title: Assessing 'radiosensitivity' with kinetic profiles of γ-H2AX, 53BP1 and BRCA1 foci.
abstract: OBJECTIVE
  DNA repair assays to identify radiosensitive patients have had limited clinical implementation due to long turn-around times or limited specificity. This study evaluates γ-H2AX-Irradiation Induced Foci (IRIF) kinetics as a more rapid surrogate for the 'gold standard' colony survival assay (CSA) using several known DNA repair disorders as reference models.
  
  
  METHODS
  Radiosensitive cells of known and unknown etiology were studied. γ-H2AX-IRIFs were quantified over 24 h, and the curves were fitted by combining logarithmic growth and exponential decay functions. Fitted values that differed from radionormal controls were considered aberrant and compared to CSA results.
  
  
  RESULTS
  We observed 87% agreement of IRIF data with the CSA for the 14 samples tested. Analysis of γ-H2AX-IRIF kinetics for known repair disorders indicated similarities between an RNF168(-/-) cell line and an RS cell of unknown etiology. These cell lines were further characterized by a reduction in BRCA1-IRIF formation and G2/M checkpoint activation.
  
  
  CONCLUSIONS
  γ-H2AX-IRIF kinetics showed high concordance with the CSA in RS populations demonstrating its potential as a more rapid surrogate assay. This method provides a means to globally identify defective DNA repair pathways in RS cells of unknown etiology through comparison with known DNA repair defects.
authors: UCLA School of Medicine, Department of Pathology and Laboratory Medicine, Los Angeles, CA 90095-1732, USA. namartin@mednet.ucla.edu
authors: Nathan T
authors: NT
authors: Martin
authors: Shareef A
authors: SA
authors: Nahas
authors: Rashmi
authors: R
authors: Tunuguntla
authors: Francesca
authors: F
authors: Fike
authors: Richard A
authors: RA
authors: Gatti
mesh_terms: D019457:Chromosome Breakage / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000235:genetics* / Q000528:radiation effects; D005434:Flow Cytometry; D059565:G2 Phase Cell Cycle Checkpoints; D005720:Gamma Rays; D005819:Genetic Markers; D006657:Histones / Q000032:analysis*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000235:genetics*; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D000071857:Tumor Suppressor p53-Binding Protein 1; D044767:Ubiquitin-Protein Ligases / Q000032:analysis*
chemical_list: D005819:Genetic Markers; C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1; C111164:BRAP protein, human; D044767:Ubiquitin-Protein Ligases