Exploration of Over Kill Effect' of High-LET Ar- and Fe-ions by Evaluating the Fraction of Non-hit Cell and Interphase Death

• MEHNATI Parinaz

  Department of Medical Biophysics & Radiation Biology, Graduate School of Medical Sciences, Kyushu University

• MORIMOTO Shigeko

  RIKEN

• YATAGAI Fumio

  RIKEN

• FURUSAWA Yoshiya

  National Institute of Radiological Sciences

• KOBAYASHI Yasuhiko

  Biotech Laboratory, JAERI

• WADA Seiichi

  Biotech Laboratory, JAERI

• KANAI Tatsuaki

  National Institute of Radiological Sciences

• HANAOKA Fumio

  RIKEN Graduate School of Frontier Biosciences, Osaka University

• SASAKI Hiroshi

  Department of Medical Biophysics & Radiation Biology, Graduate School of Medical Sciences, Kyushu University

抄録

The reason why RBE for cell killing fell to less than unity (1.0) with very high-LET heavy-ions (⁴⁰Ar: 1,640 keV/μm; ⁵⁶Fe: 780, 1,200, 2,000 keV/μm) was explored by evaluating the fraction of non-hit cell (time-lapse observation) and cells undergoing interphase death (calculation based on our previous data). CHO cells were exposed to 4 Gy (30% survival dose) of Ar (1,640 keV/μm) or Fe-ions (2,000 keV/μm). About 20% of all cells were judged to be non-hit, and about 10% cells survived radiation damage. About 70% cells died after dividing at least once (reproductive death) or without dividing (interphase death). RBE for reproductive (RBE[R]) and interphase (RBE[I]) death showed a similar LET dependence with maximum around 200 keV/μm. In this LET region, at 30% survival level, about 10% non-survivors underwent interphase death. The corresponding value for very high-LET Fe-ions (2,000 keV/μm) was not particularly high (~15%), whereas that for X-rays was less than 3%. However, reproductive death (67%) predominated over interphase death (33%) even in regard to rather severely damaged cells (1% survival level) after exposure to Fe-ions (2,000 keV/μm ). These indicate that interphase death is a type of cell death characteristic for the cells exposed to high-LET radiation and is not caused by `cellular over kill effect'. Both NHF37 (non-hit fraction at 37% survival) and inactivation cross-section for reproductive death (σ[R]) began to increase when LET exceeded 100 keV/μm. The exclusion of non-hit fraction in the calculation of surviving fraction partially prevented the fall of RBE[R] when LET exceeded 200 keV/μm. On the other hand, the mean number of lethal damage per unit dose (NLD/Gy) showed the same LET-dependent pattern as RBE[R]. These suggest that the increase in non-hit fraction and σ[R] with an increasing LET is caused by enhanced clustering of ionization and DNA damage which lowers the energy efficiency for producing damage and RBE.<br>

収録刊行物

• Journal of Radiation Research

  Journal of Radiation Research 46 (3), 343-350, 2005

  Journal of Radiation Research 編集委員会

キーワード

• Over Kill Effect
• RBE vs LET Relation
• Heavy Ions
• Non-hit Cell
• Interphase Death

詳細情報

• CRID: 1390282680191860736
• NII論文ID: 110004041134
• NII書誌ID: AA00705792
• DOI: 10.1269/jrr.46.343
• COI: 1:STN:280:DC%2BD2MrjsFGhsw%3D%3D
• ISSN: 13499157
• ISSN: 04493060
• NDL書誌ID: 7443609
• PubMed: 16210791
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I7443609
• Web Site: http://academic.oup.com/jrr/article-pdf/46/3/343/2722196/jrr-46-343.pdf
• Web Site: http://dl.ndl.go.jp/info:ndljp/pid/10918704
• Web Site: https://search.jamas.or.jp/link/ui/2006294313
• 本文言語コード: en
• データソース種別:
  • JaLC
  • NDL
  • Crossref
  • PubMed
  • NDL-Digital
  • CiNii Articles
  • KAKEN
• 抄録ライセンスフラグ: 使用不可