Neutrophil extracellular traps in homeostasis and disease.

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

The deubiquitinase OTUD1 stabilizes NRF2 to alleviate hepatic ischemia/reperfusion injury.

Hepatic ischemia/reperfusion (I/R) injury is an important cause of liver function impairment following liver surgery. The ubiquitin-proteasome system (UPS) plays a crucial role in protein quality control and has substantial impact on the hepatic I/R process. Although OTU deubiquitinase 1 (OTUD1) is involved in diverse biological processes, its specific functional implications in hepatic I/R are not yet fully understood. This study demonstrates that OTUD1 alleviates oxidative stress, apoptosis, and inflammation induced by hepatic I/R injury. Mechanistically, OTUD1 deubiquitinates and activates nuclear factor erythroid 2-related factor 2 (NRF2) through its catalytic site cysteine 320 residue and ETGE motif, thereby attenuating hepatic I/R injury. Additionally, administration of a short peptide containing the ETGE motif significantly mitigates hepatic I/R injury in mice. Overall, our study elucidates the mechanism and role of OTUD1 in ameliorating hepatic I/R injury, providing a theoretical basis for potential treatment using ETGE-peptide.

Physical exercise in liver diseases.

Liver diseases contribute to ~2 million deaths each year and account for 4% of all deaths globally. Despite various treatment options, the management of liver diseases remains challenging. Physical exercise is a promising nonpharmacological approach to maintain and restore homeostasis and effectively prevent and mitigate liver diseases. In this review, we delve into the mechanisms of physical exercise in preventing and treating liver diseases, highlighting its effects on improving insulin sensitivity, regulating lipid homeostasis, and modulating immune function. In addition, we evaluate the impact of physical exercise on various liver diseases, including liver ischemia/reperfusion injury, cardiogenic liver disease, metabolic dysfunction-associated steatotic liver disease, portal hypertension, cirrhosis, and liver cancer. In conclusion, the review underscores the effectiveness of physical exercise as a beneficial intervention in combating liver diseases.

Phosphorylation of IWS1 by AKT maintains liposarcoma tumor heterogeneity through preservation of cancer stem cell phenotypes and mesenchymal-epithelial plasticity.

Chemotherapy remains the mainstay of treatment for patients with advanced liposarcoma (LPS), but response rates are only 25% and the overall survival at 5 years is dismal at 20-34%. Translation of other therapies have not been successful and there has been no significant improvement in prognosis for nearly 20 years. The aberrant activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway has been implicated in the aggressive clinical behavior LPS and in resistance to chemotherapy, but the precise mechanism remains elusive and efforts to target AKT clinically have failed. Here we show that the AKT-mediated phosphorylation of the transcription elongation factor IWS1, promotes the maintenance of cancer stem cells in both cell and xenograft models of LPS. In addition, phosphorylation of IWS1 by AKT contributes to a "metastable" cell phenotype, characterized by mesenchymal/epithelial plasticity. The expression of phosphorylated IWS1 also promotes anchorage-dependent and independent growth, cell migration, invasion, and tumor metastasis. In patients with LPS, IWS1 expression is associated with reduced overall survival, increased frequency of recurrence, and shorter time to relapse after resection. These findings indicate that IWS1-mediated transcription elongation is an important regulator of human LPS pathobiology in an AKT-dependent manner and implicate IWS1 as an important molecular target to treat LPS.

Ultraviolet-induced fluorescence of oil spill recognition using a semi-supervised algorithm based on thickness and mixing proportion-emission matrices.

In recent years, marine oil spill accidents have been occurring frequently during extraction and transportation, and seriously damage the ecological balance. Accurate monitoring of oil spills plays a vital role in estimating oil spill volume, determination of liability, and clean-up. The oil that leaks into natural environments is not a single type of oil, but a mixture of various oil products, and the oil film thickness on the sea surface is uneven under the influence of wind and waves. Increasing the mixed oil film thickness dimension and the mix proportion dimension has been proposed to weaken the effect of the detection environment on the fluorescence measurement results. To preserve the relationships between the data of oil films with different thicknesses and the relationships between the data of oil films with different mixing proportions, the three-dimensional fluorescence spectral data of mixed oil films on a seawater surface were measured in the laboratory, producing a thickness-fluorescence matrix and a proportion-fluorescence matrix. The nonlinear variation of the fluorescence spectra was investigated according to the fluorescence lidar equation. This work pre-processes the data by sum normalization and two-dimensional principal component analysis (2DPCA) and uses the dimensionality reduction results as two feature-point views. Then, semi-supervised classification of collaborative training (co-training) with K-nearest neighbors (KNN) and a decision tree (DT) is used to identify the samples. The results show that the average overall accuracy of this coupling model can reach 100%, which is 20.49% higher than that of the thickness-only view. Using unlabeled data can reduce the cost of data acquisition, improve the classification accuracy and generalization ability, and provide theoretical significance and application prospects for discrimination of spectrally similar oil species in natural marine environments.

Intraperitoneal injection of class A TLR9 agonist enhances anti-PD-1 immunotherapy in colorectal peritoneal metastases.

Peritoneal metastases are associated with a low response rate to immune checkpoint blockade (ICB) therapy. The numbers of peritoneal resident macrophages (PRMs) are reversely correlated with the response rate to ICB therapy. We have previously shown that TLR9 in fibroblastic reticular cells (FRCs) plays a critical role in regulating peritoneal immune cell recruitment. However, the role of TLR9 in FRCs in regulating PRMs is unclear. Here, we demonstrated that the class A TLR9 agonist, ODN1585, markedly enhanced the efficacy of anti-PD-1 therapy in mouse models of colorectal peritoneal metastases. ODN1585 injected i.p. reduced the numbers of Tim4+ PRMs and enhanced CD8+ T cell antitumor immunity. Mechanistically, treatment of ODN1585 suppressed the expression of genes required for retinoid metabolism in FRCs, and this was associated with reduced expression of the PRM lineage-defining transcription factor GATA6. Selective deletion of TLR9 in FRCs diminished the benefit of ODN1585 in anti-PD-1 therapy in reducing peritoneal metastases. The crosstalk between PRMs and FRCs may be utilized to develop new strategies to improve the efficacy of ICB therapy for peritoneal metastases.

The Hepatic Pre-Metastatic Niche.

Primary tumors can communicate with the liver to establish a microenvironment that favors metastatic colonization prior to dissemination, forming what is termed the "pre-metastatic niche" (PMN). Through diverse signaling mechanisms, distant malignancies can both influence hepatic cells directly as well as recruit immune cells into the PMN. The result is a set of changes within the hepatic tissue that increase susceptibility of tumor cell invasion and outgrowth upon dissemination. Thus, the PMN offers a novel step in the traditional metastatic cascade that could offer opportunities for clinical intervention. The involved signaling molecules also offer promise as biomarkers. Ultimately, while the existence of the hepatic PMN is well-established, continued research effort and use of innovative models are required to reach a functional knowledge of PMN mechanisms that can be further targeted.

Surgery-mediated tumor-promoting effects on the immune microenvironment.

Surgical resection continues to be the mainstay treatment for solid cancers even though chemotherapy and immunotherapy have significantly improved patient overall survival and progression-free survival. Numerous studies have shown that surgery induces the dissemination of circulating tumor cells (CTCs) and that the resultant inflammatory response promotes occult tumor growth and the metastatic process by forming a supportive tumor microenvironment (TME). Surgery-induced platelet activation is one of the initial responses to a wound and the formation of fibrin clots can provide the scaffold for recruited inflammatory cells. Activated platelets can also shield CTCs to protect them from blood shear forces and promote CTCs evasion of immune destruction. Similarly, neutrophils are recruited to the fibrin clot and enhance cancer metastatic dissemination and progression by forming neutrophil extracellular traps (NETs). Activated macrophages are also recruited to surgical sites to facilitate the metastatic spread. More importantly, the body's response to surgical insult results in the recruitment and expansion of immunosuppressive cell populations (i.e. myeloid-derived suppressor cells and regulatory T cells) and in the suppression of natural killer (NK) cells that contribute to postoperative cancer recurrence and metastasis. In this review, we seek to provide an overview of the pro-tumorigenic mechanisms resulting from surgery's impact on these cells in the TME. Further understanding of these events will allow for the development of perioperative therapeutic strategies to prevent surgery-associated metastasis.

Neutrophils Extracellular Traps Inhibition Improves PD-1 Blockade Immunotherapy in Colorectal Cancer.

Immune checkpoint inhibitors can improve the prognosis of patients with advanced malignancy; however, only a small subset of advanced colorectal cancer patients in microsatellite-instability-high or mismatch-repair-deficient colorectal cancer can benefit from immunotherapy. Unfortunately, the mechanism behind this ineffectiveness is unclear. The tumor microenvironment plays a critical role in cancer immunity, and may contribute to the inhibition of immune checkpoint inhibitors and other novel immunotherapies in patients with advanced cancer. Herein, we demonstrate that the DNase I enzyme plays a pivotal role in the degradation of NETs, significantly dampening the resistance to anti-PD-1 blockade in a mouse colorectal cancer model by attenuating tumor growth. Remarkably, DNase I decreases tumor-associated neutrophils and the formation of MC38 tumor cell-induced neutrophil extracellular trap formation in vivo. Mechanistically, the inhibition of neutrophil extracellular traps with DNase I results in the reversal of anti-PD-1 blockade resistance through increasing CD8+ T cell infiltration and cytotoxicity. These findings signify a novel approach to targeting the tumor microenvironment using DNase I alone or in combination with immune checkpoint inhibitors.

Hypoxic ucMSC-secreted exosomal miR-125b promotes endothelial cell survival and migration during wound healing by targeting TP53INP1.

A hypoxic microenvironment is a common feature of skin wounds. Our previous study demonstrated that three-dimensional coculture of umbilical cord-derived mesenchymal stem cells (ucMSCs) and endothelial cells facilitates cell communication and host integration in skin tissue engineering. Here, we aimed to identify the mechanism by which ucMSCs affect endothelial cells under hypoxic conditions after skin injury. We demonstrate that hypoxia enhances the exosome-mediated paracrine function of ucMSCs, which increases endothelial cell proliferation and migration. In a mouse full-thickness skin injury model, ucMSC-derived exosomes can be taken up by endothelial cells and accelerate wound healing. Hypoxic exosomes lead to a better outcome than normoxic exosomes by promoting proliferation and inhibiting apoptosis. Mechanistically, microRNA-125b (miR-125b) transcription is induced by hypoxia in ucMSCs. After being packaged into hypoxic exosomes and transported to endothelial cells, miR-125b targets and suppresses the expression of tumor protein p53 inducible nuclear protein 1 (TP53INP1) and alleviates hypoxia-induced cell apoptosis. Inhibition of miR-125b-TP53INP1 interaction attenuates the protective effect of hypoxic exosomes. Moreover, artificial agomiR-125b can accelerate wound healing in vivo. Our findings reveal communication between ucMSCs and endothelial cells via exosomal miR-125b/TP53INP1 signaling in the hypoxic microenvironment and present hypoxic exosomes as a promising therapeutic strategy to enhance cutaneous repair.

Regulatory T-cell and neutrophil extracellular trap interaction contributes to carcinogenesis in non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Regulatory T-cells (Tregs) impair cancer immunosurveillance by creating an immunosuppressive environment that fosters tumor cell survival. Our previous findings demonstrated that neutrophil extracellular traps (NETs), which are involved both in innate and adaptive immunity, are abundant in livers affected by non-alcoholic steatohepatitis (NASH). However, how NETs interact with Tregs in the development of NASH-associated hepatocellular carcinoma (NASH-HCC) is not known. METHODS: A choline-deficient, high-fat diet+diethylnitrosamine mouse model and the stelic animal model were utilized for NASH-HCC and a western diet mouse model was used for NASH development. Treg depletion was achieved using FoxP3-DTR mice. RNA sequencing was used to explore the mechanism by which NETs could regulate Treg differentiation. Bioenergetic analyses of naïve CD4+ T-cells were assessed by Seahorse. RESULTS: Although the absolute number of CD4+ T-cells is lower in NASH livers, the Treg subpopulation is selectively increased. Depleting Tregs dramatically inhibits HCC initiation and progression in NASH. There is a positive correlation between increased NET and hepatic Treg levels. RNA sequencing data reveals that NETs impact gene expression profiles in naïve CD4+ T-cells, with the most differentially expressed genes being those involved in mitochondrial oxidative phosphorylation. By facilitating mitochondrial respiration, NETs can promote Treg differentiation. Metabolic reprogramming of naïve CD4+ T-cells by NETs requires toll-like receptor 4. Blockade of NETs in vivo using Pad4-/- mice or DNase I treatment reduces the activity of Tregs. CONCLUSIONS: Tregs can suppress immunosurveillance in the premalignant stages of NASH. NETs facilitate the crosstalk between innate and adaptive immunity in NASH by promoting Treg activity through metabolic reprogramming. Therapies targeting NETs and Treg interactions could offer a potential strategy for preventing HCC in patients with NASH. LAY SUMMARY: Regulatory T-cells (Tregs) can promote tumor development by suppressing cancer immunosurveillance, but their role in carcinogenesis during non-alcoholic steatohepatitis (NASH) progression is unknown. Herein, we discovered that selectively increased intrahepatic Tregs can promote an immunosuppressive environment in NASH livers. Neutrophil extracellular traps (NETs) link innate and adaptive immunity by promoting Treg differentiation via metabolic reprogramming of naïve CD4+ T-cells. This mechanism could be targeted to prevent liver cancer in patients with NASH.

Pre-operative exercise therapy triggers anti-inflammatory trained immunity of Kupffer cells through metabolic reprogramming.

Pre-operative exercise therapy improves outcomes for many patients who undergo surgery. Despite the well-known effects on tolerance to systemic perturbation, the mechanisms by which pre-operative exercise protects the organ that is operated on from inflammatory injury are unclear. Here, we show that four-week aerobic pre-operative exercise significantly attenuates liver injury and inflammation from ischaemia and reperfusion in mice. Remarkably, these beneficial effects last for seven more days after completing pre-operative exercising. We find that exercise specifically drives Kupffer cells toward an anti-inflammatory phenotype with trained immunity via metabolic reprogramming. Mechanistically, exercise-induced HMGB1 release enhances itaconate metabolism in the tricarboxylic acid cycle that impacts Kupffer cells in an NRF2-dependent manner. Therefore, these metabolites and cellular/molecular targets can be investigated as potential exercise-mimicking pharmaceutical candidates to protect against liver injury during surgery.

Platelet TLR4-ERK5 Axis Facilitates NET-Mediated Capturing of Circulating Tumor Cells and Distant Metastasis after Surgical Stress.

Surgical removal of malignant tumors is a mainstay in controlling most solid cancers. However, surgical insult also increases the risk of tumor recurrence and metastasis. Tissue trauma activates the innate immune system locally and systemically, mounting an inflammatory response. Platelets and neutrophils are two crucial players in the early innate immune response that heals tissues, but their actions may also contribute to cancer cell dissemination and distant metastasis. Here we report that surgical stress-activated platelets enhance the formation of platelet-tumor cell aggregates, facilitating their entrapment by neutrophil extracellular traps (NET) and subsequent distant metastasis. A murine hepatic ischemia/reperfusion (I/R) injury model of localized surgical stress showed that I/R promotes capturing of aggregated circulating tumor cells (CTC) by NETs and eventual metastasis to the lungs, which are abrogated when platelets are depleted. Hepatic I/R also increased deposition of NETs within the lung microvasculature, but depletion of platelets had no effect. TLR4 was essential for platelet activation and platelet-tumor cell aggregate formation in an ERK5-GPIIb/IIIa integrin-dependent manner. Such aggregation facilitated NET-mediated capture of CTCs in vitro under static and dynamic conditions. Blocking platelet activation or knocking out TLR4 protected mice from hepatic I/R-induced metastasis with no CTC entrapment by NETs. These results uncover a novel mechanism where platelets and neutrophils contribute to metastasis in the setting of acute inflammation. Targeted disruption of the interaction between platelets and NETs holds therapeutic promise to prevent postoperative distant metastasis. SIGNIFICANCE: Targeting platelet activation via TLR4/ERK5/integrin GPIIb/IIIa signaling shows potential for preventing NET-driven distant metastasis in patients post-resection.

Mesenchymal Stem Cells Derived Extracellular Vesicles Alleviate Traumatic Hemorrhagic Shock Induced Hepatic Injury via IL-10/PTPN22-Mediated M2 Kupffer Cell Polarization.

Traumatic hemorrhagic shock (THS) is a major cause of mortality and morbidity worldwide in severely injured patients. Mesenchymal stem cells (MSCs) possess immunomodulatory properties and tissue repair potential mainly through a paracrine pathway mediated by MSC-derived extracellular vesicles (MSC-EVs). Interleukin 10 (IL-10) is a potent anti-inflammatory cytokine that plays a crucial role during the inflammatory response, with a broad range of effects on innate and adaptive immunity, preventing damage to the host and maintaining normal tissue homeostasis. However, the function and mechanism of IL-10 in MSC-mediated protective effect in THS remain obscure. Here, we show that MSCs significantly attenuate hepatic injury and inflammation from THS in mice. Notably, these beneficial effects of MSCs disappeared when IL-10 was knocked out in EVs or when recombinant IL-10 was administered to mice. Mechanistically, MSC-EVs function to carry and deliver IL-10 as cargo. WT MSC-EVs restored the function of IL-10 KO MSCs during THS injury. We further demonstrated that EVs containing IL-10 mainly accumulated in the liver during THS, where they were captured by Kupffer cells and induced the expression of PTPN22. These effects subsequently shifted Kupffer cells to an anti-inflammatory phenotype and mitigated liver inflammation and injury. Therefore, our study indicates that MSC-EVs containing IL-10 alleviate THS-induced hepatic injury and may serve as a cell-free therapeutic approach for THS.

Surgical Stress Promotes Tumor Progression: A Focus on the Impact of the Immune Response.

Despite advances in systemic therapies, surgery is crucial for the management of solid malignancy. There is increasing evidence suggesting that the body's response to surgical stress resulting from tumor resection has direct effects on tumor cells or can alter the tumor microenvironment. Surgery can lead to the activation of early and key components of the innate and adaptative immune systems. Platelet activation and the subsequent pro-coagulation state can accelerate the growth of micrometastases. Neutrophil extracellular traps (NETs), an extracellular network of DNA released by neutrophils in response to inflammation, promote the adhesion of circulating tumor cells and the growth of existing micrometastatic disease. In addition, the immune response following cancer surgery can modulate the tumor immune microenvironment by promoting an immunosuppressive state leading to impaired recruitment of natural killer (NK) cells and regulatory T cells (Tregs). In this review, we will summarize the current understanding of mechanisms of tumor progression secondary to surgical stress. Furthermore, we will describe emerging and novel peri-operative solutions to decrease pro-tumorigenic effects from surgery.

AAV-mediated gene transfer of DNase I in the liver of mice with colorectal cancer reduces liver metastasis and restores local innate and adaptive immune response.

Liver metastasis is the main cause of colorectal cancer (CRC)-related death. Neutrophil extracellular traps (NETs) play important roles in CRC progression. Deoxyribonuclease I (DNase I) has been shown to alter NET function by cleaving DNA strands comprising the NET backbone. Moreover, DNase I displays high antimetastatic activity in multiple tumor models. To circumvent long-term daily administrations of recombinant DNase I, we have developed an adeno-associated virus (AAV) gene therapy vector to specifically express DNase I in the liver. In this study, we demonstrate AAV-mediated DNase I liver gene transfer following a single intravenous injection suppresses the development of liver metastases in a mouse model of CRC liver metastasis. Increased levels of neutrophils and NET formation in tumors are associated with poor prognosis in many patients with advanced cancers. Neutrophil infiltration and NET formation were inhibited in tumor tissues with AAV-DNase I treatment. This approach restored local immune responses at the tumor site by increasing the percentage of CD8+ T cells while keeping CD4+ T cells similar between AAV-DNase I and AAV-null treatments. Our data suggest that AAV-mediated DNase I liver gene transfer is a safe and effective modality to inhibit metastasis and represents a novel therapeutic strategy for CRC.

Neutrophil Elastase and Neutrophil Extracellular Traps in the Tumor Microenvironment.

Tumor-associated neutrophils (TANs) play a major role during cancer development and progression in the tumor microenvironment. Neutrophil elastase (NE) is a serine protease normally expressed in neutrophil primary granules. Formation of neutrophil extracellular traps (NETs), a mechanism used by neutrophils, has been traditionally associated with the capture and killing of bacteria. However, there are recent discoveries suggesting that NE secretion and NETs formation are also involved in the tumor microenvironment. Here, we focus on how NE and NETs play a key regulatory function in the tumor microenvironment, such as tumor proliferation, distant metastasis, tumor-associated thrombosis, and antitumor activity. Additionally, the potential use of NETs, NE, or associated molecules as potential disease activity biomarkers or therapeutic targets will be introduced.

Hepatic Surgical Stress Promotes Systemic Immunothrombosis That Results in Distant Organ Injury.

Innate immunity can initiate platelet activation during the development of thrombosis through a process, termed immunothrombosis. Neutrophils form neutrophil extracellular traps (NETs) that have been shown to interact directly with platelets and play pro-coagulant roles in a variety of infectious and sterile inflammatory settings. Hepatic surgical stress initiated by ischemia/reperfusion (I/R) injury has wide systemic consequences on distant organs. However, the mechanisms of this remote injury phenomenon are not well-understood. Here, we sought to determine the role of NETs in causing systemic immunothrombosis and distant organ injury following a local inflammatory insult with liver I/R. Postoperative thromboelastographic revealed that the speed of clot formation (alpha-angle) was significantly increased whereas time to clot formation (R-time) were decreased by in patients undergoing liver resection, indicating a hypercoagulable state after surgery. In mice subjected to liver I/R, circulating platelet activation and platelet-neutrophil aggregates were significantly increased. Injured distant organs such as the lung and kidney displayed NETs and platelet-rich micro-thrombi in the microvasculature following liver I/R. The immune-thrombi and organ damage were dramatically decreased when NETs were inhibited by DNase treatment. Depletion of Tlr4 on platelets limited NET-induced activation of platelets but had no effect on NET formation. Furthermore, platelet-specific TLR4 KO mice had significantly reduced distant organ injury with decreased circulating platelet activation, platelet-neutrophil aggregates following liver I/R in comparison to their control counterparts. These data establish that after an acute local inflammatory process, NET-activated platelets can lead to a systemic pro-coagulant state with resultant remote organ injury by immunothrombosis.

Immune Checkpoint Inhibitors in Hepatocellular Cancer: Current Understanding on Mechanisms of Resistance and Biomarkers of Response to Treatment.

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy worldwide and a leading cause of death worldwide. Its incidence continues to increase in the US due to hepatitis C infection and nonalcoholic steatohepatitis. Liver transplantation and resection remain the best therapeutic options for cure, but these are limited by the shortage of available organs for transplantation, diagnosis at advanced stage, and underlying chronic liver disease found in most patients with HCC. Immune checkpoint inhibitors (ICIs) have been shown to be an evolving novel treatment option in certain advanced solid tumors and have been recently approved for inoperable, advanced, and metastatic HCC. Unfortunately, a large cohort of patients with HCC fail to respond to immunotherapy. In this review, we discuss the ICIs currently approved for HCC treatment and their various mechanisms of action. We will highlight current understanding of mechanism of resistance and limitations to ICIs. Finally, we will describe emerging biomarkers of response to ICIs and address future direction on overcoming resistance to immune checkpoint therapy.

Neutrophil Extracellular Traps Drive Mitochondrial Homeostasis in Tumors to Augment Growth.

Neutrophil infiltration and neutrophil extracellular traps (NET) in solid cancers are associated with poorer prognosis, but the mechanisms are incompletely understood. We hypothesized that NETs enhance mitochondrial function in tumor cells, providing extra energy for accelerated growth. Metastatic colorectal cancer tissue showed increased intratumoral NETs and supranormal preoperative serum MPO-DNA, a NET marker. Higher MPO-DNA correlated with shorter survival. In mice, subcutaneous tumor implants and hepatic metastases grew slowly in PAD4-KO mice, genetically incapable of NETosis. In parallel experiments, human cancer cell lines grew slower in nu/nu mice treated with DNAse, which disassembles NETs. PAD4-KO tumors manifested decreased proliferation, increased apoptosis, and increased evidence of oxidative stress. PAD4-KO tumors had decreased mitochondrial density, mitochondrial DNA, a lesser degree of ATP production, along with significantly decreased mitochondrial biogenesis proteins PGC1α, TFAM, and NRF-1. In vitro, cancer cells treated with NETs upregulated mitochondrial biogenesis-associated genes, increased mitochondrial density, increased ATP production, enhanced the percentage of cancer cells with reduced mitochondrial membrane potential, and increased the oxygen consumption rate. Furthermore, NETs increased cancer cells' expression of fission and fusion-associated proteins, DRP-1 and MFN-2, and mitophagy-linked proteins, PINK1 and Parkin. All of which were decreased in PAD4-KO tumors. Mechanistically, neutrophil elastase released from NETs activated TLR4 on cancer cells, leading to PGC1α upregulation, increased mitochondrial biogenesis, and accelerated growth. Taken together, NETs can directly alter the metabolic programming of cancer cells to increase tumor growth. NETs represent a promising therapeutic target to halt cancer progression. SIGNIFICANCE: Neutrophils through the release of NETs facilitate the growth of stressed cancer cells by altering their bioenergetics, the inhibition of which induces cell death.