NK cell expression of Tim-3: First impressions matter

Interaction of the Immune System TIM-3 Protein with a Model Cellular Membrane Containing Phosphatidyl-Serine Lipids

T cell transmembrane, Immunoglobulin, and Mucin (TIM) are important immune system proteins which are especially present in T-cells and regulated the immune system by sensing cell engulfment and apoptotic processes. Their role is exerted by the capacity to detect the presence of phosphatidyl-serine lipid polar head in the outer leaflet of cellular membranes (correlated with apoptosis). In this contribution by using equilibrium and enhanced sampling molecular dynamics simulation we unravel the molecular bases and the thermodynamics of TIM, and in particular TIM-3, interaction with phosphatidyl serine in a lipid bilayer. Since TIM-3 deregulation is an important factor of pro-oncogenic tumor micro-environment understanding its functioning at a molecular level may pave the way to the development of original immunotherapeutic approaches.

Beyond T cell exhaustion: TIM-3 regulation of myeloid cells

T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) is an important immune checkpoint molecule initially identified as a marker of IFN-γ-producing CD4+ and CD8+ T cells. Since then, our understanding of its role in immune responses has significantly expanded. Here, we review emerging evidence demonstrating unexpected roles for TIM-3 as a key regulator of myeloid cell function, in addition to recent work establishing TIM-3 as a delineator of terminal T cell exhaustion, thereby positioning TIM-3 at the interface between fatigued immune responses and reinvigoration. We share our perspective on the antagonism between TIM-3 and T cell stemness, discussing both cell-intrinsic and cell-extrinsic mechanisms underlying this relationship. Looking forward, we discuss approaches to decipher the underlying mechanisms by which TIM-3 regulates stemness, which has remarkable potential for the treatment of cancer, autoimmunity, and autoinflammation.

Immune checkpoint inhibitors associated cardiovascular immune-related adverse events

Immune checkpoint inhibitors (ICIs) are specialized monoclonal antibodies (mAbs) that target immune checkpoints and their ligands, counteracting cancer cell-induced T-cell suppression. Approved ICIs like cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), its ligand PD-L1, and lymphocyte activation gene-3 (LAG-3) have improved cancer patient outcomes by enhancing anti-tumor responses. However, some patients are unresponsive, and others experience immune-related adverse events (irAEs), affecting organs like the lung, liver, intestine, skin and now the cardiovascular system. These cardiac irAEs include conditions like myocarditis, atherosclerosis, pericarditis, arrhythmias, and cardiomyopathy. Ongoing clinical trials investigate promising alternative co-inhibitory receptor targets, including T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) and T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT). This review delves into the mechanisms of approved ICIs (CTLA-4, PD-1, PD-L1, and LAG-3) and upcoming options like Tim-3 and TIGIT. It explores the use of ICIs in cancer treatment, supported by both preclinical and clinical data. Additionally, it examines the mechanisms behind cardiac toxic irAEs, focusing on ICI-associated myocarditis and atherosclerosis. These insights are vital as ICIs continue to revolutionize cancer therapy, offering hope to patients, while also necessitating careful monitoring and management of potential side effects, including emerging cardiac complications.

γδ T cells mediate robust anti-HIV functions during antiretroviral therapy regardless of immune checkpoint expression

Objectives

Although antiretroviral therapy (ART) efficiently suppresses HIV viral load, immune dysregulation and dysfunction persist in people living with HIV (PLWH). γδ T cells are functionally impaired during untreated HIV infection, but the extent to which they are reconstituted upon ART is currently unclear.

Methods

Utilising a cohort of ART-treated PLWH, we assessed the frequency and phenotype, characterised in vitro functional responses and defined the impact of immune checkpoint marker expression on effector functions of both Vδ1 and Vδ2 T cells. We additionally explore the in vitro expansion of Vδ2 T cells from PLWH on ART and the mechanisms by which such expanded cells may sense and kill HIV-infected targets.

Results

A matured NK cell-like phenotype was observed for Vδ1 T cells among 25 ART-treated individuals (PLWH/ART) studied compared to 17 HIV-uninfected controls, with heightened expression of 2B4, CD160, TIGIT and Tim-3. Despite persistent phenotypic perturbations, Vδ1 T cells from PLWH/ART exhibited strong CD16-mediated activation and degranulation, which were suppressed upon Tim-3 and TIGIT crosslinking. Vδ2 T cell degranulation responses to the phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate at concentrations up to 2 ng mL-1 were significantly impaired in an immune checkpoint-independent manner among ART-treated participants. Nonetheless, expanded Vδ2 T cells from PLWH/ART retained potent anti-HIV effector functions, with the NKG2D receptor contributing substantially to the elimination of infected cells.

Conclusion

Our findings highlight that although significant perturbations remain within the γδ T cell compartment throughout ART-treated HIV, both subsets retain the capacity for robust anti-HIV effector functions.

TIM-3 blockade in diffuse intrinsic pontine glioma models promotes tumor regression and antitumor immune memory

Diffuse intrinsic pontine glioma (DIPG) is an aggressive brain stem tumor and the leading cause of pediatric cancer-related death. To date, these tumors remain incurable, underscoring the need for efficacious therapies. In this study, we demonstrate that the immune checkpoint TIM-3 (HAVCR2) is highly expressed in both tumor cells and microenvironmental cells, mainly microglia and macrophages, in DIPG. We show that inhibition of TIM-3 in syngeneic models of DIPG prolongs survival and produces long-term survivors free of disease that harbor immune memory. This antitumor effect is driven by the direct effect of TIM-3 inhibition in tumor cells, the coordinated action of several immune cell populations, and the secretion of chemokines/cytokines that create a proinflammatory tumor microenvironment favoring a potent antitumor immune response. This work uncovers TIM-3 as a bona fide target in DIPG and supports its clinical translation.

TIM-3 as a promising target for cancer immunotherapy in a wide range of tumors

T-cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) expression has been a trending topic in recent years due to its differential expression in a wide range of neoplasms. TIM-3 is one of the key immune checkpoint receptors that interact with GAL-9, PtdSer, HMGB1 and CEACAM1. Initially identified on the surface of T helper 1 (Th1) lymphocytes and later on cytotoxic lymphocytes (CTLs), monocytes, macrophages, natural killer cells (NKs), and dendritic cells (DCs), TIM-3 plays a key role in immunoregulation. Recently, a growing body of evidence has shown that its differential expression in various tumor types indicates a specific prognosis for cancer patients. Here, we discuss which types of cancer TIM-3 can serve as a prognostic factor and the influence of coexpressed immune checkpoint inhibitors, such as LAG-3, PD-1, and CTLA-4 on patients' outcomes. Currently, experimental medicine involving TIM-3 has significantly enhanced the anti-tumor effect and improved patient survival. In this work, we summarized clinical trials incorporating TIM-3 targeting monoclonal and bispecific antibodies in monotherapy and combination therapy and highlighted the emerging role of cell-based therapies.

NBEAL2 deficiency in humans leads to low CTLA-4 expression in activated conventional T cells

Loss of NBEAL2 function leads to grey platelet syndrome (GPS), a bleeding disorder characterized by macro-thrombocytopenia and α-granule-deficient platelets. A proportion of patients with GPS develop autoimmunity through an unknown mechanism, which might be related to the proteins NBEAL2 interacts with, specifically in immune cells. Here we show a comprehensive interactome of NBEAL2 in primary T cells, based on mass spectrometry identification of altogether 74 protein association partners. These include LRBA, a member of the same BEACH domain family as NBEAL2, recessive mutations of which cause autoimmunity and lymphocytic infiltration through defective CTLA-4 trafficking. Investigating the potential association between NBEAL2 and CTLA-4 signalling suggested by the mass spectrometry results, we confirm by co-immunoprecipitation that CTLA-4 and NBEAL2 interact with each other. Interestingly, NBEAL2 deficiency leads to low CTLA-4 expression in patient-derived effector T cells, while their regulatory T cells appear unaffected. Knocking-down NBEAL2 in healthy primary T cells recapitulates the low CTLA-4 expression observed in the T cells of GPS patients. Our results thus show that NBEAL2 is involved in the regulation of CTLA-4 expression in conventional T cells and provide a rationale for considering CTLA-4-immunoglobulin therapy in patients with GPS and autoimmune disease.

Complement component C1q is an immunological rheostat that regulates Fc:Fc[Formula: see text]R interactions

Though binding sites for the complement factor C1q and the canonical fragment crystallizable (Fc) gamma receptors (Fc[Formula: see text]Rs) on immunoglobulin G (IgG) molecules overlap, how C1q decoration of immune complexes (ICs) influences their ability to engage Fc[Formula: see text]Rs remains unknown. In this report, we use recombinant human Fc multimers as stable IC mimics to show that C1q engagement of ICs directly and transiently inhibits their interactions with Fc[Formula: see text]RIII (CD16) on human natural killer (NK) cells. This inhibition occurs by C1q engagement alone as well as in concert with other serum factors. Furthermore, the inhibition of Fc[Formula: see text]RIII engagement mediated by avid binding of C1q to ICs is directly associated with IC size and dependent on the concentrations of both C1q and Fc multimers present. Functionally, C1q-mediated Fc blockade limits the ability of NK cells to induce the upregulation of the cosignaling molecule, 4-1BB (CD137), and to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Although C1q is traditionally viewed as a soluble effector molecule, we demonstrate that C1q may also take on the role of an "immunologic rheostat," buffering Fc[Formula: see text]R-mediated activation of immune cells by circulating ICs. These data define a novel role for C1q as a regulator of immune homeostasis and add to our growing understanding that complement factors mediate pleiotropic effects.

Immune checkpoints on T and NK cells in the context of HBV infection: Landscape, pathophysiology and therapeutic exploitation

In hepatitis B virus (HBV) infection, the interplay between the virus and the host immune system is crucial in determining the pathogenesis of the disease. Patients who fail to mount a sufficient and sustained anti-viral immune response develop chronic hepatitis B (CHB). T cells and natural killer (NK) cells play decisive role in viral clearance, but they are defective in chronic HBV infection. The activation of immune cells is tightly controlled by a combination of activating and inhibitory receptors, called immune checkpoints (ICs), allowing the maintenance of immune homeostasis. Chronic exposure to viral antigens and the subsequent dysregulation of ICs actively contribute to the exhaustion of effector cells and viral persistence. The present review aims to summarize the function of various ICs and their expression in T lymphocytes and NK cells in the course of HBV infection as well as the use of immunotherapeutic strategies targeting ICs in chronic HBV infection.

Clinical application and prospect of immune checkpoint inhibitors for CAR-NK cell in tumor immunotherapy

Chimeric antigen receptor (CAR) engineering of natural killer (NK) cells is an attractive research field in tumor immunotherapy. While CAR is genetically engineered to express certain molecules, it retains the intrinsic ability to recognize tumor cells through its own receptors. Additionally, NK cells do not depend on T cell receptors for cytotoxic killing. CAR-NK cells exhibit some differences to CAR-T cells in terms of more precise killing, numerous cell sources, and increased effectiveness in solid tumors. However, some problems still exist with CAR-NK cell therapy, such as cytotoxicity, low transfection efficiency, and storage issues. Immune checkpoints inhibit immune cells from performing their normal killing function, and the clinical application of immune checkpoint inhibitors for cancer treatment has become a key therapeutic strategy. The application of CAR-T cells and immune checkpoint inhibitors is being evaluated in numerous ongoing basic research and clinical studies. Immune checkpoints may affect the function of CAR-NK cell therapy. In this review, we describe the combination of existing CAR-NK cell technology with immune checkpoint therapy and discuss the research of CAR-NK cell technology and future clinical treatments. We also summarize the progress of clinical trials of CAR-NK cells and immune checkpoint therapy.

Targeting immune checkpoints: how to use natural killer cells for fighting against solid tumors

Natural killer (NK) cells are unique innate immune cells that mediate anti-viral and anti-tumor responses. Thus, they might hold great potential for cancer immunotherapy. NK cell adoptive immunotherapy in humans has shown modest efficacy. In particular, it has failed to demonstrate therapeutic efficiency in the treatment of solid tumors, possibly due in part to the immunosuppressive tumor microenvironment (TME), which reduces NK cell immunotherapy's efficiencies. It is known that immune checkpoints play a prominent role in creating an immunosuppressive TME, leading to NK cell exhaustion and tumor immune escape. Therefore, NK cells must be reversed from their dysfunctional status and increased in their effector roles in order to improve the efficiency of cancer immunotherapy. Blockade of immune checkpoints can not only rescue NK cells from exhaustion but also augment their robust anti-tumor activity. In this review, we discussed immune checkpoint blockade strategies with a focus on chimeric antigen receptor (CAR)-NK cells to redirect NK cells to cancer cells in the treatment of solid tumors.

The molecular basis of immuno-radiotherapy

PURPOSE

Radiotherapy (RT) and immunotherapy are powerful anti-tumor treatment modalities. Experimental research has demonstrated an important interplay between the cytotoxic effects of RT and the immune system. This systematic review provides an overview of the basics of anti-tumor immunity and focuses on the mechanisms underlying the interplay between RT and immune anti-tumor response that set the molecular basis of immuno-RT.

CONCLUSIONS

An 'immunity acquired equilibrium' mimicking tumor dormancy can be achieved post-irradiation treatment, with the balance shifted toward tumor eradication or regrowth when immune cells' cytotoxic effects or cancer proliferation rate prevail, respectively. RT has both immunosuppressive and immune-enhancing properties. The latter effect is also known as radio-vaccination. Its mechanisms involve up- or down-regulation of membrane molecules, such as PD-L1, HLA-class-I, CD80/86, CD47, and Fas/CD95, that play a vital role in immune checkpoint pathways and increased cytokine expression (e.g. INFα,β,γ, IL1,2, and TNFα) by cancer or immune cells. Moreover, the interactions of radiation with the tumor microenvironment (fibroblasts, tumor-infiltrating lymphocytes, monocytes, and dendritic cells are also an important component of radio-vaccination. Thus, RT may have anti-tumor vaccine properties, whose sequels can be exploited by immunotherapy agents to treat different cancer subtypes effectively.

The application of the natural killer cells, macrophages and dendritic cells in treating various types of cancer

Innate immune cells such as natural killer (NK) cells, macrophages and dendritic cells (DCs) are involved in the surveillance and clearance of tumor. Intensive research has exposed the mechanisms of recognition and elimination of tumor cells by these immune cells as well as how cancers evade immune response. Hence, harnessing the immune cells has proven to be an effective therapy in treating a variety of cancers. Strategies aimed to harness and augment effector function of these cells for cancer therapy have been the subject of intense researches over the decades. Different immunotherapeutic possibilities are currently being investigated for anti-tumor activity. Pharmacological agents known to influence immune cell migration and function include therapeutic antibodies, modified antibody molecules, toll-like receptor agonists, nucleic acids, chemokine inhibitors, fusion proteins, immunomodulatory drugs, vaccines, adoptive cell transfer and oncolytic virus–based therapy. In this review, we will focus on the preclinical and clinical applications of NK cell, macrophage and DC immunotherapy in cancer treatment.

Down-regulation of MLLT1 super elongation complex subunit impairs the anti-tumor activity of natural killer cells in esophageal cancer

Natural killer (NK) cells actively participate in anti-tumor immunity and are thus regarded as a promising tool in immunotherapy against esophageal cancer (EC). However, the mechanisms regulating NK cell activation and exhaustion have not been completely elucidated. In this study, we characterized the expression and function of MLLT1 super elongation complex subunit (MLLT1) in esophageal NK cells in a mouse EC model. MLLT1 was down-regulated in esophageal NK cells, especially NK cells expressing both T cell immunoglobulin and mucin-domain containing-3 (TIM-3) and lymphocyte activation gene3(LAG-3). In vitro knockdown of MLLT1 in NK cells resulted in significant decreases in the expression of IFN-γ and perforin, as well as impaired NK cell cytotoxicity on tumor cells. Adoptive transfer of MLLT-deficient NK cells into EC-bearing mice showed consistent impairment of NK cell anti-tumor activity, as evidenced by decreases in IFN-γ and perforin but not granzyme B. Furthermore, EC tissue cells, which were enriched from the esophagus of EC-bearing mice, induced down-regulation of MLLT1 in splenic NK cells. This down-regulation was partially restored by a TIM-3 blocking antibody. Therefore, this study indicated that TIM-3 signaling down-regulated MLLT1 in esophageal NK cells, and MLLT1 down-regulation undermined the tumoricidal function of NK cells in EC. Our study unveils a novel mechanism underlying NK cell exhaustion/dysfunction in the EC microenvironment. MLLT1 could be a potential target in future NK cell-mediated immunotherapy against EC.

The prospect of targeting T cell immunoglobulin and mucin-domain containing-3 in renal cell carcinoma immunotherapy

Despite the advances in the diagnosis and treatment of renal cell carcinoma (RCC), it remains one of the most deadly urological cancers. At present, using immune checkpoint inhibition and their combination with antiangiogenic therapy is the standard of care in patients with advanced RCC. Unfortunately, a considerable part of tumour-bearing hosts does not benefit from this type of treatment. However, our knowledge about the detailed role of mucin-domain containing-3 (TIM-3) in the RCC cells is little, and further studies are required in this field, but its significant expression in the RCC microenvironment makes this receptor a promising target for designing new monoclonal antibodies alone or in combination with other checkpoint inhibitors for RCC immunotherapy.

Targeting Tim-3 in Cancer With Resistance to PD-1/PD-L1 Blockade

Programmed death receptor 1 (PD-1) or programmed death ligand 1 (PD-L1) blocking therapy has completely changed the treatment pattern of malignant tumors. It has been tested in a wide range of malignant tumors and achieved clinical success. It might be a promising cancer treatment strategy. However, one of the important disadvantages of PD-1/PD-L1 blocking therapy is that only a few patients have a positive response to it. In addition, primary or acquired drug resistance can also lead to cancer recurrence in patients with clinical response. Therefore, it is very important to overcome the resistance of PD-1/PD-L1 blocking therapy and improve the overall response rate of patients to the immunotherapy. T cell immunoglobulin and mucin domain molecule 3 (Tim-3) belongs to the co-inhibitory receptor family involved in immune checkpoint function. Due to adaptive resistance, the expression of Tim-3 is up-regulated in PD-1/PD-L1 blocking therapy resistant tumors. Therefore, blocking the immune checkpoint Tim-3 might antagonize the resistance of PD-1/PD-L1 blocking therapy. This review systematically introduces the preclinical and clinical data of combined blockade of Tim-3 and PD-1/PD-L1 in cancer immunotherapy, and discusses the prospect of overcoming the drug resistance of PD-1/PD-L1 blockade therapy through blockade of Tim-3.

Novel Roles of the Tim Family in Immune Regulation and Autoimmune Diseases

T cell Ig and mucin domain (Tim) protein family members were identified to be important regulators of the immune response. As their name indicates, Tim proteins were originally considered a T cell-specific markers, and they mainly regulate the responses of T helper cells. However, accumulating evidence indicates that Tims are also expressed on antigen-presenting cells (APCs), such as monocytes, macrophages, dendritic cells (DCs) and B cells, and even plays various roles in natural killer cells (NKs) and mast cells. In recent years, the expression and function of Tims on different cells and the identification of new ligands for the Tim family have suggested that the Tim family plays a crucial role in immune regulation. In addition, the relationship between Tim family gene polymorphisms and susceptibility to several autoimmune diseases has expanded our knowledge of the role of Tim proteins in immune regulation. In this review, we discuss how the Tim family affects immunomodulatory function and the potential role of the Tim family in typical autoimmune diseases, including multiple sclerosis (MS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and type 1 diabetes (T1D). A deeper understanding of the immunoregulatory mechanism of the Tim family might provide new insights into the clinical diagnosis and treatment of autoimmune diseases.

The impact of hepatitis B surface antigen on natural killer cells in patients with chronic hepatitis B virus infection

BACKGROUND & AIMS

During chronic hepatitis B virus (HBV) infection, suppressed functionality of natural killer (NK) cells might contribute to HBV persistence but the underlying mechanisms remain elusive. A peculiar feature of HBV is the secretion of large amount of hepatitis B surface antigen (HBsAg). However, the effect of HBsAg quantities on NK cells is unclear. The aim was to determine the effects of HBsAg quantities on NK cell functionality in patients with chronic hepatitis B (CHB).

METHODS

Eighty CHB patients were included and categorized into four groups based on their HBsAg levels. As a control, 30 healthy donors were enrolled. NK cell frequency, phenotype and function were assessed using flow cytometry and correlated with HBsAg levels and liver enzymes.

RESULTS

Compared to the healthy controls, a reshaping of NK cell pool towards more CD56^bright NK cells was observed during CHB infection. Importantly, NK cells in patients with low HBsAg levels (<100 IU/mL) displayed an activated phenotype with increased expression of activation makers CD38, granzyme B and proliferation marker Ki-67 while presenting with defective functional responses (MIP-1β, CD107a) at the same time. Furthermore, NK cell activation was negatively correlated with patient HBsAg levels while NK function correlated with patient age.

CONCLUSIONS

The differential regulation of NK cell phenotype and function suggests that activation of NK cells in patients with low serum HBsAg levels may contribute to HBV clearance.

Inhibitory Receptors and Immune Checkpoints Regulating Natural Killer Cell Responses to Cancer

Simple Summary

Recent years marked the discovery and increased understanding of the role immune checkpoints play in immunity against cancer. This has revolutionized cancer treatment, saving the lives of many patients. For numerous years the spotlight of success has been directed towards T cells; however, it is now appreciated that other cells play vital roles in this protection. In this review we focused on cytotoxic lymphocytes Natural Killer (NK) cells, which are known to be well equipped in the fight against cancer. We explored the role of well-described and newly emerging inhibitory receptors, including immune checkpoints in regulating NK cell activity against cancer. The knowledge summarized in this review should guide the development of immunotherapies targeting inhibitory receptors with the aim of restoring NK cell responses in cancer patients.

Abstract

The discovery of immune checkpoints provided a breakthrough for cancer therapy. Immune checkpoints are inhibitory receptors that are up-regulated on chronically stimulated lymphocytes and have been shown to hinder immune responses to cancer. Monoclonal antibodies against the checkpoint molecules PD-1 and CTLA-4 have shown early clinical success against melanoma and are now approved to treat various cancers. Since then, the list of potential candidates for immune checkpoint blockade has dramatically increased. The current paradigm stipulates that immune checkpoint blockade therapy unleashes pre-existing T cell responses. However, there is accumulating evidence that some of these immune checkpoint molecules are also expressed on Natural Killer (NK) cells. In this review, we summarize our latest knowledge about targetable NK cell inhibitory receptors. We discuss the HLA-binding receptors KIRS and NKG2A, receptors binding to nectin and nectin-like molecules including TIGIT, CD96, and CD112R, and immune checkpoints commonly associated with T cells such as PD-1, TIM-3, and LAG-3. We also discuss newly discovered pathways such as IL-1R8 and often overlooked receptors such as CD161 and Siglecs. We detail how these inhibitory receptors might regulate NK cell responses to cancer, and, where relevant, we discuss their implications for therapeutic intervention.

Distinct immunopathological mechanisms of EBV-positive and EBV-negative posttransplant lymphoproliferative disorders

EBV-positive and EBV-negative posttransplant lymphoproliferative disorders (PTLDs) arise in different immunovirological contexts and might have distinct pathophysiologies. To examine this hypothesis, we conducted a multicentric prospective study with 56 EBV-positive and 39 EBV-negative PTLD patients of the K-VIROGREF cohort, recruited at PTLD diagnosis and before treatment (2013-2019), and compared them to PTLD-free Transplant Controls (TC, n = 21). We measured absolute lymphocyte counts (n = 108), analyzed NK- and T cell phenotypes (n = 49 and 94), and performed EBV-specific functional assays (n = 16 and 42) by multiparameter flow cytometry and ELISpot-IFNγ assays (n = 50). EBV-negative PTLD patients, NK cells overexpressed Tim-3; the 2-year progression-free survival (PFS) was poorer in patients with a CD4 lymphopenia (CD4⁺ <300 cells/mm³ , p <  .001). EBV-positive PTLD patients presented a profound NK-cell lymphopenia (median = 60 cells/mm³ ) and a high proportion of NK cells expressing PD-1 (vs. TC, p = .029) and apoptosis markers (vs. TC, p < .001). EBV-specific T cells of EBV-positive PTLD patients circulated in low proportions, showed immune exhaustion (p = .013 vs. TC) and poorly recognized the N-terminal portion of EBNA-3A viral protein. Altogether, this broad comparison of EBV-positive and EBV-negative PTLDs highlight distinct patterns of immunopathological mechanisms between these two diseases and provide new clues for immunotherapeutic strategies and PTLD prognosis.

Detection of Immune Checkpoint Receptors - A Current Challenge in Clinical Flow Cytometry

Immunological therapy principles are increasingly determining modern medicine. They are used to treat diseases of the immune system, for tumors, but also for infections, neurological diseases, and many others. Most of these therapies base on antibodies, but small molecules, soluble receptors or cells and modified cells are also used. The development of immune checkpoint inhibitors is amazingly fast. T-cell directed antibody therapies against PD-1 or CTLA-4 are already firmly established in the clinic. Further targets are constantly being added and it is becoming increasingly clear that their expression is not only relevant on T cells. Furthermore, we do not yet have any experience with the long-term systemic effects of the treatment. Flow cytometry can be used for diagnosis, monitoring, and detection of side effects. In this review, we focus on checkpoint molecules as target molecules and functional markers of cells of the innate and acquired immune system. However, for most of the interesting and potentially relevant parameters, there are still no test kits suitable for routine use. Here we give an overview of the detection of checkpoint molecules on immune cells in the peripheral blood and show examples of a possible design of antibody panels.

TIGIT+ TIM-3+ NK cells are correlated with NK cell exhaustion and disease progression in patients with hepatitis B virus‑related hepatocellular carcinoma

The prognosis of hepatocellular carcinoma (HCC) is extremely poor, of which hepatitis B virus-related hepatocellular carcinoma (HBV-HCC) accounts for the majority in China. Immune checkpoint inhibitors have become an effective immunotherapy method for the treatment of HCC, but they are mainly used for T cells. NK cells play a vital role as the first line of defense against tumors. Therefore, we explored the characteristic expression pattern of immune checkpoints on NK cells of HBV-HCC patients. We analyzed the correlation between the co-expression of TIGIT and TIM-3 and the clinical progress of patients with HBV-HCC. The co-expression of TIGIT and TIM-3 on NK cells is elevated in patients with HBV-HCC. TIGIT⁺TIM-3⁺NK cells showed exhausted phenotypic characteristics and displayed dysfunction manifested as weakened killing function, reduced cytokine production, and proliferation function. TIGIT⁺TIM-3⁺NK cells participate in NK cells function exhaustion and are closely related to the disease progression of patients with HBV-HCC, suggesting a new target for future immunotherapy.

Chemoradiation induces upregulation of immunogenic cell death-related molecules together with increased expression of PD-L1 and galectin-9 in gastric cancer

Surgery alone or combined with chemo- and/or radiation therapy remains the primary treatment for gastric cancer (GC) to date and immunotherapeutic tools such as monoclonal antibodies are only slowly being implemented. This is partly due to the fact that the immune microenvironment in GC during chemoradiation and other treatment modalities is still poorly understood. 7 gastric cancer (GC) cell lines were tested for their response to chemoradiation using 5-FU in combination with X-ray irradiation. We conducted flow cytometric analysis to determine the cells’ ability to undergo immunogenic cell death (ICD) and their expression of the two immunosuppressive proteins programmed death-ligand 1 (PD-L1) and galectin-9 (Gal-9). We evaluated the overall immunogenicity of two cell lines (MKN7, MKN74) in co-culture experiments with human monocyte-derived dendritic cells (Mo-DCs). Chemoradiation induces distinct responses in different GC cell lines. We observe ICD in vitro in all tested GC cell lines in the form of calreticulin (CRT) translocation to the plasma membrane. As a resistance mechanism, these cells also upregulated Gal-9 and PD-L1. Mo-DC maturation experiments showed that GCs provoked the maturation of Mo-DCs after chemoradiation in vitro. The addition of α-PD-L1 blocking antibody further enhanced the immunogenicity of these cells while improving DC viability. Blocking Tim-3, as the main receptor for Gal-9, had no such effect. Our findings suggest that the benefits of chemoradiation can substantially depend on tumor subtype and these benefits can be offset by induced immune evasion in GC. Combination treatment using checkpoint inhibitors could potentially lead to enhanced immune responses and yield better patient outcomes.

Modulation of CXCR1 and CXCR3 expression on NK cells via Tim-3 in a murine model of primary biliary cholangitis

Tim-3, which is expressed on a variety of innate immune cells including NK cells, plays a key role in many autoimmune diseases. However, the immunomodulatory actions of Tim-3 on NK cells in primary biliary cholangitis (PBC) remain uncertain. Using a murine model of PBC we evaluated the expression of Tim-3 and its ligand Gal-9 in peripheral blood, liver, and spleen. Additionally, we studied Tim-3 regulation of chemokine receptors (CXCR1 and CXCR3) in vitro. Flow cytometric analysis indicated large numbers of infiltrating NK cells in the liver which exhibited high expression of Tim-3 and CXCR3. Moreover, we found overexpression of CXCR1 in liver tissue and liver-derived NK cells in PBC mice. We also observed lower levels of soluble Tim-3 in the serum of PBC mice. In vitro experiments with liver-derived NK cells from PBC mice indicated that CXCR3 was up-regulated by treatment with recombinant mouse TIM-3 Fc (rmTim-3 Fc) to activate the Tim-3 pathway. Furthermore, stimulating normal mouse spleen NK cells with poly I:C resulted in elevated expression of CXCR1 and interferon-γ release. Nonetheless, adding rmTim-3 Fc or rmGal-9 significantly down-regulated CXCR1 expression and IFN-γ release in NK cells activated by poly I:C, proposing a means to exploit the Tim-3 pathway to reverse responses in NK cells. In conclusion, our data demonstrate that dysregulation of Tim-3/Gal-9 is involved in modulating the local immune microenvironment in PBC mice. Our findings highlight the potential of Tim-3 pathway to modulate chemokine responses in NK cells during autoimmunity.

Natural Killer Cells in Post-Transplant Lymphoproliferative Disorders

Post-transplant lymphoproliferative disorders (PTLDs) are life-threatening complications arising after solid organ or hematopoietic stem cell transplantations. Although the majority of these lymphoproliferations are of B cell origin, and are frequently associated with primary Epstein-Barr virus (EBV) infection or reactivation in the post-transplant period, rare cases of T cell and natural killer (NK) cell-originated PTLDs have also been described. A general assumption is that PTLDs result from the impairment of anti-viral and anti-tumoral immunosurveillance due to the long-term use of immunosuppressants in transplant recipients. T cell impairment is known to play a critical role in the immune-pathogenesis of post-transplant EBV-linked complications, while the role of NK cells has been less investigated, and is probably different between EBV-positive and EBV-negative PTLDs. As a part of the innate immune response, NK cells are critical for protecting hosts during the early response to virus-induced tumors. The complexity of their function is modulated by a myriad of activating and inhibitory receptors expressed on cell surfaces. This review outlines our current understanding of NK cells in the pathogenesis of PTLD, and discusses their potential implications for current PTLD therapies and novel NK cell-based therapies for the containment of these disorders.

Natural Killer Cells and Anti-Cancer Therapies: Reciprocal Effects on Immune Function and Therapeutic Response

Simple Summary

Natural Killer (NK) cells are innate lymphocytes that play an important role in the immune response against cancer. Their activity is controlled by a balance of inhibitory and activating receptors, which in cancer can be skewed to favor their suppression in support of immune escape. It is therefore imperative to find ways to optimize their antitumor functionality. In this review, we explore and discuss how their activity influences, or even mediates, the efficacy of various anti-cancer therapies and, vice versa, how their activity can be affected by these therapies. Knowledge of the mechanisms underlying these observations could provide rationales for combining anti-cancer treatments with strategies enhancing NK cell function in order to improve their therapeutic efficacy.

Abstract

Natural Killer (NK) cells are innate immune cells with the unique ability to recognize and kill virus-infected and cancer cells without prior immune sensitization. Due to their expression of the Fc receptor CD16, effector NK cells can kill tumor cells through antibody-dependent cytotoxicity, making them relevant players in antibody-based cancer therapies. The role of NK cells in other approved and experimental anti-cancer therapies is more elusive. Here, we review the possible role of NK cells in the efficacy of various anti-tumor therapies, including radiotherapy, chemotherapy, and immunotherapy, as well as the impact of these therapies on NK cell function.

Landscape of natural killer cell activity in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) encompasses a set of cancers arising from the epithelia of the upper aerodigestive tract, accounting for a significant burden of disease worldwide due to the disease’s mortality, morbidity, and predilection for recurrence. Prognosis of HNSCC in the recurrent and/or metastatic (R/M-HNSCC) setting is especially poor and effective treatment options increasingly rely on modulating T-cell antitumor responses. Still, immunotherapy response rates are generally low, prompting the exploration of novel strategies that incorporate other effector cells within the tumor microenvironment. Within the last decade, important advances have been made leveraging the powerful innate antitumor function of natural killer (NK) cells to treat solid tumors, including head and neck squamous cell carcinoma. NK cells are hybrid innate-adaptive effector cells capable of directly eliminating tumor cells in addition to initiating adaptive antitumor immune responses. In the setting of HNSCC, NK cells are important for tumor surveillance and control, and NK cell infiltration has repeatedly been associated with a favorable prognosis. Yet, HNSCC-infiltrating NK cells are susceptible to an array of immune evasion strategies employed by tumors that must be overcome to fully realize the antitumor potential of NK cells. We believe that a conceptual framework informed by the basic biological understanding of the mechanisms underlying NK cell activation can improve treatment of HNSCC, in part by selecting for patients most likely to respond to NK cell-based immunotherapy. Herein, we review the activity of NK cells in HNSCC, paying special attention to the role of environmental and genetic determinants of NK cell antitumor function. Moreover, we explore the evidence that NK cells are a crucial determinant of the efficacy of both established and emerging treatments for HNSCC.

Immune evasion mechanisms in acute myeloid leukemia: A focus on immune checkpoint pathways

Immune surveillance mechanisms comprising of adaptive and innate immune systems are naturally designed to eliminate AML development. However, leukemic cells apply various immune evasion mechanisms to deviate host immune responses resulting tumor progression. One of the recently well-known immune escape mechanisms is over-expression of immune checkpoint receptors and their ligands. Introduction of blocking antibodies targeting co-inhibitory molecules achieved invaluable success in tumor targeted therapy. Moreover, several new co-inhibitory pathways are currently studying for their potential impacts on improving anti-tumor immune responses. Although immunotherapeutic strategies based on the blockade of immune checkpoint molecules have shown promising results in a number of hematological malignances, their effectiveness in AML patients showed less remarkable success. This review discusses current knowledge about the involvement of co-inhibitory signaling pathways in immune evasion mechanisms of AML and potential application of immune checkpoint inhibitors for targeted immunotherapy of this malignancy.

Immune checkpoint molecules in natural killer cells as potential targets for cancer immunotherapy

Recent studies have demonstrated the potential of natural killer (NK) cells in immunotherapy to treat multiple types of cancer. NK cells are innate lymphoid cells that play essential roles in tumor surveillance and control that efficiently kill the tumor and do not require the major histocompatibility complex. The discovery of the NK’s potential as a promising therapeutic target for cancer is a relief to oncologists as they face the challenge of increased chemo-resistant cancers. NK cells show great potential against solid and hematologic tumors and have progressively shown promise as a therapeutic target for cancer immunotherapy. The effector role of these cells is reliant on the balance of inhibitory and activating signals. Understanding the role of various immune checkpoint molecules in the exhaustion and impairment of NK cells when their inhibitory receptors are excessively expressed is particularly important in cancer immunotherapy studies and clinical implementation. Emerging immune checkpoint receptors and molecules have been found to mediate NK cell dysfunction in the tumor microenvironment; this has brought up the need to explore further additional NK cell-related immune checkpoints that may be exploited to enhance the immune response to refractory cancers. Accordingly, this review will focus on the recent findings concerning the roles of immune checkpoint molecules and receptors in the regulation of NK cell function, as well as their potential application in tumor immunotherapy.

TIM-3 Expression Is Downregulated on Human NK Cells in Response to Cancer Targets in Synergy with Activation

Among natural killer (NK) cell receptors, the T-cell immunoglobulin and mucin-containing domain (TIM-3) has been associated with both inhibitory and activating functions, depending on context and activation pathway. Ex vivo and in vitro, expression of TIM-3 is inducible and depends on activation stimulus. Here, we report that TIM-3 expression can be downregulated on NK cells under specific conditions. When NK cells are exposed to cancer targets, they synergize with stimulation conditions to induce a substantial decrease in TIM-3 expression on their surface. We found that such downregulation occurs following prior NK activation. Downregulated TIM-3 expression correlated to lower cytotoxicity and lower interferon gamma (IFN-γ) expression, fueling the notion that TIM-3 might function as a benchmark for human NK cell dysfunction.

New immunotherapeutic drugs in advanced non-small cell lung cancer (NSCLC): from preclinical to phase I clinical trials

INTRODUCTION

The development of immune checkpoint inhibitors (ICI) has represented a revolution in the treatment of non-small cell lung cancer (NSCLC) and has established a new standard of care for different settings. However, through adaptive changes, cancer cells can develop resistance mechanisms to these drugs, hence the necessity for novel immunotherapeutic agents.

AREAS COVERED

This paper explores the immunotherapeutics currently under investigation in phase I clinical trials for the treatment of NSCLC as monotherapies and combination therapies. It provides two comprehensive tables of phase I agents which are listed according to target, drug, drug class, mechanism of action, setting, trial identifier, and trial status. A comprehensive literature search was carried out to identify eligible studies from MEDLINE/PubMed and ClinicalTrials.gov.

EXPERT OPINION

A key hurdle to success in this field is our limited understanding of the synergic interactions of the immune targets in the context of the TME. While we can recognize the links between inhibitors and some particularly promising new targets such as TIM-3 and LAG3, we continue to develop approaches to exploit their interactions to enhance the immune response of the patient to tumor cells.

Harnessing NK Cell Checkpoint-Modulating Immunotherapies

During the host immune response, the precise balance of the immune system, regulated by immune checkpoint, is required to avoid infection and cancer. These immune checkpoints are the mainstream regulator of the immune response and are crucial for self-tolerance. During the last decade, various new immune checkpoint molecules have been studied, providing an attractive path to evaluate their potential role as targets for effective therapeutic interventions. Checkpoint inhibitors have mainly been explored in T cells until now, but natural killer (NK) cells are a newly emerging target for the determination of checkpoint molecules. Simultaneously, an increasing number of therapeutic dimensions have been explored, including modulatory and inhibitory checkpoint molecules, either causing dysfunction or promoting effector functions. Furthermore, the combination of the immune checkpoint with other NK cell-based therapeutic strategies could also strengthen its efficacy as an antitumor therapy. In this review, we have undertaken a comprehensive review of the literature to date regarding underlying mechanisms of modulatory and inhibitory checkpoint molecules.

Natural Killer Cells: Tumor Surveillance and Signaling

Natural killer (NK) cells play a pivotal role in cancer immunotherapy due to their innate ability to detect and kill tumorigenic cells. The decision to kill is determined by the expression of a myriad of activating and inhibitory receptors on the NK cell surface. Cell-to-cell engagement results in either self-tolerance or a cytotoxic response, governed by a fine balance between the signaling cascades downstream of the activating and inhibitory receptors. To evade a cytotoxic immune response, tumor cells can modulate the surface expression of receptor ligands and additionally, alter the conditions in the tumor microenvironment (TME), tilting the scales toward a suppressed cytotoxic NK response. To fully harness the killing power of NK cells for clinical benefit, we need to understand what defines the threshold for activation and what is required to break tolerance. This review will focus on the intracellular signaling pathways activated or suppressed in NK cells and the roles signaling intermediates play during an NK cytotoxic response.

A Natural Impact: NK Cells at the Intersection of Cancer and HIV Disease

Despite efficient suppression of plasma viremia in people living with HIV (PLWH) on cART, evidence of HIV-induced immunosuppression remains, and normally benign and opportunistic pathogens become major sources of co-morbidities, including virus-induced cancers. In fact, cancer remains a primary cause of death even in virally suppressed PLWH. Natural killer (NK) cells provide rapid early responses to HIV infection, contribute substantially to disease modulation and vaccine protection, and are also major therapeutic targets for cancer immunotherapy. However, much like other lymphocyte populations, recent burgeoning evidence suggests that in chronic conditions like HIV, NK cells can become functionally exhausted with impaired cytotoxic function, altered cytokine production and impaired antibody-dependent cell-mediated cytotoxicity. Recent work suggests functional anergy is likely due to low-level ongoing virus replication, increased inflammatory cytokines, or increased presence of MHC^low target cells. Indeed, HIV-induced loss of NK cell-mediated control of lytic EBV infection has been specifically shown to cause lymphoma and also increases replication of CMV. In this review, we will discuss current understanding of NK cell modulation of HIV disease, reciprocal exhaustion of NK cells, and how this may impact increased cancer incidences and prospects for NK cell-targeted immunotherapies. Finally, we will review the most recent evidence supporting adaptive functions of NK cells and highlight the potential of adaptive NK cells for cancer immunotherapy.