title: Proteomic identification of putative biomarkers of radiotherapy resistance: a possible role for the 26S proteasome?
abstract: OBJECTIVE
  We aimed to identify putative predictive protein biomarkers of radioresistance.
  
  
  METHODS
  Three breast cancer cell lines (MCF7, MDA-MB-231, and T47D) were used as in vitro models to study radioresistance. Inherent radiosensitivities were examined using a clonogenic survival assay. It was revealed that each cell line differed in their response to radiotherapy. These parental breast cancer cell lines were used to establish novel derivatives (MCF7RR, MDA-MB-231RR, and T47DRR) displaying significant resistance to ionizing radiation. Derivative cells were compared with parental cells to identify putative biomarkers associated with the radioresistant phenotype. To identify these biomarkers, complementary proteomic screening approaches were exploited encompassing two-dimensional gel electrophoresis in combination with mass spectrometry, liquid chromatography coupled with tandem mass spectrometry and quantitative proteomics using iTRAQ technology.
  
  
  RESULTS
  A large number of potential biomarkers were identified, and several of these were confirmed using Western blot analysis. In particular, a decrease in the expression of the 26S proteasome was found in all radioresistant derivatives when compared with the respective parent cells. Decreased expression of this target was also found to be associated with radioresistant laryngeal tumors (P = .05) in a small pilot immunohistochemical study.
  
  
  CONCLUSIONS
  These findings suggest that the 26S proteasome may provide a general predictive biomarker for radiotherapy outcome.
authors.affiliation: Cancer Biology Proteomics Group, Postgraduate Medical Institute of the University of Hull, Hull, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Smith
authors.forename: Omar
authors.initials: O
authors.lastname: Qutob
authors.forename: Mark B
authors.initials: MB
authors.lastname: Watson
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Beavis
authors.forename: Donna
authors.initials: D
authors.lastname: Potts
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Welham
authors.forename: Veerabhadram
authors.initials: V
authors.lastname: Garimella
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lind
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Drew
authors.forename: Lynn
authors.initials: L
authors.lastname: Cawkwell
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D020411:Oligonucleotide Array Sequence Analysis; D046988:Proteasome Endopeptidase Complex / Q000096:biosynthesis* / Q000235:genetics; D040901:Proteomics; D011836:Radiation Tolerance / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D014408:Biomarkers, Tumor; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease