title: [Exploration of relationship between the expression level of DNA polymerase beta and 60Co gamma-ray radiosensitivity].
abstract: OBJECTIVE
  To explore the relationship between the expression level of DNA polymerase beta (pol beta) and 60Co gamma-ray radiosensitivity and provide a basis on improving the efficiency of radiotherapy theoretically.
  
  
  METHODS
  pol beta wild-type cells (pol beta +/+), pol beta null cells (pol beta -/-) and pol beta overexpressed cells (polp beta oe) were applied as a model system. The radiosensitivity of 60Co gamma-ray on the cell was detected by MTT assay and clone formation assay. The DCFH-DA fluorescent probe was used to examine the cellular ROS after 60Co gamma-rays radiation.
  
  
  RESULTS
  MTT assay showed that after radiation by 60Co gamma-rays followed with 72 h incubation, the cell viabilities in the three kinds of cells decreased significantly with a dose-response relationship (r-/+ = -0.976, r-/- = -0.977, r(oe) = -0.982, P<0.05). In addition, the viability of pol beta -/- cell was lower than those of other two kinds of cells at the same dose (P<0.05). Likewise, the colony number and colony formation rate in all tested cells also decreased after exposure to 60Co gamma-rays. The ROS level in the three kinds of cells was enhanced after treatment with 60Co gamma-ray, and the ROS level in pol beta -/- cells was much higher than that in the other two kinds of cells (P<0.05).
  
  
  CONCLUSIONS
  Cell death caused by 60Co gamma-ray may associated with the DNA oxidative damage mediated by ROS; Overexpression of pol beta could protect against oxidative DNA damage, thus the cell apoptosis/death, thereby leading to reducing the radiosensitivity of 60Co gamma-rays, while null of DNA pol beta could increase radiosensitivity of 60Co gamma-rays by compromising the DNA repair.
authors.affiliation: Department of Environmental Health, West China School of Public Health, Sichuan University, Chengdu 610041, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Cui
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
authors.forename: Mo
authors.initials: M
authors.lastname: Yang
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Mei
authors.initials: M
authors.lastname: Wu
authors.forename: Zun-zhen
authors.initials: ZZ
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003037:Cobalt Radioisotopes / Q000494:pharmacology*; D004249:DNA Damage / Q000528:radiation effects*; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects*; D005720:Gamma Rays; D051379:Mice; D011836:Radiation Tolerance / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D003037:Cobalt Radioisotopes; D017382:Reactive Oxygen Species; D019951:DNA Polymerase beta