TY  - JOUR
AU  - Unverricht, Marcus
AU  - von Ameln, Marcel
AU  - Kriehuber, Ralf
TI  - Induction of Chromosomal Aberrations after Exposure to the Auger Electron Emitter Iodine-125, the β–-emitter Tritium and Cesium-137 γ rays
JO  - Radiation research
VL  - 201
IS  - 5
SN  - 0033-7587
CY  - Great Falls, Va.
PB  - Radiation Research Society
M1  - FZJ-2025-01999
SP  - 479-486
PY  - 2024
AB  - The biological effectiveness of ionizing radiation dependsnot only on dose or dose rate but also on the LET (linearenergy transfer) of the radiation. For example, a particle withan LET of 100 keV/mm causes a minimum of 15 ionizationswhen traversing a single DNA double-helix molecule and,therefore, may induce complex DNA lesions, (1–5) which arerepaired less efficiently or completely (6–8) compared to alower LET radiation, resulting in a higher relative biologicaleffectiveness. When Auger electron emitters (AEE) such asiodine-125 (125I) decay, low-energy Auger electrons with ashort range of 1–10 nm (9) deposit a high amount of energy inan extremely small volume, which is why Auger electronemission is considered as high-LET radiation (10–12). Iodine-125 emits an average of 13 low-energy Auger electrons perdecay (13) and is known to induce complex DNA lesionswhen incorporated into DNA (14, 15), resulting in high-LETtype effects (e.g., cell survival curves with no shoulder region)(16–18).To investigate whether the complexity of DNA lesionsaffects the formation of chromosomal aberrations (CA),three different radiation qualities were studied, namely 137Csc rays (662 keV),125I incorporated into cellular DNA as 125I-iododeoxyuridine (125I-UdR) and 3H, incorporated into cellu-lar DNA as tritiated thymidine. DNA-incorporated tritiatedthymidine is known to have a slightly increased RBE com-pared to low-LET radiation (19) because of the low energyof the b particles emitted during decay (mean energy of 5.7keV). Energy spectra of 125I Auger electrons show maximumenergies up to 35.4 keV, with most Auger electrons havingvery low energies of 20–500 eV (9, 20). To classify the bio-logical effectiveness of the two very different radionuclides,we used c radiation as a reference radiation for comparison.In addition to the impact of varying complexity of DNAlesions induced by the radiation qualities used here on CA,this study also investigates whether the cell cycle phase in1 Marcus Unverricht-Yeboah, Forschungszentrum J€ulich, Departmentof Safety and Radiation Protection, Wilhelm-Johnen-Strasse J€ulich,Germany; email: m.unverricht@fz-juelich.de.479RADIATION RESEARCH 201, 479–486 (2024)0033-7587/24 $15.00Ó2024 by Radiation Research Society.All rights of reproduction in any form reserved.DOI: 10.1667/RADE-23-00158.1Downloaded From: https://bioone.org/journals/Radiation-Research on 23 Jan 2026Terms of Use: https://bioone.org/terms-of-usewhich the exposure occurs has an impact on the inductionof CA. Cell cycle phases differ with respect to 3D chromatinstructure, which may have an impact on the extent of thecomplexity of DNA lesions and/or their repair. Whereaschromatin in S phase and in the transcriptionally active G1phase is relatively relaxed and open, chromatin in G2 phaseand mitosis is more condensed and/or already denselypacked; this is likely the main reason why G2/M cells are themost radiosensitive cells (21). Whether DSBs are convertedinto chromosomal aberrations depends on the fidelity of dif-ferent principal DNA repair pathways: non-homologous endjoining (NHEJ), which is available throughout the cell cycle,and homologous recombination (HR), which is only activein S and G2 phase (22–26).To compare all radiation qualities and to avoid microdo-simetric approaches with rather high dose uncertainties,especially for the low-energy electrons (particularly in thecase of Auger electron emitter (AEE) 125I), the induction ofchromosomal aberrations was normalized to induction ofc-H2AX foci, which are widely regarded and accepted asan indicator of DSB (27–30).
LB  - PUB:(DE-HGF)16
C6  - 38407403
UR  - <Go to ISI:>//WOS:001226507700012
DO  - DOI:10.1667/RADE-23-00158.1
UR  - https://juser.fz-juelich.de/record/1040831
ER  -