Lactate/GPR81 recruits regulatory T cells by modulating CX3CL1 to promote immune resistance in a highly glycolytic gastric cancer

Lactate plays an important role in shaping immune tolerance in tumor microenvironment (TME) and correlates with poor prognosis in various solid tumors. Overcoming the immune resistance in an acidic TME may improve the anti-tumor immunity. Here, this study elucidated that via G-protein-coupled receptor 81 (GPR81), lactate could modulate immune tolerance in TME by recruiting regulatory T cells (Tregs) in vitro and in vivo. A high concentration of lactate was detected in cell supernatant and tissues of gastric cancer (GC), which was modulated by lactic dehydrogenase A (LDHA). GPR81 was the natural receptor of lactate and was overexpressed in different GC cell lines and samples, which correlated with poor outcomes in GC patients. Lactate/GPR81 signaling could promote the infiltration of Tregs into TME by inducing the expression of chemokine CX3CL1. GPR81 deficiency could decrease the infiltration of Tregs into TME, thereby inhibiting GC progression by weakening the inhibition of CD8+T cell function in a humanized mouse model. In conclusion, targeting the lactate/GPR81 signaling may potentially serve as a critical process to overcome immune resistance in highly glycolytic GC.

Unveiling the structural mechanisms of nonpeptide ligand recognition and activation in human chemokine receptor CCR8

The human CC chemokine receptor 8 (CCR8) is an emerging therapeutic target for cancer immunotherapy and autoimmune diseases. Understanding the molecular recognition of CCR8, particularly with nonpeptide ligands, is valuable for drug development. Here, we report three cryo-electron microscopy structures of human CCR8 complexed with Gi trimers in the ligand-free state or activated by nonpeptide agonists LMD-009 and ZK 756326. A conserved Y1.39Y3.32E7.39 motif in the orthosteric binding pocket is shown to play a crucial role in the chemokine and nonpeptide ligand recognition. Structural and functional analyses indicate that the lack of conservation in Y1143.33 and Y1724.64 among the CC chemokine receptors could potentially contribute to the selectivity of the nonpeptide ligand binding to CCR8. These findings present the characterization of the molecular interaction between a nonpeptide agonist and a chemokine receptor, aiding the development of therapeutics targeting related diseases through a structure-based approach.

"To be or not to Be": Regulatory T cells in melanoma

In spite of progresses in the therapy of different malignancies, melanoma still remains as one of lethal types of skin tumor. Melanoma is almost easily treatable by surgery alone with higher overall survival rates when it is diagnosed at early stages. However, survival rates are decreased remarkably upon survival if the tumor is progressed to advanced metastatic stages. Immunotherapeutics have been prosperous in the development of anti-tumor responses in patients with melanoma through promotion of the tumor-specific effector T cells in vivo; nonetheless, suitable clinical outcomes have not been satisfactory. One of the underlying causes of the unfavorable clinical outcomes might stem from adverse effects of regulatory T (Treg) cell, which is a prominent mechanism of tumor cells to escape from tumor-specific immune responses. Evidence shows that a poor prognosis and low survival rate in patients with melanoma can be attributed to a higher Treg cell number and function in these subjects. As a result, to promote melanoma-specific anti-tumor responses, depletion of Treg cells appears to be a promising approach; even though the clinical efficacy of different approaches to attain appropriate Treg cell depletion has been inconsistent. Here in this review, the main purpose is to assess the role of Treg cells in the initiation and perpetuation of melanoma and to discuss effective strategies for Treg cell modulation with the aim of melanoma therapy.

Comprehensive Explorations of CCL28 in Lung Adenocarcinoma Immunotherapy and Experimental Validation

Background

Chemokines have been reported to play an important role in cancer immunotherapy. This study aimed to explore the chemokines involved in lung cancer immunotherapy.

Methods

All the public data were downloaded from The Cancer Genome Atlas Program database. Quantitative real time-PCR was used to detect the mRNA level of specific molecules and Western blot was used for the protein level. Other experiments used include luciferase reporter experiments, flow cytometric analysis, Chromatin immunoprecipitation assay, ELISA and co-cultured system.

Results

We found that the CCL7, CCL11, CCL14, CCL24, CCL25, CCL26, CCL28 had a higher level, while the CCL17, CCL23 had a lower level in immunotherapy non-responders. Also, we found that immunotherapy non-responders had a higher level of CD56dim NK cells, NK cells, Th1 cells, Th2 cells and Treg, yet a lower level of iDC and Th17 cells. Biological enrichment analysis indicated that in the patients with high Treg infiltration, the pathways of pancreas beta cells, KRAS signaling, coagulation, WNT BETA catenin signaling, bile acid metabolism, interferon alpha response, hedgehog signaling, PI3K/AKT/mTOR signaling, apical surface, myogenesis were significantly enriched in. CCL7, CCL11, CCL26 and CCL28 were selected for further analysis. Compared with the patients with high CCL7, CCL11, CCL26 and CCL28 expression, the patients with low CCL7, CCL11, CCL26 and CCL28 expression had a better performance of immunotherapy response and this effect might partly be due to Treg cells. Furthermore, biological exploration and clinical correlation of CCL7, CCL11, CCL26 and CCL28 were conducted, Finally, CCL28 was selected for validation. Experiments showed that under the hypoxia condition, HIF-1α was upregulated, which can directly bind to the promoter region of CCL28 and lead to its higher level. Also, CCL28 secreted by lung cancer cells could induce Tregs infiltration.

Conclusion

Our study provides a novel insight focused on the chemokines in lung cancer immunotherapy. Also, CCL28 was identified as an underlying biomarker for lung cancer immunotherapy.

Cytokines/chemokines and soluble immune checkpoint molecules in anti-GABAB receptor encephalitis

BACKGROUND

Anti-gamma-aminobutyric-acid B receptor (anti-GABA_BR) encephalitis is a rare form of autoimmune limbic encephalitis (ALE) that is closely associated with tumor comorbidity. The purpose of this study is to identify the expressive pattern of cytokines/ chemokines and soluble immune checkpoint molecules (sICMs) in anti-GABA_BR encephalitis in order to evaluate the clinical condition and provide new treatment options.

METHODS

A total of 40 cytokines/chemokines and 10 sICMs in the serum of 10 patients with anti-GABA_BR encephalitis and eight controls were measured. The differentially expressed cytokines/chemokines and sICMs were selected to explore the correlations with disease prognosis, CSF routine and antibody titers.

RESULTS

Eight cytokines/chemokines were found to be more abundant in patients than in healthy donors (HDs), while 14 were found to be less abundant in patients. In terms of sICMs, patients' serum contained higher level of soluble ICOS and ICOSL but lower level of soluble CD86. Unfavorable prognosis was associated with high serum level of PDGFB, IL-17A, and soluble ICOSL but not with low levels of IL-4. Increased levels of IL-17A, CCL15, and soluble ICOS were found frequently in the patients with CSF-exclusive OCBs, while soluble ICOSL and CCL24 expression was lower in these patients. High levels of IL-1 F2 and TCA-3 were correlated with the presence of tumors in patients.

CONCLUSION

The majority of patients with anti- GABA_BR encephalitis had an unfavorable prognosis in one year of follow-up. Serum PDGFB, IL-17A, IL-4 and soluble ICOSL level were associated with the poor clinical outcomes in one-year follow up.

Vaccination with a shared oncogenic tumor-self antigen elicits a population of CD8+ T cells with a regulatory phenotype

Cancer immunotherapy is a powerful tool for inducing antigen-specific antitumor cytotoxic T lymphocytes (CTLs). Next-generation strategies may include vaccination against overexpressed oncogenic tumor-self antigens. Previously, we reported vaccination against the oncogenic tumor-self antigen D52 (D52) was effective in preventing tumor growth. We recently reported that D52-vaccinated IL-10-deficient mice generated a significant memory response against tumor recurrence compared to wild-type mice and that vaccine-induced CD8+ IL-10+ T cells may possess regulatory function. Herein, we extended these studies by testing the hypothesis that D52-vaccine-elicited CD8+ IL-10+ T cells represent a distinct T cell population with a regulatory phenotype. C57Black/6J mice deficient in IL-10 or IFN-γ were vaccinated with the murine orthologue of D52; vaccination of wild-type (wt) mice served as a control for comparison. T cells were isolated from all three groups of vaccinated mice, and RNA was extracted from purified CD8+ T cells for deep sequencing and expression analysis. Chemokine receptor 8 (CCR8) and inducible co-stimulator (ICOS) were overexpressed in CD8+ T cells that produced IL-10 but not IFN-γ. These surface markers are associated with IL-10 producing CD4+ T regulatory cells thus supporting the possibility that CD8+ IL-10+ T cells elicited by D52 vaccination represent a unique regulatory T cell subset. The current phenotypic analyses of D52 vaccine elicited CD8+ T cells strengthen our premise that CD8+ IL-10+ T cells elicited by D52 tumor-self protein vaccination likely contribute to the suppression of memory CTL responses and inhibition of durable tumor immunity.

Suppressive Effects of 4-(Phenylsulfanyl) Butan-2-One on CCL-1 Production via Histone Acetylation in Monocytes

The 4-(phenylsulfanyl) butan-2-one (4-PSB-2), a marine-derived compound from soft coral, was proven to have multiple biological activities including neuroprotection and potent anti-inflammatory effects. CC chemokine ligand (CCL)-1 belongs to T helper (Th)2-related chemokines that are involved in the recruitment of Th2 inflammatory cells. Histone acetylation has been recognized as a critical mechanism underlying the regulated cytokine and chemokine production. Our study tried to investigate the anti-inflammatory effect of 4-PSB-2 on CCL-1 production in human monocytes and explore possible underlying intracellular processes, including epigenetic regulation. To confirm our hypothesis, human monocyte THP-1 cell line and primary CD14⁺ cells were pretreated with various concentrations of 4-PSB-2 and then were stimulated with lipopolysaccharide (LPS). The CCL-1 concentration was measured by enzyme-linked immunosorbent assays, and the intracellular signaling pathways and epigenetic regulation of 4-PSB-2 were investigated by using Western blotting and chromatin immunoprecipitation analysis. In this study, we found that 4-PSB-2 had a suppressive effect on LPS-induced CCL-1 production. Moreover, this suppressive effect of 4-PSB-2 was mediated via intracellular signaling such as the mitogen-activated protein kinase and nuclear factor-κB pathways. In addition, 4-PSB-2 could suppress CCL-1 production by epigenetic regulation through downregulating histone H3 and H4 acetylation. In short, our study demonstrated that 4-PSB-2 may have a potential role in the treatment of allergic inflammation.

Exhaust the exhausters: Targeting regulatory T cells in the tumor microenvironment

The concept of cancer immunotherapy has gained immense momentum over the recent years. The advancements in checkpoint blockade have led to a notable progress in treating a plethora of cancer types. However, these approaches also appear to have stalled due to factors such as individuals' genetic make-up, resistant tumor sub-types and immune related adverse events (irAE). While the major focus of immunotherapies has largely been alleviating the cell-intrinsic defects of CD8⁺ T cells in the tumor microenvironment (TME), amending the relationship between tumor specific CD4⁺ T cells and CD8⁺ T cells has started driving attention as well. A major roadblock to improve the cross-talk between CD4⁺ T cells and CD8⁺ T cells is the immune suppressive action of tumor infiltrating T regulatory (Treg) cells. Despite their indispensable in protecting tissues against autoimmune threats, Tregs have also been under scrutiny for helping tumors thrive. This review addresses how Tregs establish themselves at the TME and suppress anti-tumor immunity. Particularly, we delve into factors that promote Treg migration into tumor tissue and discuss the unique cellular and humoral composition of TME that aids survival, differentiation and function of intratumoral Tregs. Furthermore, we summarize the potential suppression mechanisms used by intratumoral Tregs and discuss ways to target those to ultimately guide new immunotherapies.

CCL22-based peptide vaccines induce anti-cancer immunity by modulating tumor microenvironment

CCL22 is a macrophage-derived immunosuppressive chemokine that recruits regulatory T cells through the CCL22:CCR4 axis. CCL22 was shown to play a key role in suppressing anti-cancer immune responses in different cancer types. Recently, we showed that CCL22-specific T cells generated from cancer patients could kill CCL22-expressing tumor cells and directly influence the levels of CCL22 in vitro. The present study aimed to provide a rationale for developing a CCL22-targeting immunotherapy. Vaccination with CCL22-derived peptides induced CCL22-specific T-cell responses in both BALB/c and C57BL/6 mice, assessed by interferon-γ secretion ex vivo. Anti-tumor efficacy of the peptides was evaluated in mouse models engrafted with syngeneic tumor models showing a reduced tumor growth and prolonged survival of the treated mice. Vaccination induced changes in the cellular composition of immune cells that infiltrated the tumor microenvironment assessed with multicolor flow cytometry. In particular, the infiltration of CD8⁺ cells and M1 macrophages increased, which increased the CD8/Treg and the M1/M2 macrophage ratio. This study provided preclinical evidence that targeting CCL22 with CCL22 peptide vaccines modulated the immune milieu in the tumor microenvironment. This modulation led to an augmentation of anti-tumor responses. This study provided a rationale for developing a novel immunotherapeutic modality in cancer.

Colorectal Cancer-Infiltrating Regulatory T Cells: Functional Heterogeneity, Metabolic Adaptation, and Therapeutic Targeting

Colorectal cancer (CRC) is a heterogeneous disease with one of the highest rates of incidence and mortality among cancers worldwide. Understanding the CRC tumor microenvironment (TME) is essential to improve diagnosis and treatment. Within the CRC TME, tumor-infiltrating lymphocytes (TILs) consist of a heterogeneous mixture of adaptive immune cells composed of mainly anti-tumor effector T cells (CD4+ and CD8+ subpopulations), and suppressive regulatory CD4+ T (Treg) cells. The balance between these two populations is critical in anti-tumor immunity. In general, while tumor antigen-specific T cell responses are observed, tumor clearance frequently does not occur. Treg cells are considered to play an important role in tumor immune escape by hampering effective anti-tumor immune responses. Therefore, CRC-tumors with increased numbers of Treg cells have been associated with promoting tumor development, immunotherapy failure, and a poorer prognosis. Enrichment of Treg cells in CRC can have multiple causes including their differentiation, recruitment, and preferential transcriptional and metabolic adaptation to the TME. Targeting tumor-associated Treg cell may be an effective addition to current immunotherapy approaches. Strategies for depleting Treg cells, such as low-dose cyclophosphamide treatment, or targeting one or more checkpoint receptors such as CTLA-4 with PD-1 with monoclonal antibodies, have been explored. These have resulted in activation of anti-tumor immune responses in CRC-patients. Overall, it seems likely that CRC-associated Treg cells play an important role in determining the success of such therapeutic approaches. Here, we review our understanding of the role of Treg cells in CRC, the possible mechanisms that support their homeostasis in the tumor microenvironment, and current approaches for manipulating Treg cells function in cancer.

Tumor-Associated Regulatory T Cells in Non-Small-Cell Lung Cancer: Current Advances and Future Perspectives

Non-small-cell lung cancer (NSCLC) is one of the most threatening malignant tumors to human health, with the overall 5-year survival rate being less than 30%. Regulatory T cells (Tregs), a functional subset of T cells, maintain immunologic immunological self-tolerance and homeostasis. Accumulating evidence has uncovered their implicated roles in various cancers in recent years. In NSCLC, they are associated with staging, therapeutic efficacy, and prognosis by infiltrating in tissues and thereby attenuating immunologic anticancer effects in patients. Tumor-associated Tregs display distinct immune signatures in NSCLC compared to thymus-derived Tregs, playing an important role in remodeling the tumor microenvironment (TME). Targeting Tregs has become a novel direction for NSCLC patients, such as disrupting their immune-suppressive functions, blocking their trafficking into tumors, and inhibiting their development and/or activation. This review is aimed at elucidating the molecular mechanisms of tumor-associated Tregs in NSCLC and providing therapeutic targets relevant to Tregs.

Research Progress on the Role of Regulatory T Cell in Tumor Microenvironment in the Treatment of Breast Cancer

The tumor microenvironment (TME) is a complex ecosystem comprised of cancer cells, stromal cells, and immune cells. Analysis of the composition of TME is essential to assess the prognosis of patients with breast cancer (BC) and the efficacy of different regimes. Treg plays a crucial role in the microenvironment of breast cancer subtypes, and its function contributes to the development and progression of BC by suppressing anti-tumor immunity directly or indirectly through multiple mechanisms. In addition, conventional treatments, such as anthracycline-based neoadjuvant chemotherapy, and neo-therapies, such as immune-checkpoint blockades, have a significant impact on the absence of Tregs in BC TME, thus gaining additional anti-tumor effect to some extent. Strikingly, Treg in BC TME revealed the predicted efficacy of some therapeutic strategies. All these results suggest that we can manipulate the abundance of Treg to achieve the ultimate effect of both conventional and novel treatments. In this review, we discuss new insights into the characteristics of Treg in BC TME, the impact of different regiments on Treg, and the possibilities of Treg as a predictive marker of efficacy for certain treatments.

Transcutaneous Vagal Nerve Stimulation Alone or in Combination With Radiotherapy Stimulates Lung Tumor Infiltrating Lymphocytes But Fails to Suppress Tumor Growth

The combination of radiotherapy (RT) with immunotherapy represents a promising treatment modality for non-small cell lung cancer (NSCLC) patients. As only a minority of patients shows a persistent response today, a spacious optimization window remains to be explored. Previously we showed that fractionated RT can induce a local immunosuppressive profile. Based on the evolving concept of an immunomodulatory role for vagal nerve stimulation (VNS), we tested its therapeutic and immunological effects alone and in combination with fractionated RT in a preclinical-translational study. Lewis lung carcinoma-bearing C57Bl/6 mice were treated with VNS, fractionated RT or the combination while a patient cohort with locally advanced NSCLC receiving concurrent radiochemotherapy (ccRTCT) was enrolled in a clinical trial to receive either sham or effective VNS daily during their 6 weeks of ccRTCT treatment. Preclinically, VNS alone or with RT showed no therapeutic effect yet VNS alone significantly enhanced the activation profile of intratumoral CD8+ T cells by upregulating their IFN-γ and CD137 expression. In the periphery, VNS reduced the RT-mediated rise of splenic, but not blood-derived, regulatory T cells (Treg) and monocytes. In accordance, the serological levels of protumoral CXCL5 next to two Treg-attracting chemokines CCL1 and CCL22 were reduced upon VNS monotherapy. In line with our preclinical findings on the lack of immunological changes in blood circulating immune cells upon VNS, immune monitoring of the peripheral blood of VNS treated NSCLC patients (n=7) did not show any significant changes compared to ccRTCT alone. As our preclinical data do suggest that VNS intensifies the stimulatory profile of the tumor infiltrated CD8+ T cells, this favors further research into non-invasive VNS to optimize current response rates to RT-immunotherapy in lung cancer patients.

Splenectomy increases blood pressure and abolishes sex differences in renal T-regulatory cells in spontaneously hypertensive rats

Over the past decade there has been increasing support for a role of the immune system in the development of hypertension. Our lab has previously reported that female spontaneously hypertensive rats (SHRs) have a blood pressure (BP)-dependent increase in anti-inflammatory renal regulatory T cells (Tregs), corresponding to lower BP compared with males. However, little is known regarding the mechanism for greater renal Tregs in females. The current study was designed to test the hypothesis that the greater relative abundance of renal Tregs in female SHR is due to greater Treg production. To test this hypothesis, T cell profiles were measured in the spleen by flow cytometry in male and female SHR at 5 and 14 weeks of age. Splenic Tregs did not differ between males and females, suggesting sex differences in renal Tregs is not due to differences in production. To assess the role of the spleen in sex differences in renal Tregs and BP control, rats were randomized to receive sham surgery (CON) or splenectomy (SPLNX) at 12 weeks of age and implanted with telemeters to measure BP. After 2 weeks, kidneys were harvested for flow cytometric analysis of T cells. Splenectomy increased BP in both sexes after 2 weeks. Renal Tregs decreased in both sexes after splenectomy, abolishing the sex differences in renal Tregs. In conclusion, splenic Tregs were comparable in male and female SHRs, suggesting that sex differences in renal Tregs is due to differences in renal Treg recruitment, not Treg production.

Anticancer opportunities at every stage of chemokine function

The chemokine system, comprising 48 chemokines and 23 receptors, is critically involved in several hallmarks of cancer. Yet, despite extensive efforts from the pharmaceutical sector, only two drugs aimed at this system are currently approved for clinical use against cancer. To date, numerous pharmacological approaches have been developed to successfully intervene at different stages of chemokine function: (i) chemokine availability; (ii) chemokine-glycosaminoglycan binding; and (iii) chemokine receptor binding. Many of these strategies have been tested in preclinical cancer models, and some have advanced to clinical trials as potential anticancer therapies. Here we will review the strategies and growing pharmacological toolbox for manipulating the chemokine system in cancer, and address novel methods poised for future (pre)clinical testing.

Stem cells part of the innate and adaptive immune systems as a therapeutic for Covid-19

Some stem cell types not only release molecules that reduce viral replication, but also reduce the hypercytokinemia and inflammation induced by the immune system, and have been found to be part of the innate and adaptive immune systems. An important component of the stem cell's ability to ameliorate viral diseases, especially the complications post-clearance of the pathogen, is the ability of adult stem cells to reset the innate and adaptive immune systems from an inflammatory state to a repair state. Thus, the molecules released from certain stem cell types found to be safe and efficacious, may be an important new means for therapeutic development in Covid-19, especially for late-stage inflammation and tissue damage once the virus has cleared, particularly in the aged population.

Chemokine Receptor Antagonists: Role in Oncology

PURPOSE OF REVIEW

To evaluate the clinical potential of chemokine receptor antagonists for the treatment of patients with cancer.

RECENT FINDINGS

Chemokine receptors and their ligands can have a significant impact on the infiltration of cells into the tumor microenvironment. The receptors are increasingly being investigated as targets for the treatment of cancers. Recent studies are demonstrating the promise of chemokine receptor antagonists in this setting. There are many chemokine receptors, and each can have different functions depending on the cellular context. Targeting chemokine receptors is a promising strategy in both pre-clinical research and clinical trials. Inhibiting chemokine receptors that either recruit suppressive cells or improve cancer mobility and viability while sparing those necessary for proper immune trafficking may prove to dramatically improve treatment responses. Further research in this area is warranted and has the potential to dramatically improve patient outcomes.

Reconciling two opposing effects of radiation therapy: stimulation of cancer cell invasion and activation of anti-cancer immunity

PURPOSE

The damage caused by radiation therapy to cancerous and normal cells inevitably leads to changes in the secretome profile of pro and anti-inflammatory mediators. The inflammatory response depends on the dose of radiation and its fractionation, while the inherent radiosensitivity of each patient dictates the intensity and types of adverse reactions. This review will present an overview of two apparently opposite reactions that may occur after radiation treatment: induction of an antitumor immune response and a protumoral response. Emphasis is placed on the molecular and cellular mechanisms involved.

CONCLUSIONS

By understanding how radiation changes the balance between anti- and protumoral effects, these forces can be manipulated to optimize radiation oncology treatments.

Biological characterization of ligands targeting the human CC chemokine receptor 8 (CCR8) reveals the biased signaling properties of small molecule agonists

The human CC chemokine receptor 8 (CCR8) is a promising drug target for cancer immunotherapy and autoimmune disease. Besides human and viral chemokines, previous studies revealed diverse classes of CCR8-targeting small molecules. We characterized a selection of these CCR8 ligands (hCCL1, vCCL1, ZK756326, AZ6; CCR8 agonists and a naphthalene-sulfonamide-based CCR8 antagonist), in in vitro cell-based assays (hCCL1^AF647 binding, calcium mobilization, cellular impedance, cell migration, β-arrestin 1/2 recruitment), and used pharmacological tools to determine G protein-dependent and -independent signaling pathways elicited by these ligands. Our data reveal differences in CCR8-mediated signaling induced by chemokines versus small molecules, which was most pronounced in cell migration studies. Human CCL1 most efficiently induced cell migration whereby Gβγ signaling was indispensable. In contrast, Gβγ signaling did not contribute to cell migration induced by other CCR8 ligands (vCCL1, ZK756326, AZ6). Although all tested CCR8 agonists were full agonists for calcium mobilization, a significant contribution for Gβγ signaling herein was only apparent for human and viral CCL1. Despite both Gα_i- and Gα_q-signaling regulate intracellular Ca²⁺-release, cellular impedance experiments showed that CCR8 agonists predominantly induce Gα_i-dependent signaling. Finally, small molecule agonists displayed higher efficacy in β-arrestin 1 recruitment, which occurred independently of Gα_i signaling. Also in this latter assay, only hCCL1-induced activity was dependent on Gβγ-signaling. Our study provides insight into CCR8 signaling and function and demonstrates differential CCR8 activation by different classes of ligands. This reflects the ability of CCR8 small molecules to evoke different subsets of the receptor's signaling repertoire, which categorizes them as biased agonists.

Recruitment and Expansion of Tregs Cells in the Tumor Environment-How to Target Them?

Simple Summary

The immune response against cancer is generated by effector T cells, among them cytotoxic CD8⁺ T cells that destroy cancer cells and helper CD4⁺ T cells that mediate and support the immune response. This antitumor function of T cells is tightly regulated by a particular subset of CD4⁺ T cells, named regulatory T cells (Tregs), through different mechanisms. Even if the complete inhibition of Tregs would be extremely harmful due to their tolerogenic role in impeding autoimmune diseases in the periphery, the targeted blockade of their accumulation at tumor sites or their targeted depletion represent a major therapeutic challenge. This review focuses on the mechanisms favoring Treg recruitment, expansion and stabilization in the tumor microenvironment and the therapeutic strategies developed to block these mechanisms.

Abstract

Regulatory T cells (Tregs) are present in a large majority of solid tumors and are mainly associated with a poor prognosis, as their major function is to inhibit the antitumor immune response contributing to immunosuppression. In this review, we will investigate the mechanisms involved in the recruitment, amplification and stability of Tregs in the tumor microenvironment (TME). We will also review the strategies currently developed to inhibit Tregs’ deleterious impact in the TME by either inhibiting their recruitment, blocking their expansion, favoring their plastic transformation into other CD4⁺ T-cell subsets, blocking their suppressive function or depleting them specifically in the TME to avoid severe deleterious effects associated with Treg neutralization/depletion in the periphery and normal tissues.

Development of Anti-Mouse CC Chemokine Receptor 8 Monoclonal Antibodies for Flow Cytometry

CC chemokine receptor 8 (CCR8) belongs to the class A of G protein-coupled receptor. It is highly expressed on Treg and T helper 2 (T_H2) cells recruited to the inflammation site and is implicated in allergy and asthma. Recently, CCR8+Treg cells have been suggested to be a master regulator in the immunosuppressive tumor microenvironment; therefore, developing sensitive monoclonal antibodies (mAbs) for CCR8 has been desired. This study established a specific and sensitive mAb for mouse CCR8 (mCCR8), which is useful for flow cytometry by using the Cell-Based Immunization and Screening (CBIS) method. The established anti-mCCR8 mAb, C₈Mab-2 (rat IgG_2b, kappa), reacted with mCCR8-overexpressed Chinese hamster ovary-K1 (CHO/mCCR8) cells and P388 (mouse lymphoid neoplasma) or J774-1 (mouse macrophage-like) cells, which express endogenous mCCR8 by flow cytometry. C₈Mab-2, which was established by the CBIS method, could be useful for elucidating the mCCR8-related biological response by flow cytometry.

CTLA-4 in Regulatory T Cells for Cancer Immunotherapy

Immune checkpoint inhibitors (ICIs) have obtained durable responses in many cancers, making it possible to foresee their potential in improving the health of cancer patients. However, immunotherapies are currently limited to a minority of patients and there is a need to develop a better understanding of the basic molecular mechanisms and functions of pivotal immune regulatory molecules. Immune checkpoint cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and regulatory T (Treg) cells play pivotal roles in hindering the anticancer immunity. Treg cells suppress antigen-presenting cells (APCs) by depleting immune stimulating cytokines, producing immunosuppressive cytokines and constitutively expressing CTLA-4. CTLA-4 molecules bind to CD80 and CD86 with a higher affinity than CD28 and act as competitive inhibitors of CD28 in APCs. The purpose of this review is to summarize state-of-the-art understanding of the molecular mechanisms underlining CTLA-4 immune regulation and the correlation of the ICI response with CTLA-4 expression in Treg cells from preclinical and clinical studies for possibly improving CTLA-4-based immunotherapies, while highlighting the knowledge gap.

N-cadherin inhibitor creates a microenvironment that protect TILs from immune checkpoints and Treg cells

BACKGROUND

Few patients with prostate cancer benefit from current immunotherapies. Therefore, we aimed to explore new strategies to change this paradigm.

METHODS

Human tissues, cell lines and in vivo experiments were used to determine whether and how N-cadherin impacts the production of programmed death ligand-1 (PD-L1) and indole amine 2,3-dioxygenase (IDO-1) and whether N-cadherin can increase the production of effector (e)Treg cells. Then, we used PC3-bearing humanized non-obese diabetic/severe combined immunodeficiency IL2Rγnull (hNSG) mice with an intravenous injection of human CD34+ hematopoietic stem cells into the tail vein to evaluate whether the N-cadherin antagonist N-Ac-CHAVC-NH2 (designated ADH-1) could improve the therapeutic effect of tumor-infiltrating lymphocyte (TIL)-related treatment.

RESULTS

N-cadherin dramatically upregulated the expression of PD-L1 and IDO-1 through IFN-γ (interferongamma) signaling and increasing the production of free fatty acids that could promote the generation of eTreg cells. In preclinical experiments, immune reconstitution mediated by TILs slowed tumor growth and extended the survival time; however, this effect disappeared after immune system suppression by PD-L1, IDO-1 and eTreg cells. Furthermore, ADH-1 effectively reduced immunosuppression and enhanced TIL-related therapy.

CONCLUSIONS

These data show that the N-cadherin antagonist ADH-1 promotes TIL antitumor responses. This important hurdle must be overcome for tumors to respond to immunotherapy.

In vivo NIR-II structured-illumination light-sheet microscopy

Noninvasive optical imaging with deep tissue penetration depth and high spatiotemporal resolution is important to longitudinally studying the biology at the single-cell level in live mammals, but has been challenging due to light scattering. Here, we developed near-infrared II (NIR-II) (1,000 to 1,700 nm) structured-illumination light-sheet microscopy (NIR-II SIM) with ultralong excitation and emission wavelengths up to ∼1,540 and ∼1,700 nm, respectively, suppressing light scattering to afford large volumetric three-dimensional (3D) imaging of tissues with deep-axial penetration depths. Integrating structured illumination into NIR-II light-sheet microscopy further diminished background and improved spatial resolution by approximately twofold. In vivo oblique NIR-II SIM was performed noninvasively for 3D volumetric multiplexed molecular imaging of the CT26 tumor microenvironment in mice, longitudinally mapping out CD4, CD8, and OX40 at the single-cell level in response to immunotherapy by cytosine-phosphate-guanine (CpG), a Toll-like receptor 9 (TLR-9) agonist combined with OX40 antibody treatment. NIR-II SIM affords an additional tool for noninvasive volumetric molecular imaging of immune cells in live mammals.

Chemokine (C-C Motif) Ligand 1 Derived from Tumor-Associated Macrophages Contributes to Esophageal Squamous Cell Carcinoma Progression via CCR8-Mediated Akt/Proline-Rich Akt Substrate of 40 kDa/Mammalian Target of Rapamycin Pathway

Tumor-associated macrophages (TAMs) promote tumor progression. The number of infiltrating TAMs is associated with poor prognosis in esophageal squamous cell carcinoma (ESCC) patients; however, the mechanism underlying this phenomenon is unclear. cDNA microarray analysis indicates that the expression of chemokine (C-C motif) ligand 1 (CCL1) is up-regulated in peripheral blood monocyte-derived macrophages stimulated using conditioned media from ESCC cells (TAM-like macrophages). Here, we evaluated the role of CCL1 in ESCC progression. CCL1 was overexpressed in TAM-like macrophages, and CCR8, a CCL1 receptor, was expressed on ESCC cell surface. TAM-like macrophages significantly enhanced the motility of ESCC cells, and neutralizing antibodies against CCL1 or CCR8 suppressed this increased motility. Recombinant human CCL1 promoted ESCC cell motility via the Akt/proline-rich Akt substrate of 40 kDa/mammalian target of rapamycin pathway. Phosphatidylinositol 3-kinase or Akt inhibitors, CCR8 silencing, and neutralizing antibody against CCR8 could significantly suppress these effects. The overexpression of CCL1 in stromal cells or CCR8 in ESCC cells was significantly associated with poor overall survival (P = 0.002 or P = 0.009, respectively) and disease-free survival (P = 0.009 or P = 0.047, respectively) in patients with ESCC. These results indicate that the interaction between stromal CCL1 and CCR8 on cancer cells promotes ESCC progression via the Akt/proline-rich Akt substrate of 40 kDa/mammalian target of rapamycin pathway, thereby providing novel therapeutic targets.

Tumor-Infiltrating Regulatory T-cell Accumulation in the Tumor Microenvironment Is Mediated by IL33/ST2 Signaling

Regulatory T cells (Treg) are enriched in the tumor microenvironment (TME) and suppress antitumor immunity; however, the molecular mechanism underlying the accumulation of Tregs in the TME is poorly understood. In various tumor models, tumor-infiltrating Tregs were highly enriched in the TME and had significantly higher expression of immune checkpoint molecules. To characterize tumor-infiltrating Tregs, we performed bulk RNA sequencing (RNA-seq) and found that proliferation-related genes, immune suppression-related genes, and cytokine/chemokine receptor genes were upregulated in tumor-infiltrating Tregs compared with tumor-infiltrating CD4+Foxp3- conventional T cells or splenic Tregs from the same tumor-bearing mice. Single-cell RNA-seq and T-cell receptor sequencing also revealed active proliferation of tumor infiltrating Tregs by clonal expansion. One of these genes, ST2, an IL33 receptor, was identified as a potential factor driving Treg accumulation in the TME. Indeed, IL33-directed ST2 signaling induced the preferential proliferation of tumor-infiltrating Tregs and enhanced tumor progression, whereas genetic deletion of ST2 in Tregs limited their TME accumulation and delayed tumor growth. These data demonstrated the IL33/ST2 axis in Tregs as one of the critical pathways for the preferential accumulation of Tregs in the TME and suggests that the IL33/ST2 axis may be a potential therapeutic target for cancer immunotherapy.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of Receptors CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 Ligands

CC chemokines (or β-chemokines) are 28 chemotactic cytokines with an N-terminal CC domain that play an important role in immune system cells, such as CD4⁺ and CD8⁺ lymphocytes, dendritic cells, eosinophils, macrophages, monocytes, and NK cells, as well in neoplasia. In this review, we discuss human CC motif chemokine ligands: CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 (CC motif chemokine receptor CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 ligands). We present their functioning in human physiology and in neoplasia, including their role in the proliferation, apoptosis resistance, drug resistance, migration, and invasion of cancer cells. We discuss the significance of chemokine receptors in organ-specific metastasis, as well as the influence of each chemokine on the recruitment of various cells to the tumor niche, such as cancer-associated fibroblasts (CAF), Kupffer cells, myeloid-derived suppressor cells (MDSC), osteoclasts, tumor-associated macrophages (TAM), tumor-infiltrating lymphocytes (TIL), and regulatory T cells (T_reg). Finally, we show how the effect of the chemokines on vascular endothelial cells and lymphatic endothelial cells leads to angiogenesis and lymphangiogenesis.

Hypoxia Alters the Expression of CC Chemokines and CC Chemokine Receptors in a Tumor-A Literature Review

Hypoxia, i.e., oxygen deficiency condition, is one of the most important factors promoting the growth of tumors. Since its effect on the chemokine system is crucial in understanding the changes in the recruitment of cells to a tumor niche, in this review we have gathered all the available data about the impact of hypoxia on β chemokines. In the introduction, we present the chronic (continuous, non-interrupted) and cycling (intermittent, transient) hypoxia together with the mechanisms of activation of hypoxia inducible factors (HIF-1 and HIF-2) and NF-κB. Then we describe the effect of hypoxia on the expression of chemokines with the CC motif: CCL1, CCL2, CCL3, CCL4, CCL5, CCL7, CCL8, CCL11, CCL13, CCL15, CCL16, CCL17, CCL18, CCL19, CCL20, CCL21, CCL22, CCL24, CCL25, CCL26, CCL27, CCL28 together with CC chemokine receptors: CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10. To better understand the effect of hypoxia on neoplastic processes and changes in the expression of the described proteins, we summarize the available data in a table which shows the effect of individual chemokines on angiogenesis, lymphangiogenesis, and recruitment of eosinophils, myeloid-derived suppressor cells (MDSC), regulatory T cells (T_reg), and tumor-associated macrophages (TAM) to a tumor niche.

An Oncogenic Alteration Creates a Microenvironment that Promotes Tumor Progression by Conferring a Metabolic Advantage to Regulatory T Cells

Only a small percentage of patients afflicted with gastric cancer (GC) respond to immune checkpoint blockade (ICB). To study the mechanisms underlying this resistance, we examined the immune landscape of GC. A subset of these tumors was characterized by high frequencies of regulatory T (Treg) cells and low numbers of effector T cells. Genomic analyses revealed that these tumors bore mutations in RHOA that are known to drive tumor progression. RHOA mutations in cancer cells activated the PI3K-AKT-mTOR signaling pathway, increasing production of free fatty acids that are more effectively consumed by Treg cells than effector T cells. RHOA mutant tumors were resistant to PD-1 blockade but responded to combination of PD-1 blockade with inhibitors of the PI3K pathway or therapies targeting Treg cells. We propose that the metabolic advantage conferred by RHOA mutations enables Treg cell accumulation within GC tumors, generating an immunosuppressive TME that underlies resistance to ICB.

Wide Cytokine Analysis in Cerebrospinal Fluid at Diagnosis Identified CCL-3 as a Possible Prognostic Factor for Multiple Sclerosis

Background: Apart from IgG oligoclonal bands, no other biomarker has, to date, been validated for diagnostic and/or prognostic purposes in multiple sclerosis (MS). Aim: To investigate a wide panel of cytokines and chemokines in the cerebrospinal fluid (CSF) of relapsing-remitting MS (RRMS) patients and evaluate their association with clinical and magnetic resonance imaging (MRI) parameters, as well as their predictive clinical value. Methods: Fifty-one RRMS at clinical onset and 17 other not inflammatory neurological disorders (ONINDs) underwent brain MRI (including 3D-T1, 3D-FLAIR, and 3-DIR sequences) and CSF examination. Eighty-seven cytokines and chemokines were analyzed in CSF by Multiplex technology. Results: Compared to ONIND, CXCL-10, CXCL-11, CXCL-13, CCL-1, CCL-2, CCL-3, CCL-22, IL-16, and BAFF were significantly (p < 0.05) increased in RRMS CSF. However, only CCL-3 was associated with both MS diagnosis and IgGOB detection. Based on a 95%CI in ONIND (cut-off value: 0.798 pg/ml) and ROC analysis (cut-off value: 0.495 pg/ml), RRMS patients were stratified in CCL-3^high (>0.736 pg/mL), CCL-3^medium, and CCL-3^low (<0.495 pg/ml). Survival analysis disclosed a strong association between high CCL-3 values and disease reactivation (OR = 4.9, 95%CI: 1.8-13.3, p < 0.005) in the following 2 years. Conclusions: CCL-3 deserves further investigation as a candidate prognostic biomarker for RRMS.

Host Wnt5a Potentiates Microenvironmental Regulation of Ovarian Cancer Metastasis

The noncanonical Wnt ligand Wnt5a is found in high concentrations in ascites of women with ovarian cancer. In this study, we elucidated the role of Wnt5a in ovarian cancer metastasis. Wnt5a promoted ovarian tumor cell adhesion to peritoneal mesothelial cells as well as migration and invasion, leading to colonization of peritoneal explants. Host components of the ovarian tumor microenvironment, notably peritoneal mesothelial cells and visceral adipose, secreted Wnt5a. Conditional knockout of host WNT5A significantly reduced peritoneal metastatic tumor burden. Tumors formed in WNT5A knockout mice had elevated cytotoxic T cells, increased M1 macrophages, and decreased M2 macrophages, indicating that host Wnt5a promotes an immunosuppressive microenvironment. The Src family kinase Fgr was identified as a downstream effector of Wnt5a. These results highlight a previously unreported role for host-expressed Wnt5a in ovarian cancer metastasis and suggest Fgr as a novel target for inhibition of ovarian cancer metastatic progression.Significance: This study establishes host-derived Wnt5a, expressed by peritoneal mesothelial cells and adipocytes, as a primary regulator of ovarian cancer intraperitoneal metastatic dissemination and identifies Fgr kinase as novel target for inhibition of metastasis.

Guidance factors orchestrating regulatory T cell positioning in tissues during development, homeostasis, and response

Over their lifetime, regulatory T cells (Treg) recalibrate their expression of trafficking receptors multiple times as they progress through development, respond to immune challenges, or adapt to the requirements of functioning in various non-lymphoid tissue environments. These trafficking receptors, which include chemokine receptors and other G-protein coupled receptors, integrins, as well as selectins and their ligands, enable Treg not only to enter appropriate tissues from the bloodstream via post-capillary venules, but also to navigate these tissues to locally execute their immune-regulatory functions, and finally to seek out the right antigen-presenting cells and interact with these, in part in order to receive the signals that sustain their survival, proliferation, and functional activity, in part in order to execute their immuno-regulatory function by altering antigen presenting cell function. Here, we will review our current knowledge of when and in what ways Treg alter their trafficking properties. We will focus on the chemokine system and try to identify specialized, non-redundant roles of individual receptors as well as similarities and differences to the conventional T cell compartment.

Enhancing tumor T cell infiltration to enable cancer immunotherapy

Cancer immunotherapy has changed the treatment landscape for cancer patients, especially for those with metastatic spread. While the immunotherapeutic armamentarium is constantly growing, as exemplified by approved compounds, clinical outcome remains variable both within and across entities. A sufficient infiltration into the tumor microenvironment and successful activation of effector T lymphocytes against tumor cells have been identified as predictors for responses to T cell-based immunotherapies. However, tumor cells have developed a variety of mechanisms to reduce T cell homing and access to the tumor tissue to prevent activity of anticancer immunity. As a consequence, investigations have interrogated strategies to improve the efficacy of cancer immunotherapies by enhancing T cell infiltration into tumor tissues. In this review, we summarize mechanisms of how tumor tissue shapes immune suppressive microenvironment to prevent T cell access to the tumor site. We focus on current strategies to improve cancer immunotherapies through enhancing T cell infiltration.

Cancer Immunotherapies Targeting Tumor-Associated Regulatory T Cells

Tumor-associated regulatory T cells (Tregs) are important effectors in the tumor microenvironment (TME), acting as accomplices in the promotion of tumor progression. Currently, the importance of removing the immunosuppressive activity in the TME has received its due attention, and Tregs have been focused on. The cytokine-receptor axes are among the essential signaling pathways in immunocytes, and tumor-associated Tregs are no exception. Therefore, manipulating cytokine-receptor pathways may be a promising effective strategy for treating various malignancies. Here, we summarize the classification, immunosuppressive mechanisms, existing immunotherapies, and potential biomarkers related to tumor-infiltrating Tregs to guide the development of effective cancer immunotherapies.

Mechanisms of immune evasion in bladder cancer

With the introduction of multiple new agents, the role of immunotherapy is rapidly expanding across all malignancies. Bladder cancer is known to be immunogenic and is responsive to immunotherapy including intravesical BCG and immune checkpoint inhibitors. Multiple trials have addressed the role of checkpoint inhibitors in advanced bladder cancer, including atezolizumab, avelumab, durvalumab, nivolumab and pembrolizumab (all targeting the PD1/PD-L1 pathway). While these trials have demonstrated promising results and improvements over existing therapies, less than half of patients with advanced disease demonstrate clinical benefit from checkpoint inhibitor therapy. Recent breakthroughs in cancer biology and immunology have led to an improved understanding of the influence of the tumor microenvironment on the host’s immune system. It appears that tumors promote the formation of highly immunosuppressive microenvironments preventing generation of effective anti-tumor immune response through multiple mechanisms. Therefore, reconditioning of the tumor microenvironment and restoration of the competent immune response is essential for achieving optimal efficacy of cancer immunotherapy. In this review, we aim to discuss the major mechanisms of immune evasion in bladder cancer and highlight novel pathways and molecular targets that may help to attenuate tumor-induced immune tolerance, overcome resistance to immunotherapy and improve clinical outcomes.

Role of Focal Adhesion Kinase in Small-Cell Lung Cancer and Its Potential as a Therapeutic Target

Small-cell lung cancer (SCLC) represents 15% of all lung cancers and it is clinically the most aggressive type, being characterized by a tendency for early metastasis, with two-thirds of the patients diagnosed with an extensive stage (ES) disease and a five-year overall survival (OS) as low as 5%. There are still no effective targeted therapies in SCLC despite improved understanding of the molecular steps leading to SCLC development and progression these last years. After four decades, the only modest improvement in OS of patients suffering from ES-SCLC has recently been shown in a trial combining atezolizumab, an anti-PD-L1 immune checkpoint inhibitor, with carboplatin and etoposide, chemotherapy agents. This highlights the need to pursue research efforts in this field. Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that is overexpressed and activated in several cancers, including SCLC, and contributing to cancer progression and metastasis through its important role in cell proliferation, survival, adhesion, spreading, migration, and invasion. FAK also plays a role in tumor immune evasion, epithelial-mesenchymal transition, DNA damage repair, radioresistance, and regulation of cancer stem cells. FAK is of particular interest in SCLC, being known for its aggressiveness. The inhibition of FAK in SCLC cell lines demonstrated significative decrease in cell proliferation, invasion, and migration, and induced cell cycle arrest and apoptosis. In this review, we will focus on the role of FAK in cancer cells and their microenvironment, and its potential as a therapeutic target in SCLC.

Nlrp1b1 negatively modulates obesity-induced inflammation by promoting IL-18 production

Obesity-induced inflammation, triggered by lipid-mediated activation of the Nlrp3 inflammasome, results in glucose metabolism alterations and type 2 diabetes. This knowledge has been generated using animals deficient for any of the different components of this inflammasome (Caspase-1, Asc or Nlrp3) in the C57BL/6 background. Unlike C57BL/6 mice, which carry allele 2 of the Nlrp1b gene (Nlrp1b2), Balb/c mice that carry allele 1 (Nlrp1b1) are less prone to develop alterations in the glucose metabolism when fed with a high fat diet. However, the molecular bases for these metabolic differences are unknown. Here we show that the Nlrp1b1 allele down regulates the adipose tissue inflammatory response attenuating glucose intolerance and insulin resistance in obese C57BL/mice. Our results indicate that the positive effects of the Nlrp1b1 inflammasome on glucose tolerance and insulin sensitivity involve IL-18-mediated effects on lipolysis, pointing out that differential expression of allelic variants of genes coding for inflammasome components might control susceptibility or resistance to develop diabetes in obese individuals.

Peritumoural CCL1 and CCL22 expressing cells in hepatocellular carcinomas shape the tumour immune infiltrate

Development, course of disease and prognosis of hepatocellular carcinomas (HCC) are strongly influenced by the immune system. Immunosuppressive regulatory T cells (Treg) have been shown to negatively impact disease progression and survival. To further understand the mechanisms of Treg attraction to HCC lesions, this study provides an analysis of Treg attracting chemokines in human HCC tissues. We analysed the expression of the Treg attracting chemokines CCL1 and CCL22 as well as the infiltration of FoxP3+ Treg and CD8+ T cells in paraffin-embedded tissue sections of 62 HCC patients. Expression of both chemokines was detected in 47 of 62 tissue slides. Chemokine expression was generally higher in tumour stroma and peritumoural liver tissue than in the tumour tissue itself. CD8+ T cells and FoxP3+ Treg were found at high levels in many tumour tissues. Intratumoural infiltration of Treg positively correlated with CCL22 levels in peritumoural liver tissue. In contrast, no correlation of Treg numbers and expression of CCL1 was detected. In summary, we describe here that the chemokines CCL1 and CCL22 are expressed in HCC tissues and, to a higher extent, in the stroma and peritumoural liver tissue. CCL22 may contribute to Treg recruitment and immunosuppression, whereas the role of CCL1 remains to be defined. It will be interesting to investigate the potential of these chemokines as drug targets for cancer therapy.

Regulatory T cells in cancer immunosuppression - implications for anticancer therapy

Regulatory T (T_reg) cells, an immunosuppressive subset of CD4⁺ T cells characterized by the expression of the master transcription factor forkhead box protein P3 (FOXP3), are a component of the immune system with essential roles in maintaining self-tolerance. In addition, T_reg cells can suppress anticancer immunity, thereby hindering protective immunosurveillance of neoplasia and hampering effective antitumour immune responses in tumour-bearing hosts, thus promoting tumour development and progression. Identification of the factors that are specifically expressed in T_reg cells and/or that influence T_reg cell homeostasis and function is important to understanding cancer pathogenesis and to identifying therapeutic targets. Immune-checkpoint inhibitors (ICIs) have provided a paradigm shift in the treatment of cancer. Most immune-checkpoint molecules are expressed in T_reg cells, but the effects of ICIs on T_reg cells, and thus the contributions of these cells to treatment responses, remain unclear. Notably, evidence indicates that ICIs targeting programmed cell death 1 (PD-1) might enhance the immunosuppressive function of T_reg cells, whereas cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors might deplete these cells. Thus, although manipulation of T_reg cells is a promising anticancer therapeutic strategy, approaches to controlling these cells require further research. Herein, we discuss novel insights into the roles of T_reg cells in cancer, which can hopefully be used to develop T_reg cell-targeted therapies and facilitate immune precision medicine.

IgG4 drives M2a macrophages to a regulatory M2b-like phenotype: potential implication in immune tolerance

BACKGROUND

Macrophages can be converted in vitro into immunoregulatory M2b macrophages in the presence of immune complexes (ICs), but the role of the specific subclasses IgG1 or IgG4 in this phenotypic and functional change is not known.

OBJECTIVE

We aimed to refine the original method by applying precisely defined ICs of the subclasses IgG4 or IgG1 constructed by two independent methods.

METHODS

Monocyte-derived macrophages (MDMs) were treated with M-CSF, followed by IL-4/IL-13 to induce the M2a allergic phenotype. To mimic unspecific or allergen-specific ICs, plates were coated with myeloma IgG1 or IgG4, or with grass pollen allergen Phl p 5 followed by recombinant human Phl p 5-specific IgG1 or IgG4. M2a polarized macrophages were then added, cultured, and examined for cellular markers and cytokines by flow cytometry, ELISA, and rtPCR. Alternatively, immune complexes with IgG1 or IgG4 were formed using protein L.

RESULTS

IgG4 ICs down regulated CD163 and CD206 on M2a cells, and significantly increased IL-10, IL-6, TNFα, and CCL1 secretion, indicating a shift to an M2b-like phenotype. Treatment with IgG4 ICs resulted in expression of FcγRII and down modulation of FcγRII compared with IgG1 treated cells (P = 0.0335) or untreated cells (P < 0.00001).

CONCLUSION

Immune complexes with subclasses IgG1 and IgG4 can in vitro be generated by plate absorption, and in fluid form by protein L. Cross-linking of FcγRIIb by the IgG4 subclass redirects pro-allergic M2a macrophages to an M2b-like immunosuppressive phenotype. This suggests an interplay of macrophages with IgG4 in immune tolerance, likely relevant in allergen immunotherapy.

CCL1 is a major regulatory T cell attracting factor in human breast cancer

Background

Regulatory T cells (Treg) suppress cytotoxic T cell anti-tumoral immune responses and thereby promote tumor progression. Prevention of intratumoral Treg accumulation by inhibition of their migration to the tumor microenvironment is a promising therapeutic strategy. The aim of this study was to identify the role of the two major Treg-attracting chemokines CCL1 and CCL22 in human breast cancer.

Methods

One hundred ninety-nine tissue samples of patients with invasive breast cancer were stained for CCL1 and CCL22 by immunohistochemistry. Chemokine expression and tumor infiltration by regulatory T cells, determined by expression of the transcription factor FoxP3, were quantified and their correlation to clinical features was statistically analyzed.

Results

Both CCL1 and CCL22 were expressed in most breast cancer tissues. CCL1 was significantly over-expressed in invasive breast cancer as compared to normal breast tissue. CCL1, but surprisingly not CCL22, showed a significant correlation with the number of tumor-infiltrating FoxP3+ Treg (p< 0.001). High numbers of intratumoral CCL1 expressing cells were related to high grade tumors (G4) and a positive estrogen receptor (ER) status whereas high CCL22 expression was generally seen in lower grade tumors. The median survival of 88 patients with high intratumoral CCL1 expression was 37 months compared to 50 months for the 87 patients with low CCL1 levels, this trend was however not statistically significant.

Conclusions

We found a high expression of CCL1 in human breast cancer. CCL1 significantly correlated with the infiltration of immunosuppressive FoxP3+ Treg, that are known to negatively affect survival. Thus, CCL1 may serve as prognostic marker and novel therapeutic target in breast cancer.

Stem cells repurpose proliferation to contain a breach in their niche barrier

Adult stem cells are responsible for life-long tissue maintenance. They reside in and interact with specialized tissue microenvironments (niches). Using murine hair follicle as a model, we show that when junctional perturbations in the niche disrupt barrier function, adjacent stem cells dramatically change their transcriptome independent of bacterial invasion and become capable of directly signaling to and recruiting immune cells. Additionally, these stem cells elevate cell cycle transcripts which reduce their quiescence threshold, enabling them to selectively proliferate within this microenvironment of immune distress cues. However, rather than mobilizing to fuel new tissue regeneration, these ectopically proliferative stem cells remain within their niche to contain the breach. Together, our findings expose a potential communication relay system that operates from the niche to the stem cells to the immune system and back. The repurposing of proliferation by these stem cells patch the breached barrier, stoke the immune response and restore niche integrity.

The role of regulatory T cells in the regulation of upper airway inflammation

Allergic rhinitis (AR) and chronic rhinosinusitis with nasal polyps (CRSwNP) are inflammatory diseases of the upper airway, with a similar immunologic profile, characterized by aberrant and persistent type 2 inflammation. One cell population that has been identified as altered in both disease types is regulatory T cell (Treg). Tregs have the capacity to modulate T-effector function and suppress inflammatory cytokine production in a broad range of cell types. Given the ability of Tregs to control inflammation, the role of Tregs in respiratory diseases has attracted much attention. As discussed in this article, alterations in the Treg numbers and function, or both, have been identified in AR and CRSwNP, although much of the data is conflicting. Here, we explored what is known and, in many cases, unknown about the mechanisms by which Tregs differentiate and function, and how these functions can be controlled in the mucosal microenvironment. By gaining a greater understanding of these processes, it may be possible to harness the natural immunosuppressive activity of Tregs to ameliorate the chronic inflammation associated with AR and CRSwNP.

Targeting CCR8 Induces Protective Antitumor Immunity and Enhances Vaccine-Induced Responses in Colon Cancer

CCR8 is a chemokine receptor expressed principally on regulatory T cells (Treg) and is known to be critical for CCR8⁺ Treg-mediated immunosuppression. Recent studies have demonstrated that CCR8 is uniquely upregulated in human tumor-resident Tregs of patients with breast, colon, and lung cancer when compared with normal tissue-resident Tregs. Therefore, CCR8⁺ tumor-resident Tregs are rational targets for cancer immunotherapy. Here, we demonstrate that mAb therapy targeting CCR8 significantly suppresses tumor growth and improves long-term survival in colorectal tumor mouse models. This antitumor activity correlated with increased tumor-specific T cells, enhanced infiltration of CD4⁺ and CD8⁺ T cells, and a significant decrease in the frequency of tumor-resident CD4⁺CCR8⁺ Tregs. Tumor-specific CD8⁺ T cells displayed lower expression of exhaustion markers as well as increased functionality upon restimulation. Treatment with anti-CCR8 mAb prevented de novo induction and suppressive function of Tregs without affecting CD8⁺ T cells. Initial studies explored a combinatorial regimen using anti-CCR8 mAb therapy and a Listeria monocytogenes-based immunotherapy. Anti-CCR8 mAb therapy synergized with L. monocytogenes-based immunotherapy to significantly delay growth of established tumors and to prolong survival. Collectively, these findings identify CCR8 as a promising new target for tumor immunotherapy and provide a strong rationale for further development of this approach, either as a monotherapy or in combination with other immunotherapies.Significance: Inhibition of CCR8 represents a promising new cancer immunotherapy strategy that modulates tumor-resident regulatory T cells to enhance antitumor immunity and prolong patient survival. Cancer Res; 78(18); 5340-8. ©2018 AACR.

Peripheral Tissue Chemokines: Homeostatic Control of Immune Surveillance T Cells

Cellular immunity is governed by a complex network of migratory cues that enable appropriate immune cell responses in a timely and spatially controlled fashion. This review focuses on the chemokines and their receptors regulating the steady-state localisation of immune cells within healthy peripheral tissues. Steady-state immune cell traffic is not well understood but is thought to involve constitutive (homeostatic) chemokines. The recent discovery of tissue-resident memory T cells (T_RM cells) illustrates our need for understanding how chemokines control immune cell mobilisation and/or retention. These studies will be critical to unravel novel pathways for preserving tissue function (aging) and preventing tissue disease (vaccination).

Role of a non-canonical splice variant of the Helios gene in the differentiation of acute lymphoblastic leukemic T cells

T-cell acute lymphoblastic leukemia is a hematopoietic malignant disease, which arises from a genetic defect in the T-cell maturation signaling pathway. As a result, it is necessary to identify the molecules that impact T-cell development and control lymphoid-lineage malignancy. The present study utilized Jurkat T lymphoblastic cells as a well-established approach for the investigation into the function of the non-canonical alternative splice variant of Helios for the in vitro study of T-cell differentiation and leukemogenesis. In the present study, the Jurkat T-cell lines with stable overexpression of the wild-type (Helios-1) or the non-canonical short isoform (Helios-Δ326-1431), were established. RNA microarray, reverse transcription-quantitative polymerase chain reaction and flow cytometry were used to assess changes in the gene expression profiles and to monitor the cell surface markers during T-cell differentiation. Multiple genes associated with T-cell differentiation and leukemogenesis were identified as being either activated or suppressed. In addition, the results indicated that the stable overexpression of the Helios isoforms stimulated the differentiation pathway of the T-lineage lymphoblastic cells. Therefore, these results suggest that full-length Helios-1 has a tumor suppressor-like and immunomodulatory role, in contrast to the oncogenic function of the non-canonical short isoform Helios-Δ326-1431.

Recombinant Epinephelus lanceolatus serum amyloid A as a feed additive: Effects on immune gene expression and resistance to Vibrio alginolyticus infection in Epinephelus lanceolatus

Recombinant Epinephelus lanceolatus serum amyloid A (rElSAA) exhibits strong immunostimulant activity and enhances phagocytic clearance of bacteria by macrophages. However, the effects of dietary rElSAA supplementation on growth performance, immunomodulation and disease resistance in giant grouper have not been previously evaluated. To test whether oral administration of rElSAA affects growth, fish were fed with 0, 0.88, 4.4 or 22 mg/kg rElSAA-containing diet for 28 days. No statistically significant differences in body weight were observed between groups. Next, we tested whether oral administration of rElSAA may enhance disease resistance. Fish were fed with 0, 0.88, 4.4 or 22 mg/kg rElSAA-containing diet for 3, 7, 14, 21 or 28 days, followed by challenge with Vibrio alginolyticus. Survival was then monitored for 4 days. Fish that were fed with rElSAA-containing diet for 28 days showed significantly improved survival after infection. In addition, the expression levels of immune defense-associated genes in hepatic tissue were assessed by quantitative real-time polymerase chain reaction before and after V. alginolyticus infection. Oral administration of rElSAA increased the expression level of toll-like receptor 5, whereas the expression levels of CC chemokine 1, SAA and C reactive protein were decreased. Thus, the data suggest that rElSAA may enhance host immunity by attenuating regulatory T cell-mediated suppression of inflammation. Together, our results demonstrate that rElSAA is a promising candidate as a feed additive for giant grouper, which may effectively enhance disease resistance after being administered for several weeks.

Chemokines and cancer: new immune checkpoints for cancer therapy

The current review focuses on two chemokine-chemokine receptor interactions: CXCL10-CXCR3 and CCL1-CCR8. We show that CXCL10 acts on CD4+ and CD8+ T cells to enhance anti-tumor immunity, and explore the translational perspectives of these findings. As for CCR8 very recently, we identified a novel subset of CCR8+CD4+FOXp3+ regulatory T cells (T_reg) that are major drivers of immune regulation. We observed that one of the four CCR8 ligands, CCL1, produced by these cells, potentiates their suppressive activity via induction of CCR8, FOXp3, CD39, Granzyme-B, and IL-10 in a positive feedback mechanism, making them master drivers of immune regulation. Collectively, this suggests blocking the CCR8-CCL1 interaction, alone or combined with other immune checkpoint inhibitors, as an approach to treat malignant diseases.

Glycosylated extracellular vesicles released by glioblastoma cells are decorated by CCL18 allowing for cellular uptake via chemokine receptor CCR8

Cancer cells release extracellular vesicles (EVs) that contain functional biomolecules such as RNA and proteins. EVs are transferred to recipient cancer cells and can promote tumour progression and therapy resistance. Through RNAi screening, we identified a novel EV uptake mechanism involving a triple interaction between the chemokine receptor CCR8 on the cells, glycans exposed on EVs and the soluble ligand CCL18. This ligand acts as bridging molecule, connecting EVs to cancer cells. We show that glioblastoma EVs promote cell proliferation and resistance to the alkylating agent temozolomide (TMZ). Using in vitro and in vivo stem-like glioblastoma models, we demonstrate that EV-induced phenotypes are neutralised by a small molecule CCR8 inhibitor, R243. Interference with chemokine receptors may offer therapeutic opportunities against EV-mediated cross-talk in glioblastoma.