Comparison on the repair of potentially lethal damage between exposure to low- and high-LET radiations from Kinetics and fidelity of chromosome rejoining in normal human fibroblasts

Potentially lethal damage (PLD) and its repair (PLDR) were studied inconfluent human fibroblasts by analyzing the kinetics of chromosomebreak rejoining in X-ray or heavy- ion irradiated cells that wereeither held in non-cycling G0 phase of the cell cycle or forced toproliferate immediately after irradiation. Fusion premature chromosomecondensation (PCC) was combined with fluorescence in situhybridization (FISH) to study chromosomal aberrations in interphase.The rejoining kinetics of PCC breaks was similar for each culturecondition after both X-ray and heavy-ion irradiation. However, after 6Gy X-rays, the misrepair in cycling cells was 1.36, 2.8 times higherthan that in non-cycling cells. Twelve hours after exposure to 2 Gy of55keV/um silicon ions the misrepair in cycling cells was 0.56, only 2times higher than that in non-cycling cells. Whereas, after exposureto 2 Gy 200 keV/um or 440 keV/um iron ion beams misrepair was similarin non-cycling and cycling cells. . Since the majority of repair inG0/G1 occurs via the non-homologous end joining process (NHEJ),increased PLDR in X-ray and silicon-ion irradiated cells may resultfrom improved cell cycle specific rejoining fidelity through the NHEJpathway, which is not the case in high-LET iron-ion irradiated cells.Radiation Research Society 58th Annual Meetin