title: Assessment of DNA damage produced by 125I-triplex-forming oligonucleotides in cells.
abstract: OBJECTIVE
  Triplex-forming oligodeoxyribonucleotides (TFOs) bind specifically to their target sequences by forming hydrogen bonds within the major groove of the target duplex. When labeled with Auger-electron-emitting radioisotopes, TFOs are able to damage the target gene in a process named antigene radiotherapy. We compared radiotoxicity and the amount of DNA damage produced within cultured cells by two 125I-labeled TFOs, one with a single target in the genome and another with multiple targets.
  
  
  METHODS
  Radiotoxicity was measured by clonogenic assay while DNA damage was assessed by the number of histone gamma-H2AX foci formed at the sites of DNA double strand breaks (DSBs).
  
  
  RESULTS
  The TFO with multiple nuclear targets was 1.7 fold more radiotoxic and produced on average 1.9 fold more gamma-H2AX foci per cell than the TFO with a single target.
  
  
  CONCLUSIONS
  Since the two methods gave comparable results, measuring the number of gamma-H2AX foci per decay may be a useful procedure for the assessment of cytotoxic effects and the intranuclear localization of radionuclides when they produce DSBs.
authors.affiliation: NIH/NMD, 10 Center Dr., Room 4D45, Bethesda, MD 20892, USA.
authors.forename: Olga A
authors.initials: OA
authors.lastname: Sedelnikova
authors.forename: Irina V
authors.initials: IV
authors.lastname: Panyutin
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Neumann
authors.forename: William M
authors.initials: WM
authors.lastname: Bonner
authors.forename: Igor G
authors.initials: IG
authors.lastname: Panyutin
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects*; D004247:DNA / Q000009:adverse effects* / Q000528:radiation effects* / Q000648:ultrastructure; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D005354:Fibrosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes / Q000009:adverse effects*; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000009:adverse effects
chemical_list: C468783:H2AX protein, human; D006657:Histones; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; C051802:triplex DNA; D004247:DNA