VISTA Re-programs Macrophage Biology Through the Combined Regulation of Tolerance and Anti-inflammatory Pathways

VISTA Emerges as a Promising Target against Immune Evasion Mechanisms in Medulloblastoma

BACKGROUND

Relapsed medulloblastoma (MB) poses a significant therapeutic challenge due to its highly immunosuppressive tumor microenvironment. Immune checkpoint inhibitors (ICIs) have struggled to mitigate this challenge, largely due to low T-cell infiltration and minimal PD-L1 expression. Identifying the mechanisms driving low T-cell infiltration is crucial for developing more effective immunotherapies.

METHODS

We utilize a syngeneic mouse model to investigate the tumor immune microenvironment of MB and compare our findings to transcriptomic and proteomic data from human MB.

RESULTS

Flow cytometry reveals a notable presence of CD45hi/CD11bhi macrophage-like and CD45int/CD11bint microglia-like tumor-associated macrophages (TAMs), alongside regulatory T-cells (Tregs), expressing high levels of the inhibitory checkpoint molecule VISTA. Compared to sham control mice, the CD45hi/CD11bhi compartment significantly expands in tumor-bearing mice and exhibits a myeloid-specific signature composed of VISTA, CD80, PD-L1, CTLA-4, MHCII, CD40, and CD68. These findings are corroborated by proteomic and transcriptomic analyses of human MB samples. Immunohistochemistry highlights an abundance of VISTA-expressing myeloid cells clustering at the tumor-cerebellar border, while T-cells are scarce and express FOXP3. Additionally, tumor cells exhibit immunosuppressive properties, inhibiting CD4 T-cell proliferation in vitro. Identification of VISTA's binding partner, VSIG8, on tumor cells, and its correlation with increased VISTA expression in human transcriptomic analyses suggests a potential therapeutic target.

CONCLUSIONS

This study underscores the multifaceted mechanisms of immune evasion in MB and highlights the therapeutic potential of targeting the VISTA-VSIG axis to enhance anti-tumor responses.

Aberrant expression of B7-H4 and B7-H5 contributes to the development of cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (CSCC) is the second most common malignant tumor of the skin. B7 homolog 4 (B7-H4) and B7-H5 (B7 homolog 5) are associated with a variety of tumors. Investigate the potential role of B7-H4 and B7-H5 in regulating the tumorigenesis and progression of CSCC. B7-H4 and B7-H5 transcriptome data were collected from GEO and TCGA databases and subjected to bioinformatical analysis by protein-protein interaction (PPI) network, functional enrichment analysis, immune analysis, and drug-gene interaction prediction analysis. We characterized the expression of B7-H4 and B7-H5 in carcinoma tissues of CSCC patients by immunohistochemistry. Meanwhile, the clinical correlation of B7-H4 and B7-H5 in CSCC was explored by statistical analysis. B7-H4 and B7-H5 genes were under-expressed in CSCC and correlated with tumor staging. According to GO and KEGG Pathway enrichment analysis, B7-H4, and B7-H5 can regulate the proliferation and activation of T cells, lymphocytes, and monocytes, and the expression of cytokines, such as IL-6 and IL-10, in CSCC. B7-H4 and B7-H5 are also jointly involved in the occurrence and development of CSCC via the JAK-STAT and Notch signaling pathways. We found that B7-H4 and B7-H5 proteins were abnormally highly expressed in CSCC tissue and correlated with tumor size and stage. Our findings offer new insights into the pathogenesis of CSCC and suggest that B7-H4 and B7-H5 are novel tissue biomarkers and promising therapeutic targets for CSCC.

Buena VISTA: a promising outlook on targeting immune checkpoint regulators to combat sepsis

Regulation of T cell activation by VISTA is implicated in host organism immune response to sepsis and may be a potential therapeutic target.

Expression and function of VISTA on myeloid cells

V-domain containing Ig Suppressor of T cell Activation (VISTA) is predominantly expressed on myeloid cells and functions as a ligand/receptor/soluble molecule. In inflammatory responses and immune responses, VISTA regulates multiple functions of myeloid cells, such as chemotaxis, phagocytosis, T cell activation. Since inflammation and immune responses are critical in many diseases, VISTA is a promising therapeutic target. In this review, we will describe the expression and function of VISTA on different myeloid cells, including neutrophils, monocytes, macrophages, dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs). In addition, we will discuss whether the functions of VISTA on these cells impact the disease processing.

VISTA drives macrophages towards a pro-tumoral phenotype that promotes cancer cell phagocytosis yet down-regulates T cell responses

BACKGROUND

VISTA is a well-known immune checkpoint in T cell biology, but its role in innate immunity is less established. Here, we investigated the role of VISTA on anticancer macrophage immunity, with a focus on phagocytosis, macrophage polarization and concomitant T cell activation.

METHODS

Macrophages, differentiated from VISTA overexpressed THP-1 cells and cord blood CD34+ cell-derived monocytes, were used in phagocytosis assay using B lymphoma target cells opsonized with Rituximab. PBMC-derived macrophages were used to assess the correlation between phagocytosis and VISTA expression. qRT-PCR, flow cytometry, and enzyme-linked immunosorbent assay were performed to analyze the impact of VISTA on other checkpoints and M1/M2-like macrophage biology. Additionally, flow cytometry was used to assess the frequency of CD14+ monocytes expressing VISTA in PBMCs from 65 lymphoma patients and 37 healthy donors.

RESULTS

Ectopic expression of VISTA in the monocytic model cell line THP-1 or in primary monocytes triggered differentiation towards the macrophage lineage, with a marked increase in M2-like macrophage-related gene expression and decrease in M1-like macrophage-related gene expression. VISTA expression in THP-1 and monocyte-derived macrophages strongly downregulated expression of SIRPα, a prominent 'don't eat me' signal, and augmented phagocytic activity of macrophages against cancer cells. Intriguingly, expression of VISTA's extracellular domain alone sufficed to trigger phagocytosis in ∼ 50% of cell lines, with those cell lines also directly binding to recombinant human VISTA, indicating ligand-dependent and -independent mechanisms. Endogenous VISTA expression was predominantly higher in M2-like macrophages compared to M0- or M1-like macrophages, with a positive correlation observed between VISTA expression in M2c macrophages and their phagocytic activity. VISTA-expressing macrophages demonstrated a unique cytokine profile, characterized by reduced IL-1β and elevated IL-10 secretion. Furthermore, VISTA interacted with MHC-I and downregulated its surface expression, leading to diminished T cell activation. Notably, VISTA surface expression was identified in monocytes from all lymphoma patients but was less prevalent in healthy donors.

CONCLUSIONS

Collectively, VISTA expression associates with and drives M2-like activation of macrophages with a high phagocytic capacity yet a decrease in antigen presentation capability to T cells. Therefore, VISTA is a negative immune checkpoint regulator in macrophage-mediated immune suppression.

Repositioning baloxavir marboxil as VISTA agonist that ameliorates experimental asthma

V-type immunoglobulin domain-containing suppressor of T-cell activation (VISTA), a novel negative checkpoint regulator, plays an essential role in allergic pulmonary inflammation in mice. Treatment with a VISTA agonistic antibody could significantly improve asthma symptoms. Thus, for allergic asthma treatment, VISTA targeting may be a compelling approach. In this study, we examined the functional mechanism of VISTA in allergic pulmonary inflammation and screened the FDA-approved drugs for VISTA agonists. By using mass cytometry (CyTOF), we found that VISTA deficiency primarily increased lung macrophage infiltration in the OVA-induced asthma model, accompanied by an increased proportion of M1 macrophages (CD11b+F4/80+CD86+) and a decreased proportion of M2 macrophages (CD11b+F4/80+CD206+). Further in vitro studies showed that VISTA deficiency promoted M1 polarization and inhibited M2 polarization of bone marrow-derived macrophages (BMDMs). Importantly, we discovered baloxavir marboxil (BXM) as a VISTA agonist by virtual screening of FDA-approved drugs. The surface plasmon resonance (SPR) assays revealed that BXM (KD = 1.07 µM) as well as its active form, baloxavir acid (BXA) (KD = 0.21 µM), could directly bind to VISTA with high affinity. Notably, treatment with BXM significantly ameliorated asthma symptoms, including less lung inflammation, mucus secretion, and the generation of Th2 cytokines (IL-5, IL-13, and IL-4), which were dramatically attenuated by anti-VISTA monoclonal antibody treatment. BXM administration also reduced the pulmonary infiltration of M1 macrophages and raised M2 macrophages. Collectively, our study indicates that VISTA regulates pulmonary inflammation in allergic asthma by regulating macrophage polarization and baloxavir marboxil, and an old drug might be a new treatment for allergic asthma through targeting VISTA.

Immune dysregulation in sepsis: experiences, lessons and perspectives

Sepsis is a life-threatening organ dysfunction syndrome caused by dysregulated host responses to infection. Not only does sepsis pose a serious hazard to human health, but it also imposes a substantial economic burden on the healthcare system. The cornerstones of current treatment for sepsis remain source control, fluid resuscitation, and rapid administration of antibiotics, etc. To date, no drugs have been approved for treating sepsis, and most clinical trials of potential therapies have failed to reduce mortality. The immune response caused by the pathogen is complex, resulting in a dysregulated innate and adaptive immune response that, if not promptly controlled, can lead to excessive inflammation, immunosuppression, and failure to re-establish immune homeostasis. The impaired immune response in patients with sepsis and the potential immunotherapy to modulate the immune response causing excessive inflammation or enhancing immunity suggest the importance of demonstrating individualized therapy. Here, we review the immune dysfunction caused by sepsis, where immune cell production, effector cell function, and survival are directly affected during sepsis. In addition, we discuss potential immunotherapy in septic patients and highlight the need for precise treatment according to clinical and immune stratification.

VISTA and its ligands: the next generation of promising therapeutic targets in immunotherapy

V-domain immunoglobulin suppressor of T cell activation (VISTA) is a novel negative checkpoint receptor (NCR) primarily involved in maintaining immune tolerance. It has a role in the pathogenesis of autoimmune disorders and cancer and has shown promising results as a therapeutic target. However, there is still some ambiguity regarding the ligands of VISTA and their interactions with each other. While V-Set and Immunoglobulin domain containing 3 (VSIG-3) and P-selectin glycoprotein ligand-1(PSGL-1) have been extensively studied as ligands for VISTA, the others have received less attention. It seems that investigating VISTA ligands, reviewing their functions and roles, as well as outcomes related to their interactions, may allow an understanding of their full functionality and effects within the cell or the microenvironment. It could also help discover alternative approaches to target the VISTA pathway without causing related side effects. In this regard, we summarize current evidence about VISTA, its related ligands, their interactions and effects, as well as their preclinical and clinical targeting agents.

Immune-checkpoint protein VISTA in allergic, autoimmune disease and transplant rejection

Negative checkpoint regulators (NCRs) reduce the T cell immune response against self-antigens and limit autoimmune disease development. V-domain Ig suppressor of T cell activation (VISTA), a novel immune checkpoint in the B7 family, has recently been identified as one of the NCRs. VISTA maintains T cell quiescence and peripheral tolerance. VISTA targeting has shown promising results in treating immune-related diseases, including cancer and autoimmune disease. In this review, we summarize and discuss the immunomodulatory role of VISTA, its therapeutic potential in allergic, autoimmune disease, and transplant rejection, as well as the current therapeutic antibodies, to present a new method for regulating immune responses and achieving durable tolerance for the treatment of autoimmune disease and transplantation.

Beyond CTLA-4 and PD-1 Inhibition: Novel Immune Checkpoint Molecules for Melanoma Treatment

More than ten years after the approval of ipilimumab, immune checkpoint inhibitors (ICIs) against PD-1 and CTLA-4 have been established as the most effective treatment for locally advanced or metastatic melanoma, achieving durable responses either as monotherapies or in combinatorial regimens. However, a considerable proportion of patients do not respond or experience early relapse, due to multiple parameters that contribute to melanoma resistance. The expression of other immune checkpoints beyond the PD-1 and CTLA-4 molecules remains a major mechanism of immune evasion. The recent approval of anti-LAG-3 ICI, relatlimab, in combination with nivolumab for metastatic disease, has capitalized on the extensive research in the field and has highlighted the potential for further improvement of melanoma prognosis by synergistically blocking additional immune targets with new ICI-doublets, antibody-drug conjugates, or other novel modalities. Herein, we provide a comprehensive overview of presently published immune checkpoint molecules, including LAG-3, TIGIT, TIM-3, VISTA, IDO1/IDO2/TDO, CD27/CD70, CD39/73, HVEM/BTLA/CD160 and B7-H3. Beginning from their immunomodulatory properties as co-inhibitory or co-stimulatory receptors, we present all therapeutic modalities targeting these molecules that have been tested in melanoma treatment either in preclinical or clinical settings. Better understanding of the checkpoint-mediated crosstalk between melanoma and immune effector cells is essential for generating more effective strategies with augmented immune response.

Configuring Therapeutic Aspects of Immune Checkpoints in Lung Cancer

Immune checkpoints are unique components of the body's defense mechanism that safeguard the body from immune responses that are potent enough to harm healthy body cells. When proteins present on the surface of T cells recognize and bind to the proteins present on other tumor cells, immune checkpoints are triggered. These proteins are called immunological checkpoints. The T cells receive an on/off signal when the checkpoints interact with companion proteins. This might avert the host's immune system from eliminating cancer cells. The standard care plan for the treatment of non-small cell lung cancer (NSCLC) has been revolutionized with the use of drugs targeting immune checkpoints, in particular programmed cell death protein 1. These drugs are now extended for their potential to manage SCLC. However, it is acknowledged that these drugs have specific immune related adverse effects. Herein, we discuss the use of immune checkpoint inhibitors in patients with NSCLC and SCLC, their outcomes, and future perspectives.

VISTA Targeting of T-cell Quiescence and Myeloid Suppression Overcomes Adaptive Resistance

V domain immunoglobulin suppressor of T-cell activation (VISTA) is a premier target for cancer treatment due to its broad expression in many cancer types and enhanced expression upon development of adaptive immune checkpoint resistance. In the CT26 colorectal cancer model, monotherapy of small tumors with anti-VISTA resulted in slowed tumor growth. In a combination therapy setting, large CT26 tumors showed complete adaptive resistance to anti-PD-1/CTLA-4, but inclusion of anti-VISTA led to rejection of half the tumors. Mechanisms of enhanced antitumor immunity were investigated using single-cell RNA sequencing (scRNA-seq), multiplex image analysis, and flow cytometry of the tumor immune infiltrate. In both treatment models, anti-VISTA upregulated stimulated antigen presentation pathways and reduced myeloid-mediated suppression. Imaging revealed an anti-VISTA stimulated increase in contacts between T cells and myeloid cells, further supporting the notion of increased antigen presentation. scRNA-seq of tumor-specific CD8+ T cells revealed that anti-VISTA therapy induced T-cell pathways highly distinct from and complementary to those induced by anti-PD-1 therapy. Whereas anti-CTLA-4/PD-1 expanded progenitor exhausted CD8+ T-cell subsets, anti-VISTA promoted costimulatory genes and reduced regulators of T-cell quiescence. Notably, this is the first report of a checkpoint regulator impacting CD8+ T-cell quiescence, and the first indication that quiescence may be a target in the context of T-cell exhaustion and in cancer. This study builds a foundation for all future studies on the role of anti-VISTA in the development of antitumor immunity and provides important mechanistic insights that strongly support use of anti-VISTA to overcome the adaptive resistance seen in contemporary treatments involving PD-1 and/or CTLA-4. See related Spotlight by Wei, p. 3.

Immune cellular components and signaling pathways in the tumor microenvironment

During the past decade there has been a revolution in cancer therapeutics by the emergence of antibody-based and cell-based immunotherapies that modulate immune responses against tumors. These new therapies have extended and improved the therapeutic efficacy of chemo-radiotherapy and have offered treatment options to patients who are no longer responding to these classic anti-cancer treatments. Unfortunately, tumor eradication and long-lasting responses are observed in a small fraction of patients, whereas the majority of patients respond only transiently. These outcomes indicate that the maximum potential of immunotherapy has not been reached due to incomplete knowledge of the cellular and molecular mechanisms that guide the development of successful anti-tumor immunity and its failure. In this review, we discuss recent discoveries about the immune cellular composition of the tumor microenvironment (TME) and the role of key signaling mechanisms that compromise the function of immune cells leading to cancer immune escape.

Immune checkpoint proteins: Signaling mechanisms and molecular interactions in cancer immunotherapy

Immune checkpoint proteins (ICP) are currently one of the most novel and promising areas of immune-oncology research. This novel way of targeting tumor cells has shown favorable success over the past few years with some FDA approvals such as Ipilimumab, Nivolumab, Pembrolizumab etc. Currently, more than 3000 clinical trials of immunotherapeutic agents are ongoing with majority being ICPs. However, as the number of trials increase so do the challenges. Some challenges such as adverse side effects, non-specific binding on healthy tissues and absence of response in some subset populations are critical obstacles. For a safe and effective further therapeutic development of molecules targeting ICPs, understanding their mechanism at molecular level is crucial. Since ICPs are mostly membrane bound receptors, a number of downstream signaling pathways divaricate following ligand-receptor binding. Most ICPs are expressed on more than one type of immune cell populations. Further, the expression varies within a cell type. This naturally varied expression pattern adds to the difficulty of targeting specific effector immune cell types against cancer. Hence, understanding the expression pattern and cellular mechanism helps lay out the possible effect of any immunotherapy. In this review, we discuss the signaling mechanism, expression pattern among various immune cells and molecular interactions derived using interaction database analysis (BioGRID).

Harnessing the immune system by targeting immune checkpoints: Providing new hope for Oncotherapy

With the goal of harnessing the host’s immune system to provide long-lasting remission and cures for various cancers, the advent of immunotherapy revolutionized the cancer therapy field. Among the current immunotherapeutic strategies, immune checkpoint blockades have greatly improved the overall survival rates in certain patient populations. Of note, CTLA4 and PD-1/PD-L1 are two major non-redundant immune checkpoints implicated in promoting cancer immune evasion, and ultimately lead to relapse. Antibodies or inhibitors targeting these two c+heckpoints have achieved some encouraging clinical outcomes. Further, beyond the canonical immune checkpoints, more inhibitory checkpoints have been identified. Herein, we will summarize recent progress in immune checkpoint blockade therapies, with a specific focus on key pre-clinical and clinical results of new immune checkpoint therapies for cancer. Given the crucial roles of immune checkpoint blockade in oncotherapy, drugs targeting checkpoint molecules expressed by both cancer and immune cells are in clinical trials, which will be comprehensively summarized in this review. Taken together, investigating combinatorial therapies targeting immune checkpoints expressed by cancer cells and immune cells will greatly improve immunotherapies that enhance host elimination of tumors.

Identify the Prognostic and Immune Profile of VSIR in the Tumor Microenvironment: A Pan-Cancer Analysis

VSIR is a critical immunomodulatory receptor that inhibits T cell effector function and maintains peripheral tolerance. However, the mechanism by which VSIR participates in tumor immunity in the pan-cancer tumor microenvironment remains unclear. This study systematically explored the prognostic and immune profile of VSIR in the tumor microenvironment of 33 cancers. We compared the expression patterns and molecular features of VSIR in the normal and cancer samples both from the public databases and tumor chips. VSIR level was significantly related to patients’ prognosis and could be a promising predictor in many tumor types, such as GBM, KIRC, SKCM, READ, and PRAD. Elevated VSIR was closely correlated with infiltrated inflammatory cells, neoantigens expression, MSI, TMB, and classical immune checkpoints in the tumor microenvironment. Enrichment signaling pathways analysis indicated VSIR was involved in several immune-related pathways such as activation, proliferation, and migration of fibroblast, T cell, mast cell, macrophages, and foam cell. In addition, VSIR was found to widely express on cancer cells, fibroblasts, macrophages, and T cells in many tumor types based on the single-cell sequencing analysis and co-express with M2 macrophage markers CD68, CD163 based on the immunofluorescence staining. Finally, we predicted the sensitive drugs targeting VSIR and the immunotherapeutic value of VSIR. In sum, VSIR levels strongly correlated with the clinical outcome and tumor immunity in multiple cancer types. Therefore, therapeutic strategies targeting VSIR in the tumor microenvironment may be valuable tools for cancer immunotherapy.

EZH2 Might Affect Macrophage Chemotaxis and Anti-Inflammatory Factors by Regulating CCL2 in Dental Pulp Inflammation

Objectives

We aimed to evaluate the effects of Enhancer of Zeste Homolog 2 (EZH2) on regulation of macrophage migration and expression of anti-inflammatory genes in pulpitis.

Methods

Dental pulp inflammation was verified by histology in rat pulpitis model induced by lipopolysaccharide (LPS). Immunohistochemistry staining was used to detect changes of the expression of EZH2 and tumor necrosis factor alpha (TNF-α) in dental pulp inflammation. The expression of EZH2, CCL2, and cluster of differentiation 68 (CD68: macrophage surface marker) was measured by immunofluorescence staining. The effect of EZH2 on microphage migration was assessed by cell migration assay. The expressions of anti-inflammatory cytokine interleukins (IL-4 and IL-10) and transforming growth factor-β (TGF-β) in HDPCs which were treated by EZH2 complex, CCL2 complex, and CCL2 antibody were examined by quantitative real-time polymerase chain reaction (q-PCR).

Results

The expression of TNF-α gradually increased in dental pulp inflammation. The expression of EZH2 in dental pulp decreased in 8 hours after LPS stimulation. However, the expression of EZH2 gradually increased in dental pulp after 1 day stimulation by LPS. The results of immunofluorescence staining showed that the expressions of EZH2, CCL2, and CD68 were significantly upregulated in dental pulp inflammation of rats. EZH2 could enhance macrophage migration. And the chemotactic activity of macrophages exposed to supernatants of EZH2-treated HDPCs could be inhibited by CCL2 inhibition. In addition, EZH2 suppressed the expression of anti-inflammatory genes, but CCL2 inhibition reversed the downregulation of anti-inflammatory factors, including IL-4 and TGF-β in HDPCs.

Conclusions

EZH2 might affect chemotaxis of macrophages and the expression of anti-inflammatory factors by regulating CCL2. EZH2 plays an important role in the development of dental pulp inflammation, and it might be as a target for treatment of pulpitis.

A Dynamic Transcriptome Map of Different Tissue Microenvironment Cells Identified During Gastric Cancer Development Using Single-Cell RNA Sequencing

Gastric cancer (GC) development trends have identified multiple processes ranging from inflammation to carcinogenesis, however, key pathogenic mechanisms remain unclear. Tissue microenvironment (TME) cells are critical for the progression of malignant tumors. Here, we generated a dynamic transcriptome map of various TME cells during multi-disease stages using single-cell sequencing analysis. We observed a set of key transition markers related to TME cell carcinogenic evolution, and delineated landmark dynamic carcinogenic trajectories of these cells. Of these, macrophages, fibroblasts, and endothelial cells exerted considerable effects toward epithelial cells, suggesting these cells may be key TME factors promoting GC occurrence and development. Our results suggest a phenotypic convergence of different TME cell types toward tumor formation processes in GC. We believe our data would pave the way for early GC detection, diagnosis, and treatment therapies.

VISTA Is a Diagnostic Biomarker and Immunotherapy Target of Aggressive Feline Mammary Carcinoma Subtypes

Simple Summary

Mammary tumors are common in cats, showing aggressive behavior and few therapeutic options. Recently, feline mammary carcinomas have become a reliable cancer model for human breast cancer studies, due to the similarities between the two species. Thus, the identification of new tumor biomarkers and therapeutic targets to improve cat’s prognosis is needed. VISTA is an important immune checkpoint protein that has gained importance over the past few years in women’s cancers. In this study, the serum VISTA levels and tumor expression were analyzed in cats with mammary tumors, being correlated with other immune checkpoints. In the diseased animals, VISTA is overexpressed in more aggressive tumor subtypes (HER2-positive and triple-negative), showing a positive correlation with the expression of VISTA in tumor-infiltrating lymphocytes, and is associated with an immunosuppressive status, suggesting that VISTA could be a promising non-invasive prognostic biomarker and therapeutic target in cats with mammary carcinomas, as reported in humans.

Abstract

Feline mammary carcinoma (FMC) is a common neoplasia, showing aggressive clinicopathological features, without viable therapeutic options. The study of tumor microenvironment has gained importance, due to the ability to control tumor progression by regulating the immune response. Considering the lack of knowledge, feline serum VISTA levels from cats with mammary carcinoma were compared with healthy controls, and with serum levels of PD-1/PD-L1, CTLA-4, LAG-3, IL-6, and TNF-α. In parallel, VISTA tumor expression was evaluated in FMC samples. The obtained data revealed that serum VISTA levels were significantly higher in cats presenting HER2-positive (p = 0.0025) or triple-negative subtypes (p = 0.0019), with higher serum levels in luminal A (p = 0.0025) correlated to the presence of metastasis (p = 0.0471). Furthermore, in HER2-positive or triple-negative tumors, correlations were obtained between serum VISTA levels and the serum levels of the above-mentioned molecules. In tumors, VISTA expression revealed a stronger intensity in cancer cells, when compared to TILs (p < 0.0001). Stratifying the samples by subtypes, a higher number of VISTA-positive TILs was observed in the HER2-positive subtype, compared with triple-negative tumors (p = 0.0138). In conclusion, results support the development of therapeutic strategies for HER2-positive and triple-negative FMC subtypes, reinforcing the use of cats as a human oncology model.

Remodeling the Tumor Myeloid Landscape to Enhance Antitumor Antibody Immunotherapies

Among the diverse tumor resident immune cell types, tumor-associated macrophages (TAMs) are often the most abundant, possess an anti-inflammatory phenotype, orchestrate tumor immune evasion and are frequently associated with poor prognosis. However, TAMs can also be harnessed to destroy antibody-opsonized tumor cells through the process of antibody-dependent cellular phagocytosis (ADCP). Clinically important tumor-targeting monoclonal antibodies (mAb) such as Rituximab, Herceptin and Cetuximab, function, at least in part, by inducing macrophages to eliminate tumor cells via ADCP. For IgG mAb, this is mediated by antibody-binding activating Fc gamma receptors (FcγR), with resultant phagocytic activity impacted by the level of co-engagement with the single inhibitory FcγRIIb. Approaches to enhance ADCP in the tumor microenvironment include the repolarization of TAMs to proinflammatory phenotypes or the direct augmentation of ADCP by targeting so-called 'phagocytosis checkpoints'. Here we review the most promising new strategies targeting the cell surface molecules present on TAMs, which include the inhibition of 'don't eat me signals' or targeting immunostimulatory pathways with agonistic mAb and small molecules to augment tumor-targeting mAb immunotherapies and overcome therapeutic resistance.

VISTA: A Promising Target for Cancer Immunotherapy?

Agents targeting the B7 family co-inhibitory receptors cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed cell death protein-1 (PD-1), or its ligand (PD-L1), have a pivotal role in clinical practice. V-domain Ig suppressor of T-cell activation (VISTA) is a protein highly conserved between species, with a similar amino acid sequence to the B7 family members, characterized by a particularly structural homology to PD-1. It has been counted as an emerging target within the list of novel targetable immune checkpoints in oncology. Physiologically, VISTA exerts a regulatory function on the immune system at several levels, particularly by modulating T cells activation. Its altered activity plays a role in many autoimmune diseases, and its expression has been found to be prognostically implicated in different cancer types in preclinical models. We hereby present the main evidence on the value of VISTA as an immune checkpoint in solid and hematological malignancies. We also review its value as a potential target for cancer immunotherapy, by reporting the results of Phase I and II clinical trials assessing the use of drugs targeting VISTA. The complexity of its pathway, along with some unclear biological aspects concerning its molecular interactions, currently represent a limit to the applicability of VISTA as an effective biomarker for immunotherapy in oncology. A deeper characterization of this immune checkpoint may help defining its value within immune signatures of solid and hematological malignancies, and to design future therapeutic strategies.

The Role of V-Domain Ig Suppressor of T Cell Activation (VISTA) in Cancer Therapy: Lessons Learned and the Road Ahead

Immune checkpoints (ICs) have pivotal roles in regulating immune responses. The inhibitory ICs in the tumor microenvironment (TME) have been implicated in the immune evasion of tumoral cells. Therefore, identifying and targeting these inhibitory ICs might be critical for eliminating tumoral cells. V-domain immunoglobulin suppressor of T cell activation (VISTA) is a novel inhibitory IC that is expressed on myeloid cells, lymphoid cells, and tumoral cells; therefore, VISTA can substantially regulate innate and adaptive anti-tumoral immune responses. Besides, growing evidence indicates that VISTA blockade can enhance the sensitivity of tumoral cells to conventional IC-based immunotherapy, e.g., cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors. In this regard, the current study aimed to review the current evidence about the structure and expression pattern of VISTA, its role in TME, the clinicopathological significance of VISTA, and its prognostic values in various cancers. Besides, this review intended to collect the lessons from the recent pre-clinical and clinical studies and propose a strategy to overcome tumor immune-resistance states.

VISTA regulates microglia homeostasis and myelin phagocytosis, and is associated with MS lesion pathology

V-type immunoglobulin domain-containing suppressor of T-cell activation (VISTA) is a negative checkpoint regulator (NCR) that is involved in T-cell quiescence, inhibition of T-cell activation, and in myeloid cells regulates cytokine production, chemotaxis, phagocytosis, and tolerance induction. In the central nervous system (CNS), VISTA is expressed by microglia, the resident macrophage of the parenchyma, and expression is decreased during neuroinflammation; however, the function of VISTA in microglia is unknown. Here, we extensively analyzed VISTA expression in different MS lesion stages and characterized the function of VISTA in the CNS by deleting VISTA in microglia. VISTA is differentially expressed in distinct MS lesion stages. In mice, VISTA deletion in Cx3Cr1-expressing cells induced a more amoeboid microglia morphology, indicating an immune-activated phenotype. Expression of genes associated with cell cycle and immune-activation was increased in VISTA KO microglia. In response to LPS and during experimental autoimmune encephalomyelitis (EAE), VISTA KO and WT microglia shared similar transcriptional profiles and VISTA deletion did not affect EAE disease progression or microglia responses. VISTA KO in microglia in vitro decreased the uptake of myelin. This study demonstrates that VISTA is involved in microglia function, which likely affects healthy CNS homeostasis and neuroinflammation.

Terminating Cancer by Blocking VISTA as a Novel Immunotherapy: Hasta la vista, baby

VISTA is an up-and-coming immune checkpoint molecule that can become the target of new cancer immunotherapy treatments. Immune cells in the tumor microenvironment can largely influence the progression of cancer through inhibitory and stimulatory pathways. Indeed, VISTA is expressed on many immune cells, including T cells, myeloid-derived suppressor cells, tumor-associated macrophages, and dendritic cells. VISTA has predominantly been shown to act in an immune-suppressing manner that enables cancer progression. This review will delve into results from preclinical murine studies of anti-VISTA monoclonal antibody treatments, bring together recent studies that detect VISTA expression on immune cells from patient tumors of various cancers, and discuss ongoing clinical trials involving VISTA.

VISTA: A Target to Manage the Innate Cytokine Storm

In recent years, the success of immunotherapy targeting immunoregulatory receptors (immune checkpoints) in cancer have generated enthusiastic support to target these receptors in a wide range of other immune related diseases. While the overwhelming focus has been on blockade of these inhibitory pathways to augment immunity, agonistic triggering via these receptors offers the promise of dampening pathogenic inflammatory responses. V-domain Ig suppressor of T cell activation (VISTA) has emerged as an immunoregulatory receptor with constitutive expression on both the T cell and myeloid compartments, and whose agonistic targeting has proven a unique avenue relative to other checkpoint pathways to suppress pathologies mediated by the innate arm of the immune system. VISTA agonistic targeting profoundly changes the phenotype of human monocytes towards an anti-inflammatory cell state, as highlighted by striking suppression of the canonical markers CD14 and Fcγr3a (CD16), and the almost complete suppression of both the interferon I (IFN-I) and antigen presentation pathways. The insights from these very recent studies highlight the impact of VISTA agonistic targeting of myeloid cells, and its potential therapeutic implications in the settings of hyperinflammatory responses such as cytokine storms, driven by dysregulated immune responses to viral infections (with a focus on COVID-19) and autoimmune diseases. Collectively, these findings suggest that the VISTA pathway plays a conserved, non-redundant role in myeloid cell function.

VISTA: A Mediator of Quiescence and a Promising Target in Cancer Immunotherapy

V-domain Ig suppressor of T cell activation (VISTA) is a B7 family member that maintains T cell and myeloid quiescence and is a promising target for combination cancer immunotherapy. During inflammatory challenges, VISTA activity reprograms macrophages towards reduced production of proinflammatory cytokines and increased production of interleukin (IL)-10 and other anti-inflammatory mediators. The interaction of VISTA with its ligands is regulated by pH, and the acidic pH ~6.0 in the tumor microenvironment (TME) facilitates VISTA binding to P-selectin glycoprotein ligand 1 (PSGL-1). Targeting intratumoral pH might be a way to reduce the immunoinhibitory activity of the VISTA pathway and enhance antitumor immune responses. We review differences among VISTA therapeutics under development as candidate immunotherapies, focusing on VISTA binding partners and the unique structural features of this interaction.