Impact of dose-rate on the low-dose hyper-radiosensitivity and induced radioresistance (HRS/IRR) response*. (October 2013)

• Record Type: Journal Article
• Authors: Thomas, Charles; Martin, Jennifer; Devic, Clément; Bräuer-Krisch, Elke; Diserbo, Michel; Thariat, Juliette; Foray, Nicolas
• Is Part Of: International journal of radiation biology. Volume 89:Number 10(2013:Oct.)
• Page Start: 813
• Page End: 822
• Publication Date: 2013-10
• Subjects: Radiation -- Physiological effect -- Periodicals; Radiobiology -- Periodicals; 571.45
• DOI: 10.3109/09553002.2013.800248
• Languages: English
• ISSNs: 0955-3002

Abstract

<abstract> <title>Abstract</title> <p> <italic>Purpose</italic>: To ask whether dose-rate influences low-dose hyper- radiosensitivity and induced radioresistance (HRS/IRR) response in rat colon progressive (PRO) and regressive (REG) cells.</p> <p> <italic>Methods</italic>: Clonogenic survival was applied to tumorigenic PRO and non-tumorigenic REG cells irradiated with <sup>60</sup>Co γ-rays at 0.0025–500 mGy.min<sup>−1</sup>. Both clonogenic survival and non-homologous end-joining (NHEJ) pathway involved in DNA double-strand breaks (DSB) repair assays were applied to PRO cells irradiated at 25 mGy.min<sup>−1</sup> with 75 kV X-rays only.</p> <p> <italic>Results</italic>: Irrespective of dose-rates, marked HRS/IRR responses were observed in PRO but not in REG cells. For PRO cells, the doses at which HRS and IRR responses are maximal were dependent on dose-rate; conversely exposure times during which HRS and IRR responses are maximal (t<sub>HRSmax</sub> and t<sub>IRRmax</sub>) were independent of dose-rate. The t<sub>HRSmax</sub> and t<sub>IRRmax</sub> values were 23 ± 5 s and 66 ± 7 s (mean ± standard error of the mean [SEM], <italic>n</italic> = 7), in agreement with literature data. Repair data show that t<sub>HRSmax</sub> may correspond to exposure time during which NHEJ is deficient while t<sub>IRRmax</sub> may correspond to exposure time during which NHEJ is complete.</p> <p> <italic>Conclusion</italic>: HRS response may be maximal if exposure times are shorter than t<sub>HRSmax</sub> irrespective of dose, dose-rate and cellular model. Potential application of HRS response in radiotherapy is discussed.</p> </abstract>