title: Radiobiological effects of hypoxia-dependent uptake of 64Cu-ATSM: enhanced DNA damage and cytotoxicity in hypoxic cells.
abstract: OBJECTIVE
  Hypoxia occurs frequently in cancers and can lead to therapeutic resistance due to poor perfusion and loss of the oxygen enhancement effect. (64)Cu-ATSM has shown promise as a hypoxia diagnostic agent due to its selective uptake and retention in hypoxic cells and its emission of positrons for PET imaging. (64)Cu also emits radiotoxic Auger electrons and beta(-) particles and may therefore exhibit therapeutic potential when concentrated in hypoxic tissue.
  
  
  METHODS
  MCF-7 cells were treated with 0-10 MBq/ml (64)Cu-ATSM under differing oxygen conditions ranging from normoxia to severe hypoxia. Intracellular response to hypoxia was measured using Western blotting for expression of HIF-1alpha, while cellular accumulation of (64)Cu was measured by gamma counting. DNA damage and cytotoxicity were measured with, respectively, the Comet assay and clonogenic survival.
  
  
  RESULTS
  (64)Cu-ATSM uptake in MCF-7 cells increased as atmospheric oxygen decreased (up to 5.6 Bq/cell at 20.9% oxygen, 10.4 Bq/cell at 0.1% oxygen and 26.0 Bq/cell at anoxia). Toxicity of (64)Cu-ATSM in MCF-7 cells also increased as atmospheric oxygen decreased, with survival of 9.8, 1.5 and 0% in cells exposed to 10 MBq/ml at 20.9, 0.1 and 0% oxygen. The Comet assay revealed a statistically significant increase in (64)Cu-ATSM-induced DNA damage under hypoxic conditions.
  
  
  CONCLUSIONS
  The results support a model in which hypoxia-enhanced uptake of radiotoxic (64)Cu induces sufficient DNA damage and toxicity to overcome the documented radioresistance in hypoxic MCF-7 cells. This suggests that (64)Cu-ATSM and related complexes have potential for targeted radionuclide therapy of hypoxic tumours.
authors.affiliation: School of Biosciences, University of Kent, Canterbury, Kent, UK.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Weeks
authors.forename: Rowena L
authors.initials: RL
authors.lastname: Paul
authors.forename: Paul K
authors.initials: PK
authors.lastname: Marsden
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Blower
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Lloyd
mesh_terms: D001692:Biological Transport; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D056831:Coordination Complexes; D004249:DNA Damage; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D009942:Organometallic Compounds / Q000378:metabolism* / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism; D011853:Radiobiology; D013882:Thiosemicarbazones / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D056831:Coordination Complexes; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009942:Organometallic Compounds; D013882:Thiosemicarbazones; C089548:copper (II) diacetyl-di(N(4)-methylthiosemicarbazone); D010100:Oxygen