title: Effects of acute and chronic hypoxia on the radiosensitivity of gastric and esophageal cancer cells.
abstract: OBJECTIVE
  The aim of this study was to examine the effects of hypoxia on radiosensitivity and to analyze the mechanisms responsible for radiation resistance in gastric and esophageal cancer.
  
  
  METHODS
  A gastric cancer cell line, OCUM-12, and an esophageal cancer cell line, TE-6, were used. The effects of hypoxia with irradiation on the growth-activity, cell cycle distribution, and gene expression were examined.
  
  
  RESULTS
  Both acute and chronic hypoxia decreased radiosensitivity of cancer cells. The radiosensitivity of chronic hypoxic cells was significantly enhanced by reoxygenation. Acute and chronic all hypoxia reduced the percentage of cells in the G(2)/M and S phases, respectively. In acute hypoxia, the mRNA expression of BRCA1 and BRCA2 was reduced in cancer cells. Reoxygenation increased the expression of BRCA1 and BRCA2.
  
  
  CONCLUSIONS
  Hypoxia is associated with radiation resistance. Therefore, reoxygenation may enhance the radiosensitivity of hypoxic cells. BRCA1 and BRCA2 may be associated with factors for radiation resistance by regulation of cell cycle progression.
authors.affiliation: Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Kato
authors.forename: Masakazu
authors.initials: M
authors.lastname: Yashiro
authors.forename: Yuhiko
authors.initials: Y
authors.lastname: Fuyuhiro
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Kashiwagi
authors.forename: Junko
authors.initials: J
authors.lastname: Matsuoka
authors.forename: Toshiki
authors.initials: T
authors.lastname: Hirakawa
authors.forename: Satoru
authors.initials: S
authors.lastname: Noda
authors.forename: Naoki
authors.initials: N
authors.lastname: Aomatsu
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Taro
authors.initials: T
authors.lastname: Matsuzaki
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Sawada
authors.forename: Masaichi
authors.initials: M
authors.lastname: Ohira
authors.forename: Kosei
authors.initials: K
authors.lastname: Hirakawa
mesh_terms: D015687:Cell Hypoxia / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D004938:Esophageal Neoplasms / Q000235:genetics / Q000473:pathology*; D016193:G1 Phase / Q000187:drug effects / Q000528:radiation effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D010100:Oxygen / Q000494:pharmacology; D011836:Radiation Tolerance / Q000187:drug effects / Q000528:radiation effects; D016192:Resting Phase, Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D013274:Stomach Neoplasms / Q000235:genetics / Q000473:pathology*; D014410:Tumor Stem Cell Assay; D014965:X-Rays
chemical_list: D010100:Oxygen