title: Development and characterization of an isogenic cell line with a radioresistant phenotype.
abstract: BACKGROUND
  Radiation resistance is a major cause of death in cancer patients. Cancer cells react during radiotherapy by re-programming specific cell functions that may confer resistance to radiation. The understanding of this complex process is hindered due to the lack of appropriate study models. We describe an experimental development of a radioresistant isogenic cancer cell line, and its molecular characterization.
  
  
  METHODS
  A431-cultured cells were irradiated for 7 month until 85 Gy. Then, a selected single cell was left to grow as stable A431-R cell line. Clonogenic assay was used to determine cell survival, the α and β parameters of the LQ model, and the mean inactivation dose. The DNA repair ability of cells was evaluated by pulsed-field electrophoresis method. Differential effect of fractionated radiation was ultimately tested in xenografts. Furthermore, we used a wound healing assay, Western blot for EGFR, AKT and ERK1/2 and ELISA test for vascular endothelial growth factor (VEGF) secretion. Finally we explored CD44 marker and cell cycle distribution.
  
  
  RESULTS
  The established A431-R cell line showed radiation resistance in clonogenic assays, repair of radiation-induced DNA fragmentation and xenografted tumours. The radiation resistance was associated with in vitro higher cell growth and migration, increased levels of former oncoproteins, and secretion of VEGF.
  
  
  CONCLUSIONS
  In this model, the emergence of radiation resistance was associated with the acquisition of biological traits that support more aggressive behaviour of cancer cells. We have generated a model that will be useful for mechanistic studies and development of rational treatments against radiation resistance in cancer.
authors.affiliation: Translational Research Laboratory, Catalan Institute of Oncology - IDIBELL, Avda Gran Via de l'Hospitalet, 199-203, 08907, L'Hospitalet de Llobregat, Spain.
authors.forename: Lara I
authors.initials: LI
authors.lastname: de Llobet
authors.forename: Marta
authors.initials: M
authors.lastname: Baro
authors.forename: Agnès
authors.initials: A
authors.lastname: Figueras
authors.forename: Ignasi
authors.initials: I
authors.lastname: Modolell
authors.forename: Maria V
authors.initials: MV
authors.lastname: Da Silva
authors.forename: Purificación
authors.initials: P
authors.lastname: Muñoz
authors.forename: Arturo
authors.initials: A
authors.lastname: Navarro
authors.forename: Ricard
authors.initials: R
authors.lastname: Mesia
authors.forename: Josep
authors.initials: J
authors.lastname: Balart
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D002453:Cell Cycle; D002465:Cell Movement; D049109:Cell Proliferation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005434:Flow Cytometry; D005720:Gamma Rays; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D010641:Phenotype; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014945:Wound Healing; D023041:Xenograft Model Antitumor Assays
chemical_list: C497483:CD44 protein, human; D018960:Hyaluronan Receptors; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A