title: Hypoxia activated EGFR signaling induces epithelial to mesenchymal transition (EMT).
abstract: Metastasis is a multi-step process which requires the conversion of polarized epithelial cells to mesenchymal cells, Epithelial-Mesenchymal Transition (EMT). EMT is essential during embryonic morphogenesis and has been implicated in the progression of primary tumors towards metastasis. Hypoxia is known to induce EMT; however the molecular mechanism is still poorly understood. Using the A431 epithelial cancer cell line, we show that cells grown under hypoxic conditions migrated faster than cells grown under normal oxygen environment. Cells grown under hypoxia showed reduced adhesion to the extracellular matrix (ECM) probably due to reduced number of Vinculin patches. Growth under hypoxic conditions also led to down regulation of E-cadherin and up regulation of vimentin expression. The increased motility of cells grown under hypoxia could be due to redistribution of Rac1 to the plasma membrane as opposed to increased expression of Rac1. EGF (Epidermal Growth Factor) is a known inducer of EMT and growth of A431 cells in the absence of oxygen led to increased expression of EGFR (EGF Receptor). Treatment of A431 cells with EGF led to reduced cell adhesion to ECM, increased cell motility and other EMT characteristics. Furthermore, this transition was blocked by the monoclonal antibody Cetuximab. Cetuximab also blocked the hypoxia-induced EMT suggesting that cell growth under hypoxic conditions led to activation of EGFR signaling and induction of EMT phenotype.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
authors.forename: Ashish
authors.initials: A
authors.lastname: Misra
authors.forename: Chhiti
authors.initials: C
authors.lastname: Pandey
authors.forename: Siu Kwan
authors.initials: SK
authors.lastname: Sze
authors.forename: Thirumaran
authors.initials: T
authors.lastname: Thanabalu
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D000068818:Cetuximab; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects / Q000502:physiology; D066246:ErbB Receptors / Q000378:metabolism / Q000494:pharmacology; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction; D014746:Vimentin / Q000378:metabolism; D016596:Vinculin / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D015820:Cadherins; C107953:RAC1 protein, human; D014746:Vimentin; D016596:Vinculin; C512478:EGFR protein, human; D066246:ErbB Receptors; D020830:rac1 GTP-Binding Protein; D000068818:Cetuximab