Molecular basis for E-cadherin recognition by killer cell lectin-like receptor G1 (KLRG1)

Dysregulation of peripheral and intratumoral KLRG1+ CD8+T cells is associated with immune evasion in patients with non-small-cell lung cancer

OBJECTIVES

Killer cell lectin like receptor G1 (KLRG1) is identified as a co-inhibitory receptor for NK cells and antigen-experienced T cells. The role of KLRG1 in immune regulation in patients with non-small cell lung cancer (NSCLC) remains poorly understood.

MATERIALS AND METHODS

We measured the proportion and immune function of KLRG1+CD8+T cells derived from peripheral blood in patients with NSCLC by flow cytometry. Besides, using data from the gene expression profiles and single-cell sequencing, we explored the expression and immune role of KLRG1 in tumor tissues of patients with NSCLC. We further determined the prognostic value of KLRG1 in terms of overall survival (OS) in NSCLC patients.

RESULTS

We found that the proportion of KLRG1+CD8+T cells in peripheral blood significantly increased in patients with NSCLC as compared to those with benign pulmonary nodules and healthy donors. Peripheral KLRG1+CD8+T cell proportion was increased in elder subjects compared to that in younger ones, implying an immunosenescence phenotype. Moreover, the KLRG1+CD8+T cell levels were positively correlated with tumor size and TNM stage in the NSCLC cohort. In vitro stimulation experiments demonstrated that the KLRG1+CD8+T cells from peripheral blood expressed higher levels of Granzyme B and perforin than the KLRG1-CD8+ T cells. However, single-cell RNA sequencing data revealed that the KLRG1+CD8+ T cells were less infiltrated in tumor microenvironment and exhibited impaired cytotoxicity. The KLRG1 gene expression levels were significantly lower in tumor tissues than that in normal lung tissues, and were inversely correlated with CDH1 expression levels. Moreover, higher expression of CDH1 in tumor tissues predicted worse overall survival only in patients with KLRG1-high expression, but not in the KLRG1-low subset.

CONCLUSION

This study demonstrates that KLRG1+CD8+T cells were associated with tumor immune evasion in NSCLC and suggests KLRG1 as a potential immunotherapy target.

Structural basis of molecular recognition among classical cadherins mediating cell adhesion

Cadherins are type-I membrane glycoproteins that primarily participate in calcium-dependent cell adhesion and homotypic cell sorting in various stages of embryonic development. Besides their crucial role in cellular and physiological processes, increasing studies highlight their involvement in pathophysiological functions ranging from cancer progression and metastasis to being entry receptors for pathogens. Cadherins mediate these cellular processes through homophilic, as well as heterophilic interactions (within and outside the superfamily) by their membrane distal ectodomains. This review provides an in-depth structural perspective of molecular recognition among type-I and type-II classical cadherins. Furthermore, this review offers structural insights into different dimeric assemblies like the 'strand-swap dimer' and 'X-dimer' as well as mechanisms relating these dimer forms like 'two-step adhesion' and 'encounter complex'. Alongside providing structural details, this review connects structural studies to bond mechanics merging crystallographic and single-molecule force spectroscopic findings. Finally, the review discusses the recent discoveries on dimeric intermediates that uncover prospects of further research beyond two-step adhesion.

Regulatory ILC2-Role of IL-10 Producing ILC2 in Asthma

Over the past two decades, a growing body of evidence observations have shown group two innate lymphoid cells (ILC2) to be critical drivers of Type 2 (T2) inflammatory responses associated with allergic inflammatory conditions such as asthma. ILC2 releases copious amounts of pro-inflammatory T2 cytokines-interleukin (IL)-4, IL-5, IL-9, and IL-13. This review provides a comprehensive overview of the newly discovered regulatory subtype of ILC2 described in murine and human mucosal tissue and blood. These KLRG1+ILC2 have the capacity to produce the anti-inflammatory cytokine IL-10. Papers compiled in this review were based on queries of PubMed and Google Scholar for articles published from 2000 to 2023 using keywords "IL-10" and "ILC2". Studies with topical relevance to IL-10 production by ILC2 were included. ILC2 responds to microenvironmental cues, including retinoic acid (RA), IL-2, IL-4, IL-10, and IL-33, as well as neuropeptide mediators such as neuromedin-U (NMU), prompting a shift towards IL-10 and away from T2 cytokine production. In contrast, TGF-β attenuates IL-10 production by ILC2. Immune regulation provided by IL-10+ILC2s holds potential significance for the management of T2 inflammatory conditions. The observation of context-specific cues that alter the phenotype of ILC warrants examining characteristics of ILC subsets to determine the extent of plasticity or whether the current classification of ILCs requires refinement.

Comparative transcriptomes reveal pro-survival and cytotoxic programs of mucosal-associated invariant T cells upon Bacillus Calmette-Guérin stimulation

Mucosal-associated invariant T (MAIT) cells are protective against tuberculous and non-tuberculous mycobacterial infections with poorly understood mechanisms. Despite an innate-like nature, MAIT cell responses remain heterogeneous in bacterial infections. To comprehensively characterize MAIT activation programs responding to different bacteria, we stimulated MAIT cells with E. coli to compare with Bacillus Calmette-Guérin (BCG), which remains the only licensed vaccine and a feasible tool for investigating anti-mycobacterial immunity in humans. Upon sequencing mRNA from the activated and inactivated CD8+ MAIT cells, results demonstrated the altered MAIT cell gene profiles by each bacterium with upregulated expression of activation markers, transcription factors, cytokines, and cytolytic mediators crucial in anti-mycobacterial responses. Compared with E. coli, BCG altered more MAIT cell genes to enhance cell survival and cytolysis. Flow cytometry analyses similarly displayed a more upregulated protein expression of B-cell lymphoma 2 and T-box transcription factor Eomesodermin in BCG compared to E.coli stimulations. Thus, the transcriptomic program and protein expression of MAIT cells together displayed enhanced pro-survival and cytotoxic programs in response to BCG stimulation, supporting BCG induces cell-mediated effector responses of MAIT cells to fight mycobacterial infections.

Heterophilic recognition between E-cadherin and N-cadherin relies on same canonical binding interface as required for E-cadherin homodimerization

Cadherins are a family of cell surface glycoproteins that mediate Ca²⁺-dependent cell to cell adhesion. They organize to form large macromolecular assemblies at the junctions of cells in order to form and maintain the integrity of tissue structures, thereby playing an indispensable role in the multicellular organization. Notably, a large body of research on E- and N-cadherin, the two most widely studied members of the cadherin superfamily, suggest for homophilic associations among them to drive cell adhesion. Interestingly, latest studies also highlight for direct crosstalk among these two classical cadherins to form heterotypic connections in physiological as well as in disease environment. However, the molecular details for the heterophilic association of E-cadherin and N-cadherin has not been investigated yet, which we aimed to address in this work. Using surface plasmon resonance and flow cytometry based biophysical studies we observed heterophilic interaction between E- and N-cadherin mediated through the membrane distal ectodomains. Further, the heterodimeric interface of E-cadherin and N-cadherin was mapped using structure-guided mutational studies followed by complementary biophysical analyses to identify the important interface residues involved in the interaction. The results obtained imply significant resemblance in the interface residues of E-cadherin that are crucial for homophilic recognition of E-cadherin and heterophilic recognition of N-cadherin as well.

Lung Cancer Induces NK Cell Contractility and Cytotoxicity Through Transcription Factor Nuclear Localization

Actomyosin-mediated cellular contractility is highly conserved for mechanotransduction and signalling. While this phenomenon has been observed in adherent cell models, whether/how contractile forces regulate the function of suspension cells like natural killer (NK) cells during cancer surveillance, is unknown. Here, we demonstrated in coculture settings that the evolutionarily conserved NK cell transcription factor, Eomes, undergoes nuclear shuttling during lung cancer cell surveillance. Biophysical and biochemical analyses revealed mechanistic enhancement of NK cell actomyosin-mediated contractility, which is associated with nuclear flattening, thus enabling nuclear entry of Eomes associated with enhanced NK cytotoxicity. We found that NK cells responded to the presumed immunosuppressive TGFβ in the NK-lung cancer coculture medium to sustain its intracellular contractility through myosin light chain phosphorylation, thereby promoting Eomes nuclear localization. Therefore, our results demonstrate that lung cancer cells provoke NK cell contractility as an early phase activation mechanism and that Eomes is a plausible mechano-responsive protein for increased NK cytotoxicity. There is scope for strategic application of actomyosin-mediated contractility modulating drugs ex vivo, to reinvigorate NK cells prior to adoptive cancer immunotherapy in vivo (177 words).

E3 Ubiquitin Ligase Riplet Is Expressed in T Cells and Suppresses T Cell-Mediated Antitumor Immune Responses

The E3 ubiquitin ligase Riplet mediates retinoic acid-inducible gene-I polyubiquitination and is essential for viral-induced expression of type I IFNs in dendritic cells and macrophages. The function of Riplet in innate immunity has been well demonstrated; however, its role in adaptive immunity during the antitumor immune response is unclear. In this study, we examined the role of Riplet in the T cell-mediated antitumor immune response. Riplet was expressed in T cells and upregulated in CD8⁺ T cells in response to TCR-mediated stimulation. Furthermore, PR domain containing 1, eomesodermin, and killer cell lectin-like receptor G1 expression was increased in effector CD8⁺ T cells by Riplet knockout in vitro, which suggests that Riplet is involved in the effector function of CD8⁺ T cells. Our results indicated that Riplet deficiency augmented the antitumor response of MO4 (OVA-expressing melanoma)-bearing mice treated with OVA peptide-pulsed dendritic cells. Moreover, both CD4⁺ and CD8⁺ T cells played important roles in Riplet-mediated augmentation of the antitumor immune response. In tumor-draining lymph nodes, the Th1 response was promoted, and the induction of OVA-specific CD8⁺ T cells and IFN-γ production were enhanced by Riplet deficiency. Furthermore, the IFN-γ response and OVA-specific cytotoxicity of CD8⁺ T cells in tumor tissue were augmented by Riplet deficiency. The expression of Cxcl9fluorescence-minus-one and Cxcl10 mRNA was also enhanced in the tumor microenvironment by Riplet knockout, consistent with the augmented recruitment of CTLs. Overall, we clarified a function of Riplet in T cells, which is to suppress the antitumor immune response through modulating Th1 and CTLs.

Natural killer cells and immune-checkpoint inhibitor therapy: Current knowledge and new challenges

The discovery of immune checkpoints (ICs) and the development of specific blockers to relieve immune effector cells from this inhibiting mechanism has changed the view of anti-cancer therapy. In addition to cytotoxic T lymphocyte antigen 4 (CTLA4) and programmed death 1 (PD1), classical ICs of T lymphocytes and recently described also on a fraction of natural killer (NK) cells, several NK cell receptors, including killer immunoglobulin-like inhibitory receptors (KIRs) and NGK2A, have been recognized as checkpoint members typical of the NK cell population. This offers the opportunity of a dual-checkpoint inhibition approach, targeting classical and non-classical ICs and leading to a synergistic therapeutic effect. In this review, we will overview and discuss this new perspective, focusing on the most relevant candidates for this role among the variety of potential NK ICs. Beside listing and defining classical ICs expressed also by NK cells, or non-classical ICs either on T or on NK cells, we will address their role in NK cell survival, chronic stimulation or functional exhaustion, and the potential relevance of this phenomenon on anti-tumor immune response. Furthermore, NK ICs will be proposed as possible new targets for the development of efficient combined immunotherapy, not forgetting the relevant concerns that may be raised on NK IC blockade. Finally, the impact of epigenetic drugs in such a complex therapeutic picture will be briefly addressed.

HER2-CDH1 Interaction via Wnt/B-Catenin Is Associated with Patients' Survival in HER2-Positive Metastatic Gastric Adenocarcinoma

Simple Summary

A deeper understanding of the molecular mechanisms involved in gastric cacner (GC) pathologenesis would help the identification of prognostic biomarkers and the development of new treatments. Human epidermal growth factor receptor 2 (HER2/ErbB2), a membrane-bound receptor of the EGFR family, may be overexpressed in GC. Trastuzumab is a HER2 inhibitor used to treat HER2+ metastatic gastric cancer (mGC). The present study aims to investigate the relationship between CDH1 mRNA expression and HER2-positivity in mGC using a multiplexed gene expression profile in two series of GC patients: 38 HER2+ and HER2- mGC and 36 HER2- GC with and without metastasis. Our results revealed the relationship between CDH1 and HER2 mRNA expression in mGC via the canonical WNT/β-catenin pathway and identified EGF as an independent prognostic biomarker for survival.

Abstract

Trastuzumab is a human epidermal growth factor receptor 2 (HER2) inhibitor used to treat HER2+ metastatic gastric cancer (mGC). The present study aims to investigate the relationship between CDH1 mRNA expression and HER2-positivity in mGC using a multiplexed gene expression profile in two series of gastric cancer (GC): Series 1 (n = 38): HER2+ and HER2- mGC; Series 2 (n = 36) HER2- GC with and without metastasis. To confirm the results, the same expression profiles were analyzed in 354 GC from The Cancer Genome Atlas (TCGA) dataset. The difference in gene expression connected HER2 overexpression with canonical wingless-type (Wnt)/β-catenin pathway and immunohistochemical (IHC) expression loss of E-cadherin (E-CAD). CDH1 mRNA expression was simultaneously associated with the rs16260-A variant and an increase in E-CAD expression. Differences in retinoic acid receptor alfa (RARA), RPL19 (coding for the 60S ribosomal L19 protein), catenin delta 1 (CTNND1), and epidermal growth factor (EGF) mRNA levels—all included in the Wnt/β-catenin pathway—were found associated with overall survival (OS). RARA, CTNND1, and EGF resulted in independent OS prognostic factors. EGF was confirmed as an independent factor along with TNM stage in HER2-overpressed mGC from TCGA collection. Our study highlighted factors involved in the WNT/β-catenin pathway that interconnected E-CAD with HER2 overexpression and patient survival.

Valganciclovir as Add-On Therapy Modifies the Frequency of NK and NKT Cell Subpopulations in Disseminated Kaposi Sarcoma Patients

Simple Summary

Kaposi sarcoma is one disease that develops in people living with HIV with severe immunosuppression and impacts morbidity and associated mortality. This disease is currently treated with antiretroviral therapy and chemotherapy agents that can further contribute to immunosuppression in patients. Thus, searching for new therapies to induce a robust immune system activation in these patients is necessary. Herein, the frequency and phenotype of natural killer subpopulation cells in people living with HIV with Kaposi sarcoma were evaluated. After KS diagnosis, patients started antiretroviral therapy or valganciclovir plus antiretroviral therapy. Results showed that in patients treated with valganciclovir plus antiretroviral therapy, the expression of CD57 and CD27 proteins on natural killer cells was regulated, enhancing the immune response of the study cohort. This finding contributes to understanding more about the immune response of people living with HIV with Kaposi sarcoma.

Abstract

Human herpesvirus-8 infection (HHV-8) is the causative agent of Kaposi sarcoma (KS) and is highly prevalent among people living with HIV (KS/HIV). It has been reported that valganciclovir (VGC) reduces HHV-8 replication in KS/HIV patients. However, currently it is unclear if VGC modifies the frequency and induces changes in markers of immune regulation of immune cells necessary to eliminate HHV8-infected cells, such as Natural Killer (NK) and NK T cells (NKT). This study evaluated the effect of VGC used as antiviral HHV8 therapy in KS patients on the frequency of NK and NKT subpopulations based on the CD27 and CD57 expression, and the immunosenescence markers, PD-1 and KLRG1. Twenty KS/HIV patients were followed-up at baseline (W₀), 4 (W₄), and 12 weeks (W₁₂) of the study protocol. Among them, 10 patients received a conventional treatment scheme (CT), solely antiretroviral therapy (ART), and 10 patients received a modified treatment regime (MT), including VGC plus ART. In both groups, bleomycin/vincristine was administrated according to the treating physician’s decision. The soluble levels of IL-15, PD-L1, PD-L2, and E-cadherin were quantified across the follow-up. Our results showed that the higher IL-15 levels and lower NK frequencies cells in KS/HIV patients reach almost normal values with both treatments regimes at W₁₂. CD27+ NK and NKT cell frequencies increased since W₄ on KS/HIV patients with MT. Furthermore, PD-1 expression decreased while KLRG1 increased on NK and NKT subpopulations at W₁₂, and it is accompanied by increased PD-L1 plasma level since W₄. Our study highlights the disruption of NK and NKT subpopulations in patients with KS/HIV and explores VGC treatment’s contribution to immune reconstitution during the first weeks of treatment.

Resistance to Immunotherapy: Mechanisms and Means for Overcoming

Immune checkpoint blockade transformed cancer therapy during the last decade. However, durable responses remain uncommon, early and late relapses occur over the course of treatment, and many patients with PD-L1-expressing tumors do not respond to PD-(L)1 blockade. In addition, while some malignancies exhibit inherent resistance to treatment, others develop adaptations that allow them to evade antitumor immunity after a period of response. It is crucial to understand the pathophysiology of the tumor-immune system interplay and the mechanisms of immune escape in order to circumvent primary and acquired resistance. Here we provide an outline of the most well-defined mechanisms of resistance and shed light on ongoing efforts to reinvigorate immunoreactivity.

Targeting androgen signaling in ILC2s protects from IL-33-driven lung inflammation, independently of KLRG1

BACKGROUND

Allergic asthma is more severe and frequent in women than in men. In male mice, androgens negatively control group 2 innate lymphoid cell (ILC2) development and function by yet unknown mechanisms.

OBJECTIVES

We sought to investigate the impact of androgen on ILC2 homeostasis and IL-33-mediated inflammation in female lungs. We evaluated the role of androgen receptor (AR) signaling and the contribution of the putative inhibitory receptor killer cell lectin-like receptor G1 (KLRG1).

METHODS

Subcutaneous pellets mimicking physiological levels of androgen were used to treat female mice together with mice expressing a reporter enzyme under the control of androgen response elements and mixed bone marrow chimeras to assess the cell-intrinsic role of AR activation within ILC2s. We generated KLRG1-deficient mice.

RESULTS

We established that lung ILC2s express a functionally active AR that can be in vivo targeted with exogenous androgens to negatively control ILC2 homeostasis, proliferation, and function. Androgen signaling upregulated KLRG1 on ILC2s, which inhibited their proliferation on E-cadherin interaction. Despite evidence that KLRG1 impaired the competitive fitness of lung ILC2s during inflammation, KLRG1 deficiency neither alters in vivo ILC2 numbers and functions, nor did it lead to hyperactive ILC2s in either sexes.

CONCLUSIONS

AR agonists can be used in vivo to inhibit ILC2 homeostatic numbers and ILC2-dependent lung inflammation through cell-intrinsic AR activation. Although androgen signals in ILC2s to upregulate KLRG1, we demonstrate that KLRG1 is dispensable for androgen-mediated inhibition of pulmonary ILC2s.

Key Activating and Inhibitory Ligands Involved in the Mobilization of Natural Killer Cells for Cancer Immunotherapies

Natural killer (NK) cells are the most potent arm of the innate immune system and play an important role in immunity, alloimmunity, autoimmunity, and cancer. NK cells recognize “altered-self” cells due to oncogenic transformation or stress due to viral infection and target to kill them. The effector functions of NK cells depend on the interaction of the activating and inhibitory receptors on their surface with their cognate ligand expressed on the target cells. These activating and inhibitory receptors interact with major histocompatibility complex I (MHC I) expressed on the target cells and make decisions to mount an immune response. NK cell immune response includes cytolytic activity and secretion of cytokines to help with the ongoing immune response. The advancement of our knowledge on the expression of inhibitory and activating molecules led us to exploit these molecules in the treatment of cancer. This review discusses the importance of activating and inhibitory receptors on NK cells and their clinical importance in cancer immunotherapy.

Sex hormone regulation of innate lymphoid cells

Innate lymphoid cell (ILC) subsets at barrier surfaces contribute to maintain tissue homeostasis and appropriate responses to infection. ILCs respond to environmental factors produced by non-hematopoietic cells within tissues, but also circulating cytokines or dietary compounds which allow them to adapt to organ milieu. Among these extrinsic signals, evidence is emerging that sex steroid hormones may act in a cell-intrinsic manner to regulate the development, maintenance in tissues and effector functions of specific subsets of ILCs. Understanding the nature and molecular mechanisms of sex steroid hormone actions on ILCs is important to unravel the cause of sexual disparity in human diseases and could lead to new drug development for the treatment of chronic inflammatory diseases or cancers. This review discusses the recent development in our understanding of the cell-intrinsic actions of sex steroid hormones on ILCs and their consequences on tissue-specific immunity with a particular focus on group 2 innate lymphoid cells and NK cells.

Overview of Immunological Responses and Immunomodulation Properties of Trichuris sp.: Prospects for Better Understanding Human Trichuriasis

Trichuris sp. infection has appeared as a pathological burden in the population, but the immunomodulation features could result in an opportunity to discover novel treatments for diseases with prominent inflammatory responses. Regarding the immunological aspects, the innate immune responses against Trichuris sp. are also responsible for determining subsequent immune responses, including the activation of innate lymphoid cell type 2 (ILC2s), and encouraging the immune cell polarization of the resistant host phenotype. Nevertheless, this parasite can establish a supportive niche for worm survival and finally avoid host immune interference. Trichuris sp. could skew antigen recognition and immune cell activation and proliferation through the generation of specific substances, called excretory/secretory (ESPs) and soluble products (SPs), which mainly mediate its immunomodulation properties. Through this review, we elaborate and discuss innate–adaptive immune responses and immunomodulation aspects, as well as the clinical implications for managing inflammatory-based diseases, such as inflammatory bowel diseases, allergic, sepsis, and other autoimmune diseases.

Cadherin-mediated host-pathogen interactions

Cell adhesion molecules mediate cell-to-cell and cell-to-matrix adhesions and play an immense role in a myriad of physiological processes during the growth and development of a multicellular organism. Cadherins belong to a major group of membrane-bound cell surface proteins that, in coordination with nectins, drive the formation and maintenance of adherens junctions for mediating cell to cell adhesion, cellular communication and signalling. Alongside adhesive function, the involvement of cadherins in mediating host-pathogen interactions has been extensively explored in recent years. In this review, we provide an in-depth understanding of microbial pathogens and their virulence factors that exploit cadherins for their strategical invasion into the host cell. Furthermore, macromolecular interactions involving cadherins and various microbial factors such as secretory toxins and adhesins lead to the disintegration of host cell junctions followed by the entry of the pathogen or triggering downstream signalling pathways responsible for successful invasion of the pathogenic microbes are discussed. Besides providing a comprehensive insight into some of the structural complexes involving cadherins and microbial factors to offer the mechanistic details of host-pathogen interactions, the current review also highlights novel constituents of various cell signalling events such as endocytosis machinery elicited upon microbial infections.

T cell markers recount the course of immunosenescence in healthy individuals and chronic kidney disease

Aging results in substantial changes in almost all cellular subpopulations within the immune system, including functional and phenotypic alterations. T lymphocytes, as the main representative population of cellular immunity, have been extensively studied in terms of modifications and adjustments during aging. Phenotypic alterations are attributed to three main mechanisms; a reduction of naïve T cell population with a shift to more differentiated forms, a subsequent oligoclonal expansion of naïve T cells characterized by repertoire restriction, and replicative insufficiency after repetitive activation. These changes and the subsequent phenotypic disorders are comprised in the term "immunosenescence". Similar changes seem to occur in chronic kidney disease, with T cells of young patients resembling those of healthy older individuals. A broad range of surface markers can be utilized to identify immunosenescent T cells. In this review, we will discuss the most important senescence markers and their potential connection with impaired renal function.

E-Cadherin in Pancreatic Ductal Adenocarcinoma: A Multifaceted Actor during EMT

Epithelial-to-mesenchymal transition (EMT) is a step-wise process observed in normal and tumor cells leading to a switch from epithelial to mesenchymal phenotype. In tumors, EMT provides cancer cells with a metastatic phenotype characterized by E-cadherin down-regulation, cytoskeleton reorganization, motile and invasive potential. E-cadherin down-regulation is known as a key event during EMT. However, E-cadherin expression can be influenced by the different experimental settings and environmental stimuli so that the paradigm of EMT based on the loss of E-cadherin determining tumor cell behavior and fate often becomes an open question. In this review, we aimed at focusing on some critical points in order to improve the knowledge of the dynamic role of epithelial cells plasticity in EMT and, specifically, address the role of E-cadherin as a marker for the EMT axis.

NK cell-based therapeutics for lung cancer

Introduction: Lung cancer is a devastating disease with poor overall survival. Despite significant advances in the treatment of lung cancers using radiochemotherapy, targeted therapies and/or immune therapies prognosis remains poor. The capacity of natural killer (NK) cells to provide a first line of defense that can bridge and orchestrate innate and 'downstream' adaptive immune responses renders them to be an ideal platform on which to base new cancer therapeutics.Areas covered: We provide an overview of the mechanisms controlling the effector functions of NK cells, tumor-directed immune escape, the impact and influence of NK cells on the development of effective, protective anti-tumor immunity and the therapeutic potential of combined cytokine-, complement-dependent- and antibody-dependent cellular cytotoxicity (CDC/ADCC), NK-92-, KIR mismatch- and CAR-NK cell-based therapies.Expert opinion: Despite promising results of immuno-oncological approaches, a relevant proportion of patients do not profit from these therapies, partly due to an ineffective NK cell activation, a lack of tumor-specific NK cells, an upregulated expression of checkpoint pathways, and a low mutational burden, which hinders the development of long-term adaptive immunity. Strategies that re-activate NK cells in combination with other therapies are therefore likely to be beneficial for the clinical outcome of patients with lung cancer.Abbreviations: ADCC: antibody-dependent cell-mediated cytotoxicity; ALK: anaplastic lymphoma kinase; CAR: chimeric antigen receptor; CDC: complement-dependent cytotoxicity; CEACAM-1: carcinoembryonic antigen-related cell adhesion molecule 1; DC: dendritic cell; DNAM: activating, maturation receptor; EGFR, epidermal growth factor receptor; EMT: epithelial-to-mesenchymal transition; EpCAM: epithelial cell adhesion molecule; GM-CSF: granulocyte monocyte colony stimulating factor; HIF: hypoxia inducible factor; IDO, indoleamine 2,3-dioxygenase; IFN: interferon; IL: interleukin; ITIM/ITAM: immune tyrosine-based inhibitory/activatory motif; KIR: killer cell immunoglobulin-like receptor; LAG-3: lymphocyte activation gene 3; MDSC: myeloid derived suppressor cells; MICA/B: MHC class I-related proteins A/B; MHC: major histocompatibility complex; mTOR: mechanistic target of rapamycin; NCAM: neuronal adhesion molecule; NCR: natural cytotoxicity receptor; NK: natural killer; NSCLC: non-small cell lung cancer; PD-1: programmed cell death 1; PS: phosphatidylserine; SCLC: small cell lung cancer; STAT: signal transducer and activator of transcription; TAM: tumor-associated M2 macrophages; TCR: T cell receptor; TIGIT: T cell immunoglobulin and ITIM domain; Tim-3: T cell immunoglobulin- and mucin domain-containing 3; TNF: tumor necrosis factor; ULBP: UL16-binding protein.

Co-inhibitory T cell receptor KLRG1: human cancer expression and efficacy of neutralization in murine cancer models

Background

KLRG1 is a lymphocyte co-inhibitory, or immune checkpoint, receptor expressed predominantly on late-differentiated effector and effector memory CD8+ T and NK cells. Targeting of KLRG1 neutralization in murine cancer models has not previously been reported.

Methods

We studied KLRG1 expression in human blood and tumor samples from available genomic datasets. Anti-KLRG1 neutralizing antibody was studied in the murine 4T1 breast cancer as monotherapy, and in the MC38 colon cancer and B16F10 melanoma models as combination therapy with anti-PD-1 antibody.

Results

In human blood and tumor samples, KLRG1 expression is aligned with cytotoxic T and NK cell differentiation, and upregulated in human tumor samples after a variety of therapies, potentially contributing to adaptive resistance. In in vivo murine models, anti-KLRG1 antibody monotherapy in the 4T1 breast cancer model reduced lung metastases (decreased lung weights p=0.04; decreased nodule count p=0.002), while anti-KLRG1 + anti-PD-1 combination therapy in the MC38 colon cancer and B16F10 melanoma models produced synergistic benefit greater than anti-PD-1 alone for tumor volume (MC38 p=0.01; B16F10 p=0.007) and survival (MC38 p=0.02; B16F10 p=0.002).

Conclusions

These studies provide the first evidence that inhibition of the KLRG1 pathway enhances immune control of cancer in murine models, and provide target validation for KLRG1 targeting of human cancer. The mechanism of efficacy of KLRG1 blockade in murine models remains to be determined.

Adhesive Interactions Delineate the Topography of the Immune Synapse

T cells form adhesive contacts with antigen-presenting cells (APCs) as part of the normal surveillance process that occurs in lymph nodes and other tissues. Most of these adhesive interactions are formed by integrins that interact with ligands expressed on the surface of the APC. The interactive strength of integrins depends on their degree of membrane proximity as well as intracellular signals that dictate the conformation of the integrin. Integrins appear in different conformations that endow them with different affinities for their ligand(s). Integrin conformation and thus adhesive strength between the T cell and the APC is tuned by intracellular signals that are turned on by ligation of the T cell receptor (TCR) and chemokine receptors. During the different stages of the process, integrins, the TCR and chemokine receptors may be interconnected by the actin cytoskeleton underneath the plasma membrane, forming a chemical and physical network that facilitates the spatiotemporal dynamics, positioning, and function of these receptors and supports cell-cell adhesion during T cell activation, allowing it to perform its effector function.

Heterocellular cadherin connections: coordinating adhesive cues in homeostasis and cancer

This short insight covers some of the recent topics relevant to the field of cadherin-catenin adhesion in mediating connections between different cell types, so-called heterotypic or heterocellular connections, in both homeostasis and cancer. These scientific discoveries are increasing our understanding of how multiple cells residing in complex tissues can be instructed by cadherin adhesion receptors to regulate tissue architecture and function and how these cadherin-mediated heterocellular connections spur tumor growth and the acquisition of malignant characteristics in tumor cells. Overall, the findings that have emerged over the past few years are elucidating the complexity of the functional roles of the cadherin-catenin complexes. Future exciting research lies ahead in order to understand the physical basis of these heterotypic interactions and their influence on the behavior of heterogeneous cellular populations as well as their roles in mediating phenotypic and genetic changes as cells evolve through complex environments during morphogenesis and cancer.

A 3'UTR polymorphism marks differential KLRG1 mRNA levels through disruption of a miR-584-5p binding site and associates with pemphigus foliaceus susceptibility

Genetic variations mapping to 3' untranslated regions (3'UTRs) may overlap with microRNA (miRNA) binding sites, therefore potentially interfering with translation inhibition or messenger RNA (mRNA) degradation. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) located within the 3'UTRs of six candidate genes and predicted to interfere with miRNA ligation could account for disease-relevant differential mRNA levels. Focusing on pemphigus foliaceus (PF) - an autoimmune blistering skin condition with unique endemic patterns - we investigated whether nine 3'UTR SNPs from the CD1D, CTLA4, KLRD1, KLRG1, NKG7, and TNFSF13B genes differentially expressed in PF were disease-associated. The heterozygous genotype of the KLRG1 rs1805672 polymorphism was associated with increased predisposition to PF (A/G vs. A/A: P=0.038; OR=1.60), and a trend for augmented susceptibility was observed for carriers of the G allele (P=0.094; OR=1.44). In silico analyses suggested that rs1805672 G allele could disrupt binding of miR-584-5p, and indicated rs1805672 as an expression Quantitative Trait Locus (eQTL), with an effect on KLRG1 gene expression. Dual-luciferase assay showed that miR-584-5p mediated approximately 50% downregulation of the reporter gene's activity through the 3'UTR of KLRG1 harboring rs1805672 A allele (vs. miRNA-negative condition, P=0.006). This silencing relationship was lost after site-directed mutation to G allele (vs. miRNA-negative condition, P=0.391; vs. rs1805672 A allele, P=0.005). Collectively, these results suggest that a disease-associated SNP located within the 3'UTR of KLRG1 directly interferes with miR-584-5p binding, allowing for KLRG1 mRNA differential accumulation, which in turn may contribute to pathogenesis of autoimmune diseases, such as pemphigus.

Cadherin 6 has a functional role in platelet aggregation and thrombus formation

OBJECTIVE

Thrombosis occurs at sites of vascular injury when platelets adhere to subendothelial matrix proteins and to each other. Platelets express many surface receptor proteins, the function of several of these remains poorly characterized. Cadherin 6 is expressed on the platelet surface and contains an arginine-glycine-aspartic acid motif, suggesting that it might have a supportive role in thrombus formation. The aim of this study was to characterize the role of cadherin 6 in platelet function.

METHODS AND RESULTS

Platelet aggregation was inhibited by both antibodies and exogenous soluble cadherin 6. Platelet adhesion to immobilized cadherin 6 was inhibited by arginine-glycine-aspartic acid-serine tetrapeptides. Antibodies to α(IIb)β(3) inhibited platelet adhesion to cadherin 6. Because platelet aggregation occurs in fibrinogen and von Willebrand factor double-deficient mice, we investigated whether cadherin 6 is an alternative ligand for the integrin α(IIb)β(3). Platelet aggregation in fibrinogen and von Willebrand factor double-deficient mice was significantly inhibited by an antibody to cadherin 6. In flow-based assays, inhibition of cadherin 6 caused a marked reduction in thrombus formation in both human and mouse blood.

CONCLUSIONS

This study demonstrates the role of cadherin 6 as a novel ligand for α(IIb)β(3) and highlights its function in thrombus formation.

Regulation and function of the E-cadherin/catenin complex in cells of the monocyte-macrophage lineage and DCs

E-cadherin is best characterized as adherens junction protein, which through homotypic interactions contributes to the maintenance of the epithelial barrier function. In epithelial cells, the cytoplasmic tail of E-cadherin forms a dynamic complex with catenins and regulates several intracellular signal transduction pathways, including Wnt/β-catenin, PI3K/Akt, Rho GTPase, and NF-κB signaling. Recent progress uncovered a novel and critical role for this adhesion molecule in mononuclear phagocyte functions. E-cadherin regulates the maturation and migration of Langerhans cells, and its ligation prevents the induction of a tolerogenic state in bone marrow-derived dendritic cells (DCs). In this respect, the functionality of β-catenin could be instrumental in determining the balance between immunogenicity and tolerogenicity of DCs in vitro and in vivo. Fusion of alternatively activated macrophages and osteoclasts is also E-cadherin-dependent. In addition, the E-cadherin ligands CD103 and KLRG1 are expressed on DC-, T-, and NK-cell subsets and contribute to their interaction with E-cadherin-expressing DCs and macrophages. Here we discuss the regulation, function, and implications of E-cadherin expression in these central orchestrators of the immune system.

Fine-mapping of prostate cancer aggressiveness loci on chromosome 7q22-35

BACKGROUND

Deciphering the genetic basis of prostate cancer aggressiveness could provide valuable information for the screening and treatment of this common but complex disease. We previously detected linkage between a broad region on chromosome 7q22-35 and Gleason score-a strong predictor of prostate cancer aggressiveness. To further clarify this finding and focus on the potentially causative gene, we undertook a fine-mapping study across the 7q22-35 region.

METHODS

Our study population encompassed 698 siblings diagnosed with prostate cancer. 3,072 single nucleotide polymorphisms (SNPs) spanning the chromosome 7q22-35 region were genotyped using the Illumina GoldenGate assay. The impact of SNPs on Gleason scores were evaluated using affected sibling pair linkage and family-based association tests.

RESULTS

We confirmed the previous linkage signal and narrowed the 7q22-35 prostate cancer aggressiveness locus to a 370 kb region. Centered under the linkage peak is the gene KLRG2 (killer cell lectin-like receptor subfamily G, member 2). Association tests indicated that the potentially functional non-synonymous SNP rs17160911 in KLRG2 was significantly associated with Gleason score (P = 0.0007).

CONCLUSIONS

These findings suggest that genetic variants in the gene KLRG2 may affect Gleason score at diagnosis and hence the aggressiveness of prostate cancer.

E-cadherin expression on human carcinoma cell affects trastuzumab-mediated antibody-dependent cellular cytotoxicity through killer cell lectin-like receptor G1 on natural killer cells

Trastuzumab is a recombinant antibody drug that is widely used for the treatment of HER2-overexpressing breast carcinoma. Despite encouraging clinical results, many HER2-overexpressing carcinomas are primarily resistant to trastuzumab. We attempted to explain trastuzumab resistance and search for solutions. Since the killer cell lectin-like receptor G1 (KLRG1), an inhibitory receptor expressed on subsets of natural killer (NK) cells recognizes E-cadherin as ligands and may inhibit immune responses by regulating the effector function of NK cells, we used HER2-overexpressing carcinoma cells which were expressing E-cadherin to investigate the role of antibody-dependent cellular cytotoxicity (ADCC) through KLRG1 on NK cells in vitro and vivo. The results indicated that HER2-overexpressing carcinoma cells were killed by trastuzumab-mediated ADCC and the ADCC activity was reflected the degree of E-cadherin expression on carcinoma cells. We found that expression of E-cadherin was shown to be a predictor of response to trastuzumab-based treatment for HER2-overexpressing carcinomas, furthermore, trastuzumab-mediated ADCC was markedly enhanced by KLRG1-negative peripheral blood mononuclear cells (PBMCs(KLRG1(-))).

A protocol for the production of KLRG1 tetramer

Killer cell lectin-like receptor G1 (KLRG1) is a type II transmembrane glycoprotein inhibitory receptor belonging to the C type lectin-like superfamily. KLRG1 exists both as a monomer and as a disulfide-linked homodimer. This well-conserved receptor is found on the most mature and recently activated NK cells as well as on a subset of effector/memory T cells. Using KLRG1 tetramer as well as other methods, E-, N-, and R-cadherins were identified as KLRG1 ligands. These Ca(2+)-dependent cell-cell adhesion molecules comprises of an extracellular domain containing five cadherin repeats responsible for cell-cell interactions, a transmembrane domain and a cytoplasmic domain that is linked to the actin cytoskeleton. Generation of the KLRG1 tetramer was essential to the identification of the KLRG1 ligands. KLRG1 tetramer is also a unique tool to elucidate the roles cadherin and KLRG1 play in regulating the immune response and tissue integrity.