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Title: The Adaptive Response, Genetic Haplo-Insufficiency and Genomic Instability

The linear no-threshold (LNT) hypothesis is the driving force in the establishment of radiation protection standards. However, the scientific basis for linearity has been brought into question, particularly due to the concerns about induced radiation resistance as it pertains to oxidative stress. Specifically, we investigated the observation that tumor hypoxia is associated with malignant progression, increased metastases, chemo- and radioresistance and poor prognosis. Experiments were conducted with non-malignant 3T3/NIH cells and normal human lung fibroblasts (NHLF) that were subjected to γ-irradiation under the levels of oxygen resembling those in growing tumors, and related our data to the concentrations of dissolved oxygen (DO), which is a better indicator of the amounts of residual oxygen inside the cells cultured in the hypoxic or anoxic atmosphere. We found that at DO levels about 0.5 mg/L cells subjected to both short-term (17 hours) and prolonged (48-72 hours) hypoxia continued to proliferate, and that apoptotic events were decreased at the early hours of hypoxic treatment. We showed that the short-term hypoxia up-regulated p53-binding protein 1 (53BP1) and resulted in facilitated 53BP1 nuclear foci formation and disappearance, thus indicating the higher efficiency of DNA double strand breaks repair processes. The latter was confirmed by the lowermore » micronuclei incidence in irradiated hypoxic cells.« less
  1. Columbia Univ., New York, NY (United States). Center for Radiological Research
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
Columbia Univ., New York, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
61 RADIATION PROTECTION AND DOSIMETRY; the linear no-threshold; normal human lung fibroblasts; dissolved oxygen