Innate Lymphoid Cells in Tumor Immunity

Unveiling the link between chronic inflammation and cancer

The highly nuanced transition from an inflammatory process to tumorigenesis is of great scientific interest. While it is well known that environmental stimuli can cause inflammation, less is known about the oncogenic modifications that chronic inflammation in the tissue microenvironment can bring about, as well as how these modifications can set off pro-tumorigenic processes. It is clear that no matter where the environmental factors come from, maintaining an inflammatory microenvironment encourages carcinogenesis. In addition to encouraging angiogenesis and metastatic processes, sustaining the survival and proliferation of malignant transformed cells, and possibly altering the efficacy of therapeutic agents, inflammation can negatively regulate the antitumoral adaptive and innate immune responses. Because chronic inflammation has multiple pathways involved in tumorigenesis and metastasis, it has gained recognition as a marker of cancer and a desirable target for cancer therapy. Recent advances in our knowledge of the molecular mechanisms that drive cancer's progression demonstrate that inflammation promotes tumorigenesis and metastasis while suppressing anti-tumor immunity. In many solid tumor types, including breast, lung, and liver cancer, inflammation stimulates the activation of oncogenes and impairs the body's defenses against the tumor. Additionally, it alters the microenvironment of the tumor. As a tactical approach to cancer treatment, these findings have underscored the importance of targeting inflammatory pathways. This review highlights the role of inflammation in cancer development and metastasis, focusing on its impact on tumor progression, immune suppression, and therapy resistance. It examines current anti-inflammatory strategies, including NSAIDs, cytokine modulators, and STAT3 inhibitors, while addressing their potential and limitations. The review emphasizes the need for further research to unravel the complex mechanisms linking inflammation to cancer progression and identify molecular targets for specific cancer subtypes.

Failed Induction of the TH1 System in TH2 Dominant Patients: The Cancer-Permissive Immune Macroenvironment

Tumor microenvironment infiltration by cells of the T helper cell type 1 (TH1) system, including TH1 cells, M1 macrophages, natural killer cells, and CD8+ T cells, is associated with better cancer prognosis. In contrast, tumor microenvironment infiltration by cells of the TH2 system, including TH2 cells, M2 macrophages, and innate lymphoid cells type 2, as well as immune suppressive myeloid-derived suppressor cells and regulatory T cells, is associated with poorer cancer prognosis. Beyond the tumor itself and a myriad of other modifying factors, such as genetic and epigenetic influences on tumorigenesis, the overall immune state of the patient, termed the macroenvironment, has also been shown to significantly influence cancer outcomes. Alterations in the tricarboxylic acid (TCA) cycle (TCA cycle breaks) involving loss of function of succinate dehydrogenase, isocitrate dehydrogenase, and fumarate hydratase have been shown to be associated with an intracellular metabolic shift away from oxidative phosphorylation and into glycolysis in cells that are transforming into cancer cells. The same loss of function of succinate dehydrogenase and isocitrate dehydrogenase has also been identified as inducing a shift in macrophages toward glycolysis that is associated with M1 macrophage polarization. M1 macrophages make interleukin 12, which stimulates TH1 cells and natural killer cells to produce interferon gamma (IFN-γ), which in turn stimulates M1 macrophage activity, forming an activation loop. IFN-γ also drives activation of CD8+ T cells. Thus, M1 macrophage activation initiates and sustains activation of the TH1 system of cells. In this fashion, TCA cycle breaks at succinate dehydrogenase and isocitrate dehydrogenase that promote cellular transformation into cancer cells are also associated with upregulation of the TH1 system that provides anti-cancer immune surveillance. The TH1 and TH2 systems are known to inhibit each other's activation. It is this author's hypothesis that, in patients whose macroenvironment is sufficiently TH2-dominant, the metabolic shift toward glycolysis induced by TCA cycle breaks that gives rise to mutagenic changes in tissue parenchymal cells is not counterbalanced by adequate activation of M1 macrophages, thus giving rise to cancer cell development. For instance, the atopic TH2-high asthma phenotype, a TH2 dominance-based comorbidity, is associated with a more than doubled incidence of colon, breast, lung, and prostate cancer, compared with non-asthmatics. Failure of TCA cycle breaks to induce M1 polarization of tissue-resident macrophages yields a tissue environment in which the tissue-resident macrophages fail to routinely perform M1-associated functions such as phagocytizing newly developing cancer cells. Failure of M1 phenotypic expression in both tissue-resident macrophages and monocyte-derived macrophages recruited to the tumor microenvironment yields both a loss of direct antitumor M1 macrophage actions and failure of TH1 system activation in general, including failure of CD8+ T cell activation, yielding a cancer-permissive tumor microenvironment and a poorer prognosis in patients with existing cancers. This paper proposes a conceptual framework that connects established elements in the existing research and points to the utility of a patient profiling process, aimed at personalization of treatment through identification and targeting of elements in each patient's tumor microenvironment and macroenvironment that contribute to unfavorable prognosis.

Innate immune cells: Key players of orchestra in modulating tumor microenvironment (TME)

The tumor microenvironment (TME) with vital role in cancer progression is composed of various cells such as endothelial cells, immune cells, and mesenchymal stem cells. In particular, innate immune cells such as macrophages, dendritic cells, myeloid-derived suppressor cells, neutrophils, innate lymphoid cells, γδT lymphocytes, and natural killer cells can either promote or suppress tumor progression when present in the TME. An increase in research on the cross-talk between the TME and innate immune cells will lead to new approaches for anti-tumoral therapeutic interventions. This review primarily focuses on the biology of innate immune cells and their main functions in the TME. In addition, it summarizes several innate immune-based immunotherapies that are currently tested in clinical trials.

Dendritic Cell Vaccines Impact the Type 2 Innate Lymphoid Cell Population and Their Cytokine Generation in Mice

Dendritic cell (DC) vaccines can stimulate the immune system to target cancer antigens, making them a promising therapy in immunotherapy. Clinical trials have shown limited effectiveness of DC vaccines, highlighting the need to enhance the immune responses they generate. Innate lymphoid cells (ILCs) are a diverse group of innate leukocytes that produce various cytokines and regulate the immune system. These cells have the potential to improve immunotherapies. There is not much research on how group 2 ILCs (ILC2s) communicate with DC vaccines. Therefore, examining the roles of DC vaccination in immune responses is crucial. Our research analyzed the effects of DC vaccination on the ILC2 populations and their cytokine production. By exploring the relationship between ILC2s and DCs, we aimed to understand how this could affect DC-based immunotherapies. The results showed an increase in the number of ILC2s in the local draining lymph node and spleen of tumor-free mice, as well as in the lungs of mice challenged with tumors in a pulmonary metastasis model. This suggests a complex interplay between DC-based vaccines and ILC2s, which is further influenced by the presence of tumors.

The Potential of Dendritic-Cell-Based Vaccines to Modulate Type 3 Innate Lymphoid Cell Populations

Dendritic cell (DC) vaccines are a type of immunotherapy that relies on the communication of DCs with other aspects of the immune system. DCs are potent antigen-presenting cells involved in the activation of innate immune responses and education of adaptive immunity, making them ideal targets for immunotherapies. Innate lymphoid cells (ILCs) are relatively newly identified in the field of immunology and have important roles in health and disease. The studies described here explored the communications between type 3 ILCs (ILC3s) and DCs using a murine model of DC-based vaccination. Local and systemic changes in ILC3 populations following the administration of a DC vaccine were observed, and upon challenge with B16F10 melanoma cells, changes in ILC3 populations in the lungs were observed. The interactions between DCs and ILC3s should be further explored to determine the potential that their communications could have in health, disease, and the development of immunotherapies.

Control of innate immune response by biomaterial surface topography, energy, and stiffness

As the focus of implantable biomaterials has shifted from bioinert implants to bioactive designs, recent research has highlighted the complex interactions between cell physiologic systems and material properties, particularly physical cues. From the cells known to interact with implanted biomaterials, the response of the immune system has been a critical target of study recently. Here, we review studies characterizing the response of innate immune cells to various material cues, particularly of those at the surface of implanted materials.The innate immune system consists of cell types with various roles in inflammation. Neutrophils and macrophages serve both phagocytic and signaling roles, especially early in the inflammatory phase of biomaterial implantation. These cell types ultimately dictate the outcome of implants as chronic inflammation, fibrosis, or integration. Other cell types like dendritic cells, mast cells, natural killer cells, and innate lymphoid cells may also serve an immunomodulatory role in the biomaterial context. This review highlights recent advances in our understanding of the role of innate immunity in the response to implantable biomaterials as well as key mechanobiological findings in innate immune cells underpinning these advances. STATEMENT OF SIGNIFICANCE: This review highlights recent advances in the understanding of the role of innate immunity in the response to implantable biomaterials, especially in neutrophils and macrophages, as well as key mechanobiological findings in innate immune cells underpinning these advances. Here we discuss how physicochemical properties of biomaterials control innate immune cell behavior.

Inflammation-Induced Tumorigenesis and Metastasis

Inflammation, especially chronic inflammation, plays a pivotal role in tumorigenesis and metastasis through various mechanisms and is now recognized as a hallmark of cancer and an attractive therapeutic target in cancer. In this review, we discuss recent advances in molecular mechanisms of how inflammation promotes tumorigenesis and metastasis and suppresses anti-tumor immunity in various types of solid tumors, including esophageal, gastric, colorectal, liver, and pancreatic cancer as well as hematopoietic malignancies.

An overview of the tumor microenvironment, from cells to complex networks (Review)

For a long period, cancer has been believed to be a gene disease, in which oncogenic and suppressor mutations accumulate gradually, finally leading to the malignant transformation of cells. This vision has changed in the last few years, the involvement of the tumor microenvironment, the non-malignant part of the tumors, as an important contributor to the malignant growth being now largely recognized. There is a consensus according to which the understanding of the tumor microenvironment is important as a means to develop new approaches in the therapy of cancer. In this context, the present study is a review of the different types of non-malignant cells that can be found in tumors, with their pro or antitumoral actions, presence in tumors and therapeutic targeting. These cells establish complex relations between them, through cytokines, exosomes, cell adhesion, co-stimulation and co-inhibition; these relations will also be examined in the present work.

Mechanisms of hyperprogressive disease after immune checkpoint inhibitor therapy: what we (don't) know

Immune checkpoint inhibitors (ICIs) have made a breakthrough in the treatment of different types of tumors, leading to improvement in survival, even in patients with advanced cancers. Despite the good clinical results, a certain percentage of patients do not respond to this kind of immunotherapy. In addition, in a fraction of nonresponder patients, which can vary from 4 to 29% according to different studies, a paradoxical boost in tumor growth after ICI administration was observed: a completely unpredictable novel pattern of cancer progression defined as hyperprogressive disease. Since this clinical phenomenon has only been recently described, a universally accepted clinical definition is lacking, and major efforts have been made to uncover the biological bases underlying hyperprogressive disease. The lines of research pursued so far have focused their attention on the study of the immune tumor microenvironment or on the analysis of intrinsic genomic characteristics of cancer cells producing data that allowed us to formulate several hypotheses to explain this detrimental effect related to ICI therapy. The aim of this review is to summarize the most important works that, to date, provide important insights that are useful in understanding the mechanistic causes of hyperprogressive disease.

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.

Perspectives for the application of interleukin 15 in anti-cancer therapy

Interleukin (IL-) 15 plays a crucial role in the preservation of lymphoid cell homeostasis including maintaining a broad repertoire of naïve T, B and NK cells, eliminating effector cells and long-term survival of memory cells. It is an essential causative factor in generating CD8+ T cells of memory. In addition, it selectively promotes not only survival and proliferation, but also the effector function of antigen-specific cytotoxic T lymphocytes, even in the presence of regulatory T cells. Interleukin 15 can thus modulate immune suppression as well as promote an immune activation. All obtained data on the biology and function of IL-15 provide information essential to design the manners of its application in the fight against the solid cancers and myeloproliferative neoplasms and make it a promising therapeutic option provided that its potential is consciously used. In this paper we reviewed on the relationship between the biological properties of IL-15 and its IL-15/IL-15Rα complex and their antitumor potential in the light of recent reports about the possibilities of using these molecules in cancer therapy have been assessed.

Critical Roles of Balanced Innate Lymphoid Cell Subsets in Intestinal Homeostasis, Chronic Inflammation, and Cancer

Innate lymphoid cells (ILCs) comprise a recently identified subset of innate immune cells that are mainly localized to mucosa-associated tissues. Although they have not yet been fully characterized, they can generally be divided into ILC1s, ILC2s, and ILC3s. ILCs and their corresponding cytokines act as important mediators of the early stages of the immune response during inflammation, tissue repair, and the maintenance of epithelial integrity. Consequently, the dysregulation of ILC subsets might promote inflammation and cancer. Numerous studies have demonstrated that these cells play an important role in maintaining the microecological balance of the small intestine; however, their specific roles in mediating inflammation in this tissue and tumorigenesis remain unclear and controversial. In this review, we focus on recent progress that has helped to gain a better understanding of the role of ILCs in intestinal homeostasis, chronic inflammation, and cancer. Further focused research on the regulation and role of ILCs in intestinal homeostasis and pathology will help to reveal valuable diagnostic and therapeutic targets for the treatment of intestinal diseases.

Regulation of Immunity in Breast Cancer

Breast cancer affects millions of women worldwide, leading to many deaths and significant economic burden. Although there are numerous treatment options available, the huge potentials of immunotherapy in the management of localized and metastatic breast cancer is currently being explored. However, there are significant gaps in understanding the complex interactions between the immune system and breast cancer. The immune system can be pro-tumorigenic and anti-tumorigenic depending on the cells involved and the conditions of the tumor microenvironment. In this review, we discuss current knowledge of breast cancer, including treatment options. We also give a brief overview of the immune system and comprehensively highlight the roles of different cells of the immune system in breast tumorigenesis, including recent research discoveries. Lastly, we discuss some immunotherapeutic strategies for the management of breast cancer.

The Tumor Microenvironment Innately Modulates Cancer Progression

Cancer development and progression occurs in concert with alterations in the surrounding stroma. Cancer cells can functionally sculpt their microenvironment through the secretion of various cytokines, chemokines, and other factors. This results in a reprogramming of the surrounding cells, enabling them to play a determinative role in tumor survival and progression. Immune cells are important constituents of the tumor stroma and critically take part in this process. Growing evidence suggests that the innate immune cells (macrophages, neutrophils, dendritic cells, innate lymphoid cells, myeloid-derived suppressor cells, and natural killer cells) as well as adaptive immune cells (T cells and B cells) contribute to tumor progression when present in the tumor microenvironment (TME). Cross-talk between cancer cells and the proximal immune cells ultimately results in an environment that fosters tumor growth and metastasis. Understanding the nature of this dialog will allow for improved therapeutics that simultaneously target multiple components of the TME, increasing the likelihood of favorable patient outcomes.

IL23-Producing Human Lung Cancer Cells Promote Tumor Growth via Conversion of Innate Lymphoid Cell 1 (ILC1) into ILC3

PURPOSE

The plasticity of innate lymphoid cells (ILCs) has been reported in vitro and in the microenvironment of the intestine. However, whether ILC plasticity contributes to regulation of the tumor microenvironment remains unknown. In this study, we explored plasticity of ILCs in human lung cancer.

EXPERIMENTAL DESIGN

We analyzed immune subsets and cytokine expression in lung cancers freshly obtained from 80 patients and explored conversion of ILC1 into ILC3 in coculture with lung cancer cells. Prognostic effects of converted ILC3 and related pathway were evaluated by retrospective cohort composed of 875 patients with lung cancer.

RESULTS

Low percentages of ILC1, and high percentages of ILC3 were found in pulmonary squamous cell carcinomas (SqCC) but not adenocarcinomas (ADC). In non-small-cell lung cancers, the percentage of ILC3 was associated with IL23 expression in tumor cells but not immune cells. In cocultures, tumor cells of SqCCs converted ILC1 into ILC3 by producing IL23, thus promoting IL17-mediated tumor cell proliferation. Consistently, among IL17⁺ immune cells, the percentages of ILCs were higher in SqCCs than ADCs. Furthermore, the numbers of CD3^-RORγt⁺ ILC3, IL17 expression level, and IL23- or IL17RA-expressing tumor cells were associated with short survival of patients with SqCC but not ADC.

CONCLUSIONS

Conversion from ILC1 into ILC3 by IL23-producing SqCCs promotes IL17-mediated tumor progression, resulting in a poor prognosis.

The Role of the Immune System in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer. In immunosuppressed populations it is a source of considerable morbidity and mortality due to its enhanced recurrence and metastatic potential. In common with many malignancies, leucocyte populations are both protective against cancer development and also play a role in 'sculpting' the nascent tumor, leading to loss of immunogenicity and tumor progression. UV radiation and chronic viral carriage may represent unique risk factors for cSCC development, and the immune system plays a key role in modulating the response to both. In this review, we discuss the lessons learned from animal and ex vivo human studies of the role of individual leucocyte subpopulations in the development of cutaneous SCC. We then discuss the insights into cSCC immunity gleaned from studies in humans, particularly in populations receiving pharmacological immunosuppression such as transplant recipients. Similar insights in other malignancies have led to exciting and novel immune therapies, which are beginning to emerge into the cSCC clinical arena.

Innate lymphoid cells in intestinal cancer development

Colorectal cancer (CRC) is a highly prominent cause of cancer-related deaths worldwide. Although the functions of immune cells in the colorectal tumor microenvironment are complex and heterogeneous, dysregulated changes in the composition and activation state of immune cells are believed to represent key events supporting the establishment of pro- or anti-tumorigenic immune states. Recently, innate lymphoid cells (ILCs) emerged as central innate immune mediators during both gastrointestinal homeostasis and inflammatory pathologies. Hence, ILCs might also represent promising targets in the context of cancer therapy and are increasingly recognized as innate immune cells with potent immunomodulatory properties. In this review, we summarize the pleiotropic roles of the different ILC subsets for intestinal homeostasis and discuss the recent evidence on their potential involvement in the development and growth of intestinal cancers.

Immunogenomic Landscape Contributes to Hyperprogressive Disease after Anti-PD-1 Immunotherapy for Cancer

Although PD-1-blocking immunotherapies demonstrate significant therapeutic promise, a subset of the patients could develop hyperprogressive disease (HPD) with accelerated tumor growth after anti-PD1 immunotherapy. To elucidate the underlying mechanisms, we compared the mutational and transcriptional landscapes between the pre- and post-therapy tumors of two patients developing HPD after anti-PD-1 immunotherapy. In post-therapy HPD tumors, somatic mutations were found in known cancer genes, including tumor suppressor genes such as TSC2 and VHL, along with transcriptional upregulation of oncogenic pathways, including IGF-1, ERK/MAPK, PI3K/AKT, and TGF-β. We found that post-therapy HPD tumors were less immunogenic than pre-therapy tumors, concurrent with an increased presence of ILC3 cells, a subset of innate lymphoid cells. We also developed a gene expression signature predictive of HPD. In summary, we identified the genomics and immune features associated with HPD, which may help identify patients at risk of adverse clinical outcome after anti-PD-1 immunotherapy.

Roles of cytotoxic and helper innate lymphoid cells in cancer

Natural killer (NK) cells have long been recognized for their anti-cancer activity and are now included in the large family of innate lymphoid cells (ILCs). The discovery of new ILC subsets that, similarly to NK cells, are able to kill tumor cells encourages us to redefine NK cell role in anti-tumor immunity. Conventional NK cells circulate through the blood and screen the body for "stressed" cells. Therefore, NK cells are believed to play a key role in cancer immunosurveillance by the early elimination of cells undergoing malignant transformation. Tissue-resident ILCs might play a similar role since they are ideally located to detect the early signs of malignant transformation in their organ of residence. We are only beginning to appreciate the importance of the whole ILC family in cancer. Confusingly, these cells have been reported to both inhibit and fuel cancer progression and the factors regulating these dual functions remain unclear. Here, I review the recent advances in our understanding of cytotoxic and cytokine-producing helper ILC subsets in cancer.

Ambiguous roles of innate lymphoid cells in chronic development of liver diseases

Innate lymphoid cells (ILCs) are defined as a distinct arm of innate immunity. According to their profile of secreted cytokines and lineage-specific transcriptional factors, ILCs can be categorized into the following three groups: group 1 ILCs (including natural killer (NK) cells and ILC1s) are dependent on T-bet and can produce interferon-γ; group 2 ILCs (ILC2s) are dependent on GATA3 and can produce type 2 cytokines, including interleukin (IL)-5 and IL-13; and, group 3 ILCs (including lymphoid tissue-like cells and ILC3s) are dependent on RORγt and can produce IL-22 and IL-17. Collaborative with adaptive immunity, ILCs are highly reactive innate effectors that promptly orchestrate immunity, inflammation and tissue repair. Dysregulation of ILCs might result in inflammatory disorders. Evidence regarding the function of intrahepatic ILCs is emerging from longitudinal studies of inflammatory liver diseases wherein they exert both physiological and pathological functions, including immune homeostasis, defenses and surveillance. Their overall effect on the liver depends on the balance of their proinflammatory and antiinflammatory populations, specific microenvironment and stages of immune responses. Here, we review the current data about ILCs in chronic liver disease progression, to reveal their roles in different stages as well as to discuss their therapeutic potency as intervention targets.

Contribution to Tumor Angiogenesis From Innate Immune Cells Within the Tumor Microenvironment: Implications for Immunotherapy

The critical role of angiogenesis in promoting tumor growth and metastasis is strongly established. However, tumors show considerable variation in angiogenic characteristics and in their sensitivity to antiangiogenic therapy. Tumor angiogenesis involves not only cancer cells but also various tumor-associated leukocytes (TALs) and stromal cells. TALs produce chemokines, cytokines, proteases, structural proteins, and microvescicles. Vascular endothelial growth factor (VEGF) and inflammatory chemokines are not only major proangiogenic factors but are also immune modulators, which increase angiogenesis and lead to immune suppression. In our review, we discuss the regulation of angiogenesis by innate immune cells in the tumor microenvironment, specific features, and roles of major players: macrophages, neutrophils, myeloid-derived suppressor and dendritic cells, mast cells, γδT cells, innate lymphoid cells, and natural killer cells. Anti-VEGF or anti-inflammatory drugs could balance an immunosuppressive microenvironment to an immune permissive one. Anti-VEGF as well as anti-inflammatory drugs could therefore represent partners for combinations with immune checkpoint inhibitors, enhancing the effects of immune therapy.

Activated innate lymphoid cell populations accumulate in human tumour tissues

Background

Innate lymphoid cells (ILC) are part of a heterogeneous family of haematopoietic effector cells which lack re-arranged antigen-specific receptors. They promote host defense and contribute to tissue and metabolic homeostasis, wound healing and immune surveillance. Their role in human cancer immunity is less defined, and therefore we aimed to identify the frequency and phenotype of distinct ILC groups in various types of cancer.

Methods

Tissue samples and peripheral blood were collected from patients undergoing surgical resection of gastrointestinal and breast tumours. Single cell suspension of tumour tissue was immediately obtained following surgery using tumour dissociation.

Results

We observed significantly higher frequencies of ILC2 (p value: 0.04) in malignant breast cancer tissue and significantly higher frequencies of group 1 ILC (p value: 0.001) in malignant gastrointestinal tumours. Tumour infiltrating ILC were found to show an activated phenotype with higher expression of MHC-II, KLRG1, early activation marker CD69 and CD44.

Conclusions

Activated innate lymphoid cells infiltrate tumours dependent on tumour type and location.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4262-4) contains supplementary material, which is available to authorized users.

Innate lymphoid cells: major players in inflammatory diseases

Recent years have seen a marked increase in our understanding of innate lymphoid cells (ILCs). ILCs can be classified into different groups based on their similarity to T cell subsets in terms of their expression of key transcription factors and cytokine production. Various immunological functions of ILCs have been described, and increasing numbers of studies have implicated these cells in inflammatory disorders. Here, we detail the roles of ILCs in inflammatory diseases; we cover type 2 inflammatory diseases (such as asthma, chronic rhinosinusitis and atopic dermatitis), as well as inflammatory bowel diseases, psoriasis and other systemic or organ-specific inflammatory and autoimmune diseases. Future directions in the field are discussed, together with potential avenues of treatment.