title: Radiation-induced hyperproliferation of intestinal crypts results in elevated genome instability with inactive p53-related genomic surveillance.
abstract: OBJECTIVE
  Radiation-induced hyperproliferation of intestinal crypts is well documented, but its potential tumorigenic effects remain elusive. Here we aim to determine the genomic surveillance process during crypt hyperproliferation, and its consequential outcome after ionizing radiation.
  
  
  METHODS
  Crypt regeneration in the intestine was induced by a single dose of 12Gy abdominal irradiation. γ-H2AX, 53BP1 and DNA-PKcs were used as DNA repair surrogates to investigate the inherent ability of intestinal crypt cells to recognize and repair double-strand breaks. Ki67 staining and the 5-bromo-2'-deoxyuridine incorporation assay were used to study patterns of cell proliferation in regenerating crypts. Staining for ATM, p53, Chk1 and Chk2 was performed to study checkpoint activation and release. Apoptosis was evaluated through H&E staining and terminal deoxynucleotidyl transferase (dUTP) nick-end labeling.
  
  
  RESULTS
  The ATM-p53 pathway was immediately activated after irradiation. A second wave of DSBs in crypt cells was observed in regenerating crypts, accompanied with significantly increased chromosomal bridges. The p53-related genomic surveillance pathway was not active during the regeneration phase despite DSBs and chromosomal bridges in the cells of regenerating crypts. Non-homologous end joining (NHEJ) DSBs repair was involved in the DSBs repair process, as indicated by p-DNA-PKcs staining.
  
  
  CONCLUSIONS
  Intestinal crypt cells retained hyperproliferation with inactive p53-related genomic surveillance system. NHEJ was involved in the resultant genomic instability during hyperproliferation.
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; The School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, PR China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, PR China; University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 10049, PR China; The National Laboratory for the Heavy Ion Research Facility in Lanzhou, Lanzhou 730000, PR China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Ma
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, PR China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, PR China; University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 10049, PR China.
authors.forename: Chao
authors.initials: C
authors.lastname: Sun
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 10049, PR China; The National Laboratory for the Heavy Ion Research Facility in Lanzhou, Lanzhou 730000, PR China.
authors.forename: Yupei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 10049, PR China; The National Laboratory for the Heavy Ion Research Facility in Lanzhou, Lanzhou 730000, PR China.
authors.forename: Yang
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Heavy Ion Radiation Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, PR China; The National Laboratory for the Heavy Ion Research Facility in Lanzhou, Lanzhou 730000, PR China. Electronic address: zhangh@impcas.ac.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000528:radiation effects*; D004260:DNA Repair / Q000528:radiation effects*; D005720:Gamma Rays / Q000009:adverse effects; D016158:Genes, p53 / Q000235:genetics*; D042822:Genomic Instability / Q000235:genetics*; D007413:Intestinal Mucosa / Q000473:pathology* / Q000528:radiation effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL
keywords: Hyperproliferation; Intestinal crypt; NHEJ