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Purpose: Patients with cancer frequently undergo radiotherapy in their clinical management with unintended irradiation of blood vessels and copiously irrigated organs in which polymorphonuclear leukocytes circulate. Following the observation that such low doses of ionizing radiation are able to induce neutrophils to extrude neutrophil extracellular traps (NET), we have investigated the mechanisms, consequences, and occurrence of such phenomena in patients undergoing radiotherapy., Experimental Design: NETosis was analyzed in cultures of neutrophils isolated from healthy donors, patients with cancer, and cancer-bearing mice under confocal microscopy. Cocultures of radiation-induced NETs, immune effector lymphocytes, and tumor cells were used to study the effects of irradiation-induced NETs on immune cytotoxicity. Radiation-induced NETs were intravenously injected to mice for assessing their effects on metastasis. Circulating NETs in irradiated patients with cancer were measured using ELISA methods for detecting MPO-DNA complexes and citrullinated histone 3., Results: Irradiation of neutrophils with very low γ-radiation doses (0.5-1 Gy) elicits NET formation in a manner dependent on oxidative stress, NADPH oxidase activity, and autocrine IL8. Radiation-induced NETs interfere with NK cell and T-cell cytotoxicity. As a consequence, preinjection of irradiation-induced NETs increases the number of successful metastases in mouse tumor models. Increases in circulating NETs were readily detected in two prospective series of patients following the first fraction of their radiotherapy courses., Conclusions: NETosis is induced by low-dose ionizing irradiation in a neutrophil-intrinsic fashion, and radiation-induced NETs are able to interfere with immune-mediated cytotoxicity. Radiation-induced NETs foster metastasis in mouse models and can be detected in the circulation of patients undergoing conventional radiotherapy treatments. See related commentary by Mowery and Luke, p. 3965., (©2024 The Authors; Published by the American Association for Cancer Research.)

In humans, IL-8 (CXCL8) is a key chemokine for chemotaxis of polymorphonuclear leukocytes and monocytes/macrophages when acting on CXCR1 and CXCR2. CXCL8 activity on neutrophils includes chemotaxis and eliciting the extrusion of neutrophil extracellular traps (NETs). In this study, we show that concentrations of IL-8 that induce NETosis surpass in at least one order of magnitude those required to elicit chemoattraction in human neutrophils. IL-8-induced NETosis was less dependent on G-proteins than migration, while extracellular Ca +2 chelation similarly inhibited both processes. Reactive oxygen species (ROS) were more important for NETosis than for chemotaxis as evidenced by neutralization with N-acetyl -cysteine. Interestingly, selective blockade with anti-CXCR1 mAb inhibited NETosis much more readily than chemotaxis, while pharmacological inhibition of both CXCR1 and CXCR2, or selective inhibition for CXCR2 alone, similarly inhibited both functions. Together, these results propose a model according to which low concentrations of IL-8 in a gradient attract neutrophils to the inflammatory foci, while high receptor-saturating concentrations of IL-8 give rise to NETosis once leukocytes reach the core of the inflammatory insult., (© 2021 Wiley-VCH GmbH.)

Injection of effector proteins to block host innate immune signaling is a common strategy used by many pathogenic organisms to establish an infection. For example, pathogenic Yersinia species inject the acetyltransferase YopJ into target cells to inhibit NF-κB and MAPK signaling. To counteract this, detection of YopJ activity in myeloid cells promotes the assembly of a RIPK1-caspase-8 death-inducing platform that confers antibacterial defense. While recent studies revealed that caspase-8 cleaves the pore-forming protein gasdermin D to trigger pyroptosis in macrophages, whether RIPK1 activates additional substrates downstream of caspase-8 to promote host defense is unclear. Here, we report that the related gasdermin family member gasdermin E (GSDME) is activated upon detection of YopJ activity in a RIPK1 kinase-dependent manner. Specifically, GSDME promotes neutrophil pyroptosis and IL-1β release, which is critical for anti- Yersinia defense. During in vivo infection, IL-1β neutralization increases bacterial burden in wild-type but not Gsdme -deficient mice. Thus, our study establishes GSDME as an important mediator that counteracts pathogen blockade of innate immune signaling., Competing Interests: The authors declare no competing interest.

One of the most important mechanisms by which cancer fosters its own development is the generation of an immune microenvironment that inhibits or impairs antitumor immune responses. A cancer permissive immune microenvironment is present in a large proportion of the patients with cancer who do not respond to immunotherapy approaches intended to trigger preexisting antitumor immune responses, for instance, immune checkpoint blockade. High circulating levels of IL8 in patients with cancer quite accurately predict those who will not benefit from checkpoint-based immunotherapy. IL8 has been reported to favor cancer progression and metastases via different mechanisms, including proangiogenesis and the maintenance of cancer stem cells, but its ability to attract and functionally modulate neutrophils and macrophages is arguably one of the most important factors. IL8 does not only recruit neutrophils to tumor lesions, but also triggers the extrusion of neutrophil extracellular traps (NET). The relevance and mechanisms underlying the contribution of both neutrophils and NETs to cancer development and progression are starting to be uncovered and include both direct effects on cancer cells and changes in the tumor microenvironment, such as facilitating metastasis, awakening micrometastases from dormancy, and facilitating escape from cytotoxic immune cells. Blockade of IL8 or its receptors (CXCR1 and CXCR2) is being pursued in drug development, and clinical trials alone or in combination with anti-PD-L1 checkpoint inhibitors are already ongoing., (©2020 American Association for Cancer Research.)

Purpose: We aimed to investigate the prognostic significance of neutrophil/lymphocyte ratio (NLR), an indirect indicator for the immune response and AST/ALT ratio (De Ritis), liver enzymes that are commonly used in various clinical fields, in patients with advanced-stage pancreatic cancer., Methods: NLR and De Ritis of the patients with diagnosis of locally advanced and metastatic pancreatic cancer between the 2010-2017 were evaluated retrospectively. All patients were divided into two groups as high and low according to NLR and De Ritis cut-off values which were 2.4 and 0.75, respectively., Results: A total of 191 patients were evaluated. The mean overall survival (OS) in patients with NLR<2.4 at the time of diagnosis was 10±0.8 months, while it was 4±0.49 months in patients with NLR>2.4 (p<0.0001). The mean OS of the patients with a De Ritis <0.75 was 8±1.2 months, whereas the survival of those with De Ritis >0.75 was 6±0.74 months (p=0.024). The mean progression free survival (PFS) in patients with NLR<2.4 and De Ritis <0.75 at diagnosis were 5±0.76 months and 6±0.87 months respectively, whilst it was 3±0.37 months in patients with NLR>2.4 (p=0.017) and 4±0.3 months in patients with De Ritis >0.75 (p=0.14)., Conclusions: The NLR and De Ritis are associated with prognosis in many cancers and have been found to be associated with survival outcome in advanced-stage pancreatic cancer patients.

Neutrophils are the most abundant circulating leukocytes in humans and are essential for the defense against invading pathogens. Like many other cells of an organism, neutrophils can be highly influenced by the diet. We have previously described that mice fed a high-fat diet rich in polyunsaturated fatty acids (HFD-P) present a higher frequency of neutrophils in bone marrow than mice fed a high-fat diet rich in saturated fatty acids (HFD-S). Interestingly, such an increase correlated with improved survival against bacterium-induced sepsis. In this study, we aimed to investigate the effects of dietary polyunsaturated and saturated fatty acids on neutrophil homeostasis. We found that HFD-P specifically induced the accumulation of neutrophils in the marginal pools of the spleen and liver. The accumulation of neutrophils in the spleen was a result of a dual effect of polyunsaturated fatty acids on neutrophil homeostasis. First, polyunsaturated fatty acids enhanced the recruitment of neutrophils from the circulation into the spleen via chemokine secretion. Second, they delayed neutrophil cell death in the spleen. Interestingly, these effects were not observed in mice fed a diet rich in saturated fatty acids, suggesting that the type of fat rather than the amount of fat mediates the alterations in neutrophil homeostasis. In conclusion, our results show that dietary polyunsaturated fatty acids have a strong modulatory effect on neutrophil homeostasis that may have future clinical applications., (Copyright © 2019 American Society for Microbiology.)

Background: A high neutrophil to lymphocyte ratio (NLR) has been associated with adverse outcomes in non-small cell lung cancer (NSCLC). However, information on epidermal growth factor receptor (EGFR)-mutant advanced NSCLC is scarce, and most of the studies published have been conducted in Asian populations. We aimed to assess the influence of pretreatment NLR on progression-free survival (PFS) and overall survival (OS) in Western European patients treated with EGFR tyrosine kinase inhibitors (TKIs)., Methods: A retrospective evaluation of 41 patients with EGFR-mutant advanced NSCLC treated with EGFR TKIs between June 2010 and May 2016 was carried out. The association between several prognostic factors including pretreatment NLR and survival was analyzed., Results: Median PFS and OS were 10.58 and 20.84 months, respectively. OS for patients with a high NLR was 7.4 months, compared to 24.6 months for patients with a low NLR (p = 0.0122). In multivariate analysis, poor performance status (ECOG PS ≥ 2) and presence of ≥ 3 metastatic locations were identified as significant independent prognostic factors for worse PFS. For OS, unfavorable prognostic factors were a high NLR and central nervous system metastasis at diagnosis., Conclusion: Pretreatment NLR is an independent prognostic factor for OS in Western European patients with EGFR-mutant NSCLC treated with EGFR TKIs., (© 2018 S. Karger GmbH, Freiburg.)

Purpose: Myeloid-derived suppressor cells (MDSC) are considered an important T-cell immunosuppressive component in cancer-bearing hosts. The factors that attract these cells to the tumor microenvironment are poorly understood. IL8 (CXCL8) is a potent chemotactic factor for neutrophils and monocytes., Experimental Design: MDSC were characterized and sorted by multicolor flow cytometry on ficoll-gradient isolated blood leucokytes from healthy volunteers (n = 10) and advanced cancer patients (n = 28). In chemotaxis assays, sorted granulocytic and monocytic MDSC were tested in response to recombinant IL8, IL8 derived from cancer cell lines, and patient sera. Neutrophil extracellular traps (NETs) formation was assessed by confocal microscopy, fluorimetry, and time-lapse fluorescence confocal microscopy on short-term MDSC cultures., Results: IL8 chemoattracts both granulocytic (GrMDSC) and monocytic (MoMDSC) human MDSC. Monocytic but not granulocytic MDSC exerted a suppressor activity on the proliferation of autologous T cells isolated from the circulation of cancer patients. IL8 did not modify the T-cell suppressor activity of human MDSC. However, IL8 induced the formation of NETs in the GrMDSC subset., Conclusions: IL8 derived from tumors contributes to the chemotactic recruitment of MDSC and to their functional control. Clin Cancer Res; 22(15); 3924-36. ©2016 AACR., (©2016 American Association for Cancer Research.)