title: Enhancement of DNA double-strand break induction and cell killing by K-shell absorption of phosphorus in human cell lines.
abstract: To investigate an enhancement of DNA double-strand break (DSB) induction and cell killing effect by K-shell ionization of phosphorus atoms and Auger electrons on human cell lines.
  
  
  
  Induction of DSB, DNA damage responses, cell cycle distributions, and cell killing effects were investigated after exposures of the cells with monochromatic synchrotron radiation soft X-rays of 2153 and 2147 eV, which were the resonance peak and off peak, respectively, of the K-shell photoabsorption of phosphorus.
  
  
  
  Higher biological effects in the cells irradiated with soft X-rays at 2153 eV than at 2147 eV were observed in (i) the efficiency of 53BP1/γ-H2AX co-localized foci formation per dose and residual number of foci, (ii) prolonged phosphorylation levels of DSB repair and/or cell cycle checkpoint related proteins and G2 arrest, (iii) the cell killing effects at the 10% survival level of normal human fibroblasts, HeLa cells, and human glioblastoma M059K cells (1.2-1.5 times higher) and that of human ataxia telangiectasia mutated (ATM)-defective cells and glioblastoma DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-defective cells (1.2 times).
  
  
  
  The yield of DSB and partly less-reparable complex DNA damage induction in human cells was enhanced by K-shell photoabsorption of phosphorus and low-energy Auger electrons.
authors.affiliation: a Radiation Safety Research Center , Central Research Institute of Electric Power Industry , Komae , Tokyo.
authors.forename: Masanori
authors.initials: M
authors.lastname: Tomita
authors.affiliation: a Radiation Safety Research Center , Central Research Institute of Electric Power Industry , Komae , Tokyo.|b Proton Medical Research Group, Research and Development Department , The Wakasa Wan Energy Research Center , Tsuruga-shi , Fukui.
authors.forename: Munetoshi
authors.initials: M
authors.lastname: Maeda
authors.affiliation: c Photon Factory , Institute of Material Structure Sciences, High Energy Accelerator Research Organization (KEK) , Tsukuba , Ibaraki.
authors.forename: Noriko
authors.initials: N
authors.lastname: Usami
authors.affiliation: d Research Group for Radiation and Biomolecular Science, Quantum Beam Science Center , Japan Atomic Energy Agency , Tokai , Ibaraki , Japan.
authors.forename: Akinari
authors.initials: A
authors.lastname: Yokoya
authors.affiliation: d Research Group for Radiation and Biomolecular Science, Quantum Beam Science Center , Japan Atomic Energy Agency , Tokai , Ibaraki , Japan.
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Watanabe
authors.affiliation: c Photon Factory , Institute of Material Structure Sciences, High Energy Accelerator Research Organization (KEK) , Tsukuba , Ibaraki.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D065638:Absorption, Radiation; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics*; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000235:genetics*; D004307:Dose-Response Relationship, Radiation; D004583:Electrons / Q000627:therapeutic use; D006801:Humans; D009374:Neoplasms, Experimental / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy*; D010758:Phosphorus / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D010758:Phosphorus
keywords: Auger effect; DNA repair; Soft X-rays; cell death; double-strand break