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Title: Induction and Persistence of Large γH2AX Foci by High Linear Energy Transfer Radiation in DNA-Dependent protein kinase–Deficient Cells

Purpose: To evaluate the cell response to DNA double-strand breaks induced by low and high linear energy transfer (LET) radiations when the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), an essential protein of the nonhomologous end-joining repair pathway, lacks kinase activity. Methods and Materials: CHO10B2, a Chinese hamster ovary cell line, and its derived radiosensitive mutant cell line, irs-20, lacking DNA-PKcs activity, were evaluated after 0 to 3 Gy of γ-rays, plateau and Bragg peak protons, and lithium beams by clonogenic assay, and as a measurement of double-strand breaks, phosphorylated H2AX (γH2AX) foci number and size were quantified by immunocytofluorescence. Results: Irs-20 exhibited greater radiosensitivity and a higher amount of γH2AX foci than CHO10B2 at 6 hours after irradiation for all types of radiations. Remarkably, CHO10B2 and irs-20 maintained their difference in radiosensitivity after high-LET radiation. Six hours after low-LET radiations, irs-20 did not reach basal levels of γH2AX at high doses, whereas CHO10B2 recovered basal levels for all doses. After high-LET radiation, only CHO10B2 exhibited a reduction in γH2AX foci, but it never reached basal levels. Persistent foci in irs-20 confirmed a repair deficiency. Interestingly, after 30 minutes of high-LET radiation both cell lines exhibited large foci (size >0.9more » μm{sup 2}) related to the damage nature, whereas at 6 hours irs-20 showed a higher amount of large foci than CHO10B2, with a 7-fold increase at 3 Gy, that could also be associated to radiosensitivity. Conclusions: We demonstrated, for the first time, an association between deficient DNA-PKcs activity and not only high levels of H2AX phosphorylation but also persistence and size increase of γH2AX foci after high-LET irradiation.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [5] ;  [2] ;  [2] ;  [6] ;
  1. Departamento de Micro y Nanotecnología, Comisión Nacional de Energía Atómica, San Martín, Buenos Aires (Argentina)
  2. (Argentina)
  3. Departamento de Radiobiología, Comisión Nacional de Energía Atómica, San Martín, Buenos Aires (Argentina)
  4. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina)
  5. Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina)
  6. Escuela de Ciencia y Tecnología, Universidad Nacional de San Martín, San Martín, Buenos Aires (Argentina)
Publication Date:
OSTI Identifier:
22267950
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 87; Journal Issue: 4; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRONMENTAL POLLUTANT EFFECTS ON LIVING ORGANISMS AND BIOLOGICAL MATERIALS; 62 RADIOLOGY AND NUCLEAR MEDICINE; BIOLOGICAL PATHWAYS; BRAGG CURVE; CHO CELLS; DNA; LET; PROTEINS; PROTONS; RADIATION DOSES; RADIOSENSITIVITY; STRAND BREAKS