title: Reactive oxygen species mediate Cr(VI)-induced carcinogenesis through PI3K/AKT-dependent activation of GSK-3β/β-catenin signaling.
abstract: Cr(VI) compounds are known human carcinogens that primarily target the lungs. Cr(VI) produces reactive oxygen species (ROS), but the exact effects of ROS on the signaling molecules involved in Cr(VI)-induced carcinogenesis have not been extensively studied. Chronic exposure of human bronchial epithelial cells to Cr(VI) at nanomolar concentrations (10-100nM) for 3months not only induced cell transformation, but also increased the potential of these cells to invade and migrate. Injection of Cr(VI)-stimulated cells into nude mice resulted in the formation of tumors. Chronic exposure to Cr(VI) increased levels of intracellular ROS and antiapoptotic proteins. Transfection with catalase or superoxide dismutase (SOD) prevented Cr(VI)-mediated increases in colony formation, cell invasion, migration, and xenograft tumors. While chronic Cr(VI) exposure led to activation of signaling cascades involving PI3K/AKT/GSK-3β/β-catenin and PI3K/AKT/mTOR, transfection with catalase or SOD markedly inhibited Cr(VI)-mediated activation of these signaling proteins. Inhibitors specific for AKT or β-catenin almost completely suppressed the Cr(VI)-mediated increase in total and active β-catenin proteins and colony formation. In particular, Cr(VI) suppressed autophagy of epithelial cells under nutrition deprivation. Furthermore, there was a marked induction of AKT, GSK-3β, β-catenin, mTOR, and carcinogenic markers in tumor tissues formed in mice after injection with Cr(VI)-stimulated cells. Collectively, our findings suggest that ROS is a key mediator of Cr(VI)-induced carcinogenesis through the activation of PI3K/AKT-dependent GSK-3β/β-catenin signaling and the promotion of cell survival mechanisms via the inhibition of apoptosis and autophagy.
authors.affiliation: Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA.
authors.forename: Young-Ok
authors.initials: YO
authors.lastname: Son
authors.forename: Poyil
authors.initials: P
authors.lastname: Pratheeshkumar
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Jia
authors.initials: J
authors.lastname: Fan
authors.forename: Dong-Hern
authors.initials: DH
authors.lastname: Kim
authors.forename: Ju-Yeon
authors.initials: JY
authors.lastname: Lee
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jeong-Chae
authors.initials: JC
authors.lastname: Lee
authors.forename: Xianglin
authors.initials: X
authors.lastname: Shi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002273:Carcinogens; D045744:Cell Line, Tumor; D002465:Cell Movement; D002857:Chromium / Q000633:toxicity*; D002999:Clone Cells / Q000187:drug effects; D004578:Electron Spin Resonance Spectroscopy; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D051058:Oncogene Protein v-akt / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010957:Plasmids; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection; D051176:beta Catenin / Q000502:physiology*
chemical_list: D002273:Carcinogens; D017382:Reactive Oxygen Species; D051176:beta Catenin; D002857:Chromium; D019869:Phosphatidylinositol 3-Kinases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051058:Oncogene Protein v-akt; D038362:Glycogen Synthase Kinase 3
keywords: 5,5-dimethyl-1-pyrroline-1-oxide; CAT; COX-2; Carcinogenesis; Cell transformation; Cr(VI); DMEM; DMPO; Dulbecco's modified Eagle's medium; ESR; FBS; HIF-1α; LC3; MMPs; ROS; Reactive oxygen species (ROS); SOD; VEGF; catalase; cyclooxygenase-2; electron spin resonance; fetal bovine serum; hypoxia-inducible transcription factor-1α; mTOR; mammalian target of rapamycin; matrix metalloproteinases; microtubule-associated protein 1 light chain 3; reactive oxygen species; superoxide dismutase; vascular endothelial growth factor; β-catenin