A distinct innate lymphoid cell population regulates tumor-associated T cells

Generation of an Inhibitory NK Cell Subset by TGF-β1/IL-15 Polarization

NK cells have been shown to exhibit inflammatory and immunoregulatory functions in a variety of healthy and diseased settings. In the context of chronic viral infection and cancer, distinct NK cell populations that inhibit adaptive immune responses have been observed. To understand how these cells arise and further characterize their immunosuppressive role, we examined in vitro conditions that could polarize human NK cells into an inhibitory subset. TGF-β1 has been shown to induce regulatory T cells in vitro and in vivo; we therefore investigated if TGF-β1 could also induce immunosuppressive NK-like cells. First, we found that TGF-β1/IL-15, but not IL-15 alone, induced CD103+CD49a+ NK-like cells from peripheral blood NK cells, which expressed markers previously associated with inhibitory CD56+ innate lymphoid cells, including high expression of GITR and CD101. Moreover, supernatant from ascites collected from patients with ovarian carcinoma also induced CD103+CD49a+ NK-like cells in vitro in a TGF-β-dependent manner. Interestingly, TGF-β1/IL-15-induced CD103+CD56+ NK-like cells suppressed autologous CD4+ T cells in vitro by reducing absolute number, proliferation, and expression of activation marker CD25. Collectively, these findings provide new insight into how NK cells may acquire an inhibitory phenotype in TGF-β1-rich environments.

The immunoglobulin superfamily ligand B7H6 subjects T cell responses to NK cell surveillance

Understanding the mechanisms that regulate T cell immunity is critical for the development of effective therapies for diseases associated with T cell dysfunction, including autoimmune diseases, chronic infections, and cancer. Co-inhibitory "checkpoint molecules," such as programmed cell death protein-1, balance excessive or prolonged immune activation by T cell-intrinsic signaling. Here, by screening for mediators of natural killer (NK) cell recognition on T cells, we identified the immunoglobulin superfamily ligand B7H6 to be highly expressed by activated T cells, including patient-infused CD19-targeting chimeric antigen receptor (CAR) T cells. Unlike other checkpoint molecules, B7H6 mediated NKp30-dependent recognition and subsequent cytolysis of activated T cells by NK cells. B7H6+ T cells were prevalent in the tissue and blood of several diseases, and their abundance in tumor tissue positively correlated with clinical response in a cohort of patients with immune checkpoint inhibitor-treated esophageal cancer. In humanized mouse models, NK cell surveillance via B7H6 limited the persistence and antitumor activity of CAR T cells, and its genetic deletion enhanced T cell proliferation and persistence. Together, we provide evidence of B7H6 protein expression by activated T cells and suggest the B7H6-NKp30 axis as a therapeutically actionable NK cell-dependent immune checkpoint that regulates human T cell function.

A diversity of novel type-2 innate lymphoid cell subpopulations revealed during tumour expansion

Type 2 innate lymphoid cells (ILC2s) perform vital functions in orchestrating humoral immune responses, facilitating tissue remodelling, and ensuring tissue homeostasis. Additionally, in a role that has garnered considerably less attention, ILC2s can also enhance Th1-related cytolytic T lymphocyte immune responses against tumours. Studies have thus far generally failed to address the mystery of how one ILC2 cell-type can participate in a multiplicity of functions. Here we utilized single cell RNA sequencing analysis to create the first comprehensive atlas of naïve and tumour-associated lung ILC2s and discover multiple unique subtypes of ILC2s equipped with developmental gene programs that become skewed during tumour expansion favouring inflammation, antigen processing, immunological memory and Th1-related anti-tumour CTL responses. The discovery of these new subtypes of ILC2s challenges current paradigms of ILC2 biology and provides an explanation for their diversity of function.

Targeting Potential of Innate Lymphoid Cells in Melanoma and Other Cancers

Reinvigorating the killing function of tumor-infiltrating immune cells through the targeting of regulatory molecules expressed on lymphocytes has markedly improved the prognosis of cancer patients, particularly in melanoma. While initially thought to solely strengthen adaptive T lymphocyte anti-tumor activity, recent investigations suggest that other immune cell subsets, particularly tissue-resident innate lymphoid cells (ILCs), may benefit from immunotherapy treatment. Here, we describe the recent findings showing immune checkpoint expression on tissue-resident and tumor-infiltrating ILCs and how their effector function is modulated by checkpoint blockade-based therapies in cancer. We discuss the therapeutic potential of ILCs beyond the classical PD-1 and CTLA-4 regulatory molecules, exploring other possibilities to manipulate ILC effector function to further impede tumor growth and quench disease progression.

Protective and pathogenic functions of innate lymphoid cells in transplantation

Innate lymphoid cells (ILCs) are a family of lymphocytes with essential roles in tissue homeostasis and immunity. Along with other tissue-resident immune populations, distinct subsets of ILCs have important roles in either promoting or inhibiting immune tolerance in a variety of contexts, including cancer and autoimmunity. In solid organ and hematopoietic stem cell transplantation, both donor and recipient-derived ILCs could contribute to immune tolerance or rejection, yet understanding of protective or pathogenic functions are only beginning to emerge. In addition to roles in directing or regulating immune responses, ILCs interface with parenchymal cells to support tissue homeostasis and even regeneration. Whether specific ILCs are tissue-protective or enhance ischemia reperfusion injury or fibrosis is of particular interest to the field of transplantation, beyond any roles in limiting or promoting allograft rejection or graft-versus host disease. Within this review, we discuss the current understanding of ILCs functions in promoting immune tolerance and tissue repair at homeostasis and in the context of transplantation and highlight where targeting or harnessing ILCs could have applications in novel transplant therapies.

Concerted epithelial and stromal changes during progression of Barrett's Esophagus to invasive adenocarcinoma exposed by multi-scale, multi-omics analysis

Esophageal adenocarcinoma arises from Barrett's esophagus, a precancerous metaplastic replacement of squamous by columnar epithelium in response to chronic inflammation. Multi-omics profiling, integrating single-cell transcriptomics, extracellular matrix proteomics, tissue-mechanics and spatial proteomics of 64 samples from 12 patients' paths of progression from squamous epithelium through metaplasia, dysplasia to adenocarcinoma, revealed shared and patient-specific progression characteristics. The classic metaplastic replacement of epithelial cells was paralleled by metaplastic changes in stromal cells, ECM and tissue stiffness. Strikingly, this change in tissue state at metaplasia was already accompanied by appearance of fibroblasts with characteristics of carcinoma-associated fibroblasts and of an NK cell-associated immunosuppressive microenvironment. Thus, Barrett's esophagus progresses as a coordinated multi-component system, supporting treatment paradigms that go beyond targeting cancerous cells to incorporating stromal reprogramming.

Tumor-associated NK cells facilitate tumor growth via NKp46 in immunocompetent murine hepatocellular carcinoma

Natural killer(NK) cells comprise one subset of the innate lymphoid cells family. Despite reported anti-tumor activity of NK cells, their tangible contribution to tumor control remains controversial. This is due to the incomplete understanding of NK alterations within tumor microenvironment(TME). Here we showed, using murine hepatocellular carcinoma(HCC) model, that early NK cells deletion markedly attenuated tumor growth in a CD8⁺ T cells dependent manner. This effect was accompanied by an enhanced CD8⁺ T cells effector function in tumor rather than circulating blood. Then, we demonstrated that abundant NKp46⁺ NK subset, but not NKp46^- NK, were recruited towards tumor microenvironment during tumor progression. Frequency of intratumor NKP46⁺ NK cells were inversely related to CD8⁺ T cells activation, and positively correlated with tumor growth. Intratumor NKp46⁺ NK cells exhibited dysfunction and increased expression of inhibitory receptors, when compared with NKp46^- NK cells. Blockade of NK cells-associated NKp46 effectively attenuated HCC growth. Infusion of tumor-derived NKp46⁺ NK cells markedly enhanced HCC growth in vivo, in contrast to tumor cells inoculation alone. The further mechanistic investigations unveiled that NK cells boosted tumor growth by NKp46-mediated impairment of CD8⁺T cells effector function. Overall, this work supported a previously unappreciated regulatory property of tumor-associated NK cells in HCC, and NKp46 as a potential target against HCC in clinical setting.

Helper innate lymphoid cells as cell therapy for cancer

Although the first cancer immunotherapy was given in the clinic more than a century ago, this line of treatment has remained more of a distant goal than a practical therapy due to limited understanding of the tumour microenvironment and the mechanisms at play within it, which led to failures of numerous clinical trials. However, in the last two decades, the immune checkpoint inhibitors (ICIs) and chimeric antigen receptor-T cell therapies have revolutionized the treatment of cancer and provided proof-of-concept that immunotherapies are a viable option. So far, immunotherapies have majoritarily focused on utilizing T cells; however, T cells are not autonomous but rather function as part of, and therefore are influenced by, a vast cast of other immune cells, including innate lymphoid cells (ILCs). Here, we summarize the role of ILCs, especially helper ILCs, in tumour development, progression and metastasis, as well as their potential to be used as immunotherapy for cancer. By reviewing the studies that used helper ILCs as adoptive cell therapy (ACT), we highlight the rationale behind considering these cells as novel ACT for cancer as well as identify open questions and areas for future research.

Identification of antigenic epitopes recognized by tumor infiltrating lymphocytes in high grade serous ovarian cancer by multi-omics profiling of the auto-antigen repertoire

Immunotherapeutic strategies aimed at enhancing tumor cell killing by tumor-specific T cells hold great potential for reducing tumor burden and prolonging survival of cancer patients. Although many potential tumor antigens have been described, identifying relevant targets when designing anti-cancer vaccines or targeted cell therapies remains a challenge. To identify novel, potentially immunogenic candidate tumor antigens, we performed integrated tumor transcriptomic, seromic, and proteomic analyses of high grade serous ovarian cancer (HGSC) patient tumor samples. We identified tumor neo-antigens and over-expressed antigens using whole exome and RNA sequencing and examined these in relation to patient-matched auto-antibody repertoires. Focusing on MHC class I epitopes recognized by CD8⁺ T cells, HLA-binding epitopes were identified or predicted from the highly expressed, mutated, or auto-antibody target antigen, or MHC-associated peptides (MAPs). Recognition of candidate antigenic peptides was assessed within the tumor-infiltrating T lymphocyte (TIL) population expanded from each patient. Known tumor-associated antigens (TAA) and cancer/testis antigens (CTA) were commonly found in the auto-antibody and MAP repertoires and CD8⁺ TILs recognizing epitopes from these antigens were detected, although neither expression level nor the presence of auto-antibodies correlated with TIL recognition. Auto-antibodies against tumor-mutated antigens were found in most patients, however, no TIL recognition of the highest predicted affinity neo-epitopes was detected. Using high expression level, auto-antibody recognition, and epitope prediction algorithms, we identified epitopes in 5 novel antigens (MOB1A, SOCS3, TUBB, PRKAR1A, CCDC6) recognized by HGSC patient TILs. Furthermore, selection of epitopes from the MAP repertoire identified 5 additional targets commonly recognized by multiple patient TILs. We find that the repertoire of TIL specificities includes recognition of highly expressed and immunogenic self-antigens that are processed and presented by tumors. These results indicate an ongoing autoimmune response against a range of self-antigens targeted by HGSC TILs.

Immunobiology of high-grade serous ovarian cancer: lessons for clinical translation

Treatment of high-grade serous ovarian cancer (HGSOC) remains challenging. Although HGSOC can potentially be responsive to immunotherapy owing to endogenous immunity at the molecular or T cell level, immunotherapy for this disease has fallen short of expectations to date. This Review proposes a working classification for HGSOC based on the presence or absence of intraepithelial T cells, and elaborates the putative mechanisms that give rise to such immunophenotypes. These differences might explain the failures of existing immunotherapies, and suggest that rational therapeutic approaches tailored to each immunophenotype might meet with improved success. In T cell-inflamed tumours, treatment could focus on mobilizing pre-existing immunity and strengthening the activation of T cells embedded in intraepithelial tumour myeloid niches. Conversely, in immune-excluded and immune-desert tumours, treatment could focus on restoring inflammation by reprogramming myeloid cells, stromal cells and vascular epithelial cells. Poly(ADP-ribose) polymerase (PARP) inhibitors, low-dose radiotherapy, epigenetic drugs and anti-angiogenesis therapy are among the tools available to restore T cell infiltration in HGSOC tumours and could be implemented in combination with vaccines and redirected T cells.

Expansion of Lymphocytes from Prostatic Adenocarcinoma and Adjacent Nonmalignant Tissue

Background

The evaluation of tumour-infiltrating lymphocytes (TILs) in solid malignancies has yielded insights into immune regulation within the tumour microenvironment and has also led to the development and optimisation of adoptive T cell therapies.

Objectives

This study examined the in vitro expansion of TILs from prostate adenocarcinoma, as a preliminary step to evaluate the potential of TILs for adoptive T cell therapy. Design, Setting, and Participants. Malignant and adjacent nonmalignant tissues were obtained from fifteen men undergoing radical prostatectomy. Interventions. There were no study interventions. Outcome Measurements and Statistical Analysis. Expanded cells were analysed by flow cytometry, and the data was assessed for associations between cell subpopulations and expansion rate.

Results

Tumour-infiltrating lymphocytes could be expanded to numbers that would be needed to generate a therapeutic infusion product from nine of 15 malignant specimens (60%). The CD4⁺ T cells predominated over CD8⁺ T cells (median 56.8% CD4⁺, 30.0% CD8⁺), and furthermore, faster TIL expansion was associated with a higher proportion of CD4⁺ T cells (median 69.8% in faster-growing cultures; 36.8% in slower-growing cultures). A higher proportion of CD3⁻CD56⁺ cells versus CD3⁺ cells was associated with slower TIL expansion in cultures from malignant specimens (median 13.3% in slower-growing cultures versus 2.05% in faster-growing cultures), but not from nonmalignant specimens.

Conclusions

The expansion of TILs for potential therapeutic use is feasible. Our findings also indicate that further examination of TILs from prostate adenocarcinomas may yield insights into mechanisms of regulation of T cells within the tumour microenvironment. Further research is required to evaluate their therapeutic potential.

Emerging Concepts in Innate Lymphoid Cells, Memory, and Reproduction

Members of the innate immune system, innate lymphoid cells (ILCs), encompass five major populations (Natural Killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer cells) whose functions include defense against pathogens, surveillance of tumorigenesis, and regulation of tissue homeostasis and remodeling. ILCs are present in the uterine environment of humans and mice and are dynamically regulated during the reproductive cycle and pregnancy. These cells have been repurposed to support pregnancy promoting maternal immune tolerance and placental development. To accomplish their tasks, immune cells employ several cellular and molecular mechanisms. They have the capacity to remember a previously encountered antigen and mount a more effective response to succeeding events. Memory responses are not an exclusive feature of the adaptive immune system, but also occur in innate immune cells. Innate immune memory has already been demonstrated in monocytes/macrophages, neutrophils, dendritic cells, and ILCs. A population of decidual NK cells characterized by elevated expression of NKG2C and LILRB1 as well as a distinctive transcriptional and epigenetic profile was found to expand during subsequent pregnancies in humans. These cells secrete high amounts of interferon-γ and vascular endothelial growth factor likely favoring placentation. Similarly, uterine ILC1s in mice upregulate CXCR6 and expand in second pregnancies. These data provide evidence on the development of immunological memory of pregnancy. In this article, the characteristics, functions, and localization of ILCs are reviewed, emphasizing available data on the uterine environment. Following, the concept of innate immune memory and its mechanisms, which include epigenetic changes and metabolic rewiring, are presented. Finally, the emerging role of innate immune memory on reproduction is discussed. Advances in the comprehension of ILC functions and innate immune memory may contribute to uncovering the immunological mechanisms underlying female fertility/infertility, placental development, and distinct outcomes in second pregnancies related to higher birth weight and lower incidence of complications.

Harnessing Unconventional T Cells and Innate Lymphoid Cells to Prevent and Treat Hematological Malignancies: Prospects for New Immunotherapy

Unconventional T cells and innate lymphoid cells (ILCs) make up a heterogeneous set of cells that characteristically show prompt responses toward specific antigens. Unconventional T cells recognize non-peptide antigens, which are bound and presented by diverse non-polymorphic antigen-presenting molecules and comprise γδ T cells, MR1-restricted mucosal-associated invariant T cells (MAITs), and natural killer T cells (NKTs). On the other hand, ILCs lack antigen-specific receptors and act as the innate counterpart to the T lymphocytes found in the adaptive immune response. The alteration of unconventional T cells and ILCs in frequency and functionality is correlated with the onset of several autoimmune diseases, allergy, inflammation, and tumor. However, depending on the physio-pathological framework, unconventional T cells may exhibit either protective or pathogenic activity in a range of neoplastic diseases. Nonetheless, experimental models and clinical studies have displayed that some unconventional T cells are potential therapeutic targets, as well as prognostic and diagnostic markers. In fact, cell-mediated immune response in tumors has become the focus in immunotherapy against neoplastic disease. This review concentrates on the present knowledge concerning the function of unconventional T cell sets in the antitumor immune response in hematological malignancies, such as acute and chronic leukemia, multiple myeloma, and lymphoproliferative disorders. Moreover, we discuss the possibility that modulating the activity of unconventional T cells could be useful in the treatment of hematological neoplasms, in the prevention of specific conditions (such as graft versus host disease), and in the formulation of an effective anticancer vaccine therapy. The exact knowledge of the role of these cells could represent the prerequisite for the creation of a new form of immunotherapy for hematological neoplasms.

Plasticity of Innate Lymphoid Cells in Cancer

Innate lymphoid cells (ILCs) are a heterogenous population of the innate immune system, enriched at mucosal surfaces and are pivotal regulators of immune homeostasis. ILCs are the innate counterpart of T cells. Like T cells, ILC subsets are highly plastic with their composition and function controlled by alterations in their microenvironment. This plasticity allows for the trans-differentiation between the subsets to rapidly respond to their immune environment. The tumor microenvironment (TME) is a heterogeneous milieu characterized by different cytokines and growth factors. Through interaction with the tumor microenvironment, ILCs can transdifferentiate into different subsets resulting in pro or anti-tumor immunity. Thus, studying ILC plasticity might result in new therapeutic approaches for cancer therapy. In this review, we summarize current findings of the functional and plastic heterogeneity of ILCs in homeostasis as well as disease settings with a specific focus on cancer. We specifically highlight tumor-driven plasticity and how ILC-induced inflammation can impact the tumor microenvironment and anti-tumor immunity.

Deciphering Innate Immune Cell-Tumor Microenvironment Crosstalk at a Single-Cell Level

The tumor microenvironment encompasses various innate immune cells which regulate tumor progression. Exploiting innate immune cells is a new frontier of cancer immunotherapy. However, the classical surface markers for cell-type classification cannot always well-conclude the phenotype, which will further hinge our understanding. The innate immune cells include dendritic cells, monocytes/macrophages, natural killer cells, and innate lymphoid cells. They play important roles in tumor growth and survival, in some cases promoting cancer, in other cases negating cancer. The precise characterization of innate immune cells at the single-cell level will boost the potential of cancer immunotherapy. With the development of single-cell RNA sequencing technology, the transcriptome of each cell in the tumor microenvironment can be dissected at a single-cell level, which paves a way for a better understanding of the cell type and its functions. Here, we summarize the subtypes and functions of innate immune cells in the tumor microenvironment based on recent literature on single-cell technology. We provide updates on recent achievements and prospects for how to exploit novel functions of tumor-associated innate immune cells and target them for cancer immunotherapy.

Innate Lymphoid Cells: Role in Immune Regulation and Cancer

Simple Summary

Innate lymphoid cells (ILCs) are an emerging family of effector cells known to play a major role in innate defenses against pathogens, lymphoid organogenesis, tissue repair, and homeostasis. They are positioned strategically within tissues to provide the first line of defence and shape the ensuing adaptive immune cell response. Recent evidence suggests that ILCs contribute to immune regulation in different diseases, including cancer, and can have significant impact on disease outcome. In this review, we highlight the immunosuppressive roles of ILCs in cancer that inhibit effective immune surveillance and anti-tumour response.

Abstract

Immune regulation is composed of a complex network of cellular and molecular pathways that regulate the immune system and prevent tissue damage. It is increasingly clear that innate lymphoid cells (ILCs) are also armed with immunosuppressive capacities similar to well-known immune regulatory cells (i.e., regulatory T cells). In cancer, immunoregulatory ILCs have been shown to inhibit anti-tumour immune response through various mechanisms including: (a) direct suppression of anti-tumour T cells or NK cells, (b) inhibiting T-cell priming, and (c) promoting other immunoregulatory cells. To provide a framework of understanding the role of immunosuppressive ILCs in the context of cancer, we first outline a brief history and challenges related to defining immunosuppressive ILCs. Furthermore, we focus on the mechanisms of ILCs in suppressing anti-tumour immunity and consequentially promoting tumour progression.

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

Tissue-resident immune cells reside in distinct niches across organs, where they contribute to tissue homeostasis and rapidly respond to perturbations in the local microenvironment. Innate lymphoid cells (ILCs) are a family of innate immune cells that regulate immune and tissue homeostasis. Across anatomical locations throughout the body, ILCs adopt tissue-specific fates, differing from circulating ILC populations. Adaptations of ILCs to microenvironmental changes have been documented in several inflammatory contexts, including obesity, asthma, and inflammatory bowel disease. While our understanding of ILC functions within tissues have predominantly been based on mouse studies, development of advanced single cell platforms to study tissue-resident ILCs in humans and emerging patient-based data is providing new insights into this lymphocyte family. Within this review, we discuss current concepts of ILC fate and function, exploring tissue-specific functions of ILCs and their contribution to health and disease across organ systems.

Case Report: An "Immune-Cold" EGFR Mutant NSCLC With Strong PD-L1 Expression Shows Resistance to Chemo-Immunotherapy

Long-term survival benefit has been noticed in non-small-cell lung cancer (NSCLC) patients treated with immune checkpoint inhibitors (ICIs), such as PD-1 inhibitors. However, it is still controversial whether patients with EGFR-activating mutations may benefit from ICIs. Recently, in stage IIIA NSCLC, chemo-immunotherapy has led to significant pathological response, yet patients with the presence of known EGFR mutations were excluded from some randomized trials of neoadjuvant therapy. Herein, we report a case of a 50-year-old female patient, who was initially diagnosed as stage IIIA lung squamous cell carcinoma. Immunohistochemistry analysis showed that the patient presented with high PD-L1 expression. Then, chemo-immunotherapy was given to the patient but the disease progressed quickly with distant metastasis. A re-biopsy revealed a poorly differentiated lung adenocarcinoma together with EGFR p.L858R mutation. Then the patient received gefitinib, which resulted in significant regression of primary lung lesion. A detailed examination of pre-treatment tumor sections demonstrated rare infiltration of CD8⁺ T cells, indicating that the current patient presented with an “immune-cold” microenvironment, which might explain the primary resistance to chemo-immunotherapy. Taken together, our case indicated that comprehensive detection of PD-L1 expression, driver gene status, together with tumor immune microenvironment, may offer a better prediction of treatment efficacy.

Natural Killer Cells: the Missing Link in Effective Treatment for High-Grade Serous Ovarian Carcinoma

OPINION STATEMENT

Ovarian cancer (OC), especially high-grade serous cancer (HGSC), is a highly heterogeneous malignancy with limited options for curative treatment and a high frequency of relapse. Interactions between OC and the immune system may permit immunoediting and immune escape, and current standard of care therapies can influence immune cell infiltration and function within the tumor microenvironment. Natural killer (NK) cells are involved in cancer immunosurveillance and immunoediting and can be activated by therapy, but deliberate approaches to maximize NK cell reactivity for treatment of HGSC are in their infancy. NK cells may be the ideal target for immunotherapy of HGSC. The diverse functions of NK cells, and their established roles in immunosurveillance, make them attractive candidates for more precise and effective HGSC treatment. NK cells' functional capabilities differ because of variation in receptor expression and genetics, with meaningful impacts on their anticancer activity. Studying HGSC:NK cell interactions will define the features that predict the best outcomes for patients with the disease, but the highly diverse nature of HGSC will likely require combination therapies or approaches to simultaneously target multiple, co-existing features of the tumor to avoid tumor escape and relapse. We expect that the ideal therapy will enable NK cell infiltration and activity, reverse immunosuppression within the tumor microenvironment, and enable effector functions against the diverse subpopulations that comprise HGSC.

Investigating the Potential of Isolating and Expanding Tumour-Infiltrating Lymphocytes from Adult Sarcoma

Simple Summary

Sarcomas are rare cancers that arise from connective tissue. There are more than 50 subtypes, many of which are associated with a high risk of metastasis and poor prognosis. Subtype-specific treatment is limited and conventional treatment for advanced disease has varying effects across individuals and tumour subtypes. Adoptive cell therapy shows potential to provide more personalized treatment; this study aims to explore the potential of using tumour-infiltrating lymphocytes (TIL) to treat sarcoma. We optimized a sarcoma-specific expansion protocol and successfully expanded TILs from 54 of 92 sarcoma specimens. We characterized primarily CD4⁺ and CD8⁺ T-cells in the expanded TIL cultures and demonstrated their reactivity to general stimuli. Although sarcomas in general do not have abundant lymphocytic infiltration, our expansion protocol allowed for successful expansions of viable and reactive lymphocytes, thus showing the prospects of adopting TIL therapy in sarcoma.

Abstract

Sarcomas are a heterogeneous group of mesenchymal neoplasms, many of which are associated with a high risk of metastasis and poor prognosis. Conventional chemotherapy and targeted therapies have varying effects across individuals and tumour subtypes. The current therapies frequently provide limited clinical benefit; hence, more effective treatments are urgently needed. Recent advances in immunotherapy, such as checkpoint inhibition or adoptive cell therapy (ACT), show potential in increasing efficacy by providing a more personalized treatment. Therapy with tumour-infiltrating lymphocytes (TILs) is an emerging field in immunotherapy. Here, we collected 190 sarcoma tumour specimens from patients without pre-operative adjuvant treatment in order to isolate TILs. We compared different methods of TIL expansion and optimized a protocol specifically for efficacy in culturing TILs from sarcoma. The expanded TIL populations were characterized by flow cytometry analysis using CD3, CD4, CD8, CD14, CD19 and CD56 markers. The TIL populations were non-specifically stimulated to establish TIL reactivity. Through an optimized expansion protocol, TILs were isolated and cultured from 54 of 92 primary sarcoma specimens. The isolated TILs varied in CD4⁺ and CD8⁺ T-cell compositions and retained their ability to release IFNγ upon stimulation. Our results suggest that certain sarcoma subtypes have the potential to yield a sufficient number of TILs for TIL therapy.

Chemokines modulate glycan binding and the immunoregulatory activity of galectins

Galectins are versatile glycan-binding proteins involved in immunomodulation. Evidence suggests that galectins can control the immunoregulatory function of cytokines and chemokines through direct binding. Here, we report on an inverse mechanism in which chemokines control the immunomodulatory functions of galectins. We show the existence of several specific galectin-chemokine binding pairs, including galectin-1/CXCL4. NMR analyses show that CXCL4 binding induces changes in the galectin-1 carbohydrate binding site. Consequently, CXCL4 alters the glycan-binding affinity and specificity of galectin-1. Regarding immunomodulation, CXCL4 significantly increases the apoptotic activity of galectin-1 on activated CD8⁺ T cells, while no effect is observed in CD4⁺ T cells. The opposite is found for another galectin-chemokine pair, i.e., galectin-9/CCL5. This heterodimer significantly reduces the galectin-9 induced apoptosis of CD4⁺ T cells and not of CD8⁺ T cells. Collectively, the current study describes an immunomodulatory mechanism in which specific galectin-chemokine interactions control the glycan-binding activity and immunoregulatory function of galectins.

Beyond immune checkpoint blockade: emerging immunological strategies

The success of checkpoint inhibitors has accelerated the clinical implementation of a vast mosaic of single agents and combination immunotherapies. However, the lack of clinical translation for a number of immunotherapies as monotherapies or in combination with checkpoint inhibitors has clarified that new strategies must be employed to advance the field. The next chapter of immunotherapy should examine the immuno-oncology therapeutic failures, and consider the complexity of immune cell-cancer cell interactions to better design more effective anticancer drugs. Herein, we briefly review the history of immunotherapy and checkpoint blockade, highlighting important clinical failures. We discuss the critical aspects - beyond T cell co-receptors - of immune processes within the tumour microenvironment (TME) that may serve as avenues along which new therapeutic strategies in immuno-oncology can be forged. Emerging insights into tumour biology suggest that successful future therapeutics will focus on two key factors: rescuing T cell homing and dysfunction in the TME, and reappropriating mononuclear phagocyte function for TME inflammatory remodelling. New drugs will need to consider the complex cell networks that exist within tumours and among cancer types.

Exploring the clinical value of tumor microenvironment in platinum-resistant ovarian cancer

Platinum resistance in epithelial ovarian cancer (OvCa) is rising at an alarming rate, with recurrence of chemo-resistant high grade serous OvCa (HGSC) in roughly 75 % of all patients. Additionally, HGSC has an abysmal five-year survival rate, standing at 39 % and 17 % for FIGO stages III and IV, respectively. Herein we review the crucial cellular interactions between HGSC cells and the cellular and non-cellular components of the unique peritoneal tumor microenvironment (TME). We highlight the role of the extracellular matrix (ECM), ascitic fluid as well as the mesothelial cells, tumor associated macrophages, neutrophils, adipocytes and fibroblasts in platinum-resistance. Moreover, we underscore the importance of other immune-cell players in conferring resistance, including natural killer cells, myeloid-derived suppressive cells (MDSCs) and T-regulatory cells. We show the clinical relevance of the key platinum-resistant markers and their correlation with the major pathways perturbed in OvCa. In parallel, we discuss the effect of immunotherapies in re-sensitizing platinum-resistant patients to platinum-based drugs. Through detailed analysis of platinum-resistance in HGSC, we hope to advance the development of more effective therapy options for this aggressive disease.

A Hypothetical Model Suggesting Some Possible Ways That the Progesterone Receptor May Be Involved in Cancer Proliferation

Cancer and the fetal-placental semi-allograft share certain characteristics, e.g., rapid proliferation, the capacity to invade normal tissue, and, related to the presence of antigens foreign to the host, the need to evade immune surveillance. Many present-day methods to treat cancer use drugs that can block a key molecule that is important for one or more of these characteristics and thus reduce side effects. The ideal molecule would be one that is essential for both the survival of the fetus and malignant tumor, but not needed for normal cells. There is a potential suitable candidate, the progesterone induced blocking factor (PIBF). The parent 90 kilodalton (kDa) form seems to be required for cell-cycle regulation, required by both the fetal-placental unit and malignant tumors. The parent form may be converted to splice variants that help both the fetus and tumors escape immune surveillance, especially in the fetal and tumor microenvironment. Evidence suggests that membrane progesterone receptors are involved in PIBF production, and indeed there has been anecdotal evidence that progesterone receptor antagonists, e.g., mifepristone, can significantly improve longevity and quality of life, with few side effects.

Interleukin-33 is a Novel Immunosuppressor that Protects Cancer Cells from TIL Killing by a Macrophage-Mediated Shedding Mechanism

Recognition of specific antigens expressed in cancer cells is the initial process of cytolytic T cell-mediated cancer killing. However, this process can be affected by other non-cancerous cellular components in the tumor microenvironment. Here, it is shown that interleukin-33 (IL-33)-activated macrophages protect melanoma cells from tumor-infiltrating lymphocyte-mediated killing. Mechanistically, IL-33 markedly upregulates metalloprotease 9 (MMP-9) expression in macrophages, which acts as a sheddase to trim NKG2D, an activating receptor expressed on the surface of natural killer (NK) cells, CD8+ T cells, subsets of CD4+ T cells, iNKT cells, and γδ T cells. Further, MMP-9 also cleaves the MHC class I molecule, cell surface antigen-presenting complex molecules, expressed in melanoma cells. Consequently, IL-33-induced macrophage MMP-9 robustly mitigates the tumor killing-effect by T cells. Genetic and pharmacological loss-of-function of MMP-9 sheddase restore T cell-mediated cancer killing. Together, these data provide compelling in vitro and in vivo evidence showing novel mechanisms underlying the IL-33-macrophage-MMP-9 axis-mediated immune tolerance against cancer cells. Targeting each of these signaling components, including IL-33 and MMP-9 provides a new therapeutic paradigm for improving anticancer efficacy by immune therapy.

Interactions between islets and regulatory immune cells in health and type 1 diabetes

Type 1 diabetes results from defects in immune self-tolerance that lead to inflammatory infiltrate in pancreatic islets, beta cell dysfunction and T cell-mediated killing of beta cells. Although therapies that broadly inhibit immunity show promise to mitigate autoinflammatory damage caused by effector T cells, these are unlikely to permanently reset tolerance or promote regeneration of the already diminished pool of beta cells. An emerging concept is that certain populations of immune cells may have the capacity to both promote tolerance and support the restoration of beta cells by supporting proliferation, differentiation and/or regeneration. Here we will highlight three immune cell types-macrophages, regulatory T cells and innate lymphoid cells-for which there is evidence of dual roles of immune regulation and tissue regeneration. We explore how findings in this area from other fields might be extrapolated to type 1 diabetes and highlight recent discoveries in the context of type 1 diabetes. We also discuss technological advances that are supporting this area of research and contextualise new therapeutic avenues to consider for type 1 diabetes.

Searching for the Elusive Regulatory Innate Lymphoid Cell

The complex nature of the innate lymphoid cell (ILC) family and wide range of ILC effector functions has been the focus of intense research. In addition to important roles in host defense, ILCs have central roles in maintaining tissue homeostasis and can promote immune tolerance. Alterations within the microenvironment can impart new functions on ILCs, and can even induce conversion to a distinct ILC family member. Complicating current definitions of ILCs are recent findings of distinct regulatory ILC populations that limit inflammatory responses or recruit other immunosuppressive cells such as regulatory T cells. Whether these populations are distinct ILC family members or rather canonical ILCs that exhibit immunoregulatory functions due to microenvironment signals has been the subject of much debate. In this review, we highlight studies identifying regulatory populations of ILCs that span regulatory NK-like cells, regulatory ILCs, and IL-10-producing ILC2s.

Innate lymphoid cells (ILC) in SARS-CoV-2 infection

Innate Lymphoid Cells (ILCs) are a class of innate immune cells that form the first line of defense against internal or external abiotic and biotic challenges in the mammalian hosts. As they reside in both the lymphoid and non-lymphoid tissues, they are involved in clearing the pathogens through direct killing or by secretion of cytokines that modulate the adaptive immune responses. There is burgeoning evidence that these cells are important in clearing viral infections; therefore, it is critical to understand their role in the resolution or exacerbation of the disease caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2). In this review, we summarize the recent findings related to ILCs in response to SARS-CoV-2 infections.

Innate lymphoid cells and cancer: Role in tumor progression and inhibition

Innate lymphoid cells (ILCs), a critical component of the immune system, have recently been nominated as emerging players associated with tumor progression and inhibition. ILCs are classified into five groups: natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer (LTis) cells. NK cells and ILC1s are mainly involved in antitumor activities due to their cytotoxic and cytokine production capabilities, respectively. The current understanding of the heterogeneous behavior of ILC2s and ILC3s in tumors is limited and incomplete. Mostly, their dual roles are modulated by their resident tissues, released cytokines, cancer types, and plasticity. Based on overlap RORγt and cytokine expression, the LTi cells were previously considered part of the ILC3s ontogeny, which are essential for the formation of the secondary lymphoid organs during embryogenesis. Indeed, these facts highlight the urgency in understanding the respective mechanisms that shape the phenotypes and responses of ILCs, either on the repressive or proliferative side in the tumor microenvironment (TME). This review aims to provide an updated view of ILCs biology with respect to tumorigenesis, including a description of ILC plasticity, their interaction with other immune cells and communication with components of the TME. Taken together, targeting ILCs for cancer immunotherapy could be a promising approach against tumors that needs to be further study.

The Adverse Impact of Tumor Microenvironment on NK-Cell

NK cells are considered an important component of innate immunity, which is the first line of defensing against tumors and viral infections in the absence of prior sensitization. NK cells express an array of germline-encoded receptors, which allow them to eliminate abnormal cells and were previously considered a homogenous population of innate lymphocytes, with limited phenotypic and functional diversity. Although their characteristics are related to their developmental origins, other factors, such as tumors and viral infections, can influence their phenotype. Here, we provide an overview of NK cells in the context of the tumor microenvironment, with a primary focus on their phenotypes, functions, and roles in tumor micro-environment. A comprehensive understanding of NK cells in the tumor microenvironment will provide a theoretical basis for the development of NK cell immunotherapy.

Role of immune regulatory cells in breast cancer: Foe or friend?

Breast cancer (BC) is the most common cancer among women between the ages of 20 and 50, affecting more than 2.1 million people and causing the annual death of more than 627,000 women worldwide. Based on the available knowledge, the immune system and its components are involved in the pathogenesis of several malignancies, including BC. Cancer immunobiology suggests that immune cells can play a dual role and induce anti-tumor or immunosuppressive responses, depending on the tumor microenvironment (TME) signals. The most important effector immune cells with anti-tumor properties are natural killer (NK) cells, B, and T lymphocytes. On the other hand, immune and non-immune cells with regulatory/inhibitory phenotype, including regulatory T cells (Tregs), regulatory B cells (Bregs), tolerogenic dendritic cells (tDCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), mesenchymal stem cells (MSCs), and regulatory natural killer cells (NKregs), can promote the growth and development of tumor cells by inhibiting anti-tumor responses, inducing angiogenesis and metastasis, as well as the expression of inhibitory molecules and suppressor mediators of the immune system. However, due to the complexity of the interaction and the modification in the immune cells' phenotype and the networking of the immune responses, the exact mechanism of action of the immunosuppressive and regulatory cells is not yet fully understood. This review article reviews the immune responses involved in BC as well as the role of regulatory and inhibitory cells in the pathogenesis of the disease. Finally, therapeutic approaches based on inhibition of immunosuppressive responses derived from regulatory cells are discussed.

Innate Lymphoid Cells and Adaptive Immune Cells Cross-Talk: A Secret Talk Revealed in Immune Homeostasis and Different Inflammatory Conditions

The inflammatory immune response has evolved to protect the host from different pathogens, allergens, and endogenous death or damage-associated molecular patterns. Both innate and adaptive immune components are crucial in inducing an inflammatory immune response depending on the stimulus type and its duration of exposure or the activation of the primary innate immune response. As the source of inflammation is removed, the aggravated immune response comes to its homeostatic level. However, the failure of the inflammatory immune response to subside to its normal level generates chronic inflammatory conditions, including autoimmune diseases and cancer. Innate lymphoid cells (ILCs) are newly discovered innate immune cells, which are present in abundance at mucosal surfaces, including lungs, gastrointestinal tract, and reproductive tract. Also, they are present in peripheral blood circulation, skin, and lymph nodes. They play a crucial role in generating the pro-inflammatory immune response during diverse conditions. On the other hand, adaptive immune cells, including different types of T and B cells are major players in the pathogenesis of autoimmune diseases (type 1 diabetes mellitus, rheumatoid arthritis, psoriasis, and systemic lupus erythematosus, etc.) and cancers. Thus the article is designed to discuss the immunological role of different ILCs and their interaction with adaptive immune cells in maintaining the immune homeostasis, and during inflammatory autoimmune diseases along with other inflammatory conditions (excluding pathogen-induced inflammation), including cancer, graft-versus-host diseases, and human pregnancy.

ILC in chronic inflammation, cancer and targeting with biologicals

Since their discovery, Innate Lymphoid Cells (ILC) have emerged as important effector cells, serving multiple roles in maintaining tissue homeostasis and responding to tissue insults. As such, dysregulations of their function and distribution have been observed in a variety of immune-mediated diseases, suggesting a specific role for ILC in the pathophysiology of several disorders including chronic inflammation and cancer. Here, we provide an updated view on ILC biology dissecting their pathological or protective contribution in chronic inflammatory diseases such as multiple sclerosis, inflammatory bowel diseases, psoriasis, rheumatoid arthritis, asthma and COPD, atherosclerosis, also exploring ILC role in tumor surveillance and progression. Throughout the review, we will also highlight how the potential dual role of these cells for protective or pathogenic immunity in many inflammatory diseases makes them interesting targets for the development of novel therapeutic strategies, particularly promising.

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

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

NK cell infiltration is associated with improved overall survival in solid cancers: A systematic review and meta-analysis

The immune landscape of a tumor is highly connected to patient prognosis and response to treatment, but little is known about how natural killer (NK) cells predict overall survival (OS) among patients with solid tumors. We present the first meta-analysis on NK cell infiltration into solid tumors as a prognostic indicator for OS, considering cancer types independently, and together. Samples were collected from 1973 to 2016 with results published between 1989 and 2020. From 53 studies, we found that NK cell infiltration corresponds with decreased risk of death (HR=0.34, 95% CI: 0.26-0.46; p<0.0001). Among studies that investigated the prognostic potential of NK cells in specific regions of the tumor, intraepithelial infiltration was better predictive of OS than NK infiltration in the tumor-adjacent stroma. Generally, NK cell infiltration is lower in advanced-stage and lower-grade tumors; nevertheless, it remains prognostically beneficial. This meta-analysis highlights an important prognostic role of NK cells in solid tumors, but exposes that few studies have considered the contributions of NK cells. Toward NK cell-based immunotherapies, it will be important to understand the conditions under which NK cells can be effective agents of tumor control.

CD73 immune checkpoint defines regulatory NK cells within the tumor microenvironment

High levels of ecto-5'-nucleotidase (CD73) have been implicated in immune suppression and tumor progression, and have also been observed in cancer patients who progress on anti-PD-1 immunotherapy. Although regulatory T cells can express CD73 and inhibit T cell responses via the production of adenosine, less is known about CD73 expression in other immune cell populations. We found that tumor-infiltrating NK cells upregulate CD73 expression and the frequency of these CD73-positive NK cells correlated with larger tumor size in breast cancer patients. In addition, the expression of multiple alternative immune checkpoint receptors including LAG-3, VISTA, PD-1, and PD-L1 was significantly higher in CD73-positive NK cells than in CD73-negative NK cells. Mechanistically, NK cells transport CD73 in intracellular vesicles to the cell surface and the extracellular space via actin polymerization-dependent exocytosis upon engagement of 4-1BBL on tumor cells. These CD73-positive NK cells undergo transcriptional reprogramming and upregulate IL-10 production via STAT3 transcriptional activity, suppressing CD4-positive T cell proliferation and IFN-γ production. Taken together, our results support the notion that tumors can hijack NK cells as a means to escape immunity and that CD73 expression defines an inducible population of NK cells with immunoregulatory properties within the tumor microenvironment.

Infiltration by IL22-Producing T Cells Promotes Neutrophil Recruitment and Predicts Favorable Clinical Outcome in Human Colorectal Cancer

Immune cell infiltration in colorectal cancer effectively predicts clinical outcome. IL22, produced by immune cells, plays an important role in inflammatory bowel disease, but its relevance in colorectal cancer remains unclear. Here, we addressed the prognostic significance of IL22+ cell infiltration in colorectal cancer and its effects on the composition of tumor microenvironment. Tissue microarrays (TMA) were stained with an IL22-specific mAb, and positive immune cells were counted by expert pathologists. Results were correlated with clinicopathologic data and overall survival (OS). Phenotypes of IL22-producing cells were assessed by flow cytometry on cell suspensions from digested specimens. Chemokine production was evaluated in vitro upon colorectal cancer cell exposure to IL22, and culture supernatants were used to assess neutrophil migration in vitro Evaluation of a testing (n = 425) and a validation TMA (n = 89) revealed that high numbers of IL22 tumor-infiltrating immune cells were associated with improved OS in colorectal cancer. Ex vivo analysis indicated that IL22 was produced by CD4+ and CD8+ polyfunctional T cells, which also produced IL17 and IFNγ. Exposure of colorectal cancer cells to IL22 promoted the release of the neutrophil-recruiting chemokines CXCL1, CXCL2, and CXCL3 and enhanced neutrophil migration in vitro Combined survival analysis revealed that the favorable prognostic significance of IL22 in colorectal cancer relied on the presence of neutrophils and was enhanced by T-cell infiltration. Altogether, colorectal cancer-infiltrating IL22-producing T cells promoted a favorable clinical outcome by recruiting beneficial neutrophils capable of enhancing T-cell responses.

Innate Lymphoid Cells in the Malignant Melanoma Microenvironment

Simple Summary

Innate lymphoid cells (ILCs) are the innate counterparts of adaptive immune cells. Emerging data indicate that they are also key players in the progression of multiple tumors. In this review we briefly describe ILCs’ functions in the skin, lungs and liver. Next, we analyze the role of ILCs in primary cutaneous melanoma and in its most frequent and deadly metastases, those in liver and lung. We focus on their dual anti– and pro-tumoral functions, depending on the cross-interactions among them and with the surrounding stromal cells that form the tumor microenvironment (TME) in each organ. Next, we detail the role of extracellular vesicles secreted to the TME by ILCs and melanoma on both cell populations. We conclude that the identification of markers and tools to allow the modulation of individual ILC subsets, in addition to the development of standardized protocols, is essential for addressing the therapeutic modulation of ILCs.

Abstract

The role of innate lymphoid cells (ILCs) in cancer progression has been uncovered in recent years. ILCs are classified as Type 1, Type 2, and Type 3 ILCs, which are characterized by the transcription factors necessary for their development and the cytokines and chemokines they produce. ILCs are a highly heterogeneous cell population, showing both anti– and protumoral properties and capable of adapting their phenotypes and functions depending on the signals they receive from their surrounding environment. ILCs are considered the innate counterparts of the adaptive immune cells during physiological and pathological processes, including cancer, and as such, ILC subsets reflect different types of T cells. In cancer, each ILC subset plays a crucial role, not only in innate immunity but also as regulators of the tumor microenvironment. ILCs’ interplay with other immune and stromal cells in the metastatic microenvironment further dictates and influences this dichotomy, further strengthening the seed-and-soil theory and supporting the formation of more suitable and organ-specific metastatic environments. Here, we review the present knowledge on the different ILC subsets, focusing on their interplay with components of the tumor environment during the development of primary melanoma as well as on metastatic progression to organs, such as the liver or lung.

Regulatory functions of NK cells during infections and cancer

After recognition, NK cells can kill susceptible target cells through perforin-dependent mechanisms or by inducing death receptor-mediated apoptosis, and they can also secrete cytokines that are pivotal for immunomodulation. Despite the critical role as effector cells against tumors and virus-infected cells, NK cells have been implicated in the regulation of T cell-mediated responses in different models of autoimmunity, transplantation, and viral infections. Here, we review the mechanisms described for NK cell-mediated inhibition of adaptive immune responses, with spotlight on the emerging evidence of their regulatory role that shapes antitumor immune responses.

Natural killer cells in the human lung tumor microenvironment display immune inhibitory functions

BACKGROUND

Natural killer (NK) cells play a crucial role in tumor immunosurveillance through their cytotoxic effector functions and their capacity to interact with other immune cells to build a coordinated antitumor immune response. Emerging data reveal NK cell dysfunction within the tumor microenvironment (TME) through checkpoint inhibitory molecules associated with a regulatory phenotype.

OBJECTIVE

We aimed at analyzing the gene expression profile of intratumoral NK cells compared with non-tumorous NK cells, and to characterize their inhibitory function in the TME.

METHODS

NK cells were sorted from human lung tumor tissue and compared with non- tumoral distant lungs.

RESULTS

In the current study, we identify a unique gene signature of NK cell dysfunction in human non-small cell lung carcinoma (NSCLC). First, transcriptomic analysis reveals significant changes related to migratory pattern with a downregulation of sphingosine-1-phosphate receptor 1 (S1PR1) and CX3C chemokine receptor 1 (CX3CR1) and overexpression of C-X-C chemokine receptor type 5 (CXCR5) and C-X-C chemokine receptor type 6 (CXCR6). Second, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and killer cell lectin like receptor (KLRC1) inhibitory molecules were increased in intratumoral NK cells, and CTLA-4 blockade could partially restore MHC class II level on dendritic cell (DC) that was impaired during the DCs/NK cell cross talk. Finally, NK cell density impacts the positive prognostic value of CD8⁺ T cells in NSCLC.

CONCLUSIONS

These findings demonstrate novel molecular cues associated with NK cell inhibitory functions in NSCLC.

NK cells in the tumor microenvironment: Prognostic and theranostic impact. Recent advances and trends

NK cells orchestrate the tumor destruction and control metastasis in a coordinated way with other immune cells of the tumor microenvironment. However, NK cell infiltration in the tumor microenvironment is limited, and tumor cells have developed numerous mechanisms to escape NK cell attack. As a result, NK cells that have been able to infiltrate the tumors are exhausted, and metabolically and functionally impaired. Depending this impairment the prognostic and theranostic values of NK cells differ depending on the studies, the type of cancer, the stage of tumor and the nature of the tumor microenvironment. Extensive studies have been done to investigate different strategies to improve the NK cell function, and nowadays, a battery of therapeutic tools are being tested, with promising results.

ILC2-driven innate immune checkpoint mechanism antagonizes NK cell antimetastatic function in the lung

Metastasis constitutes the primary cause of cancer-related deaths, with the lung being a commonly affected organ. We found that activation of lung-resident group 2 innate lymphoid cells (ILC2s) orchestrated suppression of natural killer (NK) cell-mediated innate antitumor immunity, leading to increased lung metastases and mortality. Using multiple models of lung metastasis, we show that interleukin (IL)-33-dependent ILC2 activation in the lung is involved centrally in promoting tumor burden. ILC2-driven innate type 2 inflammation is accompanied by profound local suppression of interferon-γ production and cytotoxic function of lung NK cells. ILC2-dependent suppression of NK cells is elaborated via an innate regulatory mechanism, which is reliant on IL-5-induced lung eosinophilia, ultimately limiting the metabolic fitness of NK cells. Therapeutic targeting of IL-33 or IL-5 reversed NK cell suppression and alleviated cancer burden. Thus, we reveal an important function of IL-33 and ILC2s in promoting tumor metastasis via their capacity to suppress innate type 1 immunity.

Natural killer cells in cancer biology and therapy

The tumor microenvironment is highly complex, and immune escape is currently considered an important hallmark of cancer, largely contributing to tumor progression and metastasis. Named for their capability of killing target cells autonomously, natural killer (NK) cells serve as the main effector cells toward cancer in innate immunity and are highly heterogeneous in the microenvironment. Most current treatment options harnessing the tumor microenvironment focus on T cell-immunity, either by promoting activating signals or suppressing inhibitory ones. The limited success achieved by T cell immunotherapy highlights the importance of developing new-generation immunotherapeutics, for example utilizing previously ignored NK cells. Although tumors also evolve to resist NK cell-induced cytotoxicity, cytokine supplement, blockade of suppressive molecules and genetic engineering of NK cells may overcome such resistance with great promise in both solid and hematological malignancies. In this review, we summarized the fundamental characteristics and recent advances of NK cells within tumor immunometabolic microenvironment, and discussed potential application and limitations of emerging NK cell-based therapeutic strategies in the era of presicion medicine.

NK Cells Negatively Regulate CD8 T Cells to Promote Immune Exhaustion and Chronic Toxoplasma gondii Infection

NK cells regulate CD4+ and CD8+ T cells in acute viral infection, vaccination, and the tumor microenvironment. NK cells also become exhausted in chronic activation settings. The mechanisms causing these ILC responses and their impact on adaptive immunity are unclear. CD8+ T cell exhaustion develops during chronic Toxoplasma gondii (T. gondii) infection resulting in parasite reactivation and death. How chronic T. gondii infection impacts the NK cell compartment is not known. We demonstrate that NK cells do not exhibit hallmarks of exhaustion. Their numbers are stable and they do not express high PD1 or LAG3. NK cell depletion with anti-NK1.1 is therapeutic and rescues chronic T. gondii infected mice from CD8+ T cell exhaustion dependent death, increases survival after lethal secondary challenge and alters cyst burdens in brain. Anti-NK1.1 treatment increased polyfunctional CD8+ T cell responses in spleen and brain and reduced CD8+ T cell apoptosis in spleen. Chronic T. gondii infection promotes the development of a modified NK cell compartment, which does not exhibit normal NK cell characteristics. NK cells are Ly49 and TRAIL negative and are enriched for expression of CD94/NKG2A and KLRG1. These NK cells are found in both spleen and brain. They do not produce IFNγ, are IL-10 negative, do not increase PDL1 expression, but do increase CD107a on their surface. Based on the NK cell receptor phenotype we observed NKp46 and CD94-NKG2A cognate ligands were measured. Activating NKp46 (NCR1-ligand) ligand increased and NKG2A ligand Qa-1b expression was reduced on CD8+ T cells. Blockade of NKp46 rescued the chronically infected mice from death and reduced the number of NKG2A+ cells. Immunization with a single dose non-persistent 100% protective T. gondii vaccination did not induce this cell population in the spleen, suggesting persistent infection is essential for their development. We hypothesize chronic T. gondii infection induces an NKp46 dependent modified NK cell population that reduces functional CD8+ T cells to promote persistent parasite infection in the brain. NK cell targeted therapies could enhance immunity in people with chronic infections, chronic inflammation and cancer.

Eomes Expression Defines Group 1 Innate Lymphoid Cells During Metastasis in Human and Mouse

Recent studies have attempted to uncover the role of Group 1 Innate lymphoid cells (ILCs) in multiple physiological contexts, including cancer. However, the definition and precise contribution of Group 1 ILCs (constituting ILC1 and NK subsets) to metastasis is unclear due to the lack of well-defined cell markers. Here, we first identified ILC1 and NK cells in NSCLC patient blood and differentiated them based on the expression of transcription factors, T-bet and Eomes. Interestingly, Eomes downregulation in the peripheral blood NK cells of NSCLC patients positively correlated with disease progression. Additionally, we noted higher Eomes expression in NK cells (T-bet⁺Eomes^hi) compared to ILC1s (T-bet⁺Eomes^lo). We asked whether the decrease in Eomes was associated with the conversion of NK cells into ILC1 using Eomes as a reliable marker to differentiate ILC1s from NK cells. Utilizing a murine model of experimental metastasis, we observed an association between increase in metastasis and Eomes downregulation in NKp46⁺NK1.1⁺ Group 1 ILCs, which was consistent to that of human NSCLC samples. Further confirmation of this trend was achieved by flow cytometry, which identified tissue-specific Eomes^lo ILC1-like and Eomes^hi NK-like subsets in the murine metastatic lung based on cell surface markers and adoptive transfer experiments. Next, functional characterization of these cell subsets showed reduced cytotoxicity and IFNγ production in Eomes^lo ILC1s compared to Eomes^hi cells, suggesting that lower Eomes levels are associated with poor cancer immunosurveillance by Group 1 ILCs. These findings provide novel insights into the regulation of Group 1 ILC subsets during metastasis, through the use of Eomes as a reliable marker to differentiate between NK and ILC1s.

Ambiguous roles and potential therapeutic strategies of innate lymphoid cells in different types of tumor

Recent years have witnessed a significant development in the current understanding of innate lymphoid cells (ILCs) and their roles in the innate immune system, where they regulate tissue homeostasis, inflammation, as well as tumor surveillance and tumorigenesis. Based on the limited studies of ILCs in cancer, ILCs may be classified into three subgroups depending on their phenotypic and functional characteristics: Group 1 ILCs, which include natural killer cells and ILC1s; Group 2 ILCs, which only contain ILC2s and Group 3 ILCs, which comprise of LTi cells and ILC3s. Group 1 ILCs predominantly exert antitumor activities, while Group 2 ILCs and Group 3 ILCs are predominantly procarcinogenic in nature. In different types of tumor, each ILC subset behaves differently. Current research is focused on investigating how ILCs may be manipulated and employed as therapeutic strategies for the treatment of cancer. The present review aimed to summarize the characteristics and effects of ILCs in the context of tumor immunology, and provide novel insight into the pro- or anti-tumor activities of ILCs in different types of malignancy, including solid tumors, such as those in the gastrointestinal tract, lung, breast, bladder or prostate, as well as melanoma, further to hematological malignancies, with the aim to highlight potential therapeutic targets for the treatment of cancer.

Interleukin-22 regulates gastric cancer cell proliferation through regulation of the JNK signaling pathway

Inflammation is considered as one of the major hallmarks of cancer and is associated with gastric cancer. Interleukin-22 (IL-22), a member of the IL-10 family, serves an important role in inflammatory diseases and tumors. The aim of the present study was to examine the effects of IL-22 on the proliferation of gastric cancer cells (AGS cells) in vitro and explore the associated molecular mechanism. The results of a Cell Counting kit-8 assay using AGS cells transfected with an IL-22-plasmid indicated that IL-22 could promote AGS cell viability. However, when IL-22 was knocked down by IL-22-short hairpin (sh)RNA, the viability of AGS cells was significantly impaired. Western blotting results indicated that IL-22 decreased the activation of the mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, IL-22-shRNA transfection increased the activation of MAPK, as evidenced by the upregulated phosphorylation of ERK and JNK. Taken together, the results of the present study suggest that IL-22 regulated the viability of gastric cancer cells through the JNK signaling pathway, suggesting a therapeutic approach for gastric cancer via targeting IL-22.

IL-12 regulates the expansion, phenotype, and function of murine NK cells activated by IL-15 and IL-18

NK cells, which are composed of phenotypically and functionally heterogeneous subpopulations, play critical roles in immunity against cancer. The mechanism of generation of distinct subsets such as the effector and regulatory subtypes is unclear. Here, we show that this process comprises several steps, including generation of proliferating, highly cytotoxic cells activated by IL-15/IL-18 and differentiation into distinct cell populations induced with IL-12. Freshly prepared murine splenic NK cells expressed IL-15Rs and IL-18Rs and rapidly began to proliferate following stimulation with IL-15/IL-18. The proliferating NK cells highly expressed various activation markers such as B220, CD49b (DX5), lysosome-associated membrane glycoprotein 1 (LAMP-1), DNAX accessory molecule 1, perforin, and granzyme B and showed reduced expression of natural killer cell p46-related protein (NKp46) and IL-18Rα. These cells exerted strong cytotoxicity against YAC-1 cells, but did not secrete cytokines. IL-12 rapidly activated STAT4 in these cells, induced IFN-γ production, and then upregulated p21 and p27, leading to withdrawal from the cell cycle. In parallel, IL-12-stimulated cells gradually reduced cytotoxicity, decreased expression of activation markers, and instead increased expression of Sca-1, CD25, CD49a, and NKp46. Some IL-15/IL-18-induced cells strongly expressed PD-1, whereas NK cells induced with IL-15/IL-18 and IL-12 expressed high levels of T cell immunoglobulin mucin-3, LAG-3, and natural killer group 2 A. Furthermore, these cells spontaneously secreted IL-10 and TGF-β following prolonged incubation. Thus, IL-12 regulates expansion of NK cells activated with IL-15/IL-18, influences the population size of highly cytotoxic cells, and induces differentiation to unique cells sharing some phenotypes of ILCs.