title: [Expression of S100A2 in secondarily radioresistant pancreatic cancer cells and significance thereof].
abstract: OBJECTIVE
  To investigate the association of S100A2 expression with the secondary radioresistance in pancreatic cancer cells.
  
  
  METHODS
  Human pancreatic cancer cells of the line SW1990, parental line, and the secondarily radioresistant human pancreatic cancer cells of the line SW1990/R were cultured and inoculated into the wells of a 6-well plate. 5-Aza-2'-deoxycytidine (5-aza-DC) of different concentrations was added into the culture fluid. Forty-eight hours later X-ray irradiation was conducted. Cloning efficiency assay was used to assess the cell survival. The cell cycle was analyzed by flow cytometry. The mRNA expression of S100A2 was examined by real-time RT-PCR and the protein expression of S100A2 was examined by immunofluorescence quantitative analysis.
  
  
  RESULTS
  The S100A2 mRNA expression level of the SW1990 line was significantly higher than that of the SW1990/R line. Treated by 5-aza-dC, the S100A2 mRNA expression level of the SW1990/R line increased by 2 approximately 3 times. The S100A2 protein expression level of the SW1990 line was significantly higher than that of the SW1990/R line (t = 3.648, P = 0.022). Treated by 5-aza-dC, the S100A2 protein expression level of the SW1990/R line increased, by 5 times at most (t = -11.404, P = 0.001). The G(2)/M of the SW1990 line was 16.2%, significantly higher than that of the SW1990/R line (16.2%), and the G(2)/M levels of the SW1990/R line treated by 5-aza-dC of different concentrations were all increased dose-dependently. The colony-forming rates of the SW1990/R line of the 5-aza-dC + irradiation groups were all significantly lower than that of the SW1990/R line of the pure irradiation group, even the dose of 5-aza-dC was as low as 0.025 microm. The SF2 (cell survival rate with the irradiation dose of 2 Gy) of the 5-aza-dC + irradiation group was 0.122, significantly lower than that of the pure irradiation group (0.460).
  
  
  CONCLUSIONS
  The expression level of S100A2 is low in the radioresistant pancreatic cancer cells, which may be one of the mechanisms of radioresistance of these cells.
authors.affiliation: Department of General Surgery, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Wen
authors.forename: Yu-pei
authors.initials: YP
authors.lastname: Zhao
authors.forename: Ge
authors.initials: G
authors.lastname: Chen
authors.forename: Fu-quan
authors.initials: FQ
authors.lastname: Zhang
authors.forename: Tai-ping
authors.initials: TP
authors.lastname: Zhang
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D002630:Chemotactic Factors / Q000096:biosynthesis / Q000235:genetics*; D000077209:Decitabine; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D009418:S100 Proteins / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D002630:Chemotactic Factors; D012333:RNA, Messenger; D009418:S100 Proteins; C098997:S100A2 protein, human; D000077209:Decitabine; D001374:Azacitidine