Lineal energy-based evaluation of oxidative DNA damage induced by proton beams and X-rays.
OBJECTIVE
To determine the oxidative capabilities of proton beams compared to X-rays based on lineal energy (y).


METHODS
Microdosimetry was used to determine y-values of 155 MeV protons. Salmon testes deoxyribonucleic acid (ST-DNA) in solution and human tumor cells (MOLT-4) were irradiated with 200 kV X-rays (X) or 155 MeV protons at their plateau (P) and near their Bragg-peak (B). 8-Hydroxydeoxyguanosine (8-OHdG) production was determined by high performance liquid chromatography. Double-strand breaks (DSB) in ST-DNA were evaluated by agarose gel electrophoresis and DSB in cell nuclei were evaluated by immunocytochemical analysis of phosphorylated histone H2AX (γH2AX) foci. Edaravone was used as a radical scavenger.


RESULTS
8-OHdG yields in ST-DNA were significantly higher with X than with P or B, and they were significantly higher with P than with B. DSB yields in ST-DNA were higher with P than with B or X, although not statistically significant, and were nearly equal with B and X. Although γH2AX foci formation in MOLT-4 cells after each irradiation type was nearly identical, the addition of edaravone significantly inhibited foci formation only with X.


CONCLUSIONS
Our results indicated that radical-induced indirect DNA damage was significantly lower with proton beams than with X-rays.
Proton Medical Research Center, Graduate School of Comprehensive Human Sciences, University of Tsukuba.
Zhengshan
Z
Hong
Yuki
Y
Kase
Takashi
T
Moritake
Ariungerel
A
Gerelchuluun
Lue
L
Sun
Kenshi
K
Suzuki
Toshiyuki
T
Terunuma
Kiyoshi
K
Yasuoka
Hiroaki
H
Kumada
Kazunori
K
Anzai
Hideyuki
H
Sakurai
Takeji
T
Sakae
Koji
K
Tsuboi
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D045744:Cell Line, Tumor; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D018499:Linear Energy Transfer / Q000528:radiation effects*; D018384:Oxidative Stress / Q000528:radiation effects*; D017785:Photons / Q000009:adverse effects; D011522:Protons / Q000009:adverse effects*; D011874:Radiometry; D014965:X-Rays / Q000009:adverse effects
C468783:H2AX protein, human; D006657:Histones; D011522:Protons; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine