title: Prediction of clonogenic cell survival curves based on the number of residual DNA double strand breaks measured by gammaH2AX staining.
abstract: OBJECTIVE
  To assess the potential of using the residual phosphorylation of histone H2AX (gammaH2AX) after irradiation as a marker of radiosensitivity in vitro.
  
  
  METHODS
  Confluent cell cultures of FaDu and SKX human squamous cell carcinoma lines were irradiated with graded single doses. Twenty-four hours after irradiation cells were seeded for standard colony forming assay (CFA). In parallel, staining for gammaH2AX was performed to visualise the residual foci.
  
  
  RESULTS
  In the CFA, FaDu showed a higher radioresistance than SKX. After analysis of the residual foci data, we constructed 'predicted' survival curves using two different methods. First, the proportion of nuclei with <3 foci was found to correlate closely with the observed surviving fraction (SF) in FaDu, with a slight overestimation of the true SF in SKX. Second, there was a strong linear correlation of the mean number of residual foci and observed -lnSF. Based on regression analysis, we calculated the SF for both cell lines based on the mean number of residual gammaH2AX foci. This second approach again led to a good correlation of predicted and observed SF values in FaDu and a (slight) overestimation in SKX.
  
  
  CONCLUSIONS
  In the two cell lines investigated the mean number of residual foci of gammaH2AX can be used to predict differences in the radiation dose response relationship in vitro.
authors.affiliation: Department of Radiation Oncology, OncoRay-Center for Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Germany.
authors.forename: Apostolos
authors.initials: A
authors.lastname: Menegakis
authors.forename: Ala
authors.initials: A
authors.lastname: Yaromina
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eicheler
authors.forename: Annegret
authors.initials: A
authors.lastname: Dörfler
authors.forename: Bettina
authors.initials: B
authors.lastname: Beuthien-Baumann
authors.forename: Howard D
authors.initials: HD
authors.lastname: Thames
authors.forename: Michael
authors.initials: M
authors.lastname: Baumann
authors.forename: Mechthild
authors.initials: M
authors.lastname: Krause
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004273:DNA, Neoplasm / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D011836:Radiation Tolerance; D014410:Tumor Stem Cell Assay
chemical_list: D004273:DNA, Neoplasm; C468783:H2AX protein, human; D006657:Histones