title: NOX4 mediates cytoprotective autophagy induced by the EGFR inhibitor erlotinib in head and neck cancer cells.
abstract: Most head and neck squamous cell carcinomas (HNSCCs) overexpress epidermal growth factor receptor (EGFR) and EGFR inhibitors are routinely used in the treatment of HNSCC. However, many HNSCC tumors do not respond or become refractory to EGFR inhibitors. Autophagy, which is a stress-induced cellular self-degradation process, has been reported to reduce the efficacy of chemotherapy in various disease models. The purpose of this study is to determine if the efficacy of the EGFR inhibitor erlotinib is reduced by activation of autophagy via NOX4-mediated oxidative stress in HNSCC cells. Erlotinib induced the expression of the autophagy marker LC3B-II and autophagosome formation in FaDu and Cal-27 cells. Inhibition of autophagy by chloroquine and knockdown of autophagy pathway genes Beclin-1 and Atg5 sensitized both cell lines to erlotinib-induced cytotoxicity, suggesting that autophagy may serve as a protective mechanism. Treatment with catalase (CAT) and diphenylene iodonium (DPI) in the presence of erlotinib suppressed the increase in LC3B-II expression in FaDu and Cal-27 cells. Erlotinib increased NOX4 mRNA and protein expression by increasing its promoter activity and mRNA stability in FaDu cells. Knockdown of NOX4 using adenoviral siNOX4 partially suppressed erlotinib-induced LC3B-II expression, while overexpression of NOX4 increased expression of LC3B-II. These studies suggest that erlotinib may activate autophagy in HNSCC cells as a pro-survival mechanism, and NOX4 may play a role in mediating this effect.
authors.affiliation: Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, USA; Department of Pathology, The University of Iowa, Iowa City, IA, USA.
authors.forename: Arya
authors.initials: A
authors.lastname: Sobhakumari
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Schickling
authors.forename: Laurie
authors.initials: L
authors.lastname: Love-Homan
authors.forename: Ayanna
authors.initials: A
authors.lastname: Raeburn
authors.forename: Elise V M
authors.initials: EV
authors.lastname: Fletcher
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Case
authors.forename: Frederick E
authors.initials: FE
authors.lastname: Domann
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Miller
authors.forename: Andrean L
authors.initials: AL
authors.lastname: Simons
mesh_terms: D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism*; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000069347:Erlotinib Hydrochloride; D057809:HEK293 Cells; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000502:physiology*; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use; D000077195:Squamous Cell Carcinoma of Head and Neck; D014407:Tumor Cells, Cultured
chemical_list: D011799:Quinazolines; D000069347:Erlotinib Hydrochloride; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors
keywords: Autophagy; CQ; Chloroquine; DN; DPI; DUOX; Diphenylene Iodonium; Dominant negative; Dual Oxidase; EGFR; ERL; Epidermal Growth Factor Receptor; Erlotinib; GFP; Green Fluorescent Protein; HNSCC; Head and neck squamous cell carcinoma; LC3; LC3B; Light chain 3; NADPH oxidase 4; NOX4; ROS; Reactive Oxygen Species; TEM; TKI; Transmission Electron Microscopy; Tyrosine Kinase Inhibitor; UTR; Untranslated Region; WT; Wildtype
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