title: Survival Fraction at 2 Gy and γH2AX Expression Kinetics in Peripheral Blood Lymphocytes From Cancer Patients: Relationship With Acute Radiation-Induced Toxicities.
abstract: OBJECTIVE
  Predictive assays for acute radiation toxicities would be clinically relevant in radiation oncology. We prospectively examined the predictive role of the survival fraction at 2 Gy (SF2) and of γH2AX (double-strand break [DSB] DNA marker) expression kinetics in peripheral blood mononuclear cells (PBMCs) from cancer patients before radiation therapy.
  
  
  METHODS
  SF2 was measured with Trypan Blue assay in the PBMCs from 89 cancer patients undergoing radiation therapy at 4 hours (SF2[4h]) and 24 hours (SF2[24h]) after ex vivo irradiation. Using Western blot analysis and band densitometry, we further assessed the expression of γH2AX in PBMC DNA at 0 hours, 30 minutes, and 4 hours (33 patients) and 0 hour, 4 hours, and 24 hours (56 patients), following ex vivo irradiation with 2 Gy. Appropriate ratios were used to characterize each patient, and these were retrospectively correlated with early radiation therapy toxicity grade.
  
  
  RESULTS
  The SF2(4h) was inversely correlated with the toxicity grade (P=.006). The γH2AX-ratio(30min) (band density of irradiated/non-irradiated cells at 30 minutes) revealed, similarly, a significant inverse association (P=.0001). The DSB DNA repair rate from 30 minutes to 4 hours, calculated as the relative RγH2AX-ratio (γH2AX-ratio(4h)/γH2AX-ratio(30min)) showed a significant direct association with high toxicity grade (P=.01).
  
  
  CONCLUSIONS
  Our results suggest that SF2 is a significant radiation sensitivity index for patients undergoing radiation therapy. γH2AX Western blot densitometry analysis provided 2 important markers of normal tissue radiation sensitivity. Low γH2AX expression at 30 minutes was linked with high toxicity grade, suggesting that poor γH2AX repair activity within a time frame of 30 minutes after irradiation predicts for poor radiation tolerance. On the other hand, rapid γH2AX content restoration at 4 hours after irradiation, compatible with efficient DSB repair ability, predicts for increased radiation tolerance.
authors.affiliation: Department of Radiotherapy/Oncology, Radiobiology and Radiopathology Unit, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Stamatia E
authors.initials: SE
authors.lastname: Pouliliou
authors.affiliation: Department of Medical Genetics, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Theodoros S
authors.initials: TS
authors.lastname: Lialiaris
authors.affiliation: Department of Anatomy, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Thespis
authors.initials: T
authors.lastname: Dimitriou
authors.affiliation: Department of Pathology, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Giatromanolaki
authors.affiliation: Department of Internal Medicine, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Papazoglou
authors.affiliation: Department of Molecular Biology and Genetics, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Aglaia
authors.initials: A
authors.lastname: Pappa
authors.affiliation: Department of Radiotherapy/Oncology, Aristotle University of Thessalonica, Thessalonica, Greece.
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Pistevou
authors.affiliation: Department of Radiotherapy/Oncology, Radiobiology and Radiopathology Unit, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Kalamida
authors.affiliation: Department of Radiotherapy/Oncology, Radiobiology and Radiopathology Unit, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece. Electronic address: targ@her.forthnet.gr.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Koukourakis
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D005260:Female; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism / Q000528:radiation effects; D008214:Lymphocytes / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D015999:Multivariate Analysis; D009369:Neoplasms / Q000097:blood / Q000532:radiotherapy*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011836:Radiation Tolerance / Q000235:genetics; D013997:Time Factors
chemical_list: D015415:Biomarkers; C468783:H2AX protein, human; D006657:Histones