title: The mechanism of radiosensitization by YM155, a novel small molecule inhibitor of survivin expression, is associated with DNA damage repair.
abstract: OBJECTIVE
  Survivin, a member of the inhibitor of apoptosis protein family, is an attractive target for cancer therapy. We investigated the effects of YM155, a small molecule inhibitor of survivin expression, on the radiosensitivity of human non-small cell lung cancer (NSCLC) cell lines and elucidated a relationship between the cellular localization of survivin and DNA double-strand break repair.
  
  
  METHODS
  The cellular distribution of survivin was determined by Western blotting of subcellular fractions and by immunofluorescent staining in A549 NSCLC cells. Radiation-induced DNA damage was evaluated based on histone H2AX phosphorylation and foci formation. The relationship between the cellular localization of survivin and DNA double-strand break repair was analyzed by Western blotting and co-immunoprecipitations.
  
  
  RESULTS
  YM155 down-regulated survivin expression in NSCLC cells in a concentration- and time-dependent manner. An in vitro clonogenic survival assay revealed that YM155 increased the sensitivity of NSCLC cells to radiation. After irradiation, we observed a rapid accumulation of survivin in the nucleus. An immunofluorescent analysis of histone x03B3;-H2AX demonstrated that the inhibition of survivin expression by YM155 resulted in impaired DNA double-strand break repair. Co-immunoprecipitation assays using nuclear extracts revealed an interaction between survivin, Ku70, x03B3;-H2AX, and DNA-PKcs. Furthermore, S2056 autophosphorylation of DNA-PKcs was reduced in survivin-depleted cells.
  
  
  CONCLUSIONS
  These results suggested that YM155 sensitized NSCLC cells to radiation, at least in part by inhibiting DNA repair and enhancing apoptosis via the down-regulation of survivin expression. YM155 pretreatment inhibited DNA-PKcs autophosphorylation at S2056. Nuclear survivin was involved in DNA double-strand break repair via interactions with members of the DNA double-strand break repair machinery.
authors.forename: Songliu
authors.initials: S
authors.lastname: Hu
authors.forename: Songbin
authors.initials: S
authors.lastname: Fu
authors.forename: Xiangying
authors.initials: X
authors.lastname: Xu
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.forename: Jianyu
authors.initials: J
authors.lastname: Xu
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Qu
authors.forename: Hongyang
authors.initials: H
authors.lastname: Yu
authors.forename: Shan
authors.initials: S
authors.lastname: Lu
authors.forename: Wenxin
authors.initials: W
authors.lastname: Li
mesh_terms: D017209:Apoptosis; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism; D009285:Naphthoquinones / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D000077022:Survivin
chemical_list: C107489:BIRC5 protein, human; C468783:H2AX protein, human; D006657:Histones; D007093:Imidazoles; D051034:Inhibitor of Apoptosis Proteins; D009285:Naphthoquinones; D011838:Radiation-Sensitizing Agents; D000077022:Survivin; C523798:sepantronium