Short Term Hypoxia Synergizes with Interleukin 15 Priming in Driving Glycolytic Gene Transcription and Supports Human Natural Killer Cell Activities

Cellular interactions in tumor microenvironment during breast cancer progression: new frontiers and implications for novel therapeutics

The breast cancer tumor microenvironment (TME) is dynamic, with various immune and non-immune cells interacting to regulate tumor progression and anti-tumor immunity. It is now evident that the cells within the TME significantly contribute to breast cancer progression and resistance to various conventional and newly developed anti-tumor therapies. Both immune and non-immune cells in the TME play critical roles in tumor onset, uncontrolled proliferation, metastasis, immune evasion, and resistance to anti-tumor therapies. Consequently, molecular and cellular components of breast TME have emerged as promising therapeutic targets for developing novel treatments. The breast TME primarily comprises cancer cells, stromal cells, vasculature, and infiltrating immune cells. Currently, numerous clinical trials targeting specific TME components of breast cancer are underway. However, the complexity of the TME and its impact on the evasion of anti-tumor immunity necessitate further research to develop novel and improved breast cancer therapies. The multifaceted nature of breast TME cells arises from their phenotypic and functional plasticity, which endows them with both pro and anti-tumor roles during tumor progression. In this review, we discuss current understanding and recent advances in the pro and anti-tumoral functions of TME cells and their implications for developing safe and effective therapies to control breast cancer progress.

Metabolic adaptation of NK cell activity and behavior in tumors: challenges and therapeutic opportunities

The adaptation of natural killer (NK) cells to conditions in the microenvironment of tumors is deeply affected by their metabolic activity, itself a result of nutrient availability and the metabolism of the cancer cells themselves. Elevated rates of glycolysis and lipid metabolism in cancers not only lead to the accumulation of immunosuppressive byproducts but also contribute to an environment of elevated concentrations of extracellular metabolites. This results in altered NK cell bioenergetics through changes in transcriptional and translational profiles, ultimately affecting their pharmacology and impairing NK cell responses. However, understanding the metabolic processes that drive alterations in immunological signaling on NK cells remains both difficult and vastly underexplored. We discuss the varied and complex drivers of NK cell metabolism in homeostasis and the tumor microenvironment (TME), challenges associated with their targetability, and unexplored therapeutic opportunities.

Harnessing Natural Killer Cells for Lung Cancer Therapy

Lung cancer is the leading cause of cancer-related death worldwide. Although natural killer (NK) cells are garnering interest as a potential anticancer therapy because they selectively recognize and eliminate cancer cells, their use in treating solid tumors, including lung cancer, has been limited due to impediments to their efficacy, such as their limited ability to reach tumor tissues, the reduced antitumor activity of tumor-infiltrating NK cells, and the suppressive tumor microenvironment (TME). This comprehensive review provides an in-depth analysis of the cross-talk between the lung cancer TME and NK cells. We highlight the various mechanisms used by the TME to modulate NK-cell phenotypes and limit infiltration, explore the role of the TME in limiting the antitumor activity of NK cells, and discuss the current challenges and obstacles that hinder the success of NK-cell-based immunotherapy for lung cancer. Potential opportunities and promising strategies to address these challenges have been implemented or are being developed to optimize NK-cell-based immunotherapy for lung cancer. Through critical evaluation of existing literature and emerging trends, this review provides a comprehensive outlook on the future of NK-cell-based immunotherapy for treating lung cancer.

Cross-talk between insulin resistance and nitrogen species in hypoxia leads to deterioration of tissue and homeostasis

Hypoxia has been linked with insulin resistance as it produces changes in the metabolism of the cell; in which the adipocytes impede the insulin receptor tyrosine, phosphorylation, directing at decreased levels of transport of glucose. At this juncture, we are focusing on cross-talk between insulin resistance and nitrogen species in hypoxia, leading to the deterioration of tissue and homeostasis. Physiological levels of nitric oxide play a very crucial role in acting as a priority effector and signaling molecule, arbitrating the body's responses to hypoxia. Both ROS and RNS are associated with a reduction in IRS1 phosphorylation in tyrosine, which leads to reduced levels of IRS1 content and insulin response, which further leads to insulin resistance. Cellular hypoxia is a trigger to inflammatory mediators which signal tissue impairment and initiate survival requirements. But, hypoxia-mediated inflammation act as a protective role by an immune response and promotes wound healing during infection. In this review, we abridge the crosstalk between the inflammation and highlight the dysregulation in physiological consequences due to diabetes mellitus. Finally, we review various treatments available for its related physiological complications.

Intrinsic and extrinsic factors determining natural killer cell fate: Phenotype and function

Natural killer (NK) cells are derived from hematopoietic stem cells. They belong to the innate lymphoid cell family, which is an important part of innate immunity. This family plays a role in the body mainly through the release of perforin, granzyme, and various cytokines and is involved in cytotoxicity and cytokine-mediated immune regulation. NK cells involved in normal immune regulation and the tumor microenvironment (TME) can exhibit completely different states. Here, we discuss the growth, development, and function of NK cells in regard to intrinsic and extrinsic factors. Intrinsic factors are those that influence NK cells to promote cell maturation and exert their effector functions under the control of internal metabolism and self-related genes. Extrinsic factors include the metabolism of the TME and the influence of related proteins on the "fate" of NK cells. This review targets the potential of NK cell metabolism, cellular molecules, regulatory genes, and other mechanisms involved in immune regulation. We further discuss immune-mediated tumor therapy, which is the trend of current research.

Mechanisms of HIF-driven immunosuppression in tumour microenvironment

Hypoxia arises due to insufficient oxygen delivery to rapidly proliferating tumour cells that outpace the available blood supply. It is a characteristic feature of most solid tumour microenvironments and plays a critical role in regulating anti-tumour immunity, enhancing tumoral heterogeneity, and promoting therapeutic resistance and poor clinical outcomes. Hypoxia-inducible factors (HIFs) are the major hypoxia-responsive transcription factors that are activated under low oxygenation conditions and have been identified to drive multifunctional roles in tumour immune evasion. The HIF signalling network serves as an attractive target for targeted therapeutic approaches. This review aims to provide a comprehensive overview of the most crucial mechanisms by which HIF controls the expression of immunosuppressive molecules and immune checkpoints, disrupts cancer immunogenicity, and induces immunotherapeutic resistance.

Immunologic and vascular biomarkers of mortality in critical COVID-19 in a South African cohort

Introduction

Biomarkers predicting mortality among critical Coronavirus disease 2019 (COVID-19) patients provide insight into the underlying pathophysiology of fatal disease and assist with triaging of cases in overburdened settings. However, data describing these biomarkers in Sub-Saharan African populations are sparse.

Methods

We collected serum samples and corresponding clinical data from 87 patients with critical COVID-19 on day 1 of admission to the intensive care unit (ICU) of a tertiary hospital in Cape Town, South Africa, during the second wave of the COVID-19 pandemic. A second sample from the same patients was collected on day 7 of ICU admission. Patients were followed up until in-hospital death or hospital discharge. A custom-designed 52 biomarker panel was performed on the Luminex® platform. Data were analyzed for any association between biomarkers and mortality based on pre-determined functional groups, and individual analytes.

Results

Of 87 patients, 55 (63.2%) died and 32 (36.8%) survived. We found a dysregulated cytokine response in patients who died, with elevated levels of type-1 and type-2 cytokines, chemokines, and acute phase reactants, as well as reduced levels of regulatory T cell cytokines. Interleukin (IL)-15 and IL-18 were elevated in those who died, and levels reduced over time in those who survived. Procalcitonin (PCT), C-reactive protein, Endothelin-1 and vascular cell adhesion molecule-1 were elevated in those who died.

Discussion

These results show the pattern of dysregulation in critical COVID-19 in a Sub-Saharan African cohort. They suggest that fatal COVID-19 involved excessive activation of cytotoxic cells and the NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome. Furthermore, superinfection and endothelial dysfunction with thrombosis might have contributed to mortality. HIV infection did not affect the outcome. A clinically relevant biosignature including PCT, pH and lymphocyte percentage on differential count, had an 84.8% sensitivity for mortality, and outperformed the Luminex-derived biosignature.

Addressing Natural Killer Cell Dysfunction and Plasticity in Cell-Based Cancer Therapeutics

Natural killer (NK) cells are cytotoxic group 1 innate lymphoid cells (ILC), known for their role as killers of stressed, cancerous, and virally infected cells. Beyond this cytotoxic function, NK cell subsets can influence broader immune responses through cytokine production and have been linked to central roles in non-immune processes, such as the regulation of vascular remodeling in pregnancy and cancer. Attempts to exploit the anti-tumor functions of NK cells have driven the development of various NK cell-based therapies, which have shown promise in both pre-clinical disease models and early clinical trials. However, certain elements of the tumor microenvironment, such as elevated transforming growth factor (TGF)-β, hypoxia, and indoalemine-2,3-dioxygenase (IDO), are known to suppress NK cell function, potentially limiting the longevity and activity of these approaches. Recent studies have also identified these factors as contributors to NK cell plasticity, defined by the conversion of classical cytotoxic NK cells into poorly cytotoxic, tissue-resident, or ILC1-like phenotypes. This review summarizes the current approaches for NK cell-based cancer therapies and examines the challenges presented by tumor-linked NK cell suppression and plasticity. Ongoing efforts to overcome these challenges are discussed, along with the potential utility of NK cell therapies to applications outside cancer.

Chimeric antigen receptor-engineered NK cells: new weapons of cancer immunotherapy with great potential

Chimeric antigen receptor (CAR)-engineered T (CAR-T) cells have obtained prominent achievement in the clinical immunotherapy of hematological malignant tumors, leading to a rapid development of cellular immunotherapy in cancer treatment. Scientists are also aware of the prospective advantages of CAR engineering in cellular immunotherapy. Due to various limitations such as the serious side effects of CAR-T therapy, researchers began to investigate other immune cells for CAR modification. Natural killer (NK) cells are critical innate immune cells with the characteristic of non-specifically recognizing target cells and with the potential to become "off-the-shelf" products. In recent years, many preclinical studies on CAR-engineered NK (CAR-NK) cells have shown their remarkable efficacy in cancer therapy and their superiority over autologous CAR-T cells. In this review, we summarize the generation, mechanisms of anti-tumor activity and unique advantages of CAR-NK cells, and then analyze some challenges and recent clinical trials about CAR-NK cells therapy. We believe that CAR-NK therapy is a promising prospect for cancer immunotherapy in the future.

Hypoxia-inducible factor-1 alpha expression is induced by IL-2 via the PI3K/mTOR pathway in hypoxic NK cells and supports effector functions in NKL cells and ex vivo expanded NK cells

Natural killer (NK) cells are cytotoxic innate lymphocytes that are specialized to kill tumor cells. NK cells are responsive to the primary cytokine IL-2 in the tumor microenvironment (TME), to activate its effector functions against tumors. Despite their inherent ability to kill tumor cells, dysfunctional NK cells observed within advanced solid tumors are associated with poor patient survival. Hypoxia in the TME is a major contributor to immune evasion in solid tumors that could contribute to impaired NK cell function. HIF-1α is a nodal regulator of hypoxia in driving the adaptive cellular responses to changes in oxygen concentrations. Whether HIF-1α is expressed in hypoxic NK cells in the context of IL-2 and whether its expression regulates NK cell effector function are unclear. Here, we report that freshly isolated NK cells from human peripheral blood in hypoxia could not stabilize HIF-1α protein coincident with impaired anti-tumor cytotoxicity. However, ex vivo expansion of these cells restored HIF-1α levels in hypoxia to promote antitumor cytotoxic functions. Similarly, the human NK cell line NKL expressed HIF-1α upon IL-2 stimulation in hypoxia and exhibited improved anti-tumor cytotoxicity and IFN-γ secretion. We found that ex vivo expanded human NK cells and NKL cells required the concerted activation of PI3K/mTOR pathway initiated by IL-2 signaling in combination with hypoxia for HIF-1α stabilization. These findings highlight that HIF-1α stabilization in hypoxia maximizes NK cell effector function and raises the prospect of NK cells as ideal therapeutic candidates for solid tumors.

TA-MSCs, TA-MSCs-EVs, MIF: their crosstalk in immunosuppressive tumor microenvironment

As an important component of the immunosuppressive tumor microenvironment (TME), it has been established that mesenchymal stem cells (MSCs) promote the progression of tumor cells. MSCs can directly promote the proliferation, migration, and invasion of tumor cells via cytokines and chemokines, as well as promote tumor progression by regulating the functions of anti-tumor immune and immunosuppressive cells. MSCs-derived extracellular vesicles (MSCs-EVs) contain part of the plasma membrane and signaling factors from MSCs; therefore, they display similar effects on tumors in the immunosuppressive TME. The tumor-promoting role of macrophage migration inhibitory factor (MIF) in the immunosuppressive TME has also been revealed. Interestingly, MIF exerts similar effects to those of MSCs in the immunosuppressive TME. In this review, we summarized the main effects and related mechanisms of tumor-associated MSCs (TA-MSCs), TA-MSCs-EVs, and MIF on tumors, and described their relationships. On this basis, we hypothesized that TA-MSCs-EVs, the MIF axis, and TA-MSCs form a positive feedback loop with tumor cells, influencing the occurrence and development of tumors. The functions of these three factors in the TME may undergo dynamic changes with tumor growth and continuously affect tumor development. This provides a new idea for the targeted treatment of tumors with EVs carrying MIF inhibitors.

iPSCs in NK Cell Manufacturing and NKEV Development

Natural killer (NK) cell immunotherapies for cancer can complement existing T cell therapies while benefiting from advancements already made in the immunotherapy field. For NK cell manufacturing, induced pluripotent stem cells (iPSCs) offer advantages including eliminating donor variation and providing an ideal platform for genome engineering. At the same time, extracellular vesicles (EVs) have become a major research interest, and purified NK cell extracellular vesicles (NKEVs) have been shown to reproduce the key functions of their parent NK cells. NKEVs have the potential to be developed into a standalone therapeutic with reduced complexity and immunogenicity compared to cell therapies. This review explores the role iPSC technology can play in both NK cell manufacturing and NKEV development.

The Dynamic Role of NK Cells in Liver Cancers: Role in HCC and HBV Associated HCC and Its Therapeutic Implications

Hepatocellular carcinoma (HCC) remains an important complication of chronic liver disease, especially when cirrhosis occurs. Existing treatment strategies include surgery, loco-regional techniques, and chemotherapy. Natural killer cells are distinctive cytotoxic lymphocytes that play a vital role in fighting tumors and infections. As an important constituent of the innate immune system against cancer, phenotypic and functional deviations of NK cells have been demonstrated in HCC patients who also exhibit perturbation of the NK-activating receptor/ligand axis. The rate of recurrence of tumor-infiltrating and circulating NK cells are positively associated with survival benefits in HCC and have prognostic significance, suggesting that NK cell dysfunction is closely related to HCC progression. NK cells are the first-line effector cells of viral hepatitis and play a significant role by directly clearing virus-infected cells or by activating antigen-specific T cells by producing IFN-γ. In addition, chimeric antigen receptor (CAR) engineered NK cells suggest an exclusive opportunity to produce CAR-NKs with several specificities with fewer side effects. In the present review, we comprehensively discuss the innate immune landscape of the liver, particularly NK cells, and the impact of tumor immune microenvironment (TIME) on the function of NK cells and the biological function of HCC. Furthermore, the role of NK cells in HCC and HBV-induced HCC has also been comprehensively elaborated. We also elaborate on available NK cell-based immunotherapeutic approaches in HCC treatment and summarize current advancements in the treatment of HCC. This review will facilitate researchers to understand the importance of the innate immune landscape of NK cells and lead to devising innovative immunotherapeutic strategies for the systematic treatment of HCC.

The Metabolic Basis of ILC Plasticity

Innate Lymphoid Cells (ILCs) are the innate counterpart of adaptive lymphoid T cells. They are key players in the regulation of tissues homeostasis and early inflammatory host responses. ILCs are divided into three groups, and further subdivided into five subsets, that are characterised by distinct transcription factors, surface markers and their cytokine expression profiles. Group 1 ILCs, including natural killer (NK) cells and non-NK cell ILC1s, express T-bet and produce IFN-γ. Group 2 ILCs depend on GATA3 and produce IL-4, IL-5 and IL-13. Group 3 ILCs, composed of ILC3s and Lymphoid Tissue Inducer (LTi) cells, express RORγt and produce IL-17 and IL-22. Even though, the phenotype of each subset is well defined, environmental signals can trigger the interconversion of phenotypes and the plasticity of ILCs, in both mice and humans. Several extrinsic and intrinsic drivers of ILC plasticity have been described. However, the changes in cellular metabolism that underlie ILC plasticity remain largely unexplored. Given that metabolic changes critically affect fate and effector function of several immune cell types, we, here, review recent findings on ILC metabolism and discuss the implications for ILC plasticity.

Current Understanding of Hypoxia in Glioblastoma Multiforme and Its Response to Immunotherapy

Simple Summary

Glioblastoma multiforme (GBM) is the most aggressive tumor type in the central nervous system. Hypoxia, defined as a lack of sufficient oxygen in tissues, is the most detrimental factor for the survival of GBM patients, promoting drug resistance, and invasion and inhibition of immune responses. Traditionally, tumor hypoxia has been studied from a narrow viewpoint, excluding the immune system and focusing primarily on the effect of hypoxia on blood vessels and tumor cells. More recently, however, evidence highlighting the important role of immunosurveillance has been uncovered for multiple tumors, including GBM. Thus, connecting the knowledge gained from traditional hypoxia studies with findings from recent immunological studies is urgently needed to better understand the role of hypoxia in cancer.

Abstract

Hypoxia is a hallmark of glioblastoma multiforme (GBM), the most aggressive cancer of the central nervous system, and is associated with multiple aspects of tumor pathogenesis. For example, hypoxia induces resistance to conventional cancer therapies and inhibits antitumor immune responses. Thus, targeting hypoxia is an attractive strategy for GBM therapy. However, traditional studies on hypoxia have largely excluded the immune system. Recently, the critical role of the immune system in the defense against multiple tumors has become apparent, leading to the development of effective immunotherapies targeting numerous cancer types. Critically, however, GBM is classified as a “cold tumor” due to poor immune responses. Thus, to improve GBM responsiveness against immunotherapies, an improved understanding of both immune function in GBM and the role of hypoxia in mediating immune responses within the GBM microenvironment is needed. In this review, we discuss the role of hypoxia in GBM from a clinical, pathological, and immunological perspective.

Role of Exercise Intensity on Th1/Th2 Immune Modulations During the COVID-19 Pandemic

The COVID-19 pandemic has led to several pioneering scientific discoveries resulting in no effective solutions with the exception of vaccination. Moderate exercise is a significant non-pharmacological strategy, to reduce the infection-related burden of COVID-19, especially in patients who are obese, elderly, and with additional comorbidities. The imbalance of T helper type 1 (Th1) or T helper type 2 (Th2) cells has been well documented among populations who have suffered as a result of the COVID-19 pandemic, and who are at maximum risk of infection and mortality. Moderate and low intensity exercise can benefit persons at risk from the disease and survivors by favorable modulation in Th1/Th2 ratios. Moreover, in COVID-19 patients, mild to moderate intensity aerobic exercise also increases immune system function but high intensity aerobic exercise may have adverse effects on immune responses. In addition, sustained hypoxia in COVID-19 patients has been reported to cause organ failure and cell death. Hypoxic conditions have also been highlighted to be triggered in COVID-19-susceptible individuals and COVID-19 survivors. This suggests that hypoxia inducible factor (HIF 1α) might be an important focus for researchers investigating effective strategies to minimize the effects of the pandemic. Intermittent hypoxic preconditioning (IHP) is a method of exposing subjects to short bouts of moderate hypoxia interspersed with brief periods of normal oxygen concentrations (recovery). This methodology inhibits the production of pro-inflammatory factors, activates HIF-1α to activate target genes, and subsequently leads to a higher production of red blood cells and hemoglobin. This increases angiogenesis and increases oxygen transport capacity. These factors can help alleviate virus induced cardiopulmonary hemodynamic disorders and endothelial dysfunction. Therefore, during the COVID-19 pandemic we propose that populations should engage in low to moderate exercise individually designed, prescribed and specific, that utilizes IHP including pranayama (yoga), swimming and high-altitude hiking exercise. This would be beneficial in affecting HIF-1α to combat the disease and its severity. Therefore, the promotion of certain exercises should be considered by all sections of the population. However, exercise recommendations and prescription for COVID-19 patients should be structured to match individual levels of capability and adaptability.

Blocking HIF to Enhance NK Cells: Hints for New Anti-Tumor Therapeutic Strategies?

Natural Killer (NK) cells are becoming an ever more promising tool to design new anti-tumor strategies. However, two major issues are still a challenge to obtain versatile and effective NK-based therapies: the way to maximize the persistency of powerful NK effectors in the patient, and the way to overcome the multiple escape mechanisms that keep away or suppress NK cells at the tumor site. In this regard, targeting the hypoxia-inducible factors (HIFs), which is important for both tumor progression and immune suppression, may be an opportunity. Especially, in the context of the ongoing studies focused on more effective NK-based therapeutic products.

Hypoxia and the Tumor Microenvironment

Hypoxia is an important feature of the tumor microenvironment, and is closely associated with cell proliferation, angiogenesis, metabolism and the tumor immune response. All these factors can further promote tumor progression, increase tumor aggressiveness, enhance tumor metastatic potential and lead to poor prognosis. In this review, these effects of hypoxia on tumor biology will be discussed, along with their significance for tumor detection and treatment.

Conventional NK cells and tissue-resident ILC1s join forces to control liver metastasis

The liver is a major metastatic target organ, and little is known about the role of immunity in controlling hepatic metastases. Here, we discovered that the concerted and nonredundant action of two innate lymphocyte subpopulations, conventional natural killer cells (cNKs) and tissue-resident type I innate lymphoid cells (trILC1s), is essential for antimetastatic defense. Using different preclinical models for liver metastasis, we found that trILC1 controls metastatic seeding, whereas cNKs restrain outgrowth. Whereas the killing capacity of trILC1s was not affected by the metastatic microenvironment, the phenotype and function of cNK cells were affected in a cancer type-specific fashion. Thus, individual cancer cell lines orchestrate the emergence of unique cNK subsets, which respond differently to tumor-derived factors. Our findings will contribute to the development of therapies for liver metastasis involving hepatic innate cells.

Optimizing NK Cell-Based Immunotherapy in Myeloid Leukemia: Abrogating an Immunosuppressive Microenvironment

Natural killer (NK) cells are prominent cytotoxic and cytokine-producing components of the innate immune system representing crucial effector cells in cancer immunotherapy. Presently, various NK cell-based immunotherapies have contributed to the substantial improvement in the reconstitution of NK cells against advanced-staged and high-risk AML. Various NK cell sources, including haploidentical NK cells, adaptive NK cells, umbilical cord blood NK cells, stem cell-derived NK cells, chimeric antigen receptor NK cells, cytokine-induced memory-like NK cells, and NK cell lines have been identified. Devising innovative approaches to improve the generation of therapeutic NK cells from the aforementioned sources is likely to enhance NK cell expansion and activation, stimulate ex vivo and in vivo persistence of NK cells and improve conventional treatment response of myeloid leukemia. The tumor-promoting properties of the tumor microenvironment and downmodulation of NK cellular metabolic activity in solid tumors and hematological malignancies constitute a significant impediment in enhancing the anti-tumor effects of NK cells. In this review, we discuss the current NK cell sources, highlight ongoing interventions in enhancing NK cell function, and outline novel strategies to circumvent immunosuppressive factors in the tumor microenvironment to improve the efficacy of NK cell-based immunotherapy and expand their future success in treating myeloid leukemia.

Exposure to hypoxia causes stress erythropoiesis and downregulates immune response genes in spleen of mice

BACKGROUND

The spleen is the largest secondary lymphoid organ and the main site where stress erythropoiesis occurs. It is known that hypoxia triggers the expansion of erythroid progenitors; however, its effects on splenic gene expression are still unclear. Here, we examined splenic global gene expression patterns by time-series RNA-seq after exposing mice to hypoxia for 0, 1, 3, 5, 7 and 13 days.

RESULTS

Morphological analysis showed that on the 3rd day there was a significant increase in the spleen index and in the proliferation of erythroid progenitors. RNA-sequencing analysis revealed that the overall expression of genes decreased with increased hypoxic exposure. Compared with the control group, 1380, 3430, 4396, 3026, and 1636 genes were differentially expressed on days 1, 3, 5, 7 and 13, respectively. Clustering analysis of the intersection of differentially expressed genes pointed to 739 genes, 628 of which were upregulated, and GO analysis revealed a significant enrichment for cell proliferation. Enriched GO terms of downregulated genes were associated with immune cell activation. Expression of Gata1, Tal1 and Klf1 was significantly altered during stress erythropoiesis. Furthermore, expression of genes involved in the immune response was inhibited, and NK cells decreased.

CONCLUSIONS

The spleen of mice conquer hypoxia exposure in two ways. Stress erythropoiesis regulated by three transcription factors and genes in immune response were downregulated. These findings expand our knowledge of splenic transcriptional changes during hypoxia.

Metabolic Modulation of Immunity: A New Concept in Cancer Immunotherapy

Immunotherapy shifted the paradigm of cancer treatment. The clinical approval of immune checkpoint blockade and adoptive cell transfer led to considerable success in several tumor types. However, for a significant number of patients, these therapies have proven ineffective. Growing evidence shows that the metabolic requirements of immune cells in the tumor microenvironment (TME) greatly influence the success of immunotherapy. It is well established that the TME influences energy consumption and metabolic reprogramming of immune cells, often inducing them to become tolerogenic and inefficient in cancer cell eradication. Increasing nutrient availability using pharmacological modulators of metabolism or antibodies targeting specific immune receptors are strategies that support energetic rewiring of immune cells and boost their anti-tumor capacity. In this review, we describe the metabolic features of the diverse immune cell types in the context of the TME and discuss how these immunomodulatory strategies could synergize with immunotherapy to circumvent its current limitations.

Study on hypoxia-inducible factor and its roles in immune system

The Hypoxia-Inducible Factor-1 (HIF-1) is a dimeric protein complex that plays a significant role in responding to low oxygen or hypoxia concentrations. Chronic inflammation is one of the immune system responses and can increase HIF expression in involved tissues through lowering the oxygen and hypoxia. The HIF factor has many critical roles in immunity, and thus, we reviewed the crucial roles of this factor in the immune system. The results showed various key roles on the immune system, including physical defenses, innate immune (neutrophils apoptosis, macrophages) and inflammatory responses (pyrexia and local heat, iron access, etc.), upregulation in response to microbial infections, cytokines expression (IL-1, IL-2, IL-6, IL-8, IL-12, IL-18, TNF, etc.), drug targeting, etc. The HIF roles in the acquired immune system include: enhance the adaptation of cells (dendritic cells) to new conditions and triggering the signal pathways. The findings of the present review demonstrated that the HIF has important roles in the immune system, including physical defense, innate immune as well as acquired immunity; therefore, it may be considered as a potent drug targeting several diseases such as cancers, infectious diseases, etc.

STAT3 governs the HIF-1α response in IL-15 primed human NK cells

Natural killer (NK) cells mediate innate host defense against microbial infection and cancer. Hypoxia and low glucose are characteristic for these tissue lesions but do not affect early interferon (IFN) γ and CC chemokine release by interleukin 15 (IL-15) primed human NK cells in vitro. Hypoxia inducible factor 1α (HIF-1α) mediates cellular adaption to hypoxia. Its production is supported by mechanistic target of rapamycin complex 1 (mTORC1) and signal transducer and activator of transcription 3 (STAT3). We used chemical inhibition to probe the importance of mTORC1 and STAT3 for the hypoxia response and of STAT3 for the cytokine response in isolated and IL-15 primed human NK cells. Cellular responses were assayed by magnetic bead array, RT-PCR, western blotting, flow cytometry, and metabolic flux analysis. STAT3 but not mTORC1 activation was essential for HIF-1α accumulation, glycolysis, and oxygen consumption. In both primed normoxic and hypoxic NK cells, STAT3 inhibition reduced the secretion of CCL3, CCL4 and CCL5, and it interfered with IL-12/IL-18 stimulated IFNγ production, but it did not affect cytotoxic granule degranulation up on target cell contact. We conclude that IL-15 priming promotes the HIF-1α dependent hypoxia response and the early cytokine response in NK cells predominantly through STAT3 signaling.

Hypoxia/HIF Modulates Immune Responses

Oxygen availability varies throughout the human body in health and disease. Under physiological conditions, oxygen availability drops from the lungs over the blood stream towards the different tissues into the cells and the mitochondrial cavities leading to physiological low oxygen conditions or physiological hypoxia in all organs including primary lymphoid organs. Moreover, immune cells travel throughout the body searching for damaged cells and foreign antigens facing a variety of oxygen levels. Consequently, physiological hypoxia impacts immune cell function finally controlling innate and adaptive immune response mainly by transcriptional regulation via hypoxia-inducible factors (HIFs). Under pathophysiological conditions such as found in inflammation, injury, infection, ischemia and cancer, severe hypoxia can alter immune cells leading to dysfunctional immune response finally leading to tissue damage, cancer progression and autoimmunity. Here we summarize the effects of physiological and pathophysiological hypoxia on innate and adaptive immune activity, we provide an overview on the control of immune response by cellular hypoxia-induced pathways with focus on the role of HIFs and discuss the opportunity to target hypoxia-sensitive pathways for the treatment of cancer and autoimmunity.

PERK inhibition attenuates vascular remodeling in pulmonary arterial hypertension caused by BMPR2 mutation

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by excessive pulmonary vascular remodeling. However, despite advances in therapeutic strategies, patients with PAH bearing mutations in the bone morphogenetic protein receptor type 2 (BMPR2)-encoding gene present severe phenotypes and outcomes. We sought to investigate the effect of PER-like kinase (PERK), which participates in one of three major pathways associated with the unfolded protein response (UPR), on PAH pathophysiology in BMPR2 heterozygous mice. BMPR2 heterozygosity in pulmonary artery smooth muscle cells (PASMCs) decreased the abundance of the antiapoptotic microRNA miR124-3p through the arm of the UPR mediated by PERK. Hypoxia promoted the accumulation of unfolded proteins in BMPR2 heterozygous PASMCs, resulting in increased PERK signaling, cell viability, cellular proliferation, and glycolysis. Proteomic analyses revealed that PERK ablation suppressed PDGFRβ-STAT1 signaling and glycolysis in hypoxic BMPR2 heterozygous PASMCs. Furthermore, PERK ablation or PERK inhibition ameliorated pulmonary vascular remodeling in the Sugen/chronic hypoxia model of PAH, irrespective of BMPR2 status. Hence, these findings suggest that PERK inhibition is a promising therapeutic strategy for patients with PAH with or without BMPR2 mutation.

Tumor Hypoxia Regulates Immune Escape/Invasion: Influence on Angiogenesis and Potential Impact of Hypoxic Biomarkers on Cancer Therapies

The environmental and metabolic pressures in the tumor microenvironment (TME) play a key role in molding tumor development by impacting the stromal and immune cell fractions, TME composition and activation. Hypoxia triggers a cascade of events that promote tumor growth, enhance resistance to the anti-tumor immune response and instigate tumor angiogenesis. During growth, the developing angiogenesis is pathological and gives rise to a haphazardly shaped and leaky tumor vasculature with abnormal properties. Accordingly, aberrantly vascularized TME induces immunosuppression and maintains a continuous hypoxic state. Normalizing the tumor vasculature to restore its vascular integrity, should hence enhance tumor perfusion, relieving hypoxia, and reshaping anti-tumor immunity. Emerging vascular normalization strategies have a great potential in achieving a stable normalization, resulting in mature and functional blood vessels that alleviate tumor hypoxia. Biomarkers enabling the detection and monitoring of tumor hypoxia could be highly advantageous in aiding the translation of novel normalization strategies to clinical application, alone, or in combination with other treatment modalities, such as immunotherapy.

The role of hypoxia in the tumor microenvironment and development of cancer stem cell: a novel approach to developing treatment

Hypoxia is a common feature of solid tumors, and develops because of the rapid growth of the tumor that outstrips the oxygen supply, and impaired blood flow due to the formation of abnormal blood vessels supplying the tumor. It has been reported that tumor hypoxia can: activate angiogenesis, thereby enhancing invasiveness and risk of metastasis; increase survival of tumor, as well as suppress anti-tumor immunity and hamper the therapeutic response. Hypoxia mediates these effects by several potential mechanisms: altering gene expression, the activation of oncogenes, inactivation of suppressor genes, reducing genomic stability and clonal selection. We have reviewed the effects of hypoxia on tumor biology and the possible strategiesto manage the hypoxic tumor microenvironment (TME), highlighting the potential use of cancer stem cells in tumor treatment.

Arrested development: suppression of NK cell function in the tumor microenvironment

Natural killer (NK) cells are cytotoxic innate lymphocytes that protect against viral infection and tumor metastasis. Despite their inherent ability to kill a broad range of virally infected, stressed and transformed cells, low numbers of dysfunctional NK cells are often observed in many advanced solid human cancers. Here, we review the potential mechanisms that influence suboptimal mature NK cell recruitment and function in the tumor microenvironment (TME) of solid tumors. We further highlight current immunotherapy approaches aimed to circumvent NK cell dysfunction and discuss next-generation strategies to enhance adoptive NK cell therapy through targeting intrinsic and extrinsic checkpoints the regulate NK cell functionality in the TME. Understanding the mechanisms that drive NK cell dysfunction in the TME will lead to novel immunotherapeutic approaches in the fight against cancer.

Hypoxia enhances ILC3 responses through HIF-1α-dependent mechanism

Group 3 innate lymphoid cells (ILC3) have a prominent role in the maintenance of intestine mucosa homeostasis. The hypoxia-inducible factor (HIF) is an important modulator of immune cell activation and a key mechanism for cellular adaptation to oxygen deprivation. However, its role on ILC3 is not well known. In this study, we investigated how a hypoxic environment modulates ILC3 response and the subsequent participation of HIF-1 signaling in this process. We found increased proliferation and activation of intestinal ILC3 at low oxygen levels, a response that was phenocopied when HIF-1α was chemically stabilized and was reversed when HIF-1 was blocked. The increased activation of ILC3 relied on a HIF-1α-dependent transcriptional program, but not on mTOR-signaling or a switch to glycolysis. HIF-1α deficiency in RORyt compartment resulted in impaired IL-17 and IL-22 production by ILC3 in vivo, which reflected in a lower expression of their target genes in the intestinal epithelium and an increased susceptibility to Clostridiodes difficile infection. Taken together, our results show that HIF-1α activation in intestinal ILC3 is relevant for their functions in steady state and infectious conditions.

The Tumor Microenvironment-A Metabolic Obstacle to NK Cells' Activity

NK cells have unique capabilities of recognition and destruction of tumor cells, without the requirement for prior immunization of the host. Maintaining tolerance to healthy cells makes them an attractive therapeutic tool for almost all types of cancer. Unfortunately, metabolic changes associated with malignant transformation and tumor progression lead to immunosuppression within the tumor microenvironment, which in turn limits the efficacy of various immunotherapies. In this review, we provide a brief description of the metabolic changes characteristic for the tumor microenvironment. Both tumor and tumor-associated cells produce and secrete factors that directly or indirectly prevent NK cell cytotoxicity. Here, we depict the molecular mechanisms responsible for the inhibition of immune effector cells by metabolic factors. Finally, we summarize the strategies to enhance NK cell function for the treatment of tumors.

Modulating NK cell metabolism for cancer immunotherapy

Natural killer (NK) cells are lymphocytes with potent antitumor functions and, therefore, multiple NK cell-based cancer immunotherapies have been developed and are currently being tested. However, there is a necessity to find new means to improve these therapies, and immunometabolism represents an attractive target. NK cell effector functions are intricately linked to their metabolism, and modulating the latter could be the key to release their full potential. In this review, we have summarized how NK cell metabolism is regulated during some processes, such as maturation, viral infection, and cytokine stimulation. Additionally, we provide an overview of how NK cell metabolism is affected by current therapeutic approaches aimed to promote NK cell expansion and/or to increase their effector functions. We have also recapitulated several strategies that could help alleviating the metabolic impairment that characterizes tumor-infiltrating NK cells, and thus increase or restore their effector functions. Furthermore, we have reviewed several therapeutic approaches targeting cancer metabolism that could synergize with NK cell-based cancer immunotherapies, and thus enhance their efficacy.

Conditional Deletion of PGC-1α Results in Energetic and Functional Defects in NK Cells

During an immune response, natural killer (NK) cells activate specific metabolic pathways to meet the increased energetic and biosynthetic demands associated with effector functions. Here, we found in vivo activation of NK cells during Listeria monocytogenes infection-augmented transcription of genes encoding mitochondria-associated proteins in a manner dependent on the transcriptional coactivator PGC-1α. Using an Ncr1Cre-based conditional knockout mouse, we found that PGC-1α was crucial for optimal NK cell effector functions and bioenergetics, as the deletion of PGC-1α was associated with decreased cytotoxic potential and cytokine production along with altered ADP/ATP ratios. Lack of PGC-1α also significantly impaired the ability of NK cells to control B16F10 tumor growth in vivo, and subsequent gene expression analysis showed that PGC-1α mediates transcription required to maintain mitochondrial activity within the tumor microenvironment. Together, these data suggest that PGC-1α-dependent transcription of specific target genes is required for optimal NK cell function during the response to infection or tumor growth.

Hypoxia and HIF Signaling: One Axis with Divergent Effects

The correct concentration of oxygen in all tissues is a hallmark of cellular wellness, and the negative regulation of oxygen homeostasis is able to affect the cells and tissues of the whole organism. The cellular response to hypoxia is characterized by the activation of multiple genes involved in many biological processes. Among them, hypoxia-inducible factor (HIF) represents the master regulator of the hypoxia response. The active heterodimeric complex HIF α/β, binding to hypoxia-responsive elements (HREs), determines the induction of at least 100 target genes to restore tissue homeostasis. A growing body of evidence demonstrates that hypoxia signaling can act by generating contrasting responses in cells and tissues. Here, this dual and controversial role of hypoxia and the HIF signaling pathway is discussed, with particular reference to the effects induced on the complex activities of the immune system and on mechanisms determining cell and tissue responses after an injury in both acute and chronic human diseases related to the heart, lung, liver, and kidney.

Hypoxia Impairs NK Cell Cytotoxicity through SHP-1-Mediated Attenuation of STAT3 and ERK Signaling Pathways

Natural killer (NK) cells are innate immune effectors with potent antitumor activity. However, tumor cells can create an immunosuppressive microenvironment to escape immune surveillance. Although accumulating evidence indicates that microenvironmental hypoxia plays an important role in favoring tumor development and immune evasion, it remains unclear by what means hypoxia directly impairs NK cell antitumor activity. In this study, we confirmed that hypoxic NK cells showed significantly lower cytotoxicity against tumor cells. Consistent with this finding, we found that the reduction in NK cell cytotoxicity resulting from hypoxia correlated to the lower expression of granzyme B, IFN-γ, and degranulation marker CD107a, as well as activating receptors including NKp30, NKp46, and NKG2D expressed on the surface of NK cells. More importantly, we further demonstrated that a reduction in the phosphorylation levels of ERK and STAT3 secondary to hypoxia was strongly associated with the attenuated NK cell cytotoxicity. Focusing on the mechanism responsible for reduced phosphorylation levels of ERK and STAT3, we reveal that the activation of protein tyrosine phosphatase SHP-1 (Src homology region 2 domain-containing phosphatase-1) following hypoxia might play an essential role in this process. By knocking down SHP-1 or blocking its activity using a specific inhibitor TPI-1, we were able to partially restore NK cell cytotoxicity under hypoxia. Taken together, we demonstrate that hypoxia could impair NK cell cytotoxicity by decreasing the phosphorylation levels of ERK and STAT3 in a SHP-1-dependent manner. Therefore, targeting SHP-1 could provide an approach to enhance NK cell-based tumor immunotherapy.

Single-Cell RNA Sequencing of Tumor-Infiltrating NK Cells Reveals that Inhibition of Transcription Factor HIF-1α Unleashes NK Cell Activity

Enhancing immune cell functions in tumors remains a major challenge in cancer immunotherapy. Hypoxia is a common feature of solid tumors, and cells adapt by upregulating the transcription factor HIF-1α. Here, we defined the transcriptional landscape of mouse tumor-infiltrating natural killer (NK) cells by using single-cell RNA sequencing. Conditional deletion of Hif1a in NK cells resulted in reduced tumor growth, elevated expression of activation markers, effector molecules, and an enriched NF-κB pathway in tumor-infiltrating NK cells. Interleukin-18 (IL-18) from myeloid cells was required for NF-κB activation and the enhanced anti-tumor activity of Hif1a^-/- NK cells. Extended culture with an HIF-1α inhibitor increased human NK cell responses. Low HIF1A expression was associated with high expression of IFNG in human tumor-infiltrating NK cells, and an enriched NK-IL18-IFNG signature in solid tumors correlated with increased overall patient survival. Thus, inhibition of HIF-1α unleashes NK cell anti-tumor activity and could be exploited for cancer therapy.

Mechanisms of Resistance to NK Cell Immunotherapy

Immunotherapy has recently been a major breakthrough in cancer treatment. Natural killer (NK) cells are suitable targets for immunotherapy owing to their potent cytotoxic activity that may target cancer cells in a major histocompatibility complex (MHC) and antigen-unrestricted manner. Current therapies targeting NK cells include monoclonal antibodies that promote NK cell antibody-dependent cell-mediated cytotoxicity (ADCC), hematopoietic stem cell transplantation (HSCT), the adoptive transfer of NK cells, the redirection of NK cells using chimeric antigen receptor (CAR)-NK cells and the use of cytokines and immunostimulatory drugs to boost the anti-tumor activity of NK cells. Despite some encouraging clinical results, patients receiving these therapies frequently develop resistance, and a myriad of mechanisms of resistance affecting both the immune system and cancer cells have been reported. A first contributing factor that modulates the efficacy of the NK cell therapy is the genetic profile of the individual, which regulates all aspects of NK cell biology. Additionally, the resistance of cancer cells to apoptosis and the immunoediting of cancer cells, a process that decreases their immunogenicity and promotes immunosuppression, are major determinants of the resistance to NK cell therapy. Consequently, the efficacy of NK cell anti-tumor therapy is specific to each patient and disease. The elucidation of such immunosubversive mechanisms is crucial to developing new procedures and therapeutic strategies to fully harness the anti-tumor potential of NK cells.

Innate Cytokine Induced Early Release of IFNγ and CC Chemokines from Hypoxic Human NK Cells Is Independent of Glucose

Natural killer (NK) cells are among the first innate immune cells to arrive at sites of tissue inflammation and regulate the immune response to infection and tumors by the release of cytokines including interferon (IFN)γ. In vitro exposure to the innate cytokines interleukin 15 (IL-15) and IL-12/IL-18 enhances NK cell IFNγ production which, beyond 16 h of culture, was shown to depend on metabolic switching to glycolysis. NK effector responses are, however, rapid by comparison. Therefore, we sought to evaluate the importance of glycolysis for shorter-term IFNγ production, considering glucose deprivation and hypoxia as adverse tissue inflammation associated conditions. Treatments with IL-15 for 6 and 16 h were equally effective in priming early IFNγ production in human NK cells in response to secondary IL-12/IL-18 stimulation. Short-term priming was not associated with glycolytic switching but induced the release of IFNγ and, additionally, CCL3, CCL4 and CCL5 from both normoxic and hypoxic NK cells in an equally efficient and, unexpectedly, glucose independent manner. We conclude that release of IFNγ and CC chemokines in the early innate immune response is a metabolically autonomous NK effector program.

Natural Killer Cells as Sensors of Adipose Tissue Stress

Adipose tissue macrophages (ATMs) orchestrate low-grade chronic adipose tissue inflammation, linking obesity and insulin resistance. Whereas factors contributing to macrophage accumulation in adipose tissue are established, little is known regarding signals that link adipocyte stress to proinflammatory activation of macrophages. Natural killer (NK) cells are specialized innate lymphocytes that identify and respond to stressed cells. In this Opinion, we discuss the possibility of NK cells to function as sensors recognizing adipose tissue stress. We further summarize recent literature suggesting NK cells to play an important role in development of insulin resistance via secretion of cytokines that stimulate proinflammatory polarization of ATMs. This suggests adipose tissue-resident NK cells as a pharmacological target for the treatment of obesity-induced insulin resistance.

Interleukin-15 Signaling in HIF-1α Regulation in Natural Killer Cells, Insights Through Mathematical Models

Natural killer (NK) cells belong to the first line of host defense against infection and cancer. Cytokines, including interleukin-15 (IL-15), critically regulate NK cell activity, resulting in recognition and direct killing of transformed and infected target cells. NK cells have to adapt and respond in inflamed and often hypoxic areas. Cellular stabilization and accumulation of the transcription factor hypoxia-inducible factor-1α (HIF-1α) is a key mechanism of the cellular hypoxia response. At the same time, HIF-1α plays a critical role in both innate and adaptive immunity. While the HIF-1α hydroxylation and degradation pathway has been recently described with the help of mathematical methods, less is known concerning the mechanistic mathematical description of processes regulating the levels of HIF-1α mRNA and protein. In this work we combine mathematical modeling with experimental laboratory analysis and examine the dynamic relationship between HIF-1α mRNA, HIF-1α protein, and IL-15-mediated upstream signaling events in NK cells from human blood. We propose a system of non-linear ordinary differential equations with positive and negative feedback loops for describing the complex interplay of HIF-1α regulators. The experimental design is optimized with the help of mathematical methods, and numerical optimization techniques yield reliable parameter estimates. The mathematical model allows for the investigation and prediction of HIF-1α stabilization under different inflammatory conditions and provides a better understanding of mechanisms mediating cellular enrichment of HIF-1α. Thanks to the combination of in vitro experimental data and in silico predictions we identified the mammalian target of rapamycin (mTOR), the nuclear factor-κB (NF-κB), and the signal transducer and activator of transcription 3 (STAT3) as central regulators of HIF-1α accumulation. We hypothesize that the regulatory pathway proposed here for NK cells can be extended to other types of immune cells. Understanding the molecular mechanisms involved in the dynamic regulation of the HIF-1α pathway in immune cells is of central importance to the immune cell function and could be a promising strategy in the design of treatments for human inflammatory diseases and cancer.

NK Cell Metabolism and Tumor Microenvironment

Natural Killer (NK) cells are characterized by their potential to kill tumor cells by different means without previous sensitization and have, therefore, become a valuable tool in cancer immunotherapy. However, their efficacy against solid tumors is still poor and further studies are required to improve it. One of the major restrictions for NK cell activity is the immunosuppressive tumor microenvironment (TME). There, tumor and other immune cells create the appropriate conditions for tumor proliferation while, among others, preventing NK cell activation. Furthermore, NK cell metabolism is impaired in the TME, presumably due to nutrient and oxygen deprivation, and the higher concentration of tumor-derived metabolic end products, such as lactate. This metabolic restriction of NK cells limits their effector functions, and it could represent a potential target to focus on to improve the efficacy of NK cell-based therapies against solid tumors. In this review, we discuss the potential effect of TME into NK cell metabolism and its influence in NK cell effector functions.

Hepatic Tumor Microenvironments and Effects on NK Cell Phenotype and Function

The liver is a complex organ with critical physiological functions including metabolism, glucose storage, and drug detoxification. Its unique immune profile with large numbers of cytotoxic CD8+ T cells and significant innate lymphoid population, including natural killer cells, γ δ T cells, MAIT cells, and iNKTcells, suggests an important anti-tumor surveillance role. Despite significant immune surveillance in the liver, in particular large NK cell populations, hepatic cell carcinoma (HCC) is a relatively common outcome of chronic liver infection or inflammation. The liver is also the second most common site of metastatic disease. This discordance suggests immune suppression by the environments of primary and secondary liver cancers. Classic tumor microenvironments (TME) are poorly perfused, leading to accumulation of tumor cell metabolites, diminished O2, and decreased nutrient levels, all of which impact immune cell phenotype and function. Here, we focus on changes in the liver microenvironment associated with tumor presence and how they affect NK function and phenotype.

Immunometabolic Dysfunction of Natural Killer Cells Mediated by the Hypoxia-CD73 Axis in Solid Tumors

NK cell infiltration into solid tumors is often low and is largely represented by the poorly-cytotoxic CD56^bright subset. Numerous studies have demonstrated that CD73, overexpressed under conditions of hypoxia, is involved in a variety of physiological processes, while its overexpression has been correlated with tumor invasiveness, metastasis and poorer patient survival in many cancers. Hypoxia itself favors aggressive glycolytic fueling of cancer cells, in turn driving reprogramming of NK cell metabolism. In addition, the hypoxia-driven activity of CD73 immunometabolically impairs NK cells in tumors, due to its catalytic role in the generation of the highly immunosuppressive metabolite adenosine. Adenosinergic signaling was shown to alter NK cell metabolic programs, leading to tumor-promoting environments characterized by NK cell dysfunction. Despite the demonstrated role of NK cell responses in the context of CD73 targeting, the engagement of NK cells in the setting of hypoxia/CD73 signaling has not been extensively studied or exploited. Here, we discuss available evidence on the role of hypoxic signaling on CD73-mediated activity, and how this relates to the immunometabolic responses of NK cells, with a particular focus on the therapeutic targeting of these pathways.

NK Response Correlates with HIV Decrease in Pegylated IFN-α2a-Treated Antiretroviral Therapy-Suppressed Subjects

We previously reported that pegylated IFN-α2a (Peg-IFN-α2a) added to antiretroviral therapy (ART)-suppressed, HIV-infected subjects resulted in plasma HIV control and integrated HIV DNA decrease. We now evaluated whether innate NK cell activity or PBMC transcriptional profiles were associated with decreases in HIV measures. Human peripheral blood was analyzed prior to Peg-IFN-α2a administration (ART, baseline), after 5 wk of ART+Peg-IFN-α2a, and after 12 wk of Peg-IFN-α2a monotherapy (primary endpoint). After 5 wk of ART+Peg-IFN-α2a, immune subset frequencies were preserved, and induction of IFN-stimulated genes was noted in all subjects except for a subset in which the lack of IFN-stimulated gene induction was associated with increased expression of microRNAs. Viral control during Peg-IFN-α2a monotherapy was associated with 1) higher levels of NK cell activity and IFN-γ-induced protein 10 (IP-10) on ART (preimmunotherapy) and 2) downmodulation of NK cell KIR2DL1 and KIR2DL2/DL3 expression, transcriptional enrichment of expression of genes associated with NK cells in HIV controller subjects, and higher ex vivo IFN-α-induced NK cytotoxicity after 5 wk of ART+Peg-IFN-α2a. Integrated HIV DNA decline after immunotherapy was also associated with gene expression patterns indicative of cell-mediated activation and NK cytotoxicity. Overall, an increase in innate activity and NK cell cytotoxicity were identified as correlates of Peg-IFN-α2a-mediated HIV control.

Metabolic regulation of innate and adaptive lymphocyte effector responses

Innate and adaptive lymphocytes employ diverse effector programs that provide optimal immunity to pathogens and orchestrate tissue homeostasis, or conversely can become dysregulated to drive progression of chronic inflammatory diseases. Emerging evidence suggests that CD4⁺ T helper cell subsets and their innate counterparts, the innate lymphoid cell family, accomplish these complex biological roles by selectively programming their cellular metabolism in order to instruct distinct modules of lymphocyte differentiation, proliferation, and cytokine production. Further, these metabolic pathways are significantly influenced by tissue microenvironments and disease states. Here, we summarize our current knowledge on how cell-intrinsic metabolic factors modulate the context-dependent bioenergetic pathways that govern innate and adaptive lymphocytes. Further, we propose that a greater understanding of these pathways may lead to the identification of unique features in each population and provoke the development of novel therapeutic strategies to modulate lymphocytes in health and disease.

Immune Cell Metabolism in Tumor Microenvironment

Tumor microenvironment (TME) is composed of tumor cells, immune cells, cytokines, extracellular matrix, etc. The immune system and the metabolisms of glucose, lipids, amino acids, and nucleotides are integrated in the tumorigenesis and development. Cancer cells and immune cells show metabolic reprogramming in the TME, which intimately links immune cell functions and edits tumor immunology. Recent findings in immune cell metabolism hold the promising possibilities toward clinical therapeutics for treating cancer. This chapter introduces the updated understandings of metabolic reprogramming of immune cells in the TME and suggests new directions in manipulation of immune responses for cancer diagnosis and therapy.

Tumor Microenvironment-Induced Immunometabolic Reprogramming of Natural Killer Cells

Energy metabolism is key to the promotion of tumor growth, development, and metastasis. At the same time, cellular metabolism also mediates immune cell survival, proliferation and cytotoxic responses within the tumor microenvironment. The ability of natural killer cells to eradicate tumors relies on their ability to functionally persist for the duration of their anti-tumor effector activity. However, a tumor's altered metabolic requirements lead to compromised functional responses of cytokine-activated natural killer cells, which result in decreased effectiveness of adoptive cell-based immunotherapies. Tumors exert these immunosuppressive effects through a number of mechanisms, a key driver of which is hypoxia. Hypoxia also fuels the generation of adenosine from the cancer-associated ectoenzymes CD39 and CD73. Adenosine's immunosuppression manifests in decreased proliferation and impaired anti-tumor function, with adenosinergic signaling emerging as an immunometabolic checkpoint blockade target. Understanding such immunometabolic suppression is critical in directing the engineering of a new generation of natural killer cell-based immunotherapies that have the ability to more effectively target difficult-to-treat solid tumors.

Molecular definition of group 1 innate lymphoid cells in the mouse uterus

Determining the function of uterine lymphocytes is challenging because of the dynamic changes in response to sex hormones and, during pregnancy, to the invading foetal trophoblast cells. Here we provide a genome-wide transcriptome atlas of mouse uterine group 1 innate lymphoid cells (ILCs) at mid-gestation. Tissue-resident Eomes+CD49a+ NK cells (trNK), which resemble human uterine NK cells, are most abundant during early pregnancy, and have gene signatures associated with TGF-β responses and interactions with trophoblast, epithelial, endothelial, smooth muscle cells, leucocytes and extracellular matrix. Conventional NK cells expand late in gestation and may engage in crosstalk with trNK cells involving IL-18 and IFN-γ. Eomes-CD49a+ ILC1s dominate before puberty, and specifically expand in second pregnancies when the expression of the memory cell marker CXCR6 is upregulated. These results identify trNK cells as the cellular hub of uterine group 1 ILCs, and mark CXCR6+ ILC1s as potential memory cells of pregnancy.