@article{oai:repo.qst.go.jp:00047362,
 author = {Hirayama, Ryoichi and Uzawa, Akiko and Obara, Maki and Takase, Nobuhiro and Koda, Kana and Ozaki, Masakuni and Noguchi, Miho and Matsumoto, Yoshitaka and Li, Huizi and Yamashita, Kei and Koike, Sachiko and Ando, Koichi and Shirai, Toshiyuki and Matsufuji, Naruhiro and Furusawa, Yoshiya and 平山 亮一 and 鵜澤 玲子 and 小原 麻希 and 李 惠子 and 小池 幸子 and 白井 敏之 and 松藤 成弘 and 古澤 佳也},
 journal = {Mutation Research - Genetic Toxicology and Environmental Mutagenesis},
 month = {Nov},
 note = {We determined the relative biological effectiveness (RBE) and oxygen enhancement ratio (OER) of micronuclei (MN) formation in clamped (hypoxic) and non-clamped (normoxic) solid tumors in mice legs following exposure to X-rays and heavy ions. Single-cell suspensions (aerobic) of non-irradiated tumors were prepared in parallel and used directly to determine the radiation response for aerobic cells. Squamous cell carcinoma (SCCVII) cells were transplanted into the right hind legs of syngeneic C3H/He male mice. Irradiation doses with either X-rays or heavy ions at a dose-averaged LET (linear energy transfer) of 14-192keV/μm were delivered to 5-mm diameter tumors and aerobic single-cells in sample-tubes. After irradiation, the tumors were excised and trypsinized to observe MN in single-cells. The single-cell suspensions were used for MN formation assays. The RBE values increased with increasing LET. The maximum RBE values for the three different oxygen conditions; hypoxic tumor, normoxic tumor, and aerobic cells, were 8.18, 5.30, and 3.76 at an LET of 192keV/μm, respectively. After X-irradiation, the OERh/n values (hypoxic tumor/normoxic tumor) were lower than the OERh/a (hypoxic tumor/aerobic cells), and were 1.73 and 2.58, respectively. We found that the OER for the in vivo studies were smaller in comparison to that for the in vitro studies. Both of the OER values at 192keV/μm were small in comparison to those of the X-ray irradiated samples. The OERh/n and OERh/a values at 192keV/μm were 1.12 and 1.19, respectively. Our results suggest that high LET radiation has a large biological effect even if a solid tumor includes substantial numbers of hypoxic cells. To conclude, we found that the RBE values under each oxygen state for non-MN fraction increased with increasing LET and that the OER values for both tumors in vivo and cells in vitro decreased with increasing LET.},
 pages = {41--47},
 title = {Determination of the relative biological effectiveness and oxygen enhancement ratio for micronuclei formation using high-LET radiation in solid tumor cells: An in vitro and in vivo study.},
 volume = {793},
 year = {2015}
}