title: Radiation-quality dependent cellular response in mutation induction in normal human cells.
abstract: We studied cellular responses in normal human fibroblasts induced with low-dose (rate) or low-fluence irradiations of different radiation types, such as gamma rays, neutrons and high linear energy transfer (LET) heavy ions. The cells were pretreated with low-dose (rate) or low-fluence irradiations (approximately 1 mGy/7-8 h) of 137Cs gamma rays, 241Am-Be neutrons, helium, carbon and iron ions before irradiations with an X-ray challenging dose (1.5 Gy). Helium (LET = 2.3 keV/microm), carbon (LET = 13.3 keV/microm) and iron (LET = 200 keV/microm) ions were produced by the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. No difference in cell-killing effect, measured by a colony forming assay, was observed among the pretreatment with different radiation types. In mutation induction, which was detected in the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus to measure 6-thioguanine resistant clones, there was no difference in mutation frequency induced by the X-ray challenging dose between unpretreated and gamma-ray pretreated cells. In the case of the pretreatment of heavy ions, X-ray-induced mutation was around 1.8 times higher in helium-ion pretreated and 4.0 times higher in carbon-ion pretreated cells than in unpretreated cells (X-ray challenging dose alone). However, the mutation frequency in cells pretreated with iron ions was the same level as either unpretreated or gamma-ray pretreated cells. In contrast, it was reduced at 0.15 times in cells pretreated with neutrons when compared to unpretreated cells. The results show that cellular responses caused by the influence of hprt mutation induced in cells pretreated with low-dose-rate or low-fluence irradiations of different radiation types were radiation-quality dependent manner.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan. m_suzuki@nirs.go.jp
authors.forename: Masao
authors.initials: M
authors.lastname: Suzuki
authors.forename: Chizuru
authors.initials: C
authors.lastname: Tsuruoka
authors.forename: Yukio
authors.initials: Y
authors.lastname: Uchihori
authors.forename: Hisashi
authors.initials: H
authors.lastname: Kitamura
authors.forename: Cui Hua
authors.initials: CH
authors.lastname: Liu
mesh_terms: D002470:Cell Survival / Q000528:radiation effects*; D002477:Cells; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D009154:Mutation / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology* / Q000528:radiation effects