title: The effect of DN (dominant-negative) Ku70 and reoxygenation on hypoxia cell-kill: evidence of hypoxia-induced potentially lethal damage.
abstract: OBJECTIVE
  To study the effect of DN (dominant-negative) Ku70 and reoxygenation on the hypoxia-induced cell-kill.
  
  
  METHODS
  Cell lines were human colorectal carcinoma HCT8 and HT29 cells and their respective derivatives, v-HCT8 and v-HT29 infected with DNKu70-containing adenovirus. Cells were plated in glass tubes and made hypoxic by flushing N(2) gas containing 0, 0.1 or 0.5% O(2). Cell survival was determined by colony formation assay immediately after 0-96 h hypoxia. To reoxygenate medium were replaced fresh following 48 or 72 h in hypoxia and cells were incubated in aerobic environment for 2-24 h before survival assay.
  
  
  RESULTS
  When incubated in hypoxia, cells lost reproductive capability ∼ exponentially as a function of time in hypoxia, and depending on the O(2) concentration. DNKu70 rendered cells more prone to hypoxia-induced cell-kill. Following reoxygenation cell survival increased rapidly but without detectable cell proliferation during first 24 hours. This evinced hypoxia-induced potentially lethal damage (PLD) that was repairable upon reoxygenation. DNKu70 did not significantly inhibit this repair.
  
  
  CONCLUSIONS
  Hypoxia-induced cell lethality was facilitated by DNKu70, but substantially repaired upon reoxygenation. This may have negative impact on the effect of reoxygenation in cancer therapy.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, NY, USA. ysurano@aol.com
authors.forename: Muneyasu
authors.initials: M
authors.lastname: Urano
authors.forename: Gloria C
authors.initials: GC
authors.lastname: Li
authors.forename: Fuqiu
authors.initials: F
authors.lastname: He
authors.forename: Akiko
authors.initials: A
authors.lastname: Minami
authors.forename: Paul
authors.initials: P
authors.lastname: Burgman
authors.forename: C Clifton
authors.initials: CC
authors.lastname: Ling
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002470:Cell Survival; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D000072200:Ku Autoantigen; D009374:Neoplasms, Experimental / Q000473:pathology* / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D015854:Up-Regulation
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D010100:Oxygen