Neutrophils impose strong immune pressure against PfEMP1 variants implicated in cerebral malaria.

Plasmodium falciparum, the deadliest form of human malaria, remains one of the major threats to human health in endemic regions. Its virulence is attributed to its ability to modify infected red blood cells (iRBC) to adhere to endothelial receptors by placing variable antigens known as PfEMP1 on the iRBC surface. PfEMP1 expression determines the cytoadhesive properties of the iRBCs and is implicated in severe malaria. To evade antibody-mediated responses, the parasite undergoes continuous switches of expression between different PfEMP1 variants. Recently, it became clear that in addition to antibody-mediated responses, PfEMP1 triggers innate immune responses; however, the role of neutrophils, the most abundant white blood cells in the human circulation, in malaria remains elusive. Here, we show that neutrophils recognize and kill blood-stage P. falciparum isolates. We identify neutrophil ICAM-1 and specific PfEMP1 implicated in cerebral malaria as the key molecules involved in this killing. Our data provide mechanistic insight into the interactions between neutrophils and iRBCs and demonstrate the important influence of PfEMP1 on the selective innate response to cerebral malaria.

The inhibitory receptor CD300a is essential for neutrophil-mediated clearance of urinary tract infection in mice.

Neutrophils play a crucial role in immune defense against and clearance of uropathogenic Escherichia coli (UPEC)-mediated urinary tract infection, the most common bacterial infection in healthy humans. CD300a is an inhibitory receptor that binds phosphatidylserine and phosphatidylethanolamine, presented on the membranes of apoptotic cells. CD300a binding to phosphatidylserine and phosphatidylethanolamine, also known as the "eat me" signal, mediates immune tolerance to dying cells. Here, we demonstrate for the first time that CD300a plays an important role in the neutrophil-mediated immune response to UPEC-induced urinary tract infection. We show that CD300a-deficient neutrophils have impaired phagocytic abilities and despite their increased accumulation at the site of infection, they are unable to reduce bacterial burden in the bladder, which results in significant exacerbation of infection and worse host outcome. Finally, we demonstrate that UPEC's pore forming toxin α-hemolysin induces upregulation of the CD300a ligand on infected bladder epithelial cells, signaling to neutrophils to be cleared.

Interleukin-1α dependent survival of cardiac fibroblasts is associated with StAR/STARD1 expression and improved cardiac remodeling and function after myocardial infarction.

AIMS: One unaddressed aspect of healing after myocardial infarction (MI) is how non-myocyte cells that survived the ischemic injury, keep withstanding additional cellular damage by stress forms typically arising during the post-infarction inflammation. Here we aimed to determine if cell survival is conferred by expression of a mitochondrial protein novel to the cardiac proteome, known as steroidogenic acute regulatory protein, (StAR/STARD1). Further studies aimed to unravel the regulation and role of the non-steroidogenic cardiac StAR after MI. METHODS AND RESULTS: Following permanent ligation of the left anterior descending coronary artery in mouse heart, timeline western blot analyses showed that StAR expression corresponds to the inflammatory response to MI. Following the identification of StAR in mitochondria of cardiac fibroblasts in culture, confocal microscopy immunohistochemistry (IHC) identified StAR expression in left ventricular (LV) activated interstitial fibroblasts, adventitial fibroblasts and endothelial cells. Further work with the primary fibroblasts model revealed that interleukin-1α (IL-1α) signaling via NF-κB and p38 MAPK pathways efficiently upregulates the expression of the Star gene products. At the functional level, IL-1α primed fibroblasts were protected against apoptosis when exposed to cisplatin mimicry of in vivo apoptotic stress; yet, the protective impact of IL-1α was lost upon siRNA mediated StAR downregulation. At the physiological level, StAR expression was nullified during post-MI inflammation in a mouse model with global IL-1α deficiency, concomitantly resulting in a 4-fold elevation of apoptotic fibroblasts. Serial echocardiography and IHC studies of mice examined 24 days after MI revealed aggravation of LV dysfunction, LV dilatation, anterior wall thinning and adverse tissue remodeling when compared with loxP control hearts. CONCLUSIONS: This study calls attention to overlooked aspects of cellular responses evolved under the stress conditions associated with the default inflammatory response to MI. Our observations suggest that LV IL-1α is cardioprotective, and at least one mechanism of this action is mediated by induction of StAR expression in border zone fibroblasts, which renders them apoptosis resistant. This acquired survival feature also has long-term ramifications on the heart recovery by diminishing adverse remodeling and improving the heart function after MI.

MET is required for the recruitment of anti-tumoural neutrophils.

Mutations or amplification of the MET proto-oncogene are involved in the pathogenesis of several tumours, which rely on the constitutive engagement of this pathway for their growth and survival. However, MET is expressed not only by cancer cells but also by tumour-associated stromal cells, although its precise role in this compartment is not well characterized. Here we show that MET is required for neutrophil chemoattraction and cytotoxicity in response to its ligand hepatocyte growth factor (HGF). Met deletion in mouse neutrophils enhances tumour growth and metastasis. This phenotype correlates with reduced neutrophil infiltration to both the primary tumour and metastatic sites. Similarly, Met is necessary for neutrophil transudation during colitis, skin rash or peritonitis. Mechanistically, Met is induced by tumour-derived tumour necrosis factor (TNF)-α or other inflammatory stimuli in both mouse and human neutrophils. This induction is instrumental for neutrophil transmigration across an activated endothelium and for inducible nitric oxide synthase production upon HGF stimulation. Consequently, HGF/MET-dependent nitric oxide release by neutrophils promotes cancer cell killing, which abates tumour growth and metastasis. After systemic administration of a MET kinase inhibitor, we prove that the therapeutic benefit of MET targeting in cancer cells is partly countered by the pro-tumoural effect arising from MET blockade in neutrophils. Our work identifies an unprecedented role of MET in neutrophils, suggests a potential 'Achilles' heel' of MET-targeted therapies in cancer, and supports the rationale for evaluating anti-MET drugs in certain inflammatory diseases.

TRPM2 modulates neutrophil attraction to murine tumor cells by regulating CXCL2 expression.

In recent years, immune cells were shown to play critical roles in tumor growth and metastatic progression. In this context, neutrophils were shown to possess both pro- and anti-tumor properties. To exert their anti-tumor effect, neutrophils need to migrate towards, and form physical contact with tumor cells. Neutrophils secrete H2O2 in a contact-dependent mechanism, thereby inducing a lethal Ca2+ influx via the activation of the H2O2-dependent TRPM2 Ca2+ channel. Here, we explored the mechanism regulating neutrophil chemoattraction to tumor cells. Interestingly, we found that TRPM2 plays a role in this context as well, since it regulates the expression of potent neutrophil chemoattractants. Consequently, cells expressing reduced levels of TRPM2 are not approached by neutrophils. Together, these observations demonstrate how tumor cells expressing reduced levels of TRPM2 evade neutrophil cytotoxicity in two interrelated mechanisms-downregulation of neutrophil chemoattractants and blocking of the apoptotic Ca2+-dependent cascade. These observations demonstrate a critical role for TRPM2 in neutrophil-mediated immunosurveillance and identify cells expressing low levels of TRPM2, as a potential target for cancer therapy.

Pregnancy restores the regenerative capacity of the aged liver via activation of an mTORC1-controlled hyperplasia/hypertrophy switch.

Regenerative capacity is progressively lost with age. Here we show that pregnancy markedly improved liver regeneration in aged mice concomitantly with inducing a switch from proliferation-based liver regeneration to a regenerative process mediated by cell growth. We found that the key mediator of this switch was the Akt/mTORC1 pathway; its inhibition blocked hypertrophy, while increasing proliferation. Moreover, pharmacological activation of this pathway sufficed to induce the hypertrophy module, mimicking pregnancy. This treatment dramatically improved hepatic regenerative capacity and survival of old mice. Thus, cell growth-mediated mass reconstitution, which is relatively resistant to the detrimental effects of aging, is employed in a physiological situation and holds potential as a therapeutic strategy for ameliorating age-related functional deterioration.

Loss of Liver Kinase B1 (LKB1) in Beta Cells Enhances Glucose-stimulated Insulin Secretion Despite Profound Mitochondrial Defects.

The tumor suppressor liver kinase B1 (LKB1) is an important regulator of pancreatic ß cell biology. LKB1-dependent phosphorylation of distinct AMPK (adenosine monophosphate-activated protein kinase) family members determines proper ß cell polarity and restricts ß cell size, total ß cell mass, and glucose-stimulated insulin secretion (GSIS). However, the full spectrum of LKB1 effects and the mechanisms involved in the secretory phenotype remain incompletely understood. We report here that in the absence of LKB1 in ß cells, GSIS is dramatically and persistently improved. The enhancement is seen both in vivo and in vitro and cannot be explained by altered cell polarity, increased ß cell number, or increased insulin content. Increased secretion does require membrane depolarization and calcium influx but appears to rely mostly on a distal step in the secretion pathway. Surprisingly, enhanced GSIS is seen despite profound defects in mitochondrial structure and function in LKB1-deficient ß cells, expected to greatly diminish insulin secretion via the classic triggering pathway. Thus LKB1 is essential for mitochondrial homeostasis in ß cells and in parallel is a powerful negative regulator of insulin secretion. This study shows that ß cells can be manipulated to enhance GSIS to supra-normal levels even in the face of defective mitochondria and without deterioration over months.

Distinct Functions of Neutrophil in Cancer and Its Regulation.

Neutrophils are the most abundant of all white blood cells in the human circulation and are usually associated with inflammation and with fighting infections. In recent years the role immune cells play in cancer has been a matter of increasing interest. In this context the function of neutrophils is controversial as neutrophils were shown to possess both tumor promoting and tumor limiting properties. Here we provide an up-to-date review of the pro- and antitumor properties neutrophils possess as well as the environmental cues that regulate these distinct functions.

Neutrophils recruit regulatory T-cells into tumors via secretion of CCL17--a new mechanism of impaired antitumor immunity.

The mechanisms by which tumor-associated neutrophils (TANs) affect tumor growth are to a large extent unknown. Regulatory T-cells (T-regs) are functionally immune-suppressive subsets of T-cells. Depletion or inhibition of T-regs can enhance antitumor immunity. We demonstrated both by RT-PCR and by ELISA that murine TANs secrete significant amounts of the T-regs chemoattractant, CCL17, much more than circulating or splenic neutrophils, and at a level progressively increasing during tumor development. Migration assays, both in vitro and in vivo, showed recruitment of T-regs by TANs, which was inhibited with anti-CCL17 monoclonal antibodies. Systemic neutrophil depletion in tumor-bearing mice using anti-Ly6G monoclonal antibodies reduced the migration of T-regs into the tumors. We further showed, using flow cytometry, that CCL17 secretion by TANs is not limited to mouse models of cancer but is also relevant to human TANs. Our results suggest a new indirect mechanism by which TANs may inhibit antitumor immune activity, thus promoting tumor growth. We further describe, for the first time, a clear link between TANs and T-regs acting together to impair antitumor immunity.

Interactions between γδ T cells and neutrophils in cancer: knowns and unknowns.

The tumor microenvironment provides a unique opportunity to gain insight into the relationship and crosstalk between different cell types. In this context, little is known about the interaction between γδ T cells and neutrophils, which are innate immune cells abundant in the tumor microenvironment. Interestingly, both γδ T cells and neutrophils are heterogeneous, may play diverse regulatory roles, and have been shown to have both protumor and antitumor functions. In this editorial, we discuss recent advances in the understanding of interplay between γδ T cells and neutrophils in cancer and provide insights and future directions highlighting the role these interactions may play in cancer.

A Comprehensively Prognostic and Immunological Analysis of PARP11 in Pan-cancer.

Poly (ADP ribose) polymerase family member 11(PARP11) has important immune regulatory functions in viral infection and tumor immune response. Particularly, PARP11 showed protumor activities in multiple preclinical murine models. However, no systematic pan-cancer analysis has been conducted to explore PARP11 function. In this study we used multiple databases to assess PARP11 expression, which associations with clinical outcomes, immune checkpoint factors, prognostic significance, genomic characteristics, and immunological aspects. The analysis revealed varying expression levels of PARP11 across different cancer types and a significant correlation between its expression and immune cell infiltration. Insights from the CellMiner database suggest a strong link between PARP11 expression and sensitivity to anticancer drugs, highlighting its potential as a therapeutic target. Moreover, PARP11 expression correlates with patient survival during anti-PD1 and anti-CTLA4 treatments, suggested that PARP11 would be a predictor of immune checkpoint inhibitor (ICI) treatment. In summary, PARP11 would be a potential immunoregulatory target and a diagnosis and prognosis marker for certain types of cancers. The detailed mechanisms of PARP11 in tumor immune responses need to be further investigated.

IRE1 endoribonuclease signaling promotes myeloid cell infiltration in glioblastoma.

BACKGROUND: Intrinsic or environmental stresses trigger the accumulation of improperly folded proteins in the endoplasmic reticulum (ER), leading to ER stress. To cope with this, cells have evolved an adaptive mechanism named the unfolded protein response (UPR) which is hijacked by tumor cells to develop malignant features. Glioblastoma (GB), the most aggressive and lethal primary brain tumor, relies on UPR to sustain growth. We recently showed that IRE1 alpha (referred to IRE1 hereafter), 1 of the UPR transducers, promotes GB invasion, angiogenesis, and infiltration by macrophage. Hence, high tumor IRE1 activity in tumor cells predicts a worse outcome. Herein, we characterized the IRE1-dependent signaling that shapes the immune microenvironment toward monocytes/macrophages and neutrophils. METHODS: We used human and mouse cellular models in which IRE1 was genetically or pharmacologically invalidated and which were tested in vivo. Publicly available datasets from GB patients were also analyzed to confirm our findings. RESULTS: We showed that IRE1 signaling, through both the transcription factor XBP1s and the regulated IRE1-dependent decay controls the expression of the ubiquitin-conjugating E2 enzyme UBE2D3. In turn, UBE2D3 activates the NFκB pathway, resulting in chemokine production and myeloid infiltration in tumors. CONCLUSIONS: Our work identifies a novel IRE1/UBE2D3 proinflammatory axis that plays an instrumental role in GB immune regulation.

Recognition of Tumor Nidogen-1 by Neutrophil C-Type Lectin Receptors.

Neutrophil-mediated cytotoxicity toward tumor cells requires cell contact and is mediated by hydrogen peroxide. We have recently shown that Cathepsin G expressed on the neutrophil surface interacts with tumor RAGE, and this interaction facilitates neutrophil cytotoxicity. Interruption of the Cathepsin G-RAGE interaction led to 50-80% reduction in cytotoxicity, suggesting that additional interactions are also involved. Here we show that blocking antibodies to the C-type lectin receptors (CLRs) Clec4e and Dectin-1, but not those to NKG2D, attenuated murine neutrophil cytotoxicity towards murine tumor cells, suggesting a contributing role for these CLRs in neutrophil recognition of tumor cells. We further observed that the CLRs interact with tumor Nidogen-1 and Hspg2, two sulfated glycoproteins of the basement membrane. Both Nidogen-1 and Hspg2 were found to be expressed on the tumor cell surface. The knockdown of Nidogen-1, but not that of Hspg2, led to reduced susceptibility of the tumor cells to neutrophil cytotoxicity. Altogether, this study suggests a role for CLR-Nidogen-1 interaction in the recognition of tumor cells by neutrophils, and this interaction facilitates neutrophil-mediated killing of the tumor cells.

Assaying Interactions Between Neutrophils and Plasmodium falciparum-Infected Red Blood Cells.

Plasmodium falciparum, which causes the deadliest form of human malaria, is able to evade antibody-mediated immune responses through switches in expression of surface antigens. Thus, over the years, the focus of most research has been on the role of the adaptive immune response in the course of malaria. However, in recent years there is mounting evidence for the role of the innate immune response to Plasmodium infections. In this context, very little is known on the protective role of neutrophils against blood-stage parasites and the mechanisms by which they recognize and eliminate infected red blood cells. Here we describe several useful methodologies that enable the study and quantification of the interactions between human neutrophils and P. falciparum-infected red blood cells.

Asymmetric inheritance of RNA toxicity in C. elegans expressing CTG repeats.

Nucleotide repeat expansions are a hallmark of over 40 neurodegenerative diseases and cause RNA toxicity and multisystemic symptoms that worsen with age. Through an unclear mechanism, RNA toxicity can trigger severe disease manifestation in infants if the repeats are inherited from their mother. Here we use Caenorhabditis elegans bearing expanded CUG repeats to show that this asymmetric intergenerational inheritance of toxicity contributes to disease pathogenesis. In addition, we show that this mechanism is dependent on small RNA pathways with maternal repeat-derived small RNAs causing transcriptomic changes in the offspring, reduced motility, and shortened lifespan. We rescued the toxicity phenotypes in the offspring by perturbing the RNAi machinery in the affected hermaphrodites. This points to a novel mechanism linking maternal bias and the RNAi machinery and suggests that toxic RNA is transmitted to offspring, causing disease phenotypes through intergenerational epigenetic inheritance.

ICAM-1 on Breast Cancer Cells Suppresses Lung Metastasis but Is Dispensable for Tumor Growth and Killing by Cytotoxic T Cells.

Breast tumors and their derived circulating cancer cells express the leukocyte ß2 integrin ligand Intercellular adhesion molecule 1 (ICAM-1). We found that elevated ICAM-1 expression in breast cancer cells results in a favorable outcome and prolonged survival of breast cancer patients. We therefore assessed the direct in vivo contribution of ICAM-1 expressed by breast cancer cells to breast tumorigenesis and lung metastasis in syngeneic immunocompetent mice hosts using spontaneous and experimental models of the lung metastasis of the C57BL/6-derived E0771 cell line, a luminal B breast cancer subtype. Notably, the presence of ICAM-1 on E0771 did not alter tumor growth or the leukocyte composition in the tumor microenvironment. Interestingly, the elimination of Tregs led to the rapid killing of primary tumor cells independently of tumor ICAM-1 expression. The in vivo elimination of a primary E0771 tumor expressing the ovalbumin (OVA) model neoantigen by the OVA-specific OVA-tcr-I mice (OT-I) transgenic cytotoxic T lymphocytes (CTLs) also took place normally in the absence of ICAM-1 expression by E0771 breast cancer target cells. The whole lung imaging of these cells by light sheet microscopy (LSM) revealed that both Wild type (WT)- and ICAM-1-deficient E0771 cells were equally disseminated from resected tumors and accumulated inside the lung vasculature at similar magnitudes. ICAM-1-deficient breast cancer cells developed, however, much larger metastatic lesions than their control counterparts. Strikingly, the vast majority of these cells gave rise to intravascular tumor colonies both in spontaneous and experimental metastasis models. In the latter model, ICAM-1 expressing E0771- but not their ICAM-1-deficient counterparts were highly susceptible to elimination by neutrophils adoptively transferred from E0771 tumor-bearing donor mice. Ex vivo, neutrophils derived from tumor-bearing mice also killed cultured E0771 cells via ICAM-1-dependent interactions. Collectively, our results are a first indication that ICAM-1 expressed by metastatic breast cancer cells that expand inside the lung vasculature is involved in innate rather than in adaptive cancer cell killing. This is also a first indication that the breast tumor expression of ICAM-1 is not required for CTL-mediated killing but can function as a suppressor of intravascular breast cancer metastasis to lungs.

Targeted nanoparticles modify neutrophil function in vivo.

Neutrophils play critical roles in a broad spectrum of clinical conditions. Accordingly, manipulation of neutrophil function may provide a powerful immunotherapeutic approach. However, due to neutrophils characteristic short half-life and their large population number, this possibility was considered impractical. Here we describe the identification of peptides which specifically bind either murine or human neutrophils. Although the murine and human neutrophil-specific peptides are not cross-reactive, we identified CD177 as the neutrophil-expressed binding partner in both species. Decorating nanoparticles with a neutrophil-specific peptide confers neutrophil specificity and these neutrophil-specific nanoparticles accumulate in sites of inflammation. Significantly, we demonstrate that encapsulating neutrophil modifying small molecules within these nanoparticles yields specific modulation of neutrophil function (ROS production, degranulation, polarization), intracellular signaling and longevity both in vitro and in vivo. Collectively, our findings demonstrate that neutrophil specific targeting may serve as a novel mode of immunotherapy in disease.

Computational quantification and characterization of independently evolving cellular subpopulations within tumors is critical to inhibit anti-cancer therapy resistance.

BACKGROUND: Drug resistance continues to be a major limiting factor across diverse anti-cancer therapies. Contributing to the complexity of this challenge is cancer plasticity, in which one cancer subtype switches to another in response to treatment, for example, triple-negative breast cancer (TNBC) to Her2-positive breast cancer. For optimal treatment outcomes, accurate tumor diagnosis and subsequent therapeutic decisions are vital. This study assessed a novel approach to characterize treatment-induced evolutionary changes of distinct tumor cell subpopulations to identify and therapeutically exploit anticancer drug resistance. METHODS: In this research, an information-theoretic single-cell quantification strategy was developed to provide a high-resolution and individualized assessment of tumor composition for a customized treatment approach. Briefly, this single-cell quantification strategy computes cell barcodes based on at least 100,000 tumor cells from each experiment and reveals a cell-specific signaling signature (CSSS) composed of a set of ongoing processes in each cell. RESULTS: Using these CSSS-based barcodes, distinct subpopulations evolving within the tumor in response to an outside influence, like anticancer treatments, were revealed and mapped. Barcodes were further applied to assign targeted drug combinations to each individual tumor to optimize tumor response to therapy. The strategy was validated using TNBC models and patient-derived tumors known to switch phenotypes in response to radiotherapy (RT). CONCLUSIONS: We show that a barcode-guided targeted drug cocktail significantly enhances tumor response to RT and prevents regrowth of once-resistant tumors. The strategy presented herein shows promise in preventing cancer treatment resistance, with significant applicability in clinical use.

Neutrophil phenotypes and functions in cancer: A consensus statement.

Neutrophils are the first responders to infection and inflammation and are thus a critical component of innate immune defense. Understanding the behavior of neutrophils as they act within various inflammatory contexts has provided insights into their role in sterile and infectious diseases; however, the field of neutrophils in cancer is comparatively young. Here, we summarize key concepts and current knowledge gaps related to the diverse roles of neutrophils throughout cancer progression. We discuss sources of neutrophil heterogeneity in cancer and provide recommendations on nomenclature for neutrophil states that are distinct in maturation and activation. We address discrepancies in the literature that highlight a need for technical standards that ought to be considered between laboratories. Finally, we review emerging questions in neutrophil biology and innate immunity in cancer. Overall, we emphasize that neutrophils are a more diverse population than previously appreciated and that their role in cancer may present novel unexplored opportunities to treat cancer.