title: Dose-rate effect was observed in T98G glioma cells following BNCT.
abstract: BACKGROUND
  It is generally said that low LET radiation produce high dose-rate effect, on the other hand, no significant dose rate effect is observed in high LET radiation. Although high LET radiations are produced in BNCT, little is known about dose-rate effect of BNCT.
  
  
  METHODS
  T98G cells, which were tumor cells, were irradiated by neutron mixed beam with BPA. As normal tissue derived cells, Chinese hamster ovary (CHO-K1) cells and DNA double strand breaks (DNA-DSBs) repair deficient cells, xrs5 cells were irradiated by the neutrons (not including BPA). To DNA-DSBs analysis, T98G cells were stained immunochemically with 53BP1 antibody. The number of DNA-DSBs was determined by counting 53BP1 foci.
  
  
  RESULTS
  There was no dose-rate effect in xrs5 cells. D0 difference between 4cGy/min and 20cGy/min irradiation were 0.5 and 5.9 at the neutron and gamma-ray irradiation for CHO-K1, and 0.3 at the neutron for T98G cells. D0 difference between 20cGy/min and 80cGy/min irradiation for T98G cells were 1.2 and 0.6 at neutron irradiation plus BPA and gamma-ray. The differences between neutron irradiations at the dose rate in T98G cells were supported by not only the cell viability but also 53BP1 foci assay at 24h following irradiation to monitor DNA-DSBs.
  
  
  CONCLUSIONS
  Dose-rate effect of BNCT when T98G cells include 20ppm BPA was greater than that of gamma-ray irradiation. Moreover, Dose-rate effect of the neutron beam when CHO-K1 cells did not include BPA was less than that of gamma-ray irradiation These present results may suggest the importance of dose-rate effect for more efficient BNCT and the side effect reduction.
authors.affiliation: Kyoto University, Research Reactor Institute, Osaka 590-0494, Japan. Electronic address: kinashi@rri.kyoto-u.ac.jp.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kinashi
authors.affiliation: Kyoto University, Research Reactor Institute, Osaka 590-0494, Japan.
authors.forename: Kakuji
authors.initials: K
authors.lastname: Okumura
authors.affiliation: National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kubota
authors.affiliation: Osaka High-technology College, Osaka, Japan.
authors.forename: Erika
authors.initials: E
authors.lastname: Kitajima
authors.affiliation: National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Okayasu
authors.affiliation: Kyoto University, Research Reactor Institute, Osaka 590-0494, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Ono
authors.affiliation: Kyoto University, Research Reactor Institute, Osaka 590-0494, Japan.
authors.forename: Sentaro
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D001896:Boron Compounds / Q000627:therapeutic use*; D016754:Boron Neutron Capture Therapy / Q000379:methods*; D016466:CHO Cells; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics* / Q000528:radiation effects*; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D005909:Glioblastoma / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D001896:Boron Compounds; D010649:Phenylalanine; C033685:4-boronophenylalanine
keywords: BNCT; DNA-DSBs; Dose-rate effect; Glioma