Abstract
Heavy ion beams provokes heavier damages to cells than γ-, and X-ray at the same absorbed dose. On the other hand, proton beams induce almost the same damages as X-ray and γ-ray done. Such a difference seems to be due to the different distribution pattern of deposited energies along the particle track, rather than the total amount of deposited energy. The density of cellular damages generated along the track of heavy ions with high linear energy transfer (LET) might be higher than that of protons, X-rays, and γ-rays.
After the application of stimuli evoking DNA double-strand break (DSB) such as an ionizing radiation to a cell, spots of phospholyrated histone 2 AX (γ-H2AX), so-called foci, appear in the cell nucleus. γ-H2AX is thought to provide scaffolds for DSB repair proteins such as Mre11/Rad50/NBS1 complex, Rad51, Ku70, and DNA-PKcs. H2AX surrounding the DSB point phosphorylated at the serine 139 residue within a few minute after the DSB-evoking stimuli. Therefore, it is expected that the morphology of γ-H2AX foci reflect the energy deposition pattern along the particle track.
In the present study, we immunocytochemically stained γ-H2AX foci after the irradiation of X-rays(130 kVp), proton beams (200 MeV), and carbon beams (350 MeV), and compared the morphological aspects of the foci by means of a laser-confocal microscopy. We report some structural differences of γ-H2AX foci formed after carbon beam irradiation.
