T helper cell subsets can be differentiated from naïve T cells. In addition, recent findings indicate that some T helper cell subsets can emerge from other T helper cells, suggesting a certain degree of plastiticy. Here we report basic aspects of T helper cell differentiation and function while underlining some still open questions.

A structurally distinct TGF-β mimic from an intestinal helminth parasite potently induces regulatory T cells

Helminth parasites defy immune exclusion through sophisticated evasion mechanisms, including activation of host immunosuppressive regulatory T (Treg) cells. The mouse parasite Heligmosomoides polygyrus can expand the host Treg population by secreting products that activate TGF-β signalling, but the identity of the active molecule is unknown. Here we identify an H. polygyrus TGF-β mimic (Hp-TGM) that replicates the biological and functional properties of TGF-β, including binding to mammalian TGF-β receptors and inducing mouse and human Foxp3⁺ Treg cells. Hp-TGM has no homology with mammalian TGF-β or other members of the TGF-β family, but is a member of the complement control protein superfamily. Thus, our data indicate that through convergent evolution, the parasite has acquired a protein with cytokine-like function that is able to exploit an endogenous pathway of immunoregulation in the host.

Heligmosomoides polygyrus can activate mammalian TGF-β signalling pathways, but how it does so is not known. Here the authors identify and isolate a H. polygyrus TFG-β mimic that can bind both mammalian TGF-β receptor subunits, activate Smad signalling and generate inducible regulatory T cells.

Rapid and Efficient Generation of Regulatory T Cells to Commensal Antigens in the Periphery

Commensal bacteria shape the colonic regulatory T (Treg) cell population required for intestinal tolerance. However, little is known about this process. Here, we use the transfer of naive commensal-reactive transgenic T cells expressing colonic Treg T cell receptors (TCRs) to study peripheral Treg (pTreg) cell development in normal hosts. We found that T cells were activated primarily in the distal mesenteric lymph node. Treg cell induction was rapid, generating >40% Foxp3(+) cells 1 week after transfer. Contrary to prior reports, Foxp3(+) cells underwent the most cell divisions, demonstrating that pTreg cell generation can be the dominant outcome from naive T cell activation. Moreover, Notch2-dependent, but not Batf3-dependent, dendritic cells were involved in Treg cell selection. Finally, neither deletion of the conserved nucleotide sequence 1 (CNS1) region in Foxp3 nor blockade of TGF-β (transforming growth factor-β)-receptor signaling completely abrogated Foxp3 induction. Thus, these data show that pTreg cell selection to commensal bacteria is rapid, is robust, and may be specified by TGF-β-independent signals.

Interleukin 35 and Hepatocyte Growth Factor; as a novel combined immune gene therapy for Multiple Sclerosis disease

An autoimmune demyelination disease of the Central Nervous System, Multiple Sclerosis, is a chronic inflammation which mostly involves young adults. Suffering people face functional loss with a severe pain. Most current MS treatments are focused on the immune response suppression. Approved drugs suppress the inflammatory process, but factually, there is no definite cure for Multiple Sclerosis. Recently developed knowledge has demonstrated that gene and cell therapy as a hopeful approach in tissue regeneration. The authors propose a novel combined immune gene therapy for Multiple Sclerosis treatment using anti-inflammatory and remyelination of Interleukine-35 and Hepatocyte Growth Factor properties, respectively. In this hypothesis Interleukine-35 and Hepatocyte Growth Factor introduce to Mesenchymal Stem Cells of EAE mouse model via an adenovirus based vector. It is expected that Interleukine-35 and Hepatocyte Growth Factor genes expressed from MSCs could effectively perform in immunotherapy of Multiple Sclerosis.

Development of Inflammatory Bowel Disease Is Linked to a Longitudinal Restructuring of the Gut Metagenome in Mice

The gut microbiome is linked to inflammatory bowel disease (IBD) severity and altered in late-stage disease. However, it is unclear how gut microbial communities change over the course of IBD development, especially in regard to function. To investigate microbiome-mediated disease mechanisms and discover early biomarkers of IBD, we conducted a longitudinal metagenomic investigation in an established mouse model of IBD, where damped transforming growth factor β (TGF-β) signaling in T cells leads to peripheral immune activation, weight loss, and severe colitis. IBD development is associated with abnormal gut microbiome temporal dynamics, including damped acquisition of functional diversity and significant differences in abundance trajectories for KEGG modules such as glycosaminoglycan degradation, cellular chemotaxis, and type III and IV secretion systems. Most differences between sick and control mice emerge when mice begin to lose weight and heightened T cell activation is detected in peripheral blood. However, levels of lipooligosaccharide transporter abundance diverge prior to immune activation, indicating that it could be a predisease indicator or microbiome-mediated disease mechanism. Taxonomic structure of the gut microbiome also significantly changes in association with IBD development, and the abundances of particular taxa, including several species of Bacteroides, correlate with immune activation. These discoveries were enabled by our use of generalized linear mixed-effects models to test for differences in longitudinal profiles between healthy and diseased mice while accounting for the distributions of taxon and gene counts in metagenomic data. These findings demonstrate that longitudinal metagenomics is useful for discovering the potential mechanisms through which the gut microbiome becomes altered in IBD. IMPORTANCE IBD patients harbor distinct microbial communities with functional capabilities different from those seen with healthy people. But is this cause or effect? Answering this question requires data on changes in gut microbial communities leading to disease onset. By performing weekly metagenomic sequencing and mixed-effects modeling on an established mouse model of IBD, we identified several functional pathways encoded by the gut microbiome that covary with host immune status. These pathways are novel early biomarkers that may either enable microbes to live inside an inflamed gut or contribute to immune activation in IBD mice. Future work will validate the potential roles of these microbial pathways in host-microbe interactions and human disease. This study was novel in its longitudinal design and focus on microbial pathways, which provided new mechanistic insights into the role of gut microbes in IBD development.

Transcription factor c-Rel is indispensable for generation of thymic but not of peripheral Foxp3+ regulatory T cells

The transcription factor c-Rel has been shown to be crucial for development of regulatory T cells (Tregs). Recent studies have reported that the expression of transcription factor Helios in Foxp3+ Tregs correlates with thymic origin of these cells (tTregs). Notably, we found that only the Helios+Foxp3+ Treg cell population was substantially reduced in c-Rel deficient mice. In contrast to a defective tTreg development, we observed an expansion of mucosal Tregs during the induction of acute colitis in rel-/- mice. Furthermore, we found a preferential accumulation of Helios-Foxp3+ Tregs in aged c-Rel deficient mice. This unexpected finding, together with the observation that naïve CD4+ T cells convert into Tregs in vitro in the absence of c-Rel and presence of IL-2, provide an evidence that extra-thymic generation of induced and peripheral Tregs (iTregs and pTregs) is independent of c-Rel. Moreover, the treatment with IL-2/anti-IL-2 mAb (JES6-1) resulted in a widespread increase of Helios+Foxp3+ Tregs in both wild-type (WT) and rel-/- mice. These data suggest that exogenous IL-2 administration compensates for defective IL-2 production and reduced tTreg numbers in c-Rel deficient mice. Our findings reveal that c-Rel is essential for the generation of tTregs but not for that of pTregs and iTregs.

Regulatory T cells and type 2 innate lymphoid cell-dependent asthma

Group 2 innate lymphoid cells (ILC2s) are a recently identified group of cells with the potent capability to produce Th2-type cytokines such as interleukin (IL)-5 and IL-13. Several studies suggest that ILC2s play an important role in the development of allergic diseases and asthma. Activation of pulmonary ILC2s in murine models lacking T and B cells induces eosinophilia and airway hyper-reactivity (AHR), which are cardinal features of asthma. More importantly, numerous recent studies have highlighted the role of ILC2s in asthma persistence and exacerbation among human subjects, and thus, regulation of pulmonary ILC2s is a major area of investigation aimed at curbing allergic lung inflammation and exacerbation. Emerging evidence reveals that a group of regulatory T cells, induced Tregs (iTregs), effectively suppress the production of ILC2-driven, pro-inflammatory cytokines IL-5 and IL-13. The inhibitory effects of iTregs are blocked by preventing direct cellular contact or by inhibiting the ICOS-ICOS-ligand (ICOSL) pathway, suggesting that both direct contact and ICOS-ICOSL interaction are important in the regulation of ILC2 function. Also, cytokines such as IL-10 and TGF-β1 significantly reduce cytokine secretion by ILC2s. Altogether, these new findings uncover iTregs as potent regulators of ILC2 activation and implicate their utility as a therapeutic approach for the treatment of ILC2-mediated allergic asthma and respiratory disease.

Programmed death one homolog maintains the pool size of regulatory T cells by promoting their differentiation and stability

Programmed death one homolog (PD-1H) is an immunoglobulin superfamily molecule and primarily acts as a coinhibitor in the initiation of T cell response to antigens. Here, we report that genetic ablation of PD-1H in mice blocks the differentiation of naive T cells to Foxp3⁺ inducible Treg cells (iTreg) with a significant decrease of iTreg in lymphoid organs. This effect of PD-1H is highly specific for iTreg because both naturally generated iTreg in gut-related tissues and in vitro induced iTreg by TGF-β were decreased whereas the genesis of natural Treg (nTreg) remains normal. The suppressive function of both iTreg and nTreg, however, is not affected by the loss of PD-1H. In addition to decreased production, PD-1H deficient iTreg could also rapidly convert to CD4⁺ T helper 1 or T helper 17 cells in an inflammatory environment. Our results indicate that PD-1H is required for maintenance of iTreg pool size by promoting its differentiation and preventing its conversion to other CD4⁺ T cell subsets. These findings may have important implications for manipulating Tregs to control inflammation.

Induction and maintenance of regulatory T cells by transcription factors and epigenetic modifications

Regulatory T cells (Tregs) are an essential cell subset for the maintenance of immune homeostasis. Foxp3 (Forkhead box P3) is the Treg master gene which is essential for immune suppressing activity. In addition, Tregs are characterized by a distinct pattern of gene expression, including upregulation of immune-suppressive genes and silencing of inflammatory genes. The molecular mechanisms of Treg development and maintenance have been intensively investigated. Tregs are characterized by expression of the transcription factor Foxp3. Several intronic enhancers and a promoter at the Foxp3 gene locus were shown to play important roles in Treg differentiation. The enhancers have been designated as conserved non-coding sequences (CNSs) 0, 1, 2, and 3. We showed that the transcription factors Nr4a and Smad2/3 are essential for the development of thymic Tregs and induced Tregs, respectively. Recently, Treg-specific DNA demethylation has been shown to play an important role in Treg stability. DNA demethylation of CNS2 has been implicated in Treg stability, and recent reports have revealed that the ten-eleven translocation (Tet) family of demethylation factor plays an important role in CpG demethylation at CNS2. This article reviews the recent progress on the roles of transcription factors and epigenetic modifications in the differentiation, maintenance, and function of Tregs.

Zoledronic acid inhibits NFAT and IL-2 signaling pathways in regulatory T cells and diminishes their suppressive function in patients with metastatic cancer

Regulatory T cells (Treg) suppress anti-tumor immune responses and their infiltration in the tumor microenvironment is associated with inferior prognosis in cancer patients. Thus, in order to enhance anti-tumor immune responses, selective depletion of Treg is highly desired. We found that treatment with zoledronic acid (ZA) resulted in a selective decrease in the frequency of Treg that was associated with a significant increase in proliferation of T cells and natural killer (NK) cells in peripheral blood of patients with metastatic cancer. In vitro, genome-wide transcriptomic analysis revealed alterations in calcium signaling pathways in Treg following treatment with ZA. Furthermore, co-localization of the nuclear factor of activated T cells (NFAT) and forkhead box P3 (FOXP3) was significantly reduced in Treg upon ZA-treatment. Consequently, reduced expression levels of CD25, STAT5 and TGFβ were observed. Functionally, ZA-treated Treg had reduced capacity to suppress T and NK cell proliferation and anti-tumor responses compared with untreated Treg in vitro. Treatment with ZA to selectively inhibit essential signaling pathways in Treg resulting in reduced capacity to suppress effector T and NK cell responses represents a novel approach to inhibit Treg activity in patients with cancer.

Clinicopathologic and prognostic significance of regulatory T cells in patients with hepatocellular carcinoma: a meta-analysis

The clinicopathologic and prognostic significance of regulatory T cells (Tregs) in patients with hepatocellular carcinoma (HCC) remains controversial. We performed a meta-analysis to resolve this issue. PubMed, Embase, Cochrane library, and the Web of Science were searched to identify eligible studies performed up to November 2016. A total of 3,854 HCC patients from 27 cohort studies were included. The meta-analysis revealed that high levels of Tregs were associated with poor overall survival (OS; HR = 1.95, P < 0.00001) and disease-free survival (DFS; HR = 1.82, P < 0.00001). However, the prognostic effect varied greatly according to the site of the Tregs. Higher intratumoral and peripheral blood levels of Tregs were associated with shorter OS and DFS, whereas a high peritumoral Tregs level was not associated with decreased OS and DFS. Trial design, therapy and method of detection had no effect on prognosis of Tregs. Moreover, the patients with high Tregs infiltration had multiple tumors, high AFP level, poor differentiation, later TNM stage, and vascular invasion. The present study demonstrates that high levels of intratumoral and peripheral blood Tregs predict multiple tumors, high AFP level, poor differentiation, later TNM stage, and vascular invasion and might be a promising prognostic factor in patients with HCC.

TGF-β inhibits IL-7-induced proliferation in memory but not naive human CD4+ T cells

TGF-β is a potent suppressor of T cell activation and expansion. Although the antiproliferative effects of TGF-β are well characterized in TCR-activated cells, the effects of TGF-β on T cell proliferation driven by homeostatic cytokines, such as IL-7, are poorly defined. In the current study, we found that TGF-β inhibits IL-7-induced proliferation in memory, but not in naive human CD4⁺ T cells. TGF-β impaired c-myc induction in all CD4⁺ T cell maturation subsets, although the impairment was less sustained in naive CD4⁺ T cells. TGF-β had no discernible effect on IL-7R signaling (p-STAT-5, p-Akt, or p-S6) in memory T cells but selectively enhanced p-S6 signaling in naive T cells. The inhibitory effects of TGF-β on memory T cell proliferation were partially overcome by chemical inhibition of GSK-3, which also led to enhanced c-myc expression. These data suggest that TGF-β could play an important role in limiting homeostatic proliferation of memory T cells. Our observations also point toward a novel strategy to subvert TGF-β-mediated inhibition of memory T cells by targeting GSK-3 for inhibition.