title: The NADPH oxidase NOX4 inhibits hepatocyte proliferation and liver cancer progression.
abstract: The NADPH oxidase NOX4 has emerged as an important source of reactive oxygen species in signal transduction, playing roles in physiological and pathological processes. NOX4 mediates transforming growth factor-β-induced intracellular signals that provoke liver fibrosis, and preclinical assays have suggested NOX4 inhibitors as useful tools to ameliorate this process. However, the potential consequences of sustained treatment of liver cells with NOX4 inhibitors are yet unknown. The aim of this work was to analyze whether NOX4 plays a role in regulating liver cell growth either under physiological conditions or during tumorigenesis. In vitro assays proved that stable knockdown of NOX4 expression in human liver tumor cells increased cell proliferation, which correlated with a higher percentage of cells in S/G2/M phases of the cell cycle, downregulation of p21(CIP1/WAF1), increase in cyclin D1 protein levels, and nuclear localization of β-catenin. Silencing of NOX4 in untransformed human and mouse hepatocytes also increased their in vitro proliferative capacity. In vivo analysis in mice revealed that NOX4 expression was downregulated under physiological proliferative situations of the liver, such as regeneration after partial hepatectomy, as well as during pathological proliferative conditions, such as diethylnitrosamine-induced hepatocarcinogenesis. Xenograft experiments in athymic mice indicated that NOX4 silencing conferred an advantage to human hepatocarcinoma cells, resulting in earlier onset of tumor formation and increase in tumor size. Interestingly, immunochemical analyses of NOX4 expression in human liver tumor cell lines and tissues revealed decreased NOX4 protein levels in liver tumorigenesis. Overall, results described here strongly suggest that NOX4 would play a growth-inhibitory role in liver cells.
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors: Eva
authors: E
authors: Crosas-Molist
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors: Esther
authors: E
authors: Bertran
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors: Patricia
authors: P
authors: Sancho
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors: Judit
authors: J
authors: López-Luque
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors: Joan
authors: J
authors: Fernando
authors: Departamento de Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28080 Madrid, Spain.
authors: Aránzazu
authors: A
authors: Sánchez
authors: Departamento de Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28080 Madrid, Spain.
authors: Margarita
authors: M
authors: Fernández
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain.
authors: Estanis
authors: E
authors: Navarro
authors: Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, 08908 Barcelona, Spain; Departament de Ciències Fisiològiques II, Universitat de Barcelona, Campus de Bellvitge, Barcelona, Spain. Electronic address: ifabregat@idibell.cat.
authors: Isabel
authors: I
authors: Fabregat
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D063646:Carcinogenesis / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D051379:Mice; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D017382:Reactive Oxygen Species; D016212:Transforming Growth Factor beta; D019938:Cyclin D1; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human
keywords: Free radicals; Hepatocarcinogenesis; Hepatocellular carcinoma; Hepatocyte proliferation; Liver cancer; Liver regeneration; NADPH oxidase; NOX4; Reactive oxygen species