A LET-dependent decrease in the apoptotic response of normal human fibroblast cultures to isosurvival doses of -rays and energetic heavy ions

同一生存線量の線と重粒子線の照射によりヒト正常線維芽細胞に誘発されるアポトーシスはLET依存的に減少する

浜田 信行*; Ni, M.*; 舟山 知夫; 坂下 哲哉; 楚良 桜*; 中野 隆史*; 小林 泰彦

Hamada, Nobuyuki*; Ni, M.*; Funayama, Tomoo; Sakashita, Tetsuya; Sora, Sakura*; Nakano, Takashi*; Kobayashi, Yasuhiko

Biological effectiveness varies with the linear energy transfer (LET) of ionizing radiation. Plentiful evidence has been presented demonstrating that at physically equivalent doses, high-LET energetic heavy ions are more cytotoxic and genotoxic than low-LET photons like X-rays and -rays. Notwithstanding, its potential impact at isosurvival doses is yet to be characterized. Here we investigated the cell-killing effectiveness of -rays (0.2 keV/m) and five different beams of heavy ions with LET ranging from 16.2 to 1610 keV/m in confluent cultures of normal human fibroblasts. The relative biological effectiveness based on the dose giving 10% clonogenic survival peaked at 108 keV/m. In cultures exposed to the 10% survival doses, the yield of apoptotic cells escalated with time postirradiation but declined with LET. Our results imply that the cell death mode differs with LET at isosurvival levels.