title: E-Cadherin loss associated with EMT promotes radioresistance in human tumor cells.
abstract: OBJECTIVE
  Hypoxia is a hallmark of solid cancers and associated with metastases and treatment failure. During tumor progression epithelial cells often acquire mesenchymal features, a phenomenon known as epithelial-to-mesenchymal transition (EMT). Intratumoral hypoxia has been linked to EMT induction. We hypothesized that signals from the tumor microenvironment such as growth factors and tumor oxygenation collaborate to promote EMT and thereby contribute to radioresistance.
  
  
  METHODS
  Gene expression changes under hypoxia were analyzed using microarray and validated by qRT-PCR. Conversion of epithelial phenotype upon hypoxic exposure, TGFβ addition or oncogene activation was investigated by Western blot and immunofluorescence. Cell survival following ionizing radiation was assayed using clonogenic survival.
  
  
  RESULTS
  Upon hypoxia, TGFβ addition or EGFRvIII expression, MCF7, A549 and NMuMG epithelial cells acquired a spindle shape and lost cell-cell contacts. Expression of epithelial markers such as E-cadherin decreased, whereas mesenchymal markers such as vimentin and N-cadherin increased. Combining hypoxia with TGFβ or EGFRvIII expression, lead to more rapid and pronounced EMT-like phenotype. Interestingly, E-cadherin expression and the mesenchymal appearance were reversible upon reoxygenation. Mesenchymal conversion and E-cadherin loss were associated with radioresistance.
  
  
  CONCLUSIONS
  Our findings describe a mechanism by which the tumor microenvironment may contribute to tumor radioresistance via E-cadherin loss and EMT.
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Theys
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Barry
authors.initials: B
authors.lastname: Jutten
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Roger
authors.initials: R
authors.lastname: Habets
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Kim
authors.initials: K
authors.lastname: Paesmans
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Arjan J
authors.initials: AJ
authors.lastname: Groot
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.|Ontario Cancer Institute and Campbell Family Institute for Cancer Research, University Health Network, Toronto, Canada.|Departments of Radiation Oncology and Medical Biophysics, University of Toronto, Canada.
authors.forename: Brad G
authors.initials: BG
authors.lastname: Wouters
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Guido
authors.initials: G
authors.lastname: Lammering
authors.affiliation: Department of Radiation Oncology (MAASTRO lab), Maastricht University Medical Centre, The Netherlands.
authors.forename: Marc
authors.initials: M
authors.lastname: Vooijs
mesh_terms: D000704:Analysis of Variance; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism*; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D011836:Radiation Tolerance; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D059016:Tumor Microenvironment
chemical_list: D015820:Cadherins