Invasive breast cancer reprograms early myeloid differentiation in the bone marrow to generate immunosuppressive neutrophils

Comprehensive Assessment of Selected Immune Cell Subpopulations Changes in Chemotherapy-Naïve Germ Cell Tumor Patients

The pattern of immune cell distribution in testicular germ cell tumors (GCT) significantly differs from the immune environment in normal testicular tissues. The present study aimed to evaluate the role of different leukocyte subpopulation in GCTs. A cohort of 84 chemotherapy-naïve GCT patients was analyzed. Immunophenotyping of peripheral blood leukocyte subpopulations was carried out by flow cytometry. In addition, the data assessing the immunophenotypes and the baseline clinicopathological characteristics of the included subjects were statistically evaluated. Their prognostic value for the assessment of progression-free survival (PFS) and overall survival (OS) was estimated. The percentage of different innate/adaptive immune cell subpopulations was significantly associated with poor risk-related clinical features, including the number of metastatic sites, presence of retroperitoneal, mediastinal, lung, brain and non-pulmonary visceral metastases as well as with the S-stage and International Germ Cell Consensus Classification Group (IGCCCG) risk groups. In univariate analysis, the percentages of neutrophils, eosinophils, dendritic cells type 2, lymphocytes and T cytotoxic cells were significantly associated with PFS, while the neutrophil, non-classical monocyte and lymphocyte percentage were associated with OS. However, all these outcome correlations were not independent of IGCCCG in multivariate analysis. The data indicated a link among different innate/adaptive peripheral immune cell subpopulations in GCT patients. In addition, the association between these subpopulations and tumor characteristics was also investigated. The findings of the present study may contribute to a deeper understanding of the interactions between cancer and innate/adaptive immune response in GCT patients.

Neutrophils in cancer: heterogeneous and multifaceted

Neutrophils are the most abundant myeloid cells in human blood and are emerging as important regulators of cancer. However, their functional importance has often been overlooked on the basis that they are short-lived, terminally differentiated and non-proliferative. Recent studies of their prominent roles in cancer have led to a paradigm shift in our appreciation of neutrophil functional diversity. This Review describes how neutrophil diversification, which in some contexts can lead to opposing functions, is generated within the tumour microenvironment as well as systemically. We compare neutrophil heterogeneity in cancer and in other pathophysiological contexts to provide an updated overview of our current knowledge of the functions of neutrophils in cancer.

Specific targeting of cancer stem cells by immunotherapy: A possible stratagem to restrain cancer recurrence and metastasis

Cancer stem cells (CSCs), the tumor-initiating cells playing a crucial role in cancer progression, recurrence, and metastasis, have the intrinsic property of self-renewal and therapy resistance. The tumorigenic properties of these cells include generation of cellular heterogeneity and immuno-suppressive tumor microenvironment (TME), conferring them the capability to resist a variety of anti-cancer therapeutics. Further, CSCs possess several unique immunological properties that help them escape recognition by the innate and adaptive immune system and shape a TME into a pro-tumorigenic and immunosuppressive landscape. In this context, immunotherapy is considered one of the best therapeutic options for eliminating CSCs to halt cancer recurrence and metastasis. In this review, we discuss the various immunomodulatory properties of CSCs and the interaction of CSCs with the immune system enabling immune evasion. In addition, we also highlight the present research update on immunotherapeutic targeting of CSCs and the possible further scope of research on this topic. We believe that a deeper understanding of CSCs' immunological properties and the crosstalk between CSCs and the immune system can develop better innovative immune-therapeutics and enhance the efficacy of current therapy-resistant cancer treatments.

Systemic Influences of Mammary Cancer on Monocytes in Mice

There is a growing body of evidence that cancer causes systemic changes. These influences are most evident in the bone marrow and the blood, particularly in the myeloid compartment. Here, we show that there is an increase in the number of bone marrow, circulating and splenic monocytes by using mouse models of breast cancer caused by the mammary epithelial expression of the polyoma middle T antigen. Cancer does not affect ratios of classical to non-classical populations of monocytes in the circulation nor does it affect their half-lives. Single cell RNA sequencing also indicates that cancer does not induce any new monocyte populations. Cancer does not change the monocytic progenitor number in the bone marrow, but the proliferation rate of monocytes is higher, thus providing an explanation for the expansion of the circulating numbers. Deep RNA sequencing of these monocytic populations reveals that cancer causes changes in the classical monocyte compartment, with changes evident in bone marrow monocytes and even more so in the blood, suggesting influences in both compartments, with the down-regulation of interferon type 1 signaling and antigen presentation being the most prominent of these. Consistent with this analysis, down-regulated genes are enriched with STAT1/STAT2 binding sites in their promoter, which are transcription factors required for type 1 interferon signaling. However, these transcriptome changes in mice did not replicate those found in patients with breast cancer. Consequently, this mouse model of breast cancer may be insufficient to study the systemic influences of human cancer.

Tumor-Infiltrating PD-L1+ Neutrophils Induced by GM-CSF Suppress T Cell Function in Laryngeal Squamous Cell Carcinoma and Predict Unfavorable Prognosis

Purpose

Chronic inflammation contributes to tumor initiation, progression, and immune escape. Neutrophils are the major component of inflammatory response and participate in the tumorigenesis process. However, compared to other immune cells in the tumor microenvironment of laryngeal squamous cell carcinoma (LSCC), neutrophils, especially the tumor-associated neutrophils (TANs), have not yet been comprehensively explored. The mechanism for regulating the crosstalk between TANs and tumor cells still remains unclear.

Materials and Methods

The distribution profiles and phenotypic features of neutrophils and other inflammatory immune cell populations from a large LSCC patient cohort were systemically analyzed. Co-culturing of peripheral blood associated neutrophils (PANs) and TANs with PBMCs was performed, and the immunosuppression effect on T-cells was examined.

Results

LSCC microenvironment is highly inflammatory with remarkable TANs infiltration, which is often associated with unfavorable prognosis and advanced clinical stage. We find that TANs in LSCC display morphologically immature and lower apoptosis, exhibit distinctively immunosuppressive phenotype of high PD-L1, and suppress CD8⁺ T lymphocytes proliferation and activation. We subsequently discover that PD-L1⁺TANs induced by LSCC-derived GM-CSF potently impair CD8⁺ T-cells proliferation and cytokines production function, which are partially blocked by a PD-L1-neutralizing antibody. Clinical data further support GM-CSF as an unfavorable prognostic biomarker and reveal a potential association with inflammatory immune cell infiltration, in particular neutrophils.

Conclusion

Tumor-infiltrating PD-L1+ neutrophils induced by LSCC-derived GM-CSF suppress T cell proliferation and activation in the inflammatory microenvironment of LSCC and predict unfavorable prognosis. These TANs cripple antitumor T cell immunity and promote tumor progression. Our findings provide a basis for targeting PD-L1+TANs or GM-CSF as a new immunotherapeutic strategy for LSCC.

Chemokines as Regulators of Neutrophils: Focus on Tumors, Therapeutic Targeting, and Immunotherapy

Simple Summary

Neutrophils are the main leukocyte subset present in human blood and play a fundamental role in the defense against infections. Neutrophils are also an important component of the tumor stroma because they are recruited by selected chemokines produced by both cancer cells and other cells of the stroma. Even if their presence has been mostly associated with a bad prognosis, tumor-associated neutrophils are present in different maturation and activation states and can exert both protumor and antitumor activities. In addition, it is now emerging that chemokines not only induce neutrophil directional migration but also have an important role in their activation and maturation. For these reasons, chemokines and chemokine receptors are now considered targets to improve the antitumoral function of neutrophils in cancer immunotherapy.

Abstract

Neutrophils are an important component of the tumor microenvironment, and their infiltration has been associated with a poor prognosis for most human tumors. However, neutrophils have been shown to be endowed with both protumor and antitumor activities, reflecting their heterogeneity and plasticity in cancer. A growing body of studies has demonstrated that chemokines and chemokine receptors, which are fundamental regulators of neutrophils trafficking, can affect neutrophil maturation and effector functions. Here, we review human and mouse data suggesting that targeting chemokines or chemokine receptors can modulate neutrophil activity and improve their antitumor properties and the efficiency of immunotherapy.

Inflammation and Myeloid Cells in Cancer Progression and Metastasis

To date, the most immunotherapy drugs act upon T cell surface proteins to promote tumoricidal T cell activity. However, this approach has to date been unsuccessful in certain solid tumor types including pancreatic, prostate cancer and glioblastoma. Myeloid-related innate immunity can promote tumor progression through direct and indirect effects on T cell activity; improved understanding of this field may provide another therapeutic avenue for patients with these tumors. Myeloid cells can differentiate into both pro-inflammatory and anti-inflammatory mature form depending upon the microenvironment. Most cancer type exhibit oncogenic activating point mutations (ex. P53 and KRAS) that trigger cytokines production. In addition, tumor environment (ex. Collagen, Hypoxia, and adenosine) also regulated inflammatory signaling cascade. Both the intrinsic and extrinsic factor driving the tumor immune microenvironment and regulating the differentiation and function of myeloid cells, T cells activity and tumor progression. In this review, we will discuss the relationship between cancer cells and myeloid cells-mediated tumor immune microenvironment to promote cancer progression and immunotherapeutic resistance. Furthermore, we will describe how cytokines and chemokines produced by cancer cells influence myeloid cells within immunosuppressive environment. Finally, we will comment on the development of immunotherapeutic strategies with respect to myeloid-related innate immunity.

Signal-Strength and History-Dependent Innate Immune Memory Dynamics in Health and Disease

Innate immunity exhibits memory characteristics, reflected not only in selective recognition of external microbial or internal damage signals, but more importantly in history and signal-strength dependent reprogramming of innate leukocytes characterized by priming, tolerance, and exhaustion. Key innate immune cells such as monocytes and neutrophils can finely discern and attune to the duration and intensity of external signals through rewiring of internal signaling circuitries, giving rise to a vast array of discreet memory phenotypes critically relevant to managing tissue homeostasis as well as diverse repertoires of inflammatory conditions. This review will highlight recent advances in this rapidly expanding field of innate immune programming and memory, as well as its translational implication in the pathophysiology of selected inflammatory diseases.

Helicobacter pylori and gastric cancer: a lysosomal protease perspective

The intimate involvement of pathogens with the heightened risk for developing certain cancers is an area of research that has captured a great deal of attention over the last 10 years. One firmly established paradigm that highlights this aspect of disease progression is in the instance of Helicobacter pylori infection and the contribution it makes in elevating the risk for developing gastric cancer. Whilst the molecular mechanisms that pinpoint the contribution that this microorganism inflicts towards host cells during gastric cancer initiation have come into greater focus, another picture that has also emerged is one that implicates the host's immune system, and the chronic inflammation that can arise therefrom, as being a central contributory factor in disease progression. Consequently, when taken with the underlying role that the extracellular matrix plays in the development of most cancers, and how this dynamic can be modulated by proteases expressed from the tumor or inflammatory cells, a complex and detailed relationship shared between the individual cellular components and their surroundings is coming into focus. In this review article, we draw attention to the emerging role played by the cathepsin proteases in modulating the stage-specific progression of Helicobacter pylori-initiated gastric cancer and the underlying immune response, while highlighting the therapeutic significance of this dynamic and how it may be amenable for novel intervention strategies within a basic research or clinical setting.

Macrophage and Neutrophil Interactions in the Pancreatic Tumor Microenvironment Drive the Pathogenesis of Pancreatic Cancer

Simple Summary

The survival rates for patients with pancreatic adenocarcinoma are very low. This dismal prognosis is due in part to late detection and early development of metastases, and successful treatments for pancreatic adenocarcinoma are also lacking. One potential method of treatment is immunotherapy, which has been successfully implemented in several cancers. Despite success in other cancer types, there has been little progress in pancreatic adenocarcinoma. To understand these shortcomings, we explore the roles of macrophages and neutrophils, two prominent immune cell types in the pancreatic tumor environment. In this review, we discuss how macrophages and neutrophils lead to the harsh environment that is unique to pancreatic adenocarcinoma. We further explore how these immune cells can impact standard of care therapies and decrease their effectiveness. Macrophages and neutrophils could ultimately be targeted to improve outcomes for patients with pancreatic adenocarcinoma.

Abstract

Despite modest improvements in survival in recent years, pancreatic adenocarcinoma remains a deadly disease with a 5-year survival rate of only 9%. These poor outcomes are driven by failure of early detection, treatment resistance, and propensity for early metastatic spread. Uncovering innovative therapeutic modalities to target the resistance mechanisms that make pancreatic cancer largely incurable are urgently needed. In this review, we discuss the immune composition of pancreatic tumors, including the counterintuitive fact that there is a significant inflammatory immune infiltrate in pancreatic cancer yet anti-tumor mechanisms are subverted and immune behaviors are suppressed. Here, we emphasize how immune cell interactions generate tumor progression and treatment resistance. We narrow in on tumor macrophage (TAM) spatial arrangement, polarity/function, recruitment, and origin to introduce a concept where interactions with tumor neutrophils (TAN) perpetuate the microenvironment. The sequelae of macrophage and neutrophil activities contributes to tumor remodeling, fibrosis, hypoxia, and progression. We also discuss immune mechanisms driving resistance to standard of care modalities. Finally, we describe a cadre of treatment targets, including those intended to overcome TAM and TAN recruitment and function, to circumvent barriers presented by immune infiltration in pancreatic adenocarcinoma.

Impact of cancer cell-intrinsic features on neutrophil behavior

Neutrophils are multifaceted innate immune cells that play a significant role in the progression of cancer by exerting both pro- and anti-tumorigenic functions. The crosstalk between cancer cells and neutrophils is complex and emerging evidence is pointing at cancer cell-intrinsic programs regulating neutrophil abundance, phenotype and function. Cancer cell-derived soluble mediators are key players in modulating the interaction with neutrophils. Here, we review how intrinsic features of cancer cells, including cancer cell genetics, epigenetics, signaling, and metabolism, manipulate neutrophil behavior and how to target these processes to impact cancer progression. A molecular understanding of cancer cell-intrinsic properties that shape the crosstalk with neutrophils will provide novel therapeutic strategies for personalized immunomodulation in cancer patients.

Versatile neutrophil functions in cancer

Neutrophils have historically been considered a singular, terminally-differentiated cell population, replete with pre-formed granules, poised to react quickly, aggressively, and somewhat non-specifically in the face of a microbial challenge or tissue injury. However, in recent years, neutrophil biologists have started revisiting this simplistic conception. Many studies have identified complexities in neutrophil biology, and these findings have led the field to redefine neutrophil heterogeneity from multiple angles including their development and maturation, their tissue location, and their ability to respond to various (pathological) stimuli. In this review, we discuss the importance of this reassessment within the context of cancer. Experimental evidence supports that neutrophil behavior is diverse, context-dependent, and manipulable; cutting-edge technologies have enabled the identification of neutrophil heterogeneity with high resolution and in an unbiased manner, revealing what may be critical underpinnings of these diverse behaviors, and enabling sophisticated computational assessments of specific programs and interactions. We are coming ever closer to delineating a holistic picture of neutrophil heterogeneity and how it may interplay with cancer stage, tumor microenvironment, and therapy. All of this together paints a promising picture when considering how clinical practice may harness the heterogeneity of these cells, for biomarkers or therapeutic approaches, leveraging what we are learning about these powerful and plentiful immune effectors.

Tumor-associated macrophages, dendritic cells, and neutrophils: biological roles, crosstalk, and therapeutic relevance

Tumor-associated myeloid cells constitute a series of plastic and heterogeneous cell populations within the tumor microenvironment (TME), and exhibit different phenotypes and functions in response to various microenvironmental signals. In light of promising preclinical data indicating that myeloid-based therapy can effectively suppress tumor growth, a series of novel immune-based therapies and approaches are currently undergoing clinical evaluation. A better understanding of the diversity and functional roles of different myeloid cell subtypes and of how they are associated with TME remodeling may help to improve cancer therapy. Herein, we focus on myeloid cells and discuss how tumor cells can simultaneously reprogram these cells through tumor-derived factors and metabolites. In addition, we discuss the interactions between myeloid cells and other cells in the TME that have the potential to directly or indirectly regulate tumor initiation, invasion, or angiogenesis. We further discuss the current and future potential applications of myeloid cells in the development of focused therapeutic strategies in cancer treatment.

Slit2-Mediated Metabolic Reprogramming in Bone Marrow-Derived Macrophages Enhances Antitumor Immunity

Slit2 exerts antitumor effects in various cancers; however, the underlying mechanism, especially its role in regulating the immune, especially in the bone marrow niche, system is still unknown. Elucidating the behavior of macrophages in tumor progression can potentially improve immunotherapy. Using a spontaneous mammary tumor virus promoter-polyoma middle T antigen (PyMT) breast cancer mouse model, we observed that Slit2 increased the abundance of antitumor M1 macrophage in the bone marrow upon differentiation in vitro. Moreover, myeloablated PyMT mice injected with Slit2-treated bone marrow allografts showed a marked reduction in tumor growth, with enhanced recruitment of M1 macrophage in their tumor stroma. Mechanistic studies revealed that Slit2 significantly enhanced glycolysis and reduced fatty acid oxidation in bone marrow-derived macrophages (BMDMs). Slit2 treatment also altered mitochondrial respiration metabolites in macrophages isolated from healthy human blood that were treated with plasma from breast cancer patients. Overall, this study, for the first time, shows that Slit2 increases BMDM polarization toward antitumor phenotype by modulating immune-metabolism. Furthermore, this study provides evidence that soluble Slit2 could be developed as novel therapeutic strategy to enhance antitumor immune response.

Possible impact of neutrophils on immune responses during early pregnancy in ruminants

The interaction between early embryo and maternal immune system for the establishment of pregnancy is the focus of several studies; however, it remains unclear. The maternal immune response needs to keep a balance between avoiding any damage to the conceptus and maintaining its function in combating microbes as well. When conceptus-maternal crosstalk cannot achieve this balance, pregnancy losses might occur. Intercommunication between mother and conceptus is fundamental during early pregnancy to dictate the outcome of pregnancy. In ruminants, the embryo reacts with the maternal system mainly via interferon tau (IFNT) release. IFNT can act locally on the embryo and endometrial cells and systemically in several tissues and cells to regulate their response via the expression of interferon-stimulated genes (ISGs). Also, IFNT can induce the expression of inflammatory-related genes in immune cells. Day 7 embryo induces a shift in the maternal immune response towards anti-inflammatory (Th2) immune responses. During maternal recognition of pregnancy, peripheral mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs) express markers that configure an anti-inflammatory response. However, PMNs response is more sensitive to the effects of IFNT. PMNs are more likely to express interferon-stimulated genes (ISGs), transforming growth factor-beta (TGFB), interleukin 10 (IL10), and arginase-1 (ARG1), configuring one of the most rapid immune responses to early pregnancy. This review focus on the local and peripheral immune responses during early pregnancy in ruminants, mainly the PMNs function in the immune system.

Immunomodulatory effects of G-CSF in cancer: Therapeutic implications

Numerous preclinical studies have reported a pro-tumour role for granulocyte colony-stimulating factor (G-CSF) that is predominantly mediated by neutrophils and MDSCs, the major G-CSF receptor expressing populations. In the presence of G-CSF (either tumour-derived or exogenous) these myeloid populations commonly exhibit a T cell suppressive phenotype. However, the direct effects of this cytokine on other immune lineages, such as T and NK cells, are not as well established. Herein we discuss the most recent data relating to the effect of G-CSF on the major immune populations, exclusively in the context of cancer. Recent publications have drawn attention to the other tumour-promoting effects of G-CSF on myeloid cells, including NETosis, promotion of cancer stemness and skewed differentiation of bone marrow progenitors towards myelopoiesis. Although G-CSF is safely and commonly used as a supportive therapy to prevent or treat chemotherapy-associated neutropenia in cancer patients, we also discuss the potential impacts of G-CSF on other anti-cancer treatments. Importantly, considerations for immune checkpoint blockade are highlighted, as many publications report a T cell suppressive effect of G-CSF that may diminish the effectiveness of this immunotherapy.

Tumor extracellular vesicles drive metastasis (it's a long way from home)

Among a plethora of functions, extracellular vesicles released by primary tumors spread in the organism and reach distant organs where they can induce the formation of a premetastatic niche. This constitutes a favorable microenvironment for circulating tumor cells which facilitates their seeding and colonization. In this review, we describe the journey of extracellular vesicles (EVs) from the primary tumor to the future metastatic organ, with a focus on the mechanisms used by EVs to target organs with a specific tropism (i.e., organotropism). We then highlight important tumor EV cargos in the context of premetastatic niche formation and summarize their known effects on extracellular matrix remodeling, angiogenesis, vessel permeabilization, resident cell activation, recruitment of foreign cells, and ultimately the formation of a pro-inflammatory and immuno-tolerant microenvironment. Finally, we discuss current experimental limitations and remaining opened questions in light of metastatic diagnosis and potential therapies targeting PMN formation.

G-CSF - A double edge sword in neutrophil mediated immunity

Neutrophils are vital for the innate immune system's control of pathogens and neutrophil deficiency can render the host susceptible to life-threatening infections. Neutrophil responses must also be tightly regulated because excessive production, recruitment or activation of neutrophils can cause tissue damage in both acute and chronic inflammatory diseases. Granulocyte colony stimulating factor (G-CSF) is a key regulator of neutrophil biology, from production, differentiation, and release of neutrophil precursors in the bone marrow (BM) to modulating the function of mature neutrophils outside of the BM, particularly at sites of inflammation. G-CSF acts by binding to its cognate cell surface receptor on target cells, causing the activation of intracellular signalling pathways mediating the proliferation, differentiation, function, and survival of cells in the neutrophil lineage. Studies in humans and mice demonstrate that G-CSF contributes to protecting the host against infection, but conversely, it can play a deleterious role in inflammatory diseases. As such, neutrophils and the G-CSF pathway may provide novel therapeutic targets. This review will focus on understanding the role G-CSF plays in the balance between effective neutrophil mediated host defence versus neutrophil-mediated inflammation and tissue damage in various inflammatory and infectious diseases.

Myeloid cells in COVID-19 microenvironment

Varying differentiation of myeloid cells is common in tumors, inflammation, autoimmune diseases, and metabolic diseases. The release of cytokines from myeloid cells is an important driving factor that leads to severe COVID-19 cases and subsequent death. This review briefly summarizes the results of single-cell sequencing of peripheral blood, lung tissue, and cerebrospinal fluid of COVID-19 patients and describes the differentiation trajectory of myeloid cells in patients. Moreover, we describe the function and mechanism of abnormal differentiation of myeloid cells to promote disease progression. Targeting myeloid cell-derived cytokines or checkpoints is essential in developing a combined therapeutic strategy for patients with severe COVID-19.

Lung mesenchymal stromal cells influenced by Th2 cytokines mobilize neutrophils and facilitate metastasis by producing complement C3

Pre-metastatic niche formation is critical for the colonization of disseminated cancer cells in distant organs. Here we find that lung mesenchymal stromal cells (LMSCs) at pre-metastatic stage possess potent metastasis-promoting activity. RNA-seq reveals an upregulation of complement 3 (C3) in those LMSCs. C3 is found to promote neutrophil recruitment and the formation of neutrophil extracellular traps (NETs), which facilitate cancer cell metastasis to the lungs. C3 expression in LMSCs is induced and sustained by Th2 cytokines in a STAT6-dependent manner. LMSCs-driven lung metastasis is abolished in Th1-skewing Stat6-deficient mice. Blockade of IL-4 by antibody also attenuates LMSCs-driven cancer metastasis to the lungs. Consistently, metastasis is greatly enhanced in Th2-skewing T-bet-deficient mice or in nude mice adoptively transferred with T-bet-deficient T cells. Increased C3 levels are also detected in breast cancer patients. Our results suggest that targeting the Th2-STAT6-C3-NETs cascade may reduce breast cancer metastasis to the lungs.

The formation of the pre-metastatic niche enables the colonisation of disseminated cancer cells in distant organs. Here, the authors show that Th2 cytokines induce Complement 3 production in lung mesenchymal stromal cells, which recruits neutrophils and promotes the formation neutrophil extracellular traps, facilitating breast cancer cell metastasis to the lungs.

G-CSF secreted by mutant IDH1 glioma stem cells abolishes myeloid cell immunosuppression and enhances the efficacy of immunotherapy

Mutant isocitrate-dehydrogenase 1 (mIDH1) synthesizes the oncometabolite 2-hydroxyglutarate (2HG), which elicits epigenetic reprogramming of the glioma cells’ transcriptome by inhibiting DNA and histone demethylases. We show that the efficacy of immune-stimulatory gene therapy (TK/Flt3L) is enhanced in mIDH1 gliomas, due to the reprogramming of the myeloid cells’ compartment infiltrating the tumor microenvironment (TME). We uncovered that the immature myeloid cells infiltrating the mIDH1 TME are mainly nonsuppressive neutrophils and preneutrophils. Myeloid cell reprogramming was triggered by granulocyte colony-stimulating factor (G-CSF) secreted by mIDH1 glioma stem/progenitor-like cells. Blocking G-CSF in mIDH1 glioma–bearing mice restores the inhibitory potential of the tumor-infiltrating myeloid cells, accelerating tumor progression. We demonstrate that G-CSF reprograms bone marrow granulopoiesis, resulting in noninhibitory myeloid cells within mIDH1 glioma TME and enhancing the efficacy of immune-stimulatory gene therapy.

Neutrophil metabolism in the cancer context

Neutrophils are critical innate immune cells for the host anti-bacterial defense. Throughout their lifecycle, neutrophils are exposed to different microenvironments and modulate their metabolism to survive and sustain their functions. Although tumor cell metabolism has been intensively investigated, how neutrophil metabolism is affected in cancer remains largely to be discovered. Neutrophils are described as mainly glycolytic cells. However, distinct tumor-associated neutrophil (TAN) states may co-exist in tumors and adapt their metabolism to exert different or even opposing activities ranging from tumor cell killing to tumor support. In this review, we gather evidence about the metabolic mechanisms that underly TANs' pro- or anti-tumoral functions in cancer. We first discuss how tumor-secreted factors and the heterogenous tumor microenvironment can have a strong impact on TAN metabolism. We then describe alternative metabolic pathways used by TANs to exert their functions in cancer, from basic glycolysis to more recently-recognized but less understood metabolic shifts toward mitochondrial oxidative metabolism, lipid and amino acid metabolism and even autophagy. Last, we discuss promising strategies targeting neutrophil metabolism to combat cancer.

Leveling Up the Controversial Role of Neutrophils in Cancer: When the Complexity Becomes Entangled

Neutrophils are the most abundant immune cell in the circulation of human and act as gatekeepers to discard foreign elements that have entered the body. They are essential in initiating immune responses for eliminating invaders, such as microorganisms and alien particles, as well as to act as immune surveyors of cancer cells, especially during the initial stages of carcinogenesis and for eliminating single metastatic cells in the circulation and in the premetastatic organs. Since neutrophils can secrete a whole range of factors stored in their many granules as well as produce reactive oxygen and nitrogen species upon stimulation, neutrophils may directly or indirectly affect carcinogenesis in both the positive and negative directions. An intricate crosstalk between tumor cells, neutrophils, other immune cells and stromal cells in the microenvironment modulates neutrophil function resulting in both anti- and pro-tumor activities. Both the anti-tumor and pro-tumor activities require chemoattraction towards the tumor cells, neutrophil activation and ROS production. Divergence is seen in other neutrophil properties, including differential secretory repertoire and membrane receptor display. Many of the direct effects of neutrophils on tumor growth and metastases are dependent on tight neutrophil–tumor cell interactions. Among them, the neutrophil Mac-1 interaction with tumor ICAM-1 and the neutrophil L-selectin interaction with tumor-cell sialomucins were found to be involved in the neutrophil-mediated capturing of circulating tumor cells resulting in increased metastatic seeding. On the other hand, the anti-tumor function of neutrophils was found to rely on the interaction between tumor-surface-expressed receptor for advanced glycation end products (RAGE) and Cathepsin G expressed on the neutrophil surface. Intriguingly, these two molecules are also involved in the promotion of tumor growth and metastases. RAGE is upregulated during early inflammation-induced carcinogenesis and was found to be important for sustaining tumor growth and homing at metastatic sites. Cathepsin G was found to be essential for neutrophil-supported lung colonization of cancer cells. These data level up the complexity of the dual role of neutrophils in cancer.

Neutrophil expansion defines an immunoinhibitory peripheral and intratumoral inflammatory milieu in resected non-small cell lung cancer: a descriptive analysis of a prospectively immunoprofiled cohort

Background

The biological underpinnings of the prognostic and predictive significance of a relative neutrophilia in patients with non-small lung cancer (NSCLC) are undefined. We sought to comprehensively examine the relationships between circulating and intratumoral neutrophil populations and features of the immune contexture in patients undergoing NSCLC resection.

Methods

Preoperative soluble cytokine and angiogenic factors; tumor multiplex immunofluorescence; RNA, whole exome, and T-cell receptor sequencing; and flow cytometry were analyzed for relationships with populations of circulating (from complete blood counts) and intratumoral neutrophils (transcriptional signatures) in a prospectively enrolled resected NSCLC cohort (n=66). In a historical cohort (n=1524), preoperative circulating neutrophil and lymphocyte counts were analyzed for associations with overall survival (OS).

Results

Circulating neutrophil populations were positively correlated with increased tumor burden, and surgical tumor resection was followed by a subsequent reduction in peripheral neutrophil counts. Expansion of the circulating neutrophil compartment was associated with increased levels of pro-granulopoietic (IL-1β, IL-17A, TNFα, IL-6) and T_H2-associated (IL-5, IL-13) cytokines. Tumors with high intratumoral neutrophil burden were marked by a blunted T-cell response characterized by reduced expression of cytotoxic T-cell genes (CD8A, CD8B, GZMA, GZMB), decreased CD3⁺CD8⁺ cell infiltration, and diminished expression of IFNγ-related genes. The associations between increased intratumoral neutrophil burden and reduced CD3⁺CD8⁺ infiltration persisted after adjustment for tumor size, histology, mutational burden, and PD-L1 expression. In 1524 patients, elevated preoperative circulating neutrophil count was independently associated with worse OS (main effect HR 1.82, 95% CI 1.24 to 2.68, p=0.002).

Conclusions

Our findings demonstrate that neutrophil expansion reflects protumorigenic and immunosuppressive processes that manifest as worse OS in patients undergoing NSCLC resection. These results justify further investigation of therapeutic strategies targeting neutrophil-associated immune evasion.

Identification of Novel Low-Density Neutrophil Markers Through Unbiased High-Dimensional Flow Cytometry Screening in Non-Small Cell Lung Cancer Patients

Neutrophils have been described as a phenotypically heterogeneous cell type that possess both pro- and anti-tumor properties. Recently, a subset of neutrophils isolated from the peripheral blood mononuclear cell (PBMC) fraction has been described in cancer patients. These low-density neutrophils (LDNs) show a heterogeneous maturation state and have been associated with pro-tumor properties in comparison to mature, high-density neutrophils (HDNs). However, additional studies are necessary to characterize this cell population. Here we show new surface markers that allow us to discriminate between LDNs and HDNs in non-small cell lung cancer (NSCLC) patients and assess their potential as diagnostic/prognostic tool. LDNs were highly enriched in NSCLC patients (median=20.4%, range 0.3-76.1%; n=26) but not in healthy individuals (median=0.3%, range 0.1-3.9%; n=14). Using a high-dimensional human cell surface marker screen, we identified 12 surface markers that were downregulated in LDNs when compared to HDNs, while 41 surface markers were upregulated in the LDN subset. Using flow cytometry, we confirmed overexpression of CD36, CD41, CD61 and CD226 in the LDN fraction. In summary, our data support the notion that LDNs are a unique neutrophil population and provide novel targets to clarify their role in tumor progression and their potential as diagnostic and therapeutic tool.

Roles of Neutrophils in Glioma and Brain Metastases

Neutrophils, which are the most abundant circulating leukocytes in humans, are the first line of defense against bacterial and fungal infections. Recent studies have reported the role and importance of neutrophils in cancers. Glioma and brain metastases are the most common malignant tumors of the brain. The tumor microenvironment (TME) in the brain is complex and unique owing to the brain-blood barrier or brain-tumor barrier, which may prevent drug penetration and decrease the efficacy of immunotherapy. However, there are limited studies on the correlation between brain cancer and neutrophils. This review discusses the origin and functions of neutrophils. Additionally, the current knowledge on the correlation between neutrophil-to-lymphocyte ratio and prognosis of glioma and brain metastases has been summarized. Furthermore, the implications of tumor-associated neutrophil (TAN) phenotypes and the functions of TANs have been discussed. Finally, the potential effects of various treatments on TANs and the ability of neutrophils to function as a nanocarrier of drugs to the brain TME have been summarized. However, further studies are needed to elucidate the complex interactions between neutrophils, other immune cells, and brain tumor cells.

Novel oncolytic adenovirus expressing enhanced cross-hybrid IgGA Fc PD-L1 inhibitor activates multiple immune effector populations leading to enhanced tumor killing in vitro, in vivo and with patient-derived tumor organoids

Background

Despite the success of immune checkpoint inhibitors against PD-L1 in the clinic, only a fraction of patients benefit from such therapy. A theoretical strategy to increase efficacy would be to arm such antibodies with Fc-mediated effector mechanisms. However, these effector mechanisms are inhibited or reduced due to toxicity issues since PD-L1 is not confined to the tumor and also expressed on healthy cells. To increase efficacy while minimizing toxicity, we designed an oncolytic adenovirus that secretes a cross-hybrid Fc-fusion peptide against PD-L1 able to elicit effector mechanisms of an IgG1 and also IgA1 consequently activating neutrophils, a population neglected by IgG1, in order to combine multiple effector mechanisms.

Methods

The cross-hybrid Fc-fusion peptide comprises of an Fc with the constant domains of an IgA1 and IgG1 which is connected to a PD-1 ectodomain via a GGGS linker and was cloned into an oncolytic adenovirus. We demonstrated that the oncolytic adenovirus was able to secrete the cross-hybrid Fc-fusion peptide able to bind to PD-L1 and activate multiple immune components enhancing tumor cytotoxicity in various cancer cell lines, in vivo and ex vivo renal-cell carcinoma patient-derived organoids.

Results

Using various techniques to measure cytotoxicity, the cross-hybrid Fc-fusion peptide expressed by the oncolytic adenovirus was shown to activate Fc-effector mechanisms of an IgA1 (neutrophil activation) as well as of an IgG1 (natural killer and complement activation). The activation of multiple effector mechanism simultaneously led to significantly increased tumor killing compared with FDA-approved PD-L1 checkpoint inhibitor (Atezolizumab), IgG1-PDL1 and IgA-PDL1 in various in vitro cell lines, in vivo models and ex vivo renal cell carcinoma organoids. Moreover, in vivo data demonstrated that Ad-Cab did not require CD8+ T cells, unlike conventional checkpoint inhibitors, since it was able to activate other effector populations.

Conclusion

Arming PD-L1 checkpoint inhibitors with Fc-effector mechanisms of both an IgA1 and an IgG1 can increase efficacy while maintaining safety by limiting expression to the tumor using oncolytic adenovirus. The increase in tumor killing is mostly attributed to the activation of multiple effector populations rather than activating a single effector population leading to significantly higher tumor killing.

Exploring the longitudinal glioma microenvironment landscape uncovers reprogrammed pro-tumorigenic neutrophils in the bone marrow

Recent multi-omics studies show different immune tumor microenvironment (TME) compositions in glioblastoma (GBM). However, temporal comprehensive knowledge of the TME from initiation of the disease remains sparse. We use Cre recombinase (Cre)-inducible lentiviral murine GBM models to compare the cellular evolution of the immune TME in tumors initiated from different oncogenic drivers. We show that neutrophils infiltrate early during tumor progression primarily in the mesenchymal GBM model. Depleting neutrophils in vivo at the onset of disease accelerates tumor growth and reduces the median overall survival time of mice. We show that, as a tumor progresses, bone marrow-derived neutrophils are skewed toward a phenotype associated with pro-tumorigenic processes. Our findings suggest that GBM can remotely regulate systemic myeloid differentiation in the bone marrow to generate neutrophils pre-committed to a tumor-supportive phenotype. This work reveals plasticity in the systemic immune host microenvironment, suggesting an additional point of intervention in GBM treatment.

Heterogeneous Myeloid Cells in Tumors

Accumulating studies highlight a critical role of myeloid cells in cancer biology and therapy. The myeloid cells constitute the major components of tumor microenvironment (TME). The most studied tumor-associated myeloid cells (TAMCs) include monocytes, tumor-associated macrophages (TAMs), dendritic cells (DCs), cancer-related circulating neutrophils, tumor-associated neutrophils (TANs), and myeloid-derived suppressor cells (MDSCs). These heterogenous myeloid cells perform pro-tumor or anti-tumor function, exerting complex and even opposing effects on all stages of tumor development, such as malignant clonal evolution, growth, survival, invasiveness, dissemination and metastasis of tumor cells. TAMCs also reshape TME and tumor vasculature to favor tumor development. The main function of these myeloid cells is to modulate the behavior of lymphocytes, forming immunostimulatory or immunosuppressive TME cues. In addition, TAMCs play a critical role in modulating the response to cancer therapy. Targeting TAMCs is vigorously tested as monotherapy or in combination with chemotherapy or immunotherapy. This review briefly introduces the TAMC subpopulations and their function in tumor cells, TME, angiogenesis, immunomodulation, and cancer therapy.

Neutrophil Extracellular Traps: A New Player in Cancer Metastasis and Therapeutic Target

Neutrophil Extracellular Traps (NETs) are neutrophil-derived extracellular scaffolds, which typically consist of fibrous decondensed chromatins decorated with histones and granule proteins. Initially discovered as a host defence mechanism of neutrophil against pathogens, they have also been implicated in the progression of sterile inflammation-associated diseases such as autoimmune disease, diabetes, and cancer. In this review, we highlight and discuss the more recent studies on the roles of NETs in cancer development, with a special focus on cancer metastasis. Moreover, we present the strategies for targeting NETs in pre-clinical models, but also the challenging questions that need to be answered in the field.

Tumor-associated neutrophils: orchestrating cancer pathobiology and therapeutic resistance

Introduction: Neutrophils or polymorphonuclear cells (PMNs) account for a considerable portion of the tumor immune stroma. Emerging single-cell transcriptomic analyses have elucidated the striking cellular heterogeneity of PMNs during homeostasis and pathologic conditions and have established their diverse roles in cancer. PMNs have emerged as important players in cancer pathobiology and therapeutic resistance. Tumor-associated neutrophils (TANs) effector functions influence tumor development and resistance or response to therapy.Areas covered: This review focuses on PMN heterogeneity and functional diversity in the context of carcinogenesis. TANs, by activating diverse signaling pathways, contribute to cancer progression and resistance to therapies. Mechanisms by which TANs impact therapeutic resistance include alterations of the tumoral DNA damage response, angiogenesis, reactivation of cancer dormancy, enhancement of tumor cell proliferation/survival and immune evasion.Expert opinion: With the emerging phenotypic and function heterogeneity of TANs, targeting specific TAN functions in developing tumors can lead to translatable therapeutic approaches and limit drug resistance. We propose that combining specific targeting of TAN activity with standard cancer therapy can help patients achieving a complete response and prevent cancer relapse.

The tumor microenvironment and immune responses in prostate cancer patients

The landscape of cancer treatment has been transformed over the past decade by the success of immune-targeting therapies. However, despite sipuleucel-T being the first-ever approved vaccine for cancer and the first immunotherapy licensed for prostate cancer in 2010, immunotherapy has since seen limited success in the treatment of prostate cancer. The tumour microenvironment of prostate cancer presents particular barriers for immunotherapy. Moreover, prostate cancer is distinguished by being one of only two solid tumours where increased T cell-infiltration correlates with a poorer, rather than improved, outlook. Here, we discuss the specific aspects of the prostate cancer microenvironment that converge to create a challenging microenvironment, including myeloid-derived immune cells and cancer-associated fibroblasts. By exploring the immune microenvironment of defined molecular subgroups of prostate cancer, we propose an immunogenomic subtyping approach to single-agent and combination immune-targeting strategies that could lead to improved outcomes in prostate cancer treatment.

Prognostic Relevance of Neutrophil to Lymphocyte Ratio (NLR) in Luminal Breast Cancer: A Retrospective Analysis in the Neoadjuvant Setting

The neutrophil to lymphocyte ratio (NLR) is a promising predictive and prognostic factor in breast cancer. We investigated its ability to predict disease-free survival (DFS) and overall survival (OS) in patients with luminal A- or luminal B-HER2-negative breast cancer who received neoadjuvant chemotherapy (NACT). Pre-treatment complete blood cell counts from 168 consecutive patients with luminal breast cancer were evaluated to assess NLR. The study population was stratified into NLR^low or NLR^high according to a cut-off value established by receiving operator curve (ROC) analysis. Data on additional pre- and post-treatment clinical-pathological characteristics were also collected. Kaplan–Meier curves, log-rank tests, and Cox proportional hazards models were used for statistical analyses. Patients with pre-treatment NLR^low showed a significantly shorter DFS (HR: 6.97, 95% CI: 1.65–10.55, p = 0.002) and OS (HR: 7.79, 95% CI: 1.25–15.07, p = 0.021) compared to those with NLR^high. Non-ductal histology, luminal B subtype, and post-treatment Ki67 ≥ 14% were also associated with worse DFS (p = 0.016, p = 0.002, and p = 0.001, respectively). In a multivariate analysis, luminal B subtype, post-treatment Ki67 ≥ 14%, and NLR^low remained independent prognostic factors for DFS, while only post-treatment Ki67 ≥ 14% and NLR^low affected OS. The present study provides evidence that pre-treatment NLR^low helps identify women at higher risk of recurrence and death among patients affected by luminal breast cancer treated with NACT.

Tumor necrosis: A synergistic consequence of metabolic stress and inflammation

Tumor necrosis is a common histological feature and poor prognostic predictor in various cancers. Despite its significant clinical implications, the mechanism underlying tumor necrosis remains largely unclear due to lack of appropriate pre-clinical modeling. We propose that tumor necrosis is a synergistic consequence of metabolic stress and inflammation, which lead to oxidative stress-induced cell death, such as ferroptosis. As a natural consequence of tumor expansion, tumor cells are inevitably stripped of vascular supply, resulting in deprivation of oxygen and nutrients. The resulting metabolic stress has commonly been considered the cause of tumor necrosis. Recent studies found that immune cells, such as neutrophils, when recruited to tumors, can directly trigger ferroptosis in tumor cells, suggesting that immune cells can be involved in amplifying tumor necrosis. This article will discuss potential mechanisms underlying tumor necrosis development and its impact on tumor progression as well as the immune response to tumors.

Blocking immunosuppressive neutrophils deters pY696-EZH2-driven brain metastases

The functions of immune cells in brain metastases are unclear because the brain has traditionally been considered "immune privileged." However, we found that a subgroup of immunosuppressive neutrophils is recruited into the brain, enabling brain metastasis development. In brain metastatic cells, enhancer of zeste homolog 2 (EZH2) is highly expressed and phosphorylated at tyrosine-696 (pY696)-EZH2 by nuclear-localized Src tyrosine kinase. Phosphorylation of EZH2 at Y696 changes its binding preference from histone H3 to RNA polymerase II, which consequently switches EZH2's function from a methyltransferase to a transcription factor that increases c-JUN expression. c-Jun up-regulates protumorigenic inflammatory cytokines, including granulocyte colony-stimulating factor (G-CSF), which recruits Arg1⁺- and PD-L1⁺ immunosuppressive neutrophils into the brain to drive metastasis outgrowth. G-CSF-blocking antibodies or immune checkpoint blockade therapies combined with Src inhibitors impeded brain metastasis in multiple mouse models. These findings indicate that pY696-EZH2 can function as a methyltransferase-independent transcription factor to facilitate the brain infiltration of immunosuppressive neutrophils, which could be clinically targeted for brain metastasis treatment.

Granulocyte Colony-stimulating Factor Producing Oropharyngeal Squamous Cell Carcinoma

CASE REPORT

We report on the case of a 47-year old woman with granulocyte colony-stimulating factor (G-CSF)-producing relapsed oropharyngeal squamous cell cancer. Palliative immunotherapy with nivolumab was started. Absolute neutrophilic count increased during the course of immunotherapy and correlated with tumour progression. Under chemotherapy with weekly paclitaxel, dramatic tumour regression and decreasing absolute neutrophilic count were noted. G-CSF concentration in serum increased from 4.77 to 9.61 pg/ml during the final phase of tumour progression. Immunohistochemical staining of the initial biopsies showed that some of the tumour cells as well as infiltrating cells stained positively for G-CSF, and some of the tumour cells even stained positively for the G-CSF receptor.

CONCLUSION

Leukaemoid reaction in malignant disease with increased neutrophilic granulocytes has been shown to correlate with dismal prognosis in other tumours. The role of G-CSF in progression and prognosis of head and neck squamous cell carcinomas is still unclear but in patients with these tumours there seems also to be a correlation between elevated G-CSF and poor prognosis. Further systematic evaluation of G-CSF secretion in this tumour entity should clarify the role and potential treatment possibilities for these tumours.

The PD-L1/PD-1 Axis Blocks Neutrophil Cytotoxicity in Cancer

The PD-L1/PD-1 axis mediates immune tolerance and promotes tumor growth and progression via the inhibition of anti-tumor immunity. Blocking the interaction between PD-L1 and PD-1 was clinically shown to be beneficial in maintaining the anti-tumor functions of the adaptive immune system. Still, the consequences of blocking the PD-L1/PD-1 axis on innate immune responses remain largely unexplored. In this context, neutrophils were shown to consist of distinct subpopulations, which possess either pro- or anti-tumor properties. PD-L1-expressing neutrophils are considered pro-tumor as they are able to suppress cytotoxic T cells and are propagated with disease progression. That said, we found that PD-L1 expression is not limited to tumor promoting neutrophils, but is also evident in anti-tumor neutrophils. We show that neutrophil cytotoxicity is effectively and efficiently blocked by tumor cell-expressed PD-1. Furthermore, the blocking of either neutrophil PD-L1 or tumor cell PD-1 maintains neutrophil cytotoxicity. Importantly, we show that tumor cell PD-1 blocks neutrophil cytotoxicity and promotes tumor growth via a mechanism independent of adaptive immunity. Taken together, these findings highlight the therapeutic potential of enhancing anti-tumor innate immune responses via blocking of the PD-L1/PD-1 axis.

Systemic immunity in cancer

Immunotherapy has revolutionized cancer treatment, but efficacy remains limited in most clinical settings. Cancer is a systemic disease that induces many functional and compositional changes to the immune system as a whole. Immunity is regulated by interactions of diverse cell lineages across tissues. Therefore, an improved understanding of tumour immunology must assess the systemic immune landscape beyond the tumour microenvironment (TME). Importantly, the peripheral immune system is required to drive effective natural and therapeutically induced antitumour immune responses. In fact, emerging evidence suggests that immunotherapy drives new immune responses rather than the reinvigoration of pre-existing immune responses. However, new immune responses in individuals burdened with tumours are compromised even beyond the TME. Herein, we aim to comprehensively outline the current knowledge of systemic immunity in cancer.

Redox-responsive nanoassembly restrained myeloid-derived suppressor cells recruitment through autophagy-involved lactate dehydrogenase A silencing for enhanced cancer immunochemotherapy

Myeloid-derived suppressor cells (MDSCs) are the chief accomplices for assisting tumor's survival and suppressing anti-tumor immunity, which can be recruited by tumor-derived cytokines, such as granulocyte-colony stimulating factor (G-CSF) and granulocyte-macrophage colony stimulating factor (GM-CSF). The plentiful lactate dehydrogenase A (LDHA) in glycolysis is usually accompanied by abundant tumor-derived G-CSF and GM-CSF, further promoting MDSCs recruitment and immunosuppression. Herein, with the aim to achieve powerful anti-tumor immunity, an immunochemotherapy regimen basing on a redox-responsive nanoassembly (R-mPDV/PDV/DOX/siL) is developed, which integrates the combined strategy of restraining cytokines-mediated MDSCs recruitment through LDHA silencing and reinforcing tumor immunogenicity through anthracycline (DOX)-elicited immunogenic cell death (ICD) effects. This redox-responsive nanoassembly is self-assembled by three glutathione (GSH)-responsive polymers, which employ poly(δ-valerolactone) (PVL) as hydrophobic segment and 3, 3'-dithiodipropionic acid (DA) as linkage to connect hydrophilic segment. DOX is encapsulated in the core and LDHA siRNA (siL) is effectively compressed by cationic PAMAM. The cellular internalization and tumor-homing are strengthened by the specific recognition on integrin (α_vβ₃) by c(RGDfk) (RGD) ligand. After escaping from endosomes/lysosomes, R-mPDV/PDV/DOX/siL is disintegrated through GSH-elicited cleavage of DA, realizing burst release of drugs and high-efficient LDHA silencing. The reduced expression of LDHA suppresses the generation of G-CSF and GM-CSF cytokines, restrains MDSCs recruitment and reinforces anti-tumor immunity. Eventually, this therapeutic regimen of DOX and siL on R-mPDV/PDV/DOX/siL nanoassembly achieved powerful anti-tumor efficiency on 4 T1 orthotopic tumor, opening the new horizons for immunochemotherapy.

Pivotal Role for Cxcr2 in Regulating Tumor-Associated Neutrophil in Breast Cancer

Chemokines present in the tumor microenvironment are essential for the control of tumor progression. We show here that several ligands of the chemokine receptor Cxcr2 were up-regulated in the PyMT (polyoma middle T oncogene) model of breast cancer. Interestingly, the knock-down of Cxcr2 in PyMT animals led to an increased growth of the primary tumor and lung metastasis. The analysis of tumor content of PyMT-Cxcr2-/- animals highlighted an increased infiltration of tumor associated neutrophils (TANs), mirrored by a decreased recruitment of tumor associated macrophages (TAMs) compared to PyMT animals. Analysis of PyMT-Cxcr2-/- TANs revealed that they lost their killing ability compared to PyMT-Cxcr2+/+ TANs. The transcriptomic analysis of PyMT-Cxcr2-/- TANs showed that they had a more pronounced pro-tumor TAN2 profile compared to PyMT TANs. In particular, PyMT-Cxcr2-/- TANs displayed an up-regulation of the pathways involved in reactive oxygen species (ROS) production and angiogenesis and factors favoring metastasis, but reduced apoptosis. In summary, our data reveal that a lack of Cxcr2 provides TANs with pro-tumor effects.

IL-15 superagonist RLI has potent immunostimulatory properties on NK cells: implications for antimetastatic treatment

Background

As the immune system is compromised in patients with cancer, therapeutic strategies to stimulate immunity appear promising, to avoid relapse and increase long-term overall survival. Interleukin-15 (IL-15) has similar properties to IL-2, but does not cause activation-induced cell death nor activation and proliferation of regulatory T cells (Treg), which makes it a serious candidate for anticancer immunotherapy. However, IL-15 has a short half-life and high doses are needed to achieve responses. Designed to enhance its activity, receptor-linker-IL-15 (RLI) (SO-C101) is a fusion molecule of human IL-15 covalently linked to the human IL-15Rα sushi+ domain currently assessed in a phase I/Ib clinical trial on patients with advanced/metastatic solid cancer.

Methods

We investigated the antimetastatic activity of RLI in a 4T1 mouse mammary carcinoma that spontaneously metastasizes and evaluated its immunomodulatory role in the metastatic lung microenvironment. We further characterized the proliferation, maturation and cytotoxic functions of natural killer (NK) cells in tumor-free mice treated with RLI. Finally, we explored the effect of RLI on human NK cells from healthy donors and patients with non-small cell lung cancer (NSCLC).

Results

RLI treatment displayed antimetastatic properties in the 4T1 mouse model. By characterizing the lung microenvironment, we observed that RLI restored the balance between NK cells and neutrophils (CD11b⁺ Ly6G^high Ly6C^low) that massively infiltrate lungs of 4T1-tumor bearing mice. In addition, the ratio between NK cells and Treg was strongly increased by RLI treatment. Further pharmacodynamic studies in tumor-free mice revealed superior proliferative and cytotoxic functions on NK cells after RLI treatment compared with IL-15 alone. Characterization of the maturation stage of NK cells demonstrated that RLI favored accumulation of CD11b⁺ CD27^high KLRG1⁺ mature NK cells. Finally, RLI demonstrated potent immunostimulatory properties on human NK cells by inducing proliferation and activation of NK cells from healthy donors and enhancing cytotoxic responses to NKp30 crosslinking in NK cells from patients with NSCLC.

Conclusions

Collectively, our work demonstrates superior activity of RLI compared with rhIL-15 in modulating and activating NK cells and provides additional evidences for a therapeutic strategy using RLI as antimetastatic molecule.

The impact of microRNAs on myeloid-derived suppressor cells in cancer

Inflammation promotes cancer development. To a large extent, this can be attributed to the recruitment of myeloid-derived suppressor cells (MDSCs) to tumors. These cells are known for establishing an immunosuppressive tumor microenvironment by suppressing T cell activities. However, MDSCs also promote metastasis and angiogenesis. Critically, as small non-coding RNAs that regulate gene expression, microRNAs (miRNAs) control MDSC activities. In this review, we discuss how miRNA networks regulate key MDSC signaling pathways, how they shape MDSC development, differentiation and activation, and how this impacts tumor development. By targeting the expression of miRNAs in MDSCs, we can alter their main signaling pathways. In turn, this can compromise their ability to promote multiple hallmarks of cancer. Therefore, this may represent a new powerful strategy for cancer immunotherapy.

Neutrophils in cancer, a love-hate affair

Neutrophils dominate the immunological landscape of multiple types of solid tumours in mice and humans and exert different pro- or antitumoral activity. This functional heterogeneity has prompted a search for different subsets and classifications of tumour-infiltrating neutrophils with the idea of better delineating their specific roles in cancer. In this review, we describe current studies that highlight specific mechanisms by which neutrophils exert pro- or antitumoral function and focus on how distinct tumour types induce unique functional states in neutrophils, co-opt granulopoiesis, modulate neutrophil ageing and prolong the neutrophil life span. In addition, we discuss how the tissue-specific tumour stroma and the stage of the cancer influence the function and number of tumour-infiltrating neutrophils. Finally, we explore different approaches to enhance the therapeutic efficacy in cancer types dominated by neutrophils.

Redefining macrophage and neutrophil biology in the metastatic cascade

Tumor cells metastasize to distant organs through a complex series of events that are driven by tumor intrinsic and extrinsic factors. In particular, non-malignant stromal cells, including immune cells, modify tumor metastatic behavior. Of these cells, tumor-associated innate immune cells, particularly macrophages and neutrophils, suppress the cytotoxic activity of innate and adaptive killer cells and interact with tumor cells to promote their growth and malignancy. These findings in mouse cancer models suggest that targeting these sub-populations of immune cells holds therapeutic promise in treating metastatic disease. In this review, we describe the origin and role of the macrophages, neutrophils, and their progenitors in the metastatic cascade and suggest strategies that might enhance cancer therapy.

Neutrophil and Nanoparticles Delivery to Tumor: Is It Going to Carry That Weight?

The application of cell carriers for transporting nanodrugs to the tumor draws much attention as the alternative to the passive drug delivery. In this concept, the neutrophil (NΦ) is of special interest as this cell is able to uptake nanoparticles (NPs) and cross the vascular barrier in response to tumor signaling. There is a growing body of literature describing NP-NΦ interactions in vitro and in vivo that demonstrates the opportunity of using these cells to improve the efficacy of cancer therapy. However, a number of conceptual and technical issues need to be resolved for translating the technology into clinics. The current review summarizes the recent advances and challenges associated with NP-NΦ interactions, with the special focus on the complex interplay between the NP internalization pathways and the modulation of NΦ activity, and its potential consequences for nanodrug delivery.

Myelopoiesis during Solid Cancers and Strategies for Immunotherapy

Our understanding of the relationship between the immune system and cancers has undergone significant discovery recently. Immunotherapy with T cell therapies and checkpoint blockade has meaningfully changed the oncology landscape. While remarkable clinical advances in adaptive immunity are occurring, modulation of innate immunity has proven more difficult. The myeloid compartment, including macrophages, neutrophils, and dendritic cells, has a significant impact on the persistence or elimination of tumors. Myeloid cells, specifically in the tumor microenvironment, have direct contact with tumor tissue and coordinate with tumor-reactive T cells to either stimulate or antagonize cancer immunity. However, the myeloid compartment comprises a broad array of cells in various stages of development. In addition, hematopoietic stem and progenitor cells at various stages of myelopoiesis in distant sites undergo significant modulation by tumors. Understanding how tumors exert their influence on myeloid progenitors is critical to making clinically meaningful improvements in these pathways. Therefore, this review will cover recent developments in our understanding of how solid tumors modulate myelopoiesis to promote the formation of pro-tumor immature myeloid cells. Then, it will cover some of the potential avenues for capitalizing on these mechanisms to generate antitumor immunity.

Emerging roles for myeloid immune cells in bone metastasis

Metastasis, especially bone metastasis, is a major cause of cancer-related deaths, which is associated with long-term pain due to skeletal-related events and poor quality of life. Tumor cells alter the bone microenvironment through aberrant activation of osteoclasts and osteoblasts which induces bone osteolysis and release of growth factors leading to cancer growth. Though this phenomenon has been well characterized, bone-targeted therapies have shown little improvement in patient survival. Recent evidence indicates a growing appreciation for the complex bone environment, in addition to bone-remodeling stromal cells, which includes an abundance of myeloid immune cells that can either protect against or contribute to the progression of the disease within the bone cavity. Additionally, myeloid cells are recruited into primary tumor sites, where they promote development of the pre-metastatic niche and also can regulate tumor progression within the tumor-bone microenvironment through a milieu of complex mechanisms and involving heterogeneous myeloid populations. In this review, we have highlighted the complex roles of myeloid immunity in bone metastasis and hope to bring attention to the potential of novel immunotherapeutic interventions for the elimination of bone metastasis.

Granulocytes and Cells of Granulocyte Origin-The Relevant Players in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common malignancy and cause of cancer death worldwide, and it still remains a therapeutic challenge for western medicine. There is strong evidence that, in addition to genetic predispositions, environmental factors have also a substantial impact in CRC development. The risk of CRC is attributed, among others to dietary habits, alcohol consumption, whereas physical activity, food containing dietary fiber, dairy products, and calcium supplements have a protective effect. Despite progress in the available therapies, surgery remains a basic treatment option for CRC. Implementation of additional methods of treatment such as chemo- and/or targeted immunotherapy, improved survival rates, however, the results are still far from satisfactory. One of the reasons may be the lack of deeper understanding of the interactions between the tumor and different types of cells, including tumor infiltrating granulocytes. While the role of neutrophils is quite well explored in many cancers, role of eosinophils and basophils is often underestimated. As part of this review, we focused on the function of different granulocyte subsets in CRC, emphasizing the beneficial role of eosinophils and basophils, as well as dichotomic mode of neutrophils action. In addition, we addressed the current knowledge on cells of granulocyte origin, specifically granulocytic myeloid derived suppressor cells (Gr-MDSCs) and their role in development and progression of CRC.

Monocytes in the Tumor Microenvironment

Immunotherapy has revolutionized cancer treatment over the past decade. Nonetheless, prolonged survival is limited to relatively few patients. Cancers enforce a multifaceted immune-suppressive network whose nature is progressively shaped by systemic and local cues during tumor development. Monocytes bridge innate and adaptive immune responses and can affect the tumor microenvironment through various mechanisms that induce immune tolerance, angiogenesis, and increased dissemination of tumor cells. Yet monocytes can also give rise to antitumor effectors and activate antigen-presenting cells. This yin-yang activity relies on the plasticity of monocytes in response to environmental stimuli. In this review, we summarize current knowledge of the ontogeny, heterogeneity, and functions of monocytes and monocyte-derived cells in cancer, pinpointing the main pathways that are important for modeling the immunosuppressive tumor microenvironment.