title: LET dependency of heavy-ion induced apoptosis in V79 cells.
abstract: We investigated the relationship between the LET values and cell death, defined as either apoptosis or loss of reproductive integrity (reproductive death), using Chinese hamster V79 cells. The cells were irradiated with X-rays or carbon-ion beams from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). Apoptosis was defined based on the morphological change upon treating of cells with caffeine. The apoptotic index, the ratio of apoptotic cells to the total, after exposure to 2 Gy of X-rays was 0.043. Upon irradiation with carbon-ion beams, the index was gradually increased with increasing LET values, reaching a maximum of 0.076 at 110 keV/micron, and then decreased to 0.054 at 237 keV/micron. An analogous pattern of the LET dependence was observed between reproductive death and apoptotic death. The cell-survival values obtained after 2 Gy exposure (SF2) were 0.64, 0.13, and 0.24, respectively. A similar trend was found for the RBE values calculated from the initial slope for both apoptosis and reproductive death. These results strongly suggest that the target for both types of cell death is the same.
authors.affiliation: Space and Particle Radiation Science Research Group, National Institute of Radiological Sciences, Chiba, Japan. mizuho@nirs.go.jp
authors.forename: M
authors.initials: M
authors.lastname: Aoki
authors.forename: Y
authors.initials: Y
authors.lastname: Furusawa
authors.forename: T
authors.initials: T
authors.lastname: Yamada
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D002110:Caffeine / Q000494:pharmacology; D002244:Carbon / Q000009:adverse effects*; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D002460:Cell Line / Q000528:radiation effects; D002843:Chromatin / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000528:radiation effects; D004249:DNA Damage; D053938:DNA Fragmentation; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000187:drug effects / Q000528:radiation effects* / Q000648:ultrastructure; D020450:Heavy Ions / Q000009:adverse effects*; D018499:Linear Energy Transfer; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D012062:Relative Biological Effectiveness; D014965:X-Rays
chemical_list: D002843:Chromatin; D011838:Radiation-Sensitizing Agents; D002110:Caffeine; D002244:Carbon; D004247:DNA