Phenotypic and functional characteristics of blood natural killer cells from melanoma patients at different clinical stages

Identification of Natural Killer Cell-Associated Clusters in Skin Melanoma and the Impact on Prognosis and Drug Sensitivity

BACKGROUND

Skin melanoma exhibits significant heterogeneity in clinical outcomes and treatment responses among patients. This study aimed to investigate natural killer (NK) cell clusters in skin melanoma, their impact on patient prognosis, and their value as biomarkers for tailoring treatment.

METHODS

We used data from TCGA, GSE19234, GSE65904, GSE244982, and GSE78220. A gene classifier was developed to identify two distinct clusters of melanoma patients. Survival analysis, NK cell infiltration levels, and responses to immune and targeted therapies were evaluated.

RESULTS

Unsupervised clustering revealed two distinct melanoma patient clusters with significant differences in NK cell activity and clinical outcomes. Cluster 1 showed higher NK cell infiltration, better overall survival (OS) (p < 0.0001), and greater activity in NK-cell-related pathways. In contrast, Cluster 2, characterized by lower NK cell activity and higher exhaustion markers, had poorer OS. Drug sensitivity analysis indicated that Cluster 1 was more responsive to most melanoma treatments, whereas Cluster 2 had higher sensitivity to trametinib (p < 0.001). The developed gene classifier had an AUC of 0.913 and effectively differentiated between clusters. Additionally, Cluster 1 showed better responses to immunotherapy with a higher rate of complete and partial responses (p < 0.001). These findings were validated in external databases.

CONCLUSION

This study identifies two distinct NK-cell-related clusters in melanoma with differential prognoses and treatment responses. These findings underscore the importance of integrating NK-cell-related profiles into personalized treatment strategies, offering a pathway to optimize therapeutic outcomes based on specific immune profiles.

The diversity of natural killer cell functional and phenotypic states in cancer

The role of natural killer (NK) cells as immune effectors is well established, as is their utility as immunotherapeutic agents against various cancers. However, NK cells' anti-cancer roles are suppressed in cancer patients by various immunomodulatory mechanisms which alter these cells' identity, function, and potential for immunosurveillance. This manifests in abnormal NK cell responses accompanied by changes in phenotypic or genotypic identity, giving rise to specific NK cell subsets that are either hypofunctional or, more broadly, defective in their responses. Anergy, senescence, and exhaustion are some of the terms that have been used to define and characterize these NK cell functional states. These responses vary not only with cancer type but also NK cell location within tissues. Collectively, these phenomena suggest a highly plastic nature of NK cell biology in tumors. In this review, we present and discuss a summary of these functionally distinct states and provide an overview of how NK cells behave at different locations within the context of cancer.

Tumor-infiltrating lymphocytes in melanoma: from prognostic assessment to therapeutic applications

Malignant melanoma, the most aggressive form of skin cancer, is characterized by unpredictable growth patterns, and its mortality rate has remained alarmingly high over recent decades, despite various treatment approaches. One promising strategy for improving outcomes in melanoma patients lies in the early use of biomarkers to predict prognosis. Biomarkers offer a way to gauge patient outlook early in the disease course, facilitating timely, targeted intervention. In recent years, considerable attention has been given to the immune response's role in melanoma, given the tumor's high immunogenicity and potential responsiveness to immunologic treatments. Researchers are focusing on identifying predictive biomarkers by examining both cancer cell biology and immune interactions within the tumor microenvironment (TME). This approach has shed light on tumor-infiltrating lymphocytes (TILs), a type of immune cell found within the tumor. TILs have emerged as a promising area of study for their potential to serve as both a prognostic indicator and therapeutic target in melanoma. The presence of TILs in melanoma tissue can often signal a positive immune response to the cancer, with numerous studies suggesting that TILs may improve patient prognosis. This review delves into the prognostic value of TILs in melanoma, assessing how these immune cells influence patient outcomes. It explores the mechanisms through which TILs interact with melanoma cells and the potential clinical applications of leveraging TILs in treatment strategies. While TILs present a hopeful avenue for prognostication and treatment, there are still challenges. These include understanding the full extent of TIL dynamics within the TME and overcoming limitations in TIL-based therapies. Advancements in TIL characterization methods are also critical to refining TIL-based approaches. By addressing these hurdles, TIL-focused research may pave the way for improved diagnostic and therapeutic options, ultimately offering better outcomes for melanoma patients.

Vaccination with a combination of STING agonist-loaded lipid nanoparticles and CpG-ODNs protects against lung metastasis via the induction of CD11bhighCD27low memory-like NK cells

BACKGROUND

Natural killer (NK) cells are effective in attacking tumor cells that escape T cell attack. Memory NK cells are believed to function as potent effector cells in cancer immunotherapy. However, knowledge of their induction, identification, and potential in vivo is limited. Herein, we report on the induction and identification of memory-like NK cells via the action of a combination of a stimulator of interferon genes (STING) agonist loaded into lipid nanoparticles (STING-LNPs) and cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG-ODNs), and the potential of the inducted memory-like NK cells to prevent melanoma lung metastasis.

METHODS

The antitumor effects of either the STING-LNPs, CpG-ODNs, or the combination therapy were evaluated using a B16-F10 lung metastasis model. The effect of the combined treatment was evaluated by measuring cytokine production. The induction of memory-like NK cells was demonstrated via flow cytometry and confirmed through their preventative effect.

RESULTS

The combination of STING-LNPs and CpG-ODNs tended to enhance the production of interleukin 12 (IL-12) and IL-18, and exerted a therapeutic effect against B16-F10 lung metastasis. The combination therapy increased the population of CD11bhighCD27low NK cells. Although monotherapies failed to show preventative effects, the combination therapy induced a surprisingly strong preventative effect, which indicates that CD11bhighCD27low cells could be a phenotype of memory-like NK cells.

CONCLUSION

As far as could be ascertained, this is the first report of the in vivo induction, identification, and confirmation of a phenotype of the memory-like NK cells through a prophylactic effect via the use of an immunotherapeutic drug. Our findings provide novel insights into the in vivo induction of CD11bhighCD27low memory-like NK cells thus paving the way for the development of efficient immunotherapies.

The nexus of natural killer cells and melanoma tumor microenvironment: crosstalk, chemotherapeutic potential, and innovative NK cell-based therapeutic strategies

The metastasis of melanoma cells to regional lymph nodes and distant sites is an important contributor to cancer-related morbidity and mortality among patients with melanoma. This intricate process entails dynamic interactions involving tumor cells, cellular constituents, and non-cellular elements within the microenvironment. Moreover, both microenvironmental and systemic factors regulate the metastatic progression. Central to immunosurveillance for tumor cells are natural killer (NK) cells, prominent effectors of the innate immune system with potent antitumor and antimetastatic capabilities. Recognizing their pivotal role, contemporary immunotherapeutic strategies are actively integrating NK cells to combat metastatic tumors. Thus, a meticulous exploration of the interplay between metastatic melanoma and NK cells along the metastatic cascade is important. Given the critical involvement of NK cells within the melanoma tumor microenvironment, this comprehensive review illuminates the intricate relationship between components of the melanoma tumor microenvironment and NK cells, delineating their multifaceted roles. By shedding light on these critical aspects, this review advocates for a deeper understanding of NK cell dynamics within the melanoma context, driving forward transformative strategies to combat this cancer.

An increase in regulatory T cells in peripheral blood correlates with an adverse prognosis for malignant melanoma patients - A study of T cells and natural killer cells

Malignant melanoma is a highly immunogenic tumour, and the immune profile significantly influences cancer development and response to immunotherapy. The peripheral immune profile may identify high risk patients. The current study showed reduced levels of CD4+ T cells and increased levels of CD8+ T cells in peripheral blood from malignant melanoma patients compared with controls. Percentages of peripheral CD56dimCD16+ NK cells were reduced and CD56brightCD16-KIR3+ NK cells were increased in malignant melanoma patients. Late stage malignant melanoma was correlated with low levels of CD4+ T cells and high levels of CD56brightCD16-KIR3+ NK cells. Finally, high levels of Tregs in peripheral blood were correlated with poor overall survival and disease-free survival. The results indicate that changes in specific immune cell subsets in peripheral blood samples from patients at the time of diagnosis may be potential biomarkers for prognosis and survival. Further studies will enable clarification of independent roles in tumour pathogenesis.

Increased circulating monocyte MDSCs positively correlate with serum Interleukin-10 in metastatic melanoma patients

Numerous immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs) and inhibitory cytokines identified in melanoma microenvironment have the important role in immune escape. Therefore, in this study we analyzed monocytic (m)MDSCs in peripheral blood of metastatic melanoma (MM) patients. In peripheral blood of 35 MM patients and 30 healthy controls we analyzed percentage of CD14 + HLA-DR- mMDSCs in monocyte gate and the mean fluorescence intensity of Foxp3 in CD25 + CD4 + regulatory T cells by Flow cytometry. Serum levels of transforming growth factor beta, interferon-gamma, interleukin (IL)-6, IL-8, IL-10 are measured by ELISA assays. In this study MM patients have significantly higher percentage of CD14 + HLA-DR- mMDSCs, as well as increased the baseline mMDSC/PBMC subset (NK, T, B cells, monocytes) ratio. Although there is no significant difference in the percentage of mMDSCs between groups of MM patients with different localization of distant metastasis, patients with elevated serum lactate dehydrogenase (LDH) have statistically significant higher percentage of these cells compared to LDH negative patients. Furthermore, in MM patients there is statistically significant positive correlation between values of IL-10 and the percentage of mMDSCs, only. Therefore, therapeutics that target circulating mMDSCs and IL-10 may have a big importance in the improvement of antitumor immunity in MM patients.

Receptors of immune cells mediates recognition for tumors

Over the last few decades, the immune system has been steered toward eradication of cancer cells with the help of cancer immunotherapy. T cells, B cells, monocytes/macrophages, dendritic cells, T-reg cells, and natural killer (NK) cells are some of the numerous immune cell types that play a significant part in cancer cell detection and reduction of inflammation, and the antitumor response. Briefly stated, chimeric antigen receptors, adoptive transfer and immune checkpoint modulators are currently the subjects of research focus for successful immunotherapy-based treatments for a variety of cancers. This chapter discusses ongoing investigations on the mechanisms and recent developments by which receptors of immune cells especially that of lymphocytes and monocytes/macrophages regulate the detection of immune system leading to malignancies. We will also be looking into the treatment strategies based on these mechanisms.

Back to the Future: Spatiotemporal Determinants of NK Cell Antitumor Function

NK cells play a crucial role in host protection during tumorigenesis. Throughout tumor development, however, NK cells become progressively dysfunctional through a combination of dynamic tissue-specific and systemic factors. While a number of immunosuppressive mechanisms present within the tumor microenvironment have been characterized, few studies have contextualized the spatiotemporal dynamics of these mechanisms during disease progression and across anatomical sites. Understanding how NK cell immunosuppression evolves in these contexts will be necessary to optimize NK cell therapy for solid and metastatic cancers. Here, we outline the spatiotemporal determinants of antitumor NK cell regulation, including heterogeneous tumor architecture, temporal disease states, diverse cellular communities, as well as the complex changes in NK cell states produced by the sum of these higher-order elements. Understanding of the signals encountered by NK cells across time and space may reveal new therapeutic targets to harness the full potential of NK cell therapy for cancer.

NK Cells in the Tumor Microenvironment as New Potential Players Mediating Chemotherapy Effects in Metastatic Melanoma

Until the last decade, chemotherapy was the standard treatment for metastatic cutaneous melanoma, even with poor results. The introduction of immune checkpoints inhibitors (ICIs) radically changed the outcome, increasing 5-year survival from 5% to 60%. However, there is still a large portion of unresponsive patients that would need further therapies. NK cells are skin-resident innate cytotoxic lymphocytes that recognize and kill virus-infected as well as cancer cells thanks to a balance between inhibitory and activating signals delivered by surface molecules expressed by the target. Since NK cells are equipped with cytotoxic machinery but lack of antigen restriction and needing to be primed, they are nowadays gaining attention as an alternative to T cells to be exploited in immunotherapy. However, their usage suffers of the same limitations reported for T cells, that is the loss of immunogenicity by target cells and the difficulty to penetrate and be activated in the suppressive tumor microenvironment (TME). Several evidence showed that chemotherapy used in metastatic melanoma therapy possess immunomodulatory properties that may restore NK cells functions within TME. Here, we will discuss the capability of such chemotherapeutics to: i) up-regulate melanoma cells susceptibility to NK cell-mediated killing, ii) promote NK cells infiltration within TME, iii) target other immune cell subsets that affect NK cells activities. Alongside traditional systemic melanoma chemotherapy, a new pharmacological strategy based on nanocarriers loaded with chemotherapeutics is developing. The use of nanotechnologies represents a very promising approach to improve drug tolerability and effectiveness thanks to the targeted delivery of the therapeutic molecules. Here, we will also discuss the recent developments in using nanocarriers to deliver anti-cancer drugs within the melanoma microenvironment in order to improve chemotherapeutics effects. Overall, we highlight the possibility to use standard chemotherapeutics, possibly delivered by nanosystems, to enhance NK cells anti-tumor cytotoxicity. Combined with immunotherapies targeting NK cells, this may represent a valuable alternative approach to treat those patients that do not respond to current ICIs.

Adoptive NK Cell Therapy: A Promising Treatment Prospect for Metastatic Melanoma

Simple Summary

The incidence of metastatic melanoma has been increasing over the past years with current therapies showing limited efficacy to cure the disease. Therefore, other options are being investigated, such as adoptive cell therapy (ACT) where activated immune cells are infused into a patient to attack melanoma. Natural killer (NK) cells are part of the innate immune system and extremely suitable for this kind of therapy since they show minimal toxicities in the clinical setting. In this review, we focus on current strategies for NK cell therapy and the development of new approaches that hold great promise for the treatment of advanced melanoma.

Abstract

Adoptive cell therapy (ACT) represents a promising alternative approach for patients with treatment-resistant metastatic melanoma. Lately, tumor infiltrating lymphocyte (TIL) therapy and chimeric antigen receptor (CAR)-T cell therapy have shown improved clinical outcome, compared to conventional chemotherapy or immunotherapy. Nevertheless, they are limited by immune escape of the tumor, cytokine release syndrome, and manufacturing challenges of autologous therapies. Conversely, the clinical use of Natural Killer (NK) cells has demonstrated a favorable clinical safety profile with minimal toxicities, providing an encouraging treatment alternative. Unlike T cells, NK cells are activated, amongst other mechanisms, by the downregulation of HLA class I molecules, thereby overcoming the hurdle of tumor immune escape. However, impairment of NK cell function has been observed in melanoma patients, resulting in deteriorated natural defense. To overcome this limitation, “activated” autologous or allogeneic NK cells have been infused into melanoma patients in early clinical trials, showing encouraging clinical benefit. Furthermore, as several NK cell-based therapeutics are being developed for different cancers, an emerging variety of approaches to increase migration and infiltration of adoptively transferred NK cells towards solid tumors is under preclinical investigation. These developments point to adoptive NK cell therapy as a highly promising treatment for metastatic melanoma in the future.

Memory-like Differentiation Enhances NK Cell Responses to Melanoma

PURPOSE

Treatment of advanced melanoma is a clinical challenge. Natural killer (NK) cells are a promising cellular therapy for T cell-refractory cancers, but are frequently deficient or dysfunctional in patients with melanoma. Thus, new strategies are needed to enhance NK-cell antitumor responses. Cytokine-induced memory-like (ML) differentiation overcomes many barriers in the NK-cell therapeutics field, resulting in potent cytotoxicity and enhanced cytokine production against blood cancer targets. However, the preclinical activity of ML NK against solid tumors remains largely undefined.

EXPERIMENTAL DESIGN

Phenotypic and functional alterations of blood and advanced melanoma infiltrating NK cells were evaluated using mass cytometry. ML NK cells from healthy donors (HD) and patients with advanced melanoma were evaluated for their ability to produce IFNγ and kill melanoma targets in vitro and in vivo using a xenograft model.

RESULTS

NK cells in advanced melanoma exhibited a decreased cytotoxic potential compared with blood NK cells. ML NK cells differentiated from HD and patients with advanced melanoma displayed enhanced IFNγ production and cytotoxicity against melanoma targets. This included ML differentiation enhancing melanoma patients' NK-cell responses against autologous targets. The ML NK-cell response against melanoma was partially dependent on the NKG2D- and NKp46-activating receptors. Furthermore, in xenograft NSG mouse models, human ML NK cells demonstrated superior control of melanoma, compared with conventional NK cells.

CONCLUSIONS

Blood NK cells from allogeneic HD or patients with advanced melanoma can be differentiated into ML NK cells for use as a novel immunotherapeutic treatment for advanced melanoma, which warrants testing in early-phase clinical trials.

Specific Patterns of Blood ILCs in Metastatic Melanoma Patients and Their Modulations in Response to Immunotherapy

Simple Summary

Anti-CTLA-4 and anti-PD-1 immune checkpoints inhibitors (ICI) have revolutionized the treatment of metastatic melanoma patients, leading to durable responses. However, some patients still not respond to this clinically used immunotherapies and there is a lack of biomarkers leading to the choice of first-line therapies. Innate lymphoid cells (ILC) express immune checkpoint receptors and are involved in anti-melanoma immune response. The aim of this article is to study ILCs from peripheral blood of melanoma patients receiving Ipilimumab, an anti-CTLA-4 treatment, and their association with clinical responses to this therapy. Our results show an impact of Ipilimumab on ILCs proportions and phenotype in blood. Moreover, the presence of anergic CD56^dimCD16⁻DNAM-1⁻ NK cells were associated with progression of the disease. These findings demonstrate the important role of ILC in the response to ICI.

Abstract

Immunotherapy targeting immune checkpoint receptors brought a breakthrough in the treatment of metastatic melanoma patients. However, a number of patients still resist these immunotherapies. Present on CD8⁺T cells, immune checkpoint receptors are expressed by innate lymphoid cells (ILCs), which may contribute to the clinical response. ILCs are composed of natural killer (NK) cells, which are cytotoxic effectors involved in tumor immunosurveillance. NK cell activation is regulated by a balance between activating receptors that detect stress molecules on tumor cells and HLA-I-specific inhibitory receptors. Helper ILCs (h-ILCs) are newly characterized ILCs that secrete cytokines and regulate the immune homeostasis of tissue. We investigated the modulation of blood ILCs in melanoma patients treated with ipilimumab. Circulating ILCs from metastatic stage IV melanoma patients and healthy donors were studied for their complete phenotypic status. Patients were studied before and at 3, 6, and 12 weeks of ipilimumab treatment. A comparison of blood ILC populations from donors and melanoma patients before treatment showed changes in proportions of ILC subsets, and a significant inverse correlation of CD56^dim NK cells and h-ILC subsets was identified in patients. During treatment with ipilimumab, percentages of all ILC subsets were reduced. Ipilimumab also impacted the expression of the CD96/TIGIT/DNAM-1 pathway in all ILCs and increased CD161 and CTLA-4 expression by h-ILCs. When considering the response to the treatment, patients without disease control were characterized by higher percentages of CD56^bright NK cells and ILC1. Patients with disease control displayed larger populations of activated CD56^dimCD16⁺ DNAM-1⁺ NK cells, while anergic CD56^dimCD16⁻DNAM-1⁻ NK cells were prominent in patients without disease control. These results provide original findings on the distribution of ILC subsets in advanced melanoma patients and their modulation through immunotherapy. The effects of ipilimumab on these ILC subsets may critically influence therapeutic outcomes. These data indicate the importance of considering these innate cell subsets in immunotherapeutic strategies for melanoma patients.

Targeting novel inhibitory receptors in cancer immunotherapy

T cells play a critical role in promoting tumor regression in both experimental models and humans. Yet, T cells that are chronically exposed to tumor antigen during cancer progression can become dysfunctional/exhausted and fail to induce tumor destruction. Such tumor-induced T cell dysfunction may occur via multiple mechanisms. In particular, immune checkpoint inhibitory receptors that are upregulated by tumor-infiltrating lymphocytes in many cancers limit T cell survival and function. Overcoming this inhibitory receptor-mediated T cell dysfunction has been a central focus of recent developments in cancer immunotherapy. Immunotherapies targeting inhibitory receptor pathways such as programmed cell death 1 (PD-1)/programmed death ligand 1 and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), alone or in combination, confer significant clinical benefits in multiple tumor types. However, many patients with cancer do not respond to immune checkpoint blockade, and dual PD-1/CTLA-4 blockade may cause serious adverse events, which limits its indications. Targeting novel non-redundant inhibitory receptor pathways contributing to tumor-induced T cell dysfunction in the tumor microenvironment may prove efficacious and non-toxic. This review presents preclinical and clinical findings supporting the roles of two key pathways-T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) and T cell immunoreceptor with Ig and ITIM domain (TIGIT)/CD226/CD96/CD112R-in cancer immunotherapy.

IL-6-induced CD39 expression on tumor-infiltrating NK cells predicts poor prognosis in esophageal squamous cell carcinoma

Natural killer (NK) cells, a predominant innate lymphocyte subset, mediates eradicating malignant cells. Purinergic signaling by ectonucleotidase CD39 can suppress T-cell response in caner. However, the role of CD39 in NK cells has not been fully elucidated. Here, we characterized CD39 expression on NK cells and its clinical relevance in esophageal squamous cell carcinoma (ESCC). Peripheral blood and tissue samples were collected from 36 ESCC patients. We observed that the proportion of NK cells significantly decreased but CD39 was obviously up-regulated on NK cells from cancerous tissues compared to paired peripheral blood in ESCC patients. Furthermore, tumor-infiltrating NK cells with high CD39 expression exhibited a phenotype of functional impairment. In vitro, conditioned media of ESCC cell lines could induce CD39 expression on peripheral NK cells from healthy donors. IL-6 was identified as the major cytokine produced by ESCC cell lines and also elevated in both tumor tissues and blood serum from ESCC patients. Recombinant IL-6 significantly induced surface CD39 expression in human NK cells, while IL-6-receptor antagonist tocilizumab prevented this effect. Finally, tumor-infiltrating CD39+ NK cells were correlated with poor prognosis in ESCC patients. Thus, tumor-derived IL-6 might impair NK cell functions through induction of CD39 expression. CD39+ NK cells may serve as a potential prognostic biomarker for ESCC patients.

Toward a Better Understanding of Bioassays for the Development of Biopharmaceuticals by Exploring the Structure-Antibody-Dependent Cellular Cytotoxicity Relationship in Human Primary Cells

Pharmaceutical manufacturing relies on rigorous methods of quality control of drugs and in particular of the physico-chemical and functional characterizations of monoclonal antibodies. To that end, robust bioassays are very often limited to reporter gene assays and the use of immortalized cell lines that are supposed to mimic immune cells such as natural killer (NK) cells to the detriment of primary materials, which are appreciated for their biological validity but are also difficult to exploit due to the great diversity between individuals. Here, we characterized the phenotype of the peripheral blood circulating cytotoxic cells of 30 healthy donors, in particular the repertoire of cytotoxic markers, using flow cytometry. In parallel, we characterized the antibody-dependent cellular cytotoxicity (ADCC) effector functions of these primary cells by measuring their cytolytic activity against a cancer cell-line expressing HER2 in the presence of trastuzumab and with regards to FCGR3A genotype. We could not establish a correlation or grouping of individuals using the data generated from whole peripheral blood mononuclear cells, however the isolation of the CD56-positive population, which is composed not only of NK cells but also of natural killer T (NKT) and γδ-T cells, as well as subsets of activated cytotoxic T cells, monocytes and dendritic cells, made it possible to standardize the parameters of the ADCC and enhance the overall functional avidity without however eliminating the inter-individual diversity. Finally, the use of primary CD56+ cells in ADCC experiments comparing glycoengineered variants of trastuzumab was conclusive to test the limits of this type of ex vivo system. Although the effector functions of CD56+ cells reflected to some extent the in vitro receptor binding properties and cytolytic activity data using NK92 cells, as previously published, reaching a functional avidity plateau could limit their use in a quality control framework.

PD-1 checkpoint blockade in advanced melanoma patients: NK cells, monocytic subsets and host PD-L1 expression as predictive biomarker candidates

Blockade of the PD-1 receptor has revolutionized the treatment of metastatic melanoma, with significant increases in overall survival (OS) and a dramatic improvement in patient quality of life. Despite the success of this approach, the number of benefitting patients is limited and there is a need for predictive biomarkers as well as a deeper mechanistic analysis of the cellular populations involved in clinical responses. With the aim to find predictive biomarkers for PD-1 checkpoint blockade, an in-depth immune monitoring study was conducted in 36 advanced melanoma patients receiving pembrolizumab or nivolumab treatment at Karolinska University Hospital. Blood samples were collected before treatment and before administration of the second and fourth doses. Peripheral blood mononuclear cells were isolated and stained for flow cytometric analysis within 2 h of sample collection. Overall survival and progression-free survival (PFS) were inversely correlated with CD69 expression NK cells. In the myeloid compartment, high frequencies of non-classical monocytes and low frequencies of monocytic myeloid derived suppressor cells (MoMDSCs) correlated with response rates and OS. A deeper characterization of monocytic subsets showed that PD-L1 expression in MDSCs, non-classical and intermediate monocytes was significantly increased in patients with shorter PFS in addition to correlating inversely with OS. Our results suggest that cellular populations other than T cells can be critical in the outcome of PD-1 blockade treatment. Specifically, the frequencies of activated NK cells and monocytic subsets are inversely correlated with survival and clinical benefit, suggesting that their role as predictive biomarkers should be further evaluated.

IL15 Stimulation with TIGIT Blockade Reverses CD155-mediated NK-Cell Dysfunction in Melanoma

PURPOSE

Natural killer (NK) cells play a critical role in tumor immunosurveillance. Multiple activating and inhibitory receptors (IR) regulate NK-cell-mediated tumor control. The IR T-cell immunoglobulin and ITIM domain (TIGIT) and its counter-receptor CD226 exert opposite effects on NK-cell-mediated tumor reactivity.

EXPERIMENTAL DESIGN

We evaluated the frequency, phenotype, and functions of NK cells freshly isolated from healthy donors and patients with melanoma with multiparameter flow cytometry. We assessed TIGIT and CD226 cell surface expression and internalization upon binding to CD155. We evaluated the role of IL15 and TIGIT blockade in increasing NK-cell-mediated cytotoxicity in vitro and in two mouse models.

RESULTS

NK cells are present at low frequencies in metastatic melanoma, are dysfunctional, and downregulate both TIGIT and CD226 expression. As compared with TIGIT^- NK cells, TIGIT⁺ NK cells exhibit higher cytotoxic capacity and maturation, but paradoxically lower cytotoxicity against CD155⁺ MHC class I-deficient melanoma cells. Membrane bound CD155 triggers CD226 internalization and degradation, resulting in decreased NK-cell-mediated tumor reactivity. IL15 increases TIGIT and CD226 gene expression by tumor-infiltrating NK cells (TiNKs) and, together with TIGIT blockade, increases NK-cell-mediated melanoma cytotoxicity in vitro and decreases tumor metastasis in two mouse melanoma models. Specific deletion of TIGIT on transferred NK cells enhances the antimetastatic activity of IL15, while CD226 blockade decreases the effects of IL15 and TIGIT blockade.

CONCLUSIONS

Our findings support the development of novel combinatorial immunotherapy with IL15 and TIGIT blockade to promote NK-cell-mediated destruction of MHC class I-deficient melanoma, which are refractory to CD8⁺ T-cell-mediated immunity.See related commentary by Pietra et al., p. 5274.

New avenues for melanoma immunotherapy: Natural Killer cells?

Human solid malignant tumours may be particularly resistant to conventional therapies. Among solid tumours, immunological features of cutaneous melanoma have been well characterized in the past and today melanoma patients are routinely treated with the anti-immune checkpoints immunotherapy that has completely changed metastatic melanoma treatment and prognosis. Two cytotoxic cell populations may lead to the physical elimination of tumour cell targets: cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Tumour recognition by CTLs depends on major histocompatibility complex (MHC) class I molecules, while NK cells recognize tumours expressing low or null levels of MHC class I molecules. Despite this well-established complementarity, NK cells are still left behind in the optimization of innovative immunotherapy approaches. NK cells are members of innate lymphoid cells (ILCs) that play a critical role in early host defence against invading pathogens and transformed cells. Recent findings suggest that NK cell frequencies directly correlate with the overall survival of ipilimumab-treated melanoma patients. Furthermore, in vitro and in vivo evidences indicate that NK cells can selectively kill cancer stem cells, reducing tumour size and delaying metastatic progression. The aim of this review is to provide a survey of the evidences indicating NK cells as an excellent candidate to complement the newest solid tumour immunotherapy approaches.

The Composition of Circulating Leukocytes Varies With Age and Melanoma Onset in the MeLiM Pig Biomedical Model

Immunological research in pigs benefits from many improvements with a direct impact on the veterinary control of pig husbandry and on biomedical models. We compiled the available knowledge to develop gating strategies to monitor simultaneously all blood immune cell types by multicolor flow cytometry in Melanoblastoma-bearing Libechov Minipigs (MeLiM). The MeLiM pig spontaneously develops cutaneous melanomas that regress few months later. We monitored lymphoid and myeloid cell subsets in 3 to 21 weeks old pigs. Interestingly, neutrophils, type III monocytes (CD163⁺ CD14⁺ MHC II^-) and CD4^- CD8α^- T cells are less abundant in oldest animals in contrast to eosinophils, type II monocytes (CD163^- CD14^low MHC II⁺), B cells, γδ T cells, CD4⁺ CD8α⁺ and CD4^- CD8α⁺ T cells. Melanoma occurrence led to changes in the blood cell composition. Higher proportions of NK cells, CD4⁺ and CD4⁺ CD8α⁺ T cells, and CD21^- B cells among B cells are found in young melanoma-bearing piglets, consistent with the immune-mediated spontaneous regression in the MeLiM model.

Discovery of specialized NK cell populations infiltrating human melanoma metastases

NK cells contribute to protective antitumor immunity, but little is known about the functional states of NK cells in human solid tumors. To address this issue, we performed single-cell RNA-seq analysis of NK cells isolated from human melanoma metastases, including lesions from patients who had progressed following checkpoint blockade. This analysis identified major differences in the transcriptional programs of tumor-infiltrating compared with circulating NK cells. Tumor-infiltrating NK cells represented 7 clusters with distinct gene expression programs indicative of significant functional specialization, including cytotoxicity and chemokine synthesis programs. In particular, NK cells from 3 clusters expressed high levels of XCL1 and XCL2, which encode 2 chemokines known to recruit XCR1+ cross-presenting DCs into tumors. In contrast, NK cells from 2 other clusters showed a higher level of expression of cytotoxicity genes. These data reveal key features of NK cells in human tumors and identify NK cell populations with specialized gene expression programs.

Effect of cytokines on NK cell activity and activating receptor expression in high-risk cutaneous melanoma patients

OBJECTIVE

Stage II melanoma patients have high risk for regional and distant metastases and may benefit from novel therapeutic strategies. To clarify the role of NK cells in Stage II melanoma, we characterized the cytotoxic activity of NK cells and the expression of various activating and inhibitory receptors in high-risk cutaneous melanoma patients (Stages IIB and IIC) compared to low-risk patients (Stage IA).

MATERIALS AND METHODS

Native and cytokine-treated peripheral blood mononuclear cells were used for functional and phenotypical analyses.

RESULTS

Compared to Stage IA-B patients, Stage IIB-C patients showed significantly decreased NK cell activity, as well as decreased expression of the activating NKG2D and CD161 receptors, most likely due to increased serum levels of the immunosuppressive cytokine TGF-β1 in these patients. Interestingly, treatment of periperal blood mononuclear cells with IFN-α, IL-2, IL-12 or the combination of IL-12 and IL-18 significantly induced NK cell activity for both groups of melanoma patients. However, only low-risk patients had a significant increase in the expression of the NKG2D receptor after in vitro treatment with IFN-α, as well as an significant increase in the expression of CD161 after treatment with IFN-α or IL-12. Although IL-2 induced the expression of NKG2D in both groups of patients, this increase was significantly lower in high-risk melanoma.

CONCLUSION

NK cell parameters may be useful as biomarkers of disease progression in localized melanoma patients. Our results further suggest that the use of NK cell-activating cytokines in combination with inhibitors of immunosuppressive factors like TGF-β1 could be a therapeutic option for the treatment of high-risk cutaneous melanoma patients.

In Vitro Killing of Colorectal Carcinoma Cells by Autologous Activated NK Cells is Boosted by Anti-Epidermal Growth Factor Receptor-induced ADCC Regardless of RAS Mutation Status

Treatment of advanced metastatic colorectal cancer (mCRC) patients is associated with a poor prognosis and significant morbidity. Moreover, targeted therapies such as anti-epidermal growth factor receptor (EGFR) have no effect in metastatic patients with tumors harboring a mutation in the RAS gene. The failure of conventional treatment to improve outcomes in mCRC patients has prompted the development of adoptive immunotherapy approaches including natural killer (NK)-based therapies. In this study, after confirmation that patients' NK cells were not impaired in their cytotoxic activity, evaluated against long-term tumor cell lines, we evaluated their interactions with autologous mCRC cells. Molecular and phenotypical evaluation of mCRC cells, expanded in vitro from liver metastasis, showed that they expressed high levels of polio virus receptor and Nectin-2, whereas UL16-binding proteins were less expressed in all tumor samples evaluated. Two different patterns of MICA/B and HLA class I expression on the membrane of mCRC were documented; approximately half of mCRC patients expressed high levels of these molecules on the membrane surface, whereas, in the remaining, very low levels were documented. Resting NK cells were unable to display sizeable levels of cytotoxic activity against mCRC cells, whereas their cytotoxic activity was enhanced after overnight or 5-day incubation with IL-2 or IL-15. The susceptibility of NK-mediated mCRC lysis was further significantly enhanced after coating with cetuximab, irrespective of their RAS mutation and HLA class I expression. These data open perspectives for combined NK-based immunotherapy with anti-epidermal growth factor receptor antibodies in a cohort of mCRC patients with a poor prognosis refractory to conventional therapies.

NKG2D/NKG2-Ligand Pathway Offers New Opportunities in Cancer Treatment

The antitumor functions of NK cells are regulated by the integration of positive and negative signals triggered by numerous membrane receptors present on the NK cells themselves. Among the main activating receptors, NKG2D binds several stress-induced molecules on tumor targets. Engagement of NKG2D by its ligands (NKG2D-Ls) induces NK cell activation leading to production of cytokines and target cell lysis. These effects have therapeutic potential as NKG2D-Ls are widely expressed by solid tumors, whereas their expression in healthy cells is limited. Here, we describe the genetic and environmental factors regulating the NKG2D/NKG2D-L pathway in tumors. NKG2D-L expression is linked to cellular stress and cell proliferation, and has been associated with oncogenic mutations. Tumors have been found to alter their to NKG2D-L expression as they progress, which interferes with the antitumor function of the pathway. Nevertheless, this pathway could be advantageously exploited for cancer therapy. Various cancer treatments, including chemotherapy and targeted therapies, indirectly interfere with the cellular and soluble forms of NKG2D-Ls. In addition, NKG2D introduced into chimeric antigen receptors in T- and NK cells is a promising tumor immunotherapy approach.

Circulating CD56bright NK cells inversely correlate with survival of melanoma patients

The roles of NK cells in human melanoma remain only partially understood. We characterized NK cells from peripheral blood ex vivo by flow cytometry obtained from late stage (III/IV) melanoma patients. Interestingly, we found that the abundance of CD56bright NK cells negatively correlate with overall patient survival, together with distant metastases, in a multivariate cox regression analysis. The patients' CD56bright NK cells showed upregulation of CD11a, CD38 and CD95 as compared to healthy controls, pointing to an activated phenotype as well as a possible immune regulatory role in melanoma patients. After stimulation in vitro, CD56bright NK cells produced less TNFα and GMCSF in patients than controls. Furthermore, IFNγ production by the CD56bright NK cells correlated inversely with overall survival. Our results highlight that abundance and function of CD56bright NK cells are associated with melanoma patient survival, emphasizing the potential of NK cell subsets for biomarker discovery and future therapeutic targeting.

CD56dim CD16- Natural Killer Cell Profiling in Melanoma Patients Receiving a Cancer Vaccine and Interferon-α

Natural killer (NK) cells are innate cytotoxic and immunoregulatory lymphocytes that have a central role in anti-tumor immunity and play a critical role in mediating cellular immunity in advanced cancer immunotherapies, such as dendritic cell (DC) vaccines. Our group recently tested a novel recombinant adenovirus-transduced autologous DC-based vaccine that simultaneously induces T cell responses against three melanoma-associated antigens for advanced melanoma patients. Here, we examine the impact of this vaccine as well as the subsequent systemic delivery of high-dose interferon-α2b (HDI) on the circulatory NK cell profile in melanoma patients. At baseline, patient NK cells, particularly those isolated from high-risk patients with no measurable disease, showed altered distribution of CD56^dim CD16⁺ and CD56^dim CD16⁻ NK cell subsets, as well as elevated serum levels of immune suppressive MICA, TN5E/CD73 and tactile/CD96, and perforin. Surprisingly, patient NK cells displayed a higher level of activation than those from healthy donors as measured by elevated CD69, NKp44 and CCR7 levels, and enhanced K562 killing. Elevated cytolytic ability strongly correlated with increased representation of CD56^dim CD16⁺ NK cells and amplified CD69 expression on CD56^dim CD16⁺ NK cells. While intradermal DC immunizations did not significantly impact circulatory NK cell activation and distribution profiles, subsequent HDI injections enhanced CD56^bright CD16⁻ NK cell numbers when compared to patients that did not receive HDI. Phenotypic analysis of tumor-infiltrating NK cells showed that CD56^dim CD16⁻ NK cells are the dominant subset in melanoma tumors. NanoString transcriptomic analysis of melanomas resected at baseline indicated that there was a trend of increased CD56^dim NK cell gene signature expression in patients with better clinical response. These data indicate that melanoma patient blood NK cells display elevated activation levels, that intra-dermal DC immunizations did not effectively promote systemic NK cell responses, that systemic HDI administration can modulate NK cell subset distributions and suggest that CD56^dim CD16⁻ NK cells are a unique non-cytolytic subset in melanoma patients that may associate with better patient outcome.

Circulating NKp46+ Natural Killer cells have a potential regulatory property and predict distinct survival in Non-Small Cell Lung Cancer

Natural killer (NK) cells are innate effector lymphocytes widely involved in cancer immunosurveillance. In this study, we described three circulating NK cell subsets in patients with non-small cell lung cancer (NSCLC). Compared to healthy donors (HD), lower rate of the cytotoxic CD56^dim CD16⁺ NK cells was found in NSCLC patients (76.1% vs 82.4%, P = 0.0041). In contrast, the rate of CD56^bright NK cells was similar between patients and HD. We showed in NSCLC patients a higher rate of a NK cell subset with CD56^dim CD16^- phenotype (16.7% vs 9.9% P = 0.0001). The degranulation property and cytokines production were mainly drive by CD56^dim CD16^- NK cell subset in patients. Analysis of natural cytotoxicity receptors (NCRs) expression identified four distinct clusters of patients with distinct NK cell subset profiles as compared to one major cluster in HD. Notably the cluster characterized by a low circulating level of NKp46⁺ NK cell subsets was absent in HD. We showed that the rate of circulating NKp46⁺ CD56^dim CD16⁺ NK cells influenced the patients' survival. Indeed, the median overall survival in patients exhibiting high versus low level of this NK cell subset was 16 and 27 months respectively (P = 0.02). Finally, we demonstrated that blocking NKp46 receptor in vitro was able to restore spontaneous tumor specific T cell responses in NSCLC patients. In conclusion, this study showed a distinct distribution and phenotype of circulating NK cell subsets in NSCLC. It also supports the regulatory role of NKp46⁺ NK cell subset in NSCLC patients.

Altered NKp30, NKp46, NKG2D, and DNAM-1 Expression on Circulating NK Cells Is Associated with Tumor Progression in Human Gastric Cancer

Natural killer (NK) cell activity is influenced by a complex integration of signaling pathways activated downstream of both activating and inhibitory surface receptors. The tumor microenvironment can suppress NK cell activity, and there is a great clinical interest in understanding whether modulating tumor-mediated NK cell suppression and/or boosting preexisting NK cell numbers in cancer patients is therapeutically viable. To this light, we characterized the surface receptor phenotypes of peripheral blood NK cells and examined their clinical relevance to human gastric cancer (GC). We found that the proportion of peripheral blood NK cells which expressed the activating receptors NKp30, NKp46, NKG2D, and DNAM-1 was significantly decreased in GC patients compared to healthy donors, and that this decrease was positively associated with tumor progression. At the same time, plasma TGF-β1 concentrations were significantly increased in GC patients and negatively correlated with the proportion of NKp30, NKp46, NKG2D, and DNAM-1 expressing NK cells. Furthermore, TGF-β1 significantly downregulated the expression of NKp30, NKp46, NKG2D, and DNAM-1 on NK cells in vitro, and the addition of galunisertib, an inhibitor of the TGF-β receptor subunit I, reversed this downregulation. Altogether, our data suggest that the decreased expression of activating receptors NKp30, NKp46, NKG2D, and DNAM-1 on peripheral blood NK cells is positively associated with GC progression, and that TGF-β1-mediated NK cell suppression may be a therapeutically targetable characteristic of GC.

Oncogenes in immune cells as potential therapeutic targets

The role of deregulated expression of oncogenes and tumor-suppressor genes in tumor development has been intensively investigated for decades. However, expression of oncogenes and their potential role in immune cell defects during carcinogenesis and tumor progression have not been thoroughly assessed. The defects in proto-oncogenes have been well documented and evaluated mostly in tumor cells, despite the fact that proto-oncogenes are expressed in all cells, including cells of the immune system. In this review, key studies from immune-mediated diseases that may be associated with oncogene signaling pathways are refocused to provide groundwork for beginning to understand the effects of oncogenes in and on the cancer-related immune system dysfunction.

Natural killer cell activity for IFN-gamma production as a supportive diagnostic marker for gastric cancer

BACKGROUND/AIM

Decreased Natural killer cell activity (NKA) for interferon-gamma production (NKA-IFNγ) has been reported in cancer patients. The aim of this study was to determine the diagnostic performance of NKA-IFNγ for gastric cancer (GC).

RESULTS

NKA-IFNγ levels were decreased in 261 GC patients with all stages of tumor compared to those in 48 healthy donors (P < 0.001), and lower levels of NKA-IFNγ were associated with higher GC stages. NKA-IFNγ levels were also associated with clinicopathological parameters including tumor size, depth of invasion, and lymph node metastasis. NKA-INFγ assay had better diagnostic value (AUC = 0.822) compared to serum CEA (0.624) or CA19-9 assay (0.566) (P < 0.001). Using different cut-off levels, serum CEA and CA19-9 showed sensitivities of 6.1-14.2% and 4.2-28.0%, respectively, which were much lower than that of NKA-IFNγ (55.6-66.7%).

METHODS

This study included 261 patients with newly diagnosed GC and 48 healthy donors. NKA for IFNγ was determined by enzyme immunoassay after incubation of whole blood, and diagnostic performance was evaluated.

CONCLUSIONS

NK cell activities for IFNγ production could be used as a supportive non-invasive tumor marker for GC diagnosis.

Patient's Natural Killer Cells in the Era of Targeted Therapies: Role for Tumor Killers

Natural killer (NK) cells are potent antitumor effectors, involved in hematological malignancies and solid tumor immunosurveillance. They infiltrate various solid tumors, and their numbers are correlated with good outcome. The function of NK cells extends their lytic capacities toward tumor cells expressing stress-induced ligands, through secretion of immunoregulatory cytokines, and interactions with other immune cells. Altered NK cell function due to tumor immune escape is frequent in advanced tumors; however, strategies to release the function of NK infiltrating tumors are emerging. Recent therapies targeting specific oncogenic mutations improved the treatment of cancer patients, but patients often relapse. The actual development consists in combined therapeutic strategies including agents targeting the proliferation of tumor cells and others restorating functional antitumor immune effectors for efficient and durable efficacy of anticancer treatment. In that context, we discuss the recent results of the literature to propose hypotheses concerning the potential use of NK cells, potent antitumor cytotoxic effectors, to design novel antitumor strategies.

Shifting the Balance of Activating and Inhibitory Natural Killer Receptor Ligands on BRAFV600E Melanoma Lines with Vemurafenib

Over 60% of human melanoma tumors bear a mutation in the BRAF gene. The most frequent mutation is a substitution at codon 600 (V600E), leading to a constitutively active BRAF and overactivation of the MAPK pathway. Patients harboring mutated BRAF respond to kinase inhibitors such as vemurafenib. However, these responses are transient, and relapses are frequent. Melanoma cells are efficiently lysed by activated natural killer (NK) cells. Melanoma cells express several stress-induced ligands that are recognized by activating NK-cell receptors. We have investigated the effect of vemurafenib on the immunogenicity of seven BRAF-mutated melanoma cells to NK cells and on their growth and sensitivity to NK-cell-mediated lysis. We showed that vemurafenib treatment modulated expression of ligands for two activating NK receptors, increasing expression of B7-H6, a ligand for NKp30, and decreasing expression of MICA and ULBP2, ligands for NKG2D. Vemurafenib also increased expression of HLA class I and HLA-E molecules, likely leading to higher engagement of inhibitory receptors (KIRs and NKG2A, respectively), and decreased lysis of vemurafenib-treated melanoma cell lines by cytokine-activated NK cells. Finally, we showed that whereas batimastat (a broad-spectrum matrix metalloprotease inhibitor) increased cell surface ULBP2 by reducing its shedding, vemurafenib lowered soluble ULBP2, indicating that BRAF signal inhibition diminished expression of both cell-surface and soluble forms of NKG2D ligands. Vemurafenib, inhibiting BRAF signaling, shifted the balance of activatory and inhibitory NK ligands on melanoma cells and displayed immunoregulatory effects on NK-cell functional activities. Cancer Immunol Res; 5(7); 582-93. ©2017 AACR.

Immune biomarkers for prognosis and prediction of responses to immune checkpoint blockade in cutaneous melanoma

Existing clinical, anatomopathological and molecular biomarkers fail to reliably predict the prognosis of cutaneous melanoma. Biomarkers for determining which patients receive adjuvant therapies are needed. The emergence of new technologies and the discovery of new immune populations with different prognostic values allow the immune network in the tumor to be better understood. Importantly, new molecules identified and expressed by immune cells have been shown to reduce the antitumor immune efficacy of therapies, prompting researchers to develop antibodies targeting these so-called "immune checkpoints", which have now entered the oncotherapeutic armamentarium.

Phenotypic and Functional Dysregulated Blood NK Cells in Colorectal Cancer Patients Can Be Activated by Cetuximab Plus IL-2 or IL-15

The clinical outcome of colorectal cancer (CRC) is associated with the immune response; thus, these tumors could be responsive to different immune therapy approaches. Natural killer (NK) cells are key antitumor primary effectors that can eliminate CRC cells without prior immunization. We previously determined that NK cells from the local tumor environment of CRC tumors display a profoundly altered phenotype compared with circulating NK cells from healthy donors (HD). In this study, we evaluated peripheral blood NK cells from untreated patients and their possible role in metastasis progression. We observed profound deregulation in receptor expression even in early stages of disease compared with HD. CRC-NK cells displayed underexpression of CD16, NKG2D, DNAM-1, CD161, NKp46, and NKp30 activating receptors, while inhibitory receptors CD85j and NKG2A were overexpressed. This inhibited phenotype affected cytotoxic functionality against CRC cells and interferon-γ production. We also determined that NKp30 and NKp46 are the key receptors involved in detriment of CRC-NK cells’ antitumor activity. Moreover, NKp46 expression correlated with relapse-free survival of CRC patients with a maximum follow-up of 71 months. CRC-NK cells also exhibited altered antibody-dependent cellular cytotoxicity function responding poorly to cetuximab. IL-2 and IL-15 in combination with cetuximab stimulated NK cell, improving cytotoxicity. These results show potential strategies to enhance CRC-NK cell activity.

Intratumoral natural killer cells show reduced effector and cytolytic properties and control the differentiation of effector Th1 cells

Natural killer (NK) cells are known to have effector and cytolytic properties to kill virus infected or tumor cells spontaneously. Due to these properties, NK cells have been used as an adoptive cellular therapy to control tumor growth in various clinical trials but have shown limited clinical benefits. This indicates that our knowledge about phenotypic and functional differences in NK cells within the tumor microenvironment and secondary lymphoid tissues is incomplete. In this work, we report that B16F10 cell-induced melanoma recruits the CD11b⁺CD27⁺ subset of NK cells at a very early stage during tumor progression. These intratumoral NK cells showed increased expression of CD69, reduced inhibitory receptor KLRG1, and decreased proliferative ability. As compared to splenic NK cells, intratumoral NK cells showed decreased expression of activating receptors NKG2D, Ly49D and Ly49H; increased inhibitory receptors, NKG2A and Ly49A; decreased cytokines IFNγ and GM-CSF; decreased cytokine receptors IL-21R, IL-6Rα, and CD122 expression. Depletion of NK cells led to decrease peripheral as well as intratumoral effector CD4⁺T-bet⁺ cells (Th1), and increased tumor growth. Furthermore, purified NK cells showed increased differentiation of Th1 cells in an IFNγ-dependent manner. Anti-NKG2D in the culture promoted differentiation of effector Th1 cells. Collectively, these observations suggest that intratumoral NK cells possess several inhibitory functions that can be partly reversed by signaling through the NKG2D receptor or by cytokine stimulation, which then leads to increased differentiation of effector Th1 cells.

Highly effective NK cells are associated with good prognosis in patients with metastatic prostate cancer

Clinical outcome of patients with metastatic prostate cancer (mPC) at diagnosis is heterogeneous and unpredictable; thus alternative treatments such as immunotherapy are investigated. We retrospectively analyzed natural killer (NK) cells by flow cytometry in peripheral blood from 39 mPC patients, with 5 year-follow-up, and their correlation with time to castration resistance (TCR) and overall survival (OS). In parallel, NK functionality was carried out against prostate tumor cell lines, analyzed for the expression of NK cell ligands, to identify the receptors involved in PC recognition. NK cells from patients with longer TCR and OS displayed high expression of activating receptors and high cytotoxicity. The activating receptors NKp30 and NKp46 were the most obvious predictive markers of OS and TCR in a larger cohort of mPC patients (OS: p= 0.0018 and 0.0009; TCR: p= 0.007 and < 0.0001 respectively, log-rank test). Importantly, blocking experiments revealed that NKp46, along with NKG2D and DNAM-1 and, to a lesser extent NKp30, were involved in prostate tumor recognition by NK cells. These results identify NK cells as potential predictive biomarkers to stratify patients who are likely to have longer castration response, and pave the way to explore therapies aimed at enhancing NK cells in mPC patients.

Progressive natural killer cell dysfunction associated with alterations in subset proportions and receptor expression in soft-tissue sarcoma patients

Immunotherapy is currently investigated as treatment option in many types of cancer. So far, results from clinical trials have demonstrated that significant benefit from immunomodulatory therapies is restricted to patients with select histologies. To broaden the potential use of these therapies, a deeper understanding for mechanisms of immunosuppression in patients with cancer is needed. Soft-tissue sarcoma (STS) presents a medical challenge with significant mortality even after multimodal treatment. We investigated function and immunophenotype of peripheral natural killer (NK) cells from chemotherapy-naive STS patients (1st line) and STS patients with progression or relapse after previous chemotherapeutic treatment (2nd line). We found NK cells from peripheral blood of both STS patient cohorts to be dysfunctional, being unable to lyse K562 target cells while NK cells from renal cell cancer (RCC) patients did not display attenuated lytic activity. Ex vivo stimulation of NK cells from STS patients with interleukin-2 plus TKD restored cytotoxic function. Furthermore, altered NK cell subset composition with reduced proportions of CD56(dim) cells could be demonstrated, increasing from 1st- to 2nd-line patients. 2nd-line patients additionally displayed significantly reduced expression of receptors (NKG2D), mediators (CD3ζ), and effectors (perforin) of NK cell activation. In these patients, we also detected fewer NK cells with CD57 expression, a marker for terminally differentiated cytotoxic NK cells. Our results elucidate mechanisms of NK cell dysfunction in STS patients with advanced disease. Markers like NKG2D, CD3ζ, and perforin are candidates to characterize NK cells with effective antitumor function for immunotherapeutic interventions.

NKp30 isoforms and NKp30 ligands are predictive biomarkers of response to imatinib mesylate in metastatic GIST patients

Despite effective targeted therapy acting on KIT and PDGFRA tyrosine kinases, gastrointestinal stromal tumors (GIST) escape treatment by acquiring mutations conveying resistance to imatinib mesylate (IM). Following the identification of NKp30-based immunosurveillance of GIST and the off-target effects of IM on NK cell functions, we investigated the predictive value of NKp30 isoforms and NKp30 soluble ligands in blood for the clinical response to IM. The relative expression and the proportions of NKp30 isoforms markedly impacted both event-free and overall survival, in two independent cohorts of metastatic GIST. Phenotypes based on disbalanced NKp30B/NKp30C ratio (ΔBC^low) and low expression levels of NKp30A were identified in one third of patients with dismal prognosis across molecular subtypes. This ΔBC^low blood phenotype was associated with a pro-inflammatory and immunosuppressive tumor microenvironment. In addition, detectable levels of the NKp30 ligand sB7-H6 predicted a worse prognosis in metastatic GIST. Soluble BAG6, an alternate ligand for NKp30 was associated with low NKp30 transcription and had additional predictive value in GIST patients with high NKp30 expression. Such GIST microenvironments could be rescued by therapy based on rIFN-α and anti-TRAIL mAb which reinstated innate immunity.

NKp30 isoforms and NKp46 transcripts in metastatic melanoma patients: Unique NKp30 pattern in rare melanoma patients with favorable evolution

Given the NK cell-based immunosurveillance of melanoma, we investigated the prognostic value of NKp46 transcript and NKp30 isoform (NKp30A, NKp30B and NKp30C) profiling in blood of 187 melanoma patients including 13 long survivors (LS), metastatic patients that have controlled the disease. Compared to healthy volunteers (HV), patients had reduced amounts of transcripts of the three NKp30 isoforms (NKp30 A, B and C) but similar ratios between NKp30 isoforms (ΔAB, ΔAC, ΔBC). Stratification of patients according to disease stage showed higher NKp30C and lower NKp46 transcripts in stage IV patients. Furthermore, patients with previous history of conventional chemotherapy displayed reduced NKp30A transcripts. The expression levels of NKp30 isoforms failed to predict survival from sampling of patients, while NKp46 expression predicted melanoma outcome. LS patients displayed elevated NKp30A levels, accordingly high ΔAB and ΔBC ratios, and a unique pattern of rare allelic variants of NKp30 SNPs. Moreover, NK cells from LS displayed correlated NKp30/NKp46 membrane expression, high spontaneous and NKp30- or NKp46-triggered degranulation. These data outline the impact of NKp30 and NKp46 transcripts on melanoma evolution and identify unique genetic features of NKp30 associated with higher NK activation in rare LS melanoma patients that control a metastatic disease.

Natural Killer Cell Recognition of Melanoma: New Clues for a More Effective Immunotherapy

Natural killer (NK) cells participate in the early immune response against melanoma and also contribute to the development of an adequate adaptive immune response by their crosstalk with dendritic cells and cytokine secretion. Melanoma resistance to conventional therapies together with its high immunogenicity justifies the development of novel therapies aimed to stimulate effective immune responses against melanoma. However, melanoma cells frequently escape to CD8 T cell recognition by the down-regulation of major histocompatibility complex (MHC) class I molecules. In this scenario, NK cells emerge as potential candidates for melanoma immunotherapy due to their capacity to recognize and destroy melanoma cells expressing low levels of MHC class I molecules. In addition, the possibility to combine immune checkpoint blockade with other NK cell potentiating strategies (e.g., cytokine induction of activating receptors) has opened new perspectives in the potential use of adoptive NK cell-based immunotherapy in melanoma.

Bench to bedside: NK cells and control of metastasis

Natural killer (NK) cells play a critical role in host immune responses against tumor growth and metastasis. The numerous mechanisms used by NK cells to regulate and control cancer metastasis include interactions with tumor cells via specific receptors and ligands as well as direct cytotoxicity and cytokine-induced effector mechanisms. NK cells also play a role in tumor immunosurveillance and inhibition of metastases formation by recognition and killing of tumor cells. In this review, we provide an overview of the molecular mechanisms of NK cell responses against tumor metastases and discuss multiple strategies by which tumors evade NK cell-mediated surveillance. With an increasing understanding of the molecular mechanisms driving NK cell activity, there is a growing potential for the development of new cancer immunotherapies. Here we provide a historical background on NK cell-based therapies and discuss the implications of recent and ongoing clinical trials using novel NK cell-based immunotherapy.

Prognostic and predictive significance of immune cells infiltrating cutaneous melanoma

The tumor microenvironment is shaped by interactions between malignant cells and host cells representing an integral component of solid tumors. Host cells, including elements of the innate and adaptive immune system, can exert both positive and negative effects on the outcome of the disease. In melanoma, studies on the prognostic impact of the lymphoid infiltrate in general, and that of T cells, yielded controversial results. According to our studies and data in the literature, a high peritumoral density of activated T cells, increased amount of B lymphocytes and mature dendritic cells (DCs) predicted longer survival, while intense infiltration by plasmacytoid DCs or neutrophil granulocytes could be associated with poor prognosis. Besides its prognostic value, evaluation of the components of immune infiltrate could provide biomarkers for predicting the efficacy of the treatment and disease outcome in patients treated with immunotherapy or other, non-immune-based modalities as chemo-, radio-, or targeted therapy.

Characterization of the Microenvironment in Positive and Negative Sentinel Lymph Nodes from Melanoma Patients

Melanomas are aggressive skin tumors characterized by high metastatic potential. Our previous results indicate that Natural Killer (NK) cells may control growth of melanoma. The main defect of blood NK cells was a decreased expression of activating NCR1/NKp46 receptor and a positive correlation of NKp46 expression with disease outcome in stage IV melanoma patients was found. In addition, in stage III melanoma patients, we identified a new subset of mature NK cells in macro-metastatic Lymph nodes (LN). In the present studies, we evaluated the numbers of NK cells infiltrating primary cutaneous melanoma and analyzed immune cell subsets in a series of sentinel lymph nodes (SLN). First, we show that NKp46+ NK cells infiltrate primary cutaneous melanoma. Their numbers were related to age of patients and not to Breslow thickness. Then, a series of patients with tumor-negative or -positive sentinel lymph nodes matched for Breslow thickness of the cutaneous melanoma was constituted. We investigated the distribution of macrophages (CD68), endothelial cells, NK cells, granzyme B positive (GrzB+) cells and CD8+ T cells in the SLN. Negative SLN (SLN-) were characterized by frequent adipose involution and follicular hyperplasia compared to positive SLN (SLN+). High densities of macrophages and endothelial cells (CD34), prominent in SLN+, infiltrate SLN and may reflect a tumor favorable microenvironment. Few but similar numbers of NK and GrzB+ cells were found in SLN- and SLN+: NK cells and GrzB+ cells were not correlated. Numerous CD8+ T cells infiltrated SLN with a trend for higher numbers in SLN-. Moreover, CD8+ T cells and GrzB+ cells correlated in SLN- not in SLN+. We also observed that the numbers of CD8+ T cells negatively correlated with endothelial cells in SLN-. The numbers of NK, GrzB+ or CD8+ T cells had no significant impact on overall survival. However, we found that the 5 year-relapse rate was higher in SLN with higher numbers of NK cells.

Overexpression of CD85j in TNBC patients inhibits Cetuximab-mediated NK-cell ADCC but can be restored with CD85j functional blockade

Clinical studies suggest that triple negative breast cancer (TNBC) patients with epidermal growth factor receptor (EGFR)-expressing tumors could benefit from therapy with Cetuximab, which targets EGFR. NK cells are the primary effectors of antibody (Ab)-dependent cell-mediated cytotoxicity (ADCC) and thus play a role in Ab-based therapies. We have previously described diminished levels of Cetuximab-mediated ADCC in vitro in patients with advanced breast cancer. Here, we investigated the potential causes of this NK-cell functional deficiency. We characterized NK-cell activating/inhibitory receptors in the peripheral blood of breast cancer patients and found CD85j inhibitory receptor overexpression. The capacity of NK cells to perform Cetuximab-triggered ADCC against TNBC cells correlated inversely with CD85j expression, even in the presence of the stimulatory cytokines IL-2 or IL-15. Hence, patients expressing high levels of CD85j had an impaired ability to lyse TNBC cells in the presence of Cetuximab. We also found that CD85j overexpression was associated with HLA-I and soluble HLA-G expression by tumors. A CD85j functional blockade with a CD85j antagonist Ab restored ADCC levels in breast cancer patients and reverted this negative effect. Our data suggest that strategies that overcome the hurdles of immune activation could improve Cetuximab clinical efficacy.