NADPH Oxidase 1 and NADPH Oxidase 4 Have Opposite Prognostic Effects for Patients with Hepatocellular Carcinoma after Hepatectomy

Dissecting the role of the NADPH oxidase NOX4 in TGF-beta signaling in hepatocellular carcinoma

The NADPH oxidase NOX4 has been proposed as necessary for the apoptosis induced by the Transforming Growth Factor-beta (TGF-β) in hepatocytes and hepatocellular carcinoma (HCC) cells. However, whether NOX4 is required for TGF-β-induced canonical (SMADs) or non-canonical signals is not fully understood yet, neither its potential involvement in other parallel actions induced by TGF-β. In this work we have used CRISPR Cas9 technology to stable attenuate NOX4 expression in HCC cells. Results have indicated that NOX4 is required for an efficient SMAD2/3 phosphorylation in response to TGF-β, whereas non-canonical signals, such as the phosphorylation of the Epidermal Growth Receptor or AKT, are higher in NOX4 silenced cells. TGF-β-mediated inhibition of cell proliferation and viability is attenuated in NOX4 silenced cells, correlating with decreased response in terms of apoptosis, and maintenance of high expression of MYC and CYCLIN D1. These results would indicate that NOX4 is required for all the tumor suppressor actions of TGF-β in HCC. However, analysis in human HCC tumors has revealed a worse prognosis for patients showing high expression of TGF-β1-related genes concomitant with high expression of NOX4. Deepening into other tumorigenic actions of TGF-β that may contribute to tumor progression, we found that NOX4 is also required for TGF-β-induced migratory effects. The Epithelial-Mesenchymal transition (EMT) program does not appear to be affected by attenuation of NOX4 levels. However, TGF-β-mediated regulation of cytoskeleton dynamics and focal adhesions require NOX4, which is necessary for TGF-β-induced increase in the chaperone Hsp27 and correct subcellular localization of Hic-5 within focal adhesions, as well for upregulation of the metalloprotease MMP9. All these results together point to NOX4 as a key element in the whole TGF-β signaling in HCC cells, revealing an unknown role for NOX4 as tumor promoter in HCC patients presenting activation of the TGF-β pathway.

Oxidative Stress in Liver Pathophysiology and Disease

The liver is an organ that is particularly exposed to reactive oxygen species (ROS), which not only arise during metabolic functions but also during the biotransformation of xenobiotics. The disruption of redox balance causes oxidative stress, which affects liver function, modulates inflammatory pathways and contributes to disease. Thus, oxidative stress is implicated in acute liver injury and in the pathogenesis of prevalent infectious or metabolic chronic liver diseases such as viral hepatitis B or C, alcoholic fatty liver disease, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Moreover, oxidative stress plays a crucial role in liver disease progression to liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Herein, we provide an overview on the effects of oxidative stress on liver pathophysiology and the mechanisms by which oxidative stress promotes liver disease.

The NADPH oxidase NOX4 regulates redox and metabolic homeostasis preventing HCC progression

BACKGROUND AND AIMS

The NADPH oxidase NOX4 plays a tumor-suppressor function in HCC. Silencing NOX4 confers higher proliferative and migratory capacity to HCC cells and increases their in vivo tumorigenic potential in xenografts in mice. NOX4 gene deletions are frequent in HCC, correlating with higher tumor grade and worse recurrence-free and overall survival rates. However, despite the accumulating evidence of a protective regulatory role in HCC, the cellular processes governed by NOX4 are not yet understood. Accordingly, the aim of this work was to better understand the molecular mechanisms regulated by NOX4 in HCC in order to explain its tumor-suppressor action.

APPROACH AND RESULTS

Experimental models: cell-based loss or gain of NOX4 function experiments, in vivo hepatocarcinogenesis induced by diethylnitrosamine in Nox4 -deficient mice, and analyses in human HCC samples. Methods include cellular and molecular biology analyses, proteomics, transcriptomics, and metabolomics, as well as histological and immunohistochemical analyses in tissues. Results identified MYC as being negatively regulated by NOX4. MYC mediated mitochondrial dynamics and a transcriptional program leading to increased oxidative metabolism, enhanced use of both glucose and fatty acids, and an overall higher energetic capacity and ATP level. NOX4 deletion induced a redox imbalance that augmented nuclear factor erythroid 2-related factor 2 (Nrf2) activity and was responsible for MYC up-regulation.

CONCLUSIONS

Loss of NOX4 in HCC tumor cells induces metabolic reprogramming in a Nrf2/MYC-dependent manner to promote HCC progression.

A spotlight on the interplay between Wnt/β-catenin signaling and circular RNAs in hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the deadliest cancers due to multifocal development and distant metastasis resulting from late diagnosis. Consequently, new approaches to HCC diagnosis and treatment are required to reduce mortality rates. A large body of evidence suggests that non-coding RNAs (ncRNAs) are important in cancer initiation and progression. Cancer cells release many of these ncRNAs into the blood or urine, enabling their use as a diagnostic tool. Circular RNAs (CircRNAs) are as a members of the ncRNAs that regulate cancer cell expansion, migration, metastasis, and chemoresistance through different mechanisms such as the Wnt/β-catenin Signaling pathway. The Wnt/β-catenin pathway plays prominent roles in several biological processes including organogenesis, stem cell regeneration, and cell survival. Aberrant signaling of both pathways mentioned above could affect the progression and metastasis of many cancers, including HCC. Based on several studies investigated in the current review, circRNAs have an effect on HCC formation and progression by sponging miRNAs and RNA-binding proteins (RBPs) and regulating the Wnt/β-catenin signaling pathway. Therefore, circRNAs/miRNAs or RBPs/Wnt/β-catenin signaling pathway could be considered promising prognostic and therapeutic targets in HCC.

Depletion of Tip60/Kat5 affects the hepatic antioxidant system in mice

Tat-interactive protein 60 kDa (TIP60, also known as lysine acetyltransferase 5 [KAT5]) is a member of the MYST protein family with histone acetyltransferase activity. Recent studies have reported that TIP60 has multiple functions in many signal transduction mechanisms, especially p53-mediated apoptosis. Although the activation of apoptosis signaling pathways requires the presence of cellular reactive oxygen species (ROS) at a certain level, an imbalance between the production and consumption of ROS in cells results in oxidative stress (OS). In this study, we investigated for the first time how the absence of the Tip60 gene in the liver affects gene expression, enzyme activity, and protein expression of the hepatic antioxidant members localized in the cytoplasm, including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione S-transferase (GST). First, we successfully generated liver-specific Tip60 knockout mice (mutants) using Cre/LoxP recombination. The reduced glutathione level and nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) expression, a marker of OS, increased significantly in the Tip60 mutant liver. Gene expression, activity, and protein expression of the enzymatic antioxidant system, including SOD, CAT, GR, GPx, and GST were investigated in mutants and control groups. Despite a significant correlation between the gene, enzyme activity, and protein content for CAT and GR, this was not true for SOD and GPx. The overall results suggest that TIP60 acts on the hepatic antioxidant system both at the gene and protein levels, but the actual effect of the deletion of Tip60 is observed at the protein level, especially for SOD and GPx.

Osteopontin promotes hepatocellular carcinoma progression through inducing JAK2/STAT3/NOX1-mediated ROS production

Osteopontin (OPN) is a multifunctional cytokine that can impact cancer progression. Therefore, it is crucial to determine the key factors involved in the biological role of OPN for the development of treatment. Here, we investigated that OPN promoted hepatocellular carcinoma (HCC) cell proliferation and migration by increasing Reactive oxygen species (ROS) production and disclosed the underlying mechanism. Knockdown of OPN suppressed ROS production in vitro and in vivo, whereas treatment with human recombinant OPN produced the opposite effect. N-Acetyl-L-cysteine (NAC, ROS scavenger) partially blocked HCC cell proliferation and migration induced by OPN. Mechanistically, OPN induced ROS production in HCC cells by upregulating the expression of NADPH oxidase 1 (NOX1). NOX1 knockdown in HCC cells partially abrogated the cell proliferation and migration induced by OPN. Moreover, inhibition of JAK2/STAT3 phosphorylation effectively decreased the transcription of NOX1, upregulated by OPN. In addition, NOX1 overexpression increased JAK2 and STAT3 phosphorylation by increasing ROS production, creating a positive feedback loop for stimulating JAK2/STAT3 signaling induced by OPN. This study for the first time demonstrated that HCC cells utilized OPN to generate ROS for tumor progression, and disruption of OPN/NOX1 axis might be a promising therapeutic strategy for HCC.

Prognostic Value of NOX4 Expression in Cancer Patients: A Systematic Review and Meta-analysis

Background. Recent studies have shown that nicotinamide adenosine dinucleotide phosphate oxidase 4 (NOX4) is related to cancer development, proliferation, invasion, epithelial-to-mesenchymal transition, and metastasis. The prognostic value of NOX4 expression although has been reported in various cancers, it remains unclear as several studies have reported conflicting results. Therefore, the purpose of this study was to systematically investigate the prognostic value of NOX4 expression in cancer patients. Method. Appropriate studies were collected by searching the PubMed, EMBASE, and Cochrane library databases, and the prognostic value of NOX4 expression in cancer patients was assessed through a meta-analysis. Results. Nine eligible studies involving 2675 cancer patients were included in this meta-analysis. We found that NOX4 expression is related to prognosis in cancer patients. In particular, high expression of NOX4 was significantly associated with overall survival in patients with gastrointestinal cancer (hazard ratio [HR]: 1.83, 95% confidence interval [CI]: 1.39–2.42, $p<0.001$ ). Conclusion. NOX4 expression is significantly correlated with overall survival in patients with gastrointestinal cancer, indicating that it could be a potential prognostic marker.

Overexpression of DUOX2 mediates doxorubicin resistance and predicts prognosis of pancreatic cancer

BACKGROUND

Dysregulation of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) family is frequently observed in cancers and associated with their development and progression. However, the expression, role, and clinical significance of the NOX family members in pancreatic cancer remain unexplored.

METHODS

The expression levels of the 7 NOX family genes were analyzed in Gene Expression Omnibus (GEO) datasets. The messenger RNA (mRNA) expression and gene alterations were explored using The Cancer Genome Atlas (TCGA) data portal. Clinical significance analyses of the NOX family genes were conducted among pancreatic cancer patients. The expression and prognostic value of dual oxidase 2 (DUOX2) were then validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC) in an independent validation cohort. The function of DUOX2 was analyzed by gene set enrichment analysis (GSEA) and its effect on the chemosensitivity of pancreatic cancer cells was detected by Cell Counting Kit-8 (CCK-8) assay.

RESULTS

Results showed that NOX1, NOX2 (CYBB), NOX4, DUOX1, and DUOX2 were upregulated, while NOX3 and NOX5 were downregulated in pancreatic cancer tissues compared with nontumor tissues. Genomic alteration analysis demonstrated that deregulation of NOX family genes was partially caused by genomic alterations. Survival analyses showed that only DUOX2 was associated with overall survival (OS) and relapse-free survival (RFS) of pancreatic cancer patients. The DUOX2 gene was observed to be markedly overexpressed in pancreatic cancer. In the GSEA results for pancreatic cancer patients, DUOX2 was significantly associated with oxidoreductase activity acting on nicotinamide adenine dinucleotide hydrogen (NADH) or NADPH and uridine 5'-diphospho-glucuronosyltansferase (UDP) glycosyltransferase activity. Knockdown of DUOX2 in pancreatic cancer cells increased their sensitivity to doxorubicin.

CONCLUSIONS

Overexpression of DUOX2 is correlated with prognosis and recurrence in pancreatic cancer patients and acts as a good marker for pancreatic cancer course prediction; furthermore, DUOX2 might be a therapeutic target for pancreatic cancer patients.

The TGF-β/NADPH Oxidases Axis in the Regulation of Liver Cell Biology in Health and Disease

The Transforming Growth Factor-beta (TGF-β) pathway plays essential roles in liver development and homeostasis and become a relevant factor involved in different liver pathologies, particularly fibrosis and cancer. The family of NADPH oxidases (NOXs) has emerged in recent years as targets of the TGF-β pathway mediating many of its effects on hepatocytes, stellate cells and macrophages. This review focuses on how the axis TGF-β/NOXs may regulate the biology of different liver cells and how this influences physiological situations, such as liver regeneration, and pathological circumstances, such as liver fibrosis and cancer. Finally, we discuss whether NOX inhibitors may be considered as potential therapeutic tools in liver diseases.

The Role of Oxidative Stress in NAFLD-NASH-HCC Transition-Focus on NADPH Oxidases

A peculiar role for oxidative stress in non-alcoholic fatty liver disease (NAFLD) and its transition to the inflammatory complication non-alcoholic steatohepatitis (NASH), as well as in its threatening evolution to hepatocellular carcinoma (HCC), is supported by numerous experimental and clinical studies. NADPH oxidases (NOXs) are enzymes producing reactive oxygen species (ROS), whose abundance in liver cells is closely related to inflammation and immune responses. Here, we reviewed recent findings regarding this topic, focusing on the role of NOXs in the different stages of fatty liver disease and describing the current knowledge about their mechanisms of action. We conclude that, although there is a consensus that NOX-produced ROS are toxic in non-neoplastic conditions due to their role in the inflammatory vicious cycle sustaining the transition of NAFLD to NASH, their effect is controversial in the neoplastic transition towards HCC. In this regard, there are indications of a differential effect of NOX isoforms, since NOX1 and NOX2 play a detrimental role, whereas increased NOX4 expression appears to be correlated with better HCC prognosis in some studies. Further studies are needed to fully unravel the mechanisms of action of NOXs and their relationships with the signaling pathways modulating steatosis and liver cancer development.

Genetic deletion of Nox4 enhances cancerogen-induced formation of solid tumors

The stereotype of ROS produced by NADPH oxidases as cause of malignant diseases persists in a generalized manner. In fact, high levels of ROS formation could be harmful in the context of a disease process. This study demonstrates that loss of the NADPH oxidase Nox4, as a constitutive source of ROS, promotes cancerogen-induced formation of solid tumors. Accordingly, a certain tonic, constitutive low level of Nox4-derived hydrogen peroxide appears to reduce the risk of cancerogen-induced tumor formation.

Reactive oxygen species (ROS) can cause cellular damage and promote cancer development. Besides such harmful consequences of overproduction of ROS, all cells utilize ROS for signaling purposes and stabilization of cell homeostasis. In particular, the latter is supported by the NADPH oxidase 4 (Nox4) that constitutively produces low amounts of H₂O₂. By that mechanism, Nox4 forces differentiation of cells and prevents inflammation. We hypothesize a constitutive low level of H₂O₂ maintains basal activity of cellular surveillance systems and is unlikely to be cancerogenic. Utilizing two different murine models of cancerogen-induced solid tumors, we found that deletion of Nox4 promotes tumor formation and lowers recognition of DNA damage. Nox4 supports phosphorylation of H2AX (γH2AX), a prerequisite of DNA damage recognition, by retaining a sufficiently low abundance of the phosphatase PP2A in the nucleus. The underlying mechanism is continuous oxidation of AKT by Nox4. Interaction of oxidized AKT and PP2A captures the phosphatase in the cytosol. Absence of Nox4 facilitates nuclear PP2A translocation and dephosphorylation of γH2AX. Simultaneously AKT is left phosphorylated. Thus, in the absence of Nox4, DNA damage is not recognized and the increased activity of AKT supports proliferation. The combination of both events results in genomic instability and promotes tumor formation. By identifying Nox4 as a protective source of ROS in cancerogen-induced cancer, we provide a piece of knowledge for understanding the role of moderate production of ROS in preventing the initiation of malignancies.

NOX1 inhibition attenuates the development of a pro-tumorigenic environment in experimental hepatocellular carcinoma

Background

The poor prognosis of advanced HCC and limited efficacy of current systemic treatments emphasize the need for new or combined targeted therapies. The development of HCC is a multistage process in which liver injury appears in a complex microenvironment associated with oxidative stress. NOX enzymes are the main source of ROS during hepatocarcinogenesis and NOX1 in particular has shown correlation with poor prognosis of HCC patients. This study evaluates the effect of pharmacological NOX1 inhibition on the development and progression of HCC and its effect on the tumor microenvironment.

Methods

The in vitro cytotoxic effects of the NOX1 inhibitor GKT771 (Genkyotex) on human Huh7 and Hep3B and murine Hepa1-6 HCC cell lines, the human THP1 monocyte cell line and mouse macrophages were evaluated via MTT, LDH activity and CaspGlo® assays. In order to induce in vivo HCC, male SV129 wild-type mice received weekly IP injections of diethylnitrosamine (DEN) (35 mg/kg) for 20–25 weeks. Mice were treated with vehicle or GKT771 (30 mg/kg) via oral gavage, daily or twice daily, in preventive and therapeutic studies. The liver damage was evaluated for inflammation, angiogenesis, fibrosis and HCC development via histology, RT-qPCR, multiplex analyses and ROS levels.

Results

A concentration-dependent reduction in cellular activity of the human HCC cell lines without cytotoxicity was observed. GKT771 treatment reduced LPS-induced pro-inflammatory bone-marrow derived macrophage polarization. DEN injections resulted in 100 % tumor formation and the induction of HCC markers which could be reduced by twice daily dosing of GKT771 at early onset of advanced HCC. DEN-induced HCC resulted in an upregulation of pro-inflammatory, angiogenic and fibrotic markers which was less pronounced in GKT771 treated mice in all treatment regimens. In line, liver fibrosis was induced in HCC mice and this to a lesser extend upon GKT771 treatment.

Conclusions

NOX1 inhibition showed to be safe and well tolerated and was able to attenuate the induction of a pro-inflammatory, angiogenic and pro-fibrotic microenvironment suggesting that this might be a promising adjuvant therapeutic strategy in the treatment of advanced HCC.

The NADPH Oxidase Isoform 1 Contributes to Angiotensin II-Mediated DNA Damage in the Kidney

In higher concentrations, the blood pressure regulating hormone angiotensin II leads to vasoconstriction, hypertension, and oxidative stress by activating NADPH oxidases which are a major enzymatic source of reactive oxygen species (ROS). With the help of knockout animals, the impact of the three predominant NADPH oxidases present in the kidney, i.e., Nox1, Nox2 and Nox4 on angiotensin II-induced oxidative damage was studied. Male wildtype (WT) C57BL/6 mice, Nox1-, Nox2- and Nox4-deficient mice were equipped with osmotic minipumps, delivering either vehicle (PBS) or angiotensin II, for 28 days. Angiotensin II increased blood pressure and urinary albumin levels significantly in all treated mouse strains. In Nox1 knockout mice these increases were significantly lower than in WT, or Nox2 knockout mice. In WT mice, angiotensin II also raised systemic oxidative stress, ROS formation and DNA lesions in the kidney. A local significantly increased ROS production was also found in Nox2 and Nox4 knockout mice but not in Nox1 knockout mice who further had significantly lower systemic oxidative stress and DNA damage than WT animals. Nox2 and Nox4 knockout mice had increased basal DNA damage, concealing possible angiotensin II-induced increases. In conclusion, in the kidney, Nox1 seemed to play a role in angiotensin II-induced DNA damage.

Mechanism of the Regulatory Effect of Overexpression of circMTO1 on Proliferation and Apoptosis of Hepatoma Cells via miR-9-5p/NOX4 Axis

Purpose

To investigate the potential role of the circMTO1/miR-9-5p/NOX4 axis in liver cancer.

Materials and Methods

Human genome-wide circrna microarray V2 was used for analyzing the expression profile of circRNAs in human tissue samples. The TargetScan database was used to predict target genes. Gene overexpression and silencing in hepatoma cell lines were achieved by transfecting the cells with suitable constructs. Quantitative real time PCR and Western blotting were used to analyze gene and protein expression levels. CCK-8 analysis was performed to detect cell proliferation and the transwell assay for analyzing cell migration. Annexin V-FITC/PI staining and immunohistochemistry were respectively used to detect apoptosis and protein expression.

Results

CircMTO1 were down-regulated in the liver cancer tissues and cell lines compared to their respective normal controls. TargetScan database screening and dual luciferase assay revealed that circMTO1 was a molecular sponge of miR-9-5p, and NOX4 was the target gene of miR-9-5p. Overexpression of circMTO1 and NOX4 inhibited proliferation and migration of hepatoma cells, while the overexpression of miR-9-5p had the opposite effects. In contrast, overexpression of circMTO1 and NOX4 promoted apoptosis, while that of miR-9-5p decreased the cell apoptosis rates.

Conclusion

Overexpression of CircMTO1 acts as tumor suppressor in liver cancer by sponging miR-9-5p, which upregulates NOX4.

High nuclear NADPH oxidase 4 expression levels are correlated with cancer development and poor prognosis in hepatocellular carcinoma

NADPH oxidase (NOX) is a key source of reactive oxygen species (ROS). This study aimed to verify NOX2 and NOX4 expression levels in hepatocellular carcinoma (HCC). A total of 134 matched pairs of HCC cells and non-tumour hepatocytes from 134 patients were examined by immunohistochemical staining, and the association of NOX2 and NOX4 expression with clinicopathological parameters was analysed. Western blotting in four HCC cell lines and reverse transcription digital droplet polymerase chain reaction (RT-ddPCR) in 20 pairs of HCC and non-tumour tissue samples were also performed to detect NOX4. Cytoplasmic NOX2 and nuclear NOX4 expression levels were shown by immunohistochemistry to be higher in HCC cells than in non-tumour hepatocytes (p<0.001 each). The western blotting results for NOX4 in four HCC cell lines were consistent with the immunohistochemical results. Increased cytoplasmic expression of NOX2 and NOX4 in HCC cells was significantly correlated with liver cirrhosis (p<0.001 and p<0.031, respectively). However, decreased cytoplasmic expression of NOX2 and NOX4 was significantly correlated with advanced pathological TNM stage (p<0.029 and p<0.007, respectively). Multivariate analysis with clinicopathological parameters showed that high nuclear and low cytoplasmic NOX4 expression levels are correlated with short overall survival (p=0 .021). Our findings imply that cytoplasmic NOX2 and nuclear NOX4 expression is upregulated during HCC development. In particular, NOX4 translocation into the nucleus may affect the development and progression of HCC. NOX2 and NOX4 could be diagnostic markers and have therapeutic implications in HCC.

NADPH Oxidase 1 in Liver Macrophages Promotes Inflammation and Tumor Development in Mice

BACKGROUND & AIMS

Although there are associations among oxidative stress, reduced nicotinamide adenine dinucleotide phosphate oxidase (NOX) activation, and hepatocellular carcinoma (HCC) development, it is not clear how NOX contributes to hepatocarcinogenesis. We studied the functions of different NOX proteins in mice after administration of a liver carcinogen.

METHODS

Fourteen-day-old Nox1^-/- mice, Nox4^-/- mice, Nox1^-/-Nox4^-/- (double-knockout) mice, and wild-type (WT) C57BL/6 mice were given a single intraperitoneal injection of diethylnitrosamine (DEN) and liver tumors were examined at 9 months. We also studied the effects of DEN in mice with disruption of Nox1 specifically in hepatocytes (Nox1^ΔHep), hepatic stellate cells (Nox1^ΔHep), or macrophages (Nox1^ΔMac). Some mice were also given injections of the NOX1-specific inhibitor ML171. To study the acute effects of DEN, 8-12-week-old mice were given a single intraperitoneal injection, and liver and serum were collected at 72 hours. Liver tissues were analyzed by histologic examination, quantitative polymerase chain reaction, and immunoblots. Hepatocytes and macrophages were isolated from WT and knockout mice and analyzed by immunoblots.

RESULTS

Nox4^-/- mice and WT mice developed liver tumors within 9 months after administration of DEN, whereas Nox1^-/- mice developed 80% fewer tumors, which were 50% smaller than those of WT mice. Nox1^ΔHep and Nox1^ΔHSC mice developed liver tumors of the same number and size as WT mice, whereas Nox1^ΔMac developed fewer and smaller tumors, similar to Nox1^-/- mice. After DEN injection, levels of tumor necrosis factor, interleukin 6 (IL6), and phosphorylated signal transducer and activator of transcription 3 were increased in livers from WT, but not Nox1^-/- or Nox1^ΔMac, mice. Conditioned medium from necrotic hepatocytes induced expression of NOX1 in cultured macrophages, followed by expression of tumor necrosis factor, IL6, and other inflammatory cytokines; this medium did not induce expression of IL6 or cytokines in Nox1^ΔMac macrophages. WT mice given DEN followed by ML171 developed fewer and smaller liver tumors than mice given DEN followed by vehicle.

CONCLUSIONS

In mice given injections of a liver carcinogen (DEN), expression of NOX1 by macrophages promotes hepatic tumorigenesis by inducing the production of inflammatory cytokines. We propose that upon liver injury, damage-associated molecular patterns released from dying hepatocytes activate liver macrophages to produce cytokines that promote tumor development. Strategies to block NOX1 or these cytokines might be developed to slow hepatocellular carcinoma progression.

NOX4, a new genetic target for anti-cancer therapy in digestive system cancer

Oxidative stress has been implicated as an important factor in tumorigenesis and tumor progression. The nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit 4 (NOX4), a substrate of NADPH that can generate H₂ O₂ reactive oxygen species, has been reported to be highly expressed in gastrointestinal tumors. In this review we summarize the available evidence on the biological function of NOX4 in digestive system tumors by focusing on its correlation with classical cell signaling pathways, including VEGF, MAPK and PI3K/AKT, and with biochemical mediators, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), activator protein (AP)-1 and transforming growth factor (TGF)-β. According to the clinical and database studies on tumors of the digestive system, such as colorectal, gastric and pancreatic cancer, there are significant associations between NOX4 expression and tumor prognosis as well as patient's survival. Animal studies using NOX4 inhibitors such as diphenylene iodonium and GKT137831, which selectively block NOX4, indicate their potential as therapeutic agents for targeting cancer cells.

Three variants in the nicotinamide adenine dinucleotide phosphate oxidase complex are associated with HCV-related liver damage

Approximately 71 million people are chronically infected with the hepatitis C virus (HCV), a potentially lethal pathogen. HCV generates oxidative stress correlating with disease severity. HCV proteins increase reactive oxygen species production by stimulating nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity. Reactive oxygen species are necessary for host defense and cell signaling; however, elevated NOX activity contributes to cancer, and NOX overexpression is associated with hepatic fibrosis. Our aim was to investigate whether single nucleotide polymorphisms (SNPs) in NOX family members are associated with HCV-related liver damage. Three hundred and thirty-one individuals of European ancestry and 90 individuals of African ancestry, all diagnosed with HCV, were genotyped for 243 tagSNPs in NOX enzymes and their regulatory factors. Pathology scores were available for 288 Caucasians and 71 Africans, and mortality status was determined for all subjects. SNPs were tested for association with pathology scores and as predictors of mortality. In Africans, homozygosity for the A allele of rs12753665 (neutrophil cytosolic factor 2) and homozygosity for the T allele of rs760519 (neutrophil cytosolic factor 4) were associated with and predictive of higher rates of advanced fibrosis and cirrhosis compared to other genotypes after controlling for age and sex. In Caucasians, homozygosity for the T allele of rs2292464 (dual oxidase 1) was associated with and predictive of decreased periportal inflammation after controlling for age and sex. No SNPs were significant predictors of mortality. Conclusion: In this exploratory study, three NOX-related polymorphisms in two ethnic groups were significantly associated with hepatic inflammation and fibrosis. Future studies investigating these SNPs in larger cohorts of patients with HCV are warranted. (Hepatology Communications 2017;1:973-982).

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

Gene expression of NOX family members and their clinical significance in hepatocellular carcinoma

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex-derived reactive oxygen species (ROS) promote chronic liver inflammation and remodeling that can drive hepatocellular carcinoma development. The role of NOX expression in hepatocellular carcinoma (HCC) has been partially investigated; however, the clinical relevance of collective or individual NOX family member expression for HCC survival remains unclear. Here, we obtained NOX mRNA expression data for 377 HCC samples and 21 normal liver controls from the TCGA data portal and performed Kaplan-Meier survival, gene ontology functional enrichment, and gene set enrichment analyses. Although most NOX genes exhibited little change, some were significantly induced in HCC compared to that in normal controls. In addition, HCC survival analyses indicated better overall survival in patients with high NOX4 and DUOX1 expression, whereas patients with high NOX1/2/5 expression showed poor prognoses. Gene-neighbour and gene set enrichment analyses revealed that NOX1/2/5 were strongly correlated with genes associated with cancer cell survival and metastasis, whereas increased NOX4 and DUOX1 expression was associated with genes that inhibit tumour progression. On the basis of these data, NOX family gene expression analysis could be a predictor of survival and identify putative therapeutic targets in HCC.

The NADPH oxidase NOX4 represses epithelial to amoeboid transition and efficient tumour dissemination

Epithelial to mesenchymal transition is a common event during tumour dissemination. However, direct epithelial to amoeboid transition has not been characterized to date. Here we provide evidence that cells from hepatocellular carcinoma (HCC), a highly metastatic cancer, undergo epithelial to amoeboid transition in physiological environments, such as organoids or three-dimensional complex matrices. Furthermore, the NADPH oxidase NOX4 inhibits this transition and therefore suppresses efficient amoeboid bleb-based invasion. Moreover, NOX4 expression is associated with E-cadherin levels and inversely correlated with invasive features. NOX4 is necessary to maintain parenchymal structures, increase cell-cell and cell-to-matrix adhesion, and impair actomyosin contractility and amoeboid invasion. Importantly, NOX4 gene deletions are frequent in HCC patients, correlating with higher tumour grade. Contrary to that observed in mesenchymal cell types, here NOX4 suppresses Rho and Cdc42 GTPase expression and downstream actomyosin contractility. In HCC patients, NOX4 expression inversely correlates with RhoC and Cdc42 levels. Moreover, low expression of NOX4 combined with high expression of either RhoC or Cdc42 is associated with worse prognosis. Therefore, loss of NOX4 increases actomyosin levels and favours an epithelial to amoeboid transition contributing to tumour aggressiveness.

The effects of urotensin II on migration and invasion are mediated by NADPH oxidase-derived reactive oxygen species through the c-Jun N-terminal kinase pathway in human hepatoma cells

AIMS

Urotensin II (UII) is a vasoactive neuropeptide involved in migration and invasion in various cell types. However, the effects of UII on human hepatoma cells still remain unclear. The aim of this study was to investigate the role and mechanism of UII on migration and invasion in human hepatoma cells.

METHODS

Migration was measured by wound healing assays and a Transwell^® methodology, and invasion was analyzed using Matrigel^® invasion chambers. Reactive oxygen species (ROS) levels were detected using a 2', 7'-dichlorofluorescein diacetate probe, and flow cytometry, and protein expression levels were evaluated by western blotting. Cell proliferation and actin polymerization were examined using cell proliferation reagent WST-1 and F-actin immunohistochemistry staining.

RESULTS

Exposure to UII promoted migration and invasion in hepatoma cells compared with that in cells without UII. UII also increased matrix metalloproteinase-2 (MMP2) expression in a time-independent manner. Furthermore, UII markedly enhanced ROS generation and NADPH oxidase subunit expression, and consequently facilitated the phosphorylation of c-Jun N-terminal kinase (JNK). The UT antagonist urantide or the antioxidant/NADPH oxidase inhibitor apocynin decreased UII-induced ROS production. JNK phosphorylation, migration, invasion, and MMP9/2 expression were also reversed by pretreatment with apocynin. Urantide and JNK inhibitor SP600125 abrogated migration, invasion, or MMP9/2 expression in response to UII. UII induced actin polymerization and fascin protein expression, and could be reversed by apocynin and SP600125.

CONCLUSIONS

Exogenous UII induced migration and invasion in hepatoma cells that mainly involved NADPH oxidase-derived ROS through JNK activation. UT played an additional role in regulating hepatoma cells migration and invasion. Thus, our data suggested an important effect of UII in hepatocellular carcinoma metastasis.

IKKα regulates human keratinocyte migration through surveillance of the redox environment

Although the functions of H₂O₂ in epidermal wound repair are conserved throughout evolution, the underlying signaling mechanisms are largely unknown. In this study we used human keratinocytes (HEK001) to investigate H₂O₂-dependent wound repair mechanisms. Scratch wounding led to H₂O₂ production in two or three cell layers at the wound margin within ∼30 min and subsequent cysteine modification of proteins via sulfenylation. Intriguingly, exogenous H₂O₂ treatment resulted in preferential sulfenylation of keratinocytes that adopted a migratory phenotype and detached from neighboring cells, suggesting that one of the primary functions of H₂O₂ is to stimulate signaling factors involved in cell migration. Based on previous findings that revealed epidermal growth factor receptor (EGFR) involvement in H₂O₂-dependent cell migration, we analyzed oxidation of a candidate upstream target, the inhibitor of κB kinase α (IKKα; encoded by CHUK), as a mechanism of action. We show that IKKα is sulfenylated at a conserved cysteine residue in the kinase domain, which correlates with de-repression of EGF promoter activity and increased EGF expression. Thus, this indicates that IKKα promotes migration through dynamic interactions with the EGF promoter depending on the redox state within cells.

Summary: This study provides a newly identified mechanism by which H₂O₂-dependent oxidation of the inhibitor of κB kinase α and de-repression of epidermal growth factor promoter activity stimulates keratinocyte migration.

The Janus-Faced Role of Antioxidants in Cancer Cachexia: New Insights on the Established Concepts

Chronic inflammation and excessive loss of skeletal muscle usually occur during cancer cachexia, leading to functional impairment and delaying the cure of cancer. The release of cytokines by tumor promotes the formation of reactive oxygen species (ROS), which in turn regulate catabolic pathways involved in muscle atrophy. ROS also exert a dual role within tumor itself, as they can either promote proliferation and vascularization or induce senescence and apoptosis. Accordingly, previous studies that used antioxidants to modulate these ROS-dependent mechanisms, in cancer and cancer cachexia, have obtained contradictory results, hence the need to gather the main findings of these studies and draw global conclusions in order to stimulate more oriented research in this field. Based on the literature reviewed in this paper, it appears that antioxidant supplementation is (1) beneficial in cancer cachectic patients with antioxidant deficiencies, (2) most likely harmful in cancer patients with adequate antioxidant status (i.e., lung, gastrointestinal, head and neck, and esophageal), and (3) not recommended when undergoing radiotherapy. At the moment, measuring the blood levels of antioxidants may help to identify patients with systemic deficiencies. This approach is simple to realize but could not be a gold standard method for cachexia, as it does not necessarily reflect the redox state in other organs, like muscle.