DNA damage during reoxygenation elicits a Chk2-dependent checkpoint response.
Due to the abnormal vasculature of solid tumors, tumor cell oxygenation can change rapidly with the opening and closing of blood vessels, leading to the activation of both hypoxic response pathways and oxidative stress pathways upon reoxygenation. Here, we report that ataxia telangiectasia mutated-dependent phosphorylation and activation of Chk2 occur in the absence of DNA damage during hypoxia and are maintained during reoxygenation in response to DNA damage. Our studies involving oxidative damage show that Chk2 is required for G2 arrest. Following exposure to both hypoxia and reoxygenation, Chk2-/- cells exhibit an attenuated G2 arrest, increased apoptosis, reduced clonogenic survival, and deficient phosphorylation of downstream targets. These studies indicate that the combination of hypoxia and reoxygenation results in a G2 checkpoint response that is dependent on the tumor suppressor Chk2 and that this checkpoint response is essential for tumor cell adaptation to changes that result from the cycling nature of hypoxia and reoxygenation found in solid tumors.
CCSR South, Room 1255, Department of Radiation Oncology, Stanford University, Stanford, CA 94305-5152, USA.
Rachel A
RA
Freiberg
Ester M
EM
Hammond
Mary Jo
MJ
Dorie
Scott M
SM
Welford
Amato J
AJ
Giaccia
D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology; D001260:Ataxia Telangiectasia / Q000378:metabolism / Q000473:pathology; D002277:Carcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015687:Cell Hypoxia; D002470:Cell Survival; D064447:Checkpoint Kinase 2; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D016195:G2 Phase / Q000502:physiology*; D006801:Humans; D010100:Oxygen / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism
D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D013912:Threonine; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases; D010100:Oxygen; D000111:Acetylcysteine