title: Snail-induced epithelial-to-mesenchymal transition of MCF-7 breast cancer cells: systems analysis of molecular changes and their effect on radiation and drug sensitivity.
abstract: BACKGROUND
  Epithelial-to-mesenchymal transition (EMT) has been associated with the acquisition of metastatic potential and the resistance of cancer cells to therapeutic treatments. MCF-7 breast cancer cells engineered to constitutively express the zinc-finger transcriptional repressor gene Snail (MCF-7-Snail cells) have been previously shown to display morphological and molecular changes characteristic of EMT. We report here the results of a comprehensive systems level molecular analysis of changes in global patterns of gene expression and levels of glutathione and reactive oxygen species (ROS) in MCF-7-Snail cells and the consequence of these changes on the sensitivity of cells to radiation treatment and therapeutic drugs.
  
  
  METHODS
  Snail-induced changes in global patterns of gene expression were identified by microarray profiling using the Affymetrix platform (U133 Plus 2.0). The resulting data were processed and analyzed by a variety of system level analytical methods. Levels of ROS and glutathione (GSH) were determined by fluorescent and luminescence assays, and nuclear levels of NF-κB protein were determined by an ELISA based method. The sensitivity of cells to ionizing radiation and anticancer drugs was determined using a resazurin-based cell cytotoxicity assay.
  
  
  RESULTS
  Constitutive ectopic expression of Snail in epithelial-like, luminal A-type MCF-7 cells induced significant changes in the expression of >7600 genes including gene and miRNA regulators of EMT. Mesenchymal-like MCF-7-Snail cells acquired molecular profiles characteristic of triple-negative, claudin-low breast cancer cells, and displayed increased sensitivity to radiation treatment, and increased, decreased or no change in sensitivity to a variety of anticancer drugs. Elevated ROS levels in MCF-7-Snail cells were unexpectedly not positively correlated with NF-κB activity.
  
  
  CONCLUSIONS
  Ectopic expression of Snail in MCF-7 cells resulted in morphological and molecular changes previously associated with EMT. The results underscore the complexity and cell-type dependent nature of the EMT process and indicate that EMT is not necessarily predictive of decreased resistance to radiation and drug-based therapies.
authors.affiliation: Integrated Cancer Research Center, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, 315 Ferst Dr., Atlanta, GA, 30332, USA.
authors.forename: Roman
authors.initials: R
authors.lastname: Mezencev
authors.affiliation: Integrated Cancer Research Center, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, 315 Ferst Dr., Atlanta, GA, 30332, USA.
authors.forename: Lilya V
authors.initials: LV
authors.lastname: Matyunina
authors.affiliation: Integrated Cancer Research Center, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, 315 Ferst Dr., Atlanta, GA, 30332, USA.
authors.forename: Neda
authors.initials: N
authors.lastname: Jabbari
authors.affiliation: Integrated Cancer Research Center, School of Biology, and Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, 315 Ferst Dr., Atlanta, GA, 30332, USA. john.mcdonald@biology.gatech.edu.
authors.forename: John F
authors.initials: JF
authors.lastname: McDonald
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D061986:MCF-7 Cells; D016328:NF-kappa B / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D011836:Radiation Tolerance / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071250:Snail Family Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D016328:NF-kappa B; D009363:Neoplasm Proteins; D017382:Reactive Oxygen Species; C000604407:SNAI1 protein, human; D000071250:Snail Family Transcription Factors
keywords: Drug resistance; Epithelial-to-mesenchymal transition; Glutathione; MCF-7; NF-κB; Radiation sensitivity; Reactive oxygen species; Slug; Snail; Triple-negative breast-cancer