Induction and Rejoining of DNA Double Strand Breaks Assessed by H2AX Phosphorylation in Melanoma Cells Irradiated with Proton and Lithium Beams

Induction of in situ DNA double-strand breaks and apoptosis by 200 MeV protons and 10 MV X-rays in human tumour cell lines

“…Since their method to detect DDSB was pulsed field gel electrophoresis and the irradiation dose was 108 Gy, their results and ours may not be directly comparable. Thus, although the results obtained here may differ in part from previously published studies (Belli et al 1996, Ibań ez et al 2009), the reasons for these differences are not well clarified, and continued data analysis is required to elucidate the mechanisms that underlie the differences.…”

“…We found that the number of DDSB induced in the middle of 6 cm SOBP of 200 MeV protons in early periods after irradiation was significantly higher than that induced by 10 MV X-rays, which has not yet been reported. Ibań ez et al reported that there was no significant increase in the number of foci after irradiation at plateau and at Bragg peak of low energy proton beams compared to that induced 30 min after grays irradiation (Ibań ez et al 2009). The estimated energy of protons used in our study ranges from 0-60 MeV in the middle of SOBP with an estimated dose-average LET of 2.2 keV/mm, and a reference radiation quality used here was 10 MV X-rays.…”

“…Thus, the difference in the number of foci most likely represents a direct measure of the difference in radiation quality. It has been reported that foci become visible 10 min after irradiation and reach a maximum number at 30 min (Jakob et al 2003, Pilch et al 2003, Desai et al 2005aand 2005b, Mahrhofer et al 2006, Kinner et al 2008, Ibań ez et al 2009). After this point, the number of foci decreases gradually along with rejoining by repair processes, which is compatible with our observations in this study.…”

“…Also reported values of dose average LET of 60 Co gamma rays range from 0.2-0.49 (Ibań ez et al 2009, International Commission on Radiation Units and Measurements (ICRU) report 16, 197016, , Ziegler et al 1985. These values are probably without cut-off energy values (unrestricted).…”

The DNA-Damage Response to Ionizing Radiation in Human Lymphocytes

“…Furthermore , we found a size increase of -H2AX foci in cells irradiated with protons, as compared with gamma irradiations, probably as a consequence of DSBs clusters induced by high-LET radiation. Our results are in accordance with those in melanoma cells exposed to low-and high-LET radiation (Ibañez et al, 2009). …”