@article{oai:repo.qst.go.jp:00046593,
 author = {Hirayama, Ryoichi and Uzawa, Akiko and Takase, Nobuhiro and Matsumoto, Yoshitaka and Noguchi, Miho and Koda, Kana and Ozaki, Masakuni and Yamashita, Kei and Li, Huizi and Kase, Yuki and Matsufuji, Naruhiro and Koike, Sachiko and Masunaga, Shinichiro and Ando, Koichi and Okayasu, Ryuichi and Furusawa, Yoshiya and Hirayama, Ryoichi and Uzawa, Akiko and Matsumoto, Yoshitaka and Koda, Kana and Ozaki, Masakuni and Yamashita, Kei and Li, Huizi and Matsufuji, Naruhiro and Koike, Sachiko and Okayasu, Ryuichi and Furusawa, Yoshiya},
 issue = {1-2},
 journal = {Genetic Toxicology and Environmental Mutagenesis : A Section of Mutation Research},
 month = {Aug},
 note = {The aim of this study was to measure the RBE (relative biological effectiveness) and OER (oxygen enhancement ratio) for survival of cells within implanted solid tumors following exposure to 290 MeV/nucleon carbon-ion beams or X-rays.  Squamous cell carcinoma cells (SCCVII) were transplanted into the right hind legs of syngeneic C3H male mice.  Irradiation with either carbon-ion beams with a 6-cm spread-out Bragg peak (SOBP, at 46 and 80 keV/micron) or X-rays was delivered to 5-mm or less diameter tumors.  We defined three different oxygen statuses of the irradiated cells.  Hypoxic and normoxic conditions in tumors were produced by clamping or not clamping the leg to avoid blood flow.  Furthermore, single-cell suspensions were prepared from non-irradiated tumors and directly used to determine the radiation response of aerobic cells.  Single-cell suspensions (aerobic condition) were fully air-saturated.  Single-cell suspensions were prepared from excised and trypsinized tumors, and were used for in vivo-in vitro colony formation assays to obtain cell survival curves.  The RBE and OER values for cell survival were evaluated by D10 values (the dose required to reduce surviving fraction to 10%).  The RBE values increased with increasing LET in SOBP beams.  The maximum RBE values in three different oxygen conditions; hypoxic tumor, normoxic tumor and aerobic cells, were 2.16, 1.76 and 1.66 at an LET of 80 keV/micron, respectively.  After X-ray irradiation the OERh/n values (hypoxic tumor/normoxic tumor) were lower than the OERh/a (hypoxic tumor/aerobic cells), and were 1.87 +/- 0.13 and 2.52 +/- 0.11, respectively.  The aerobic cell samples that were sensitive to X-rays under normoxic conditions may contain a hypoxic fraction.  In fact we found that the normoxic tumors (< 5 mm diameter) contained approximately 10% hypoxic cells using the paired survival curve method with three or more independent experiments.  The OER values of carbon-ion irradiated samples were small in comparison to that of X-ray irradiated samples.  However, no significant changes of the OER at proximal and distal positions within the SOBP carbon-ion beams were observed in both pairs.  To conclude, we found that the RBE values for cell survival increased with increasing LET and that the OER values changed little with increasing LET within the SOBP carbon-ion beams.},
 pages = {146--151},
 title = {Evaluation of SCCVII tumor cell survival in clamped and non-clamped solid tumors exposed to carbon-ion beams in comparison to X-rays},
 volume = {756},
 year = {2013}
}