title: The radiosensitizing effect of Paeonol on lung adenocarcinoma by augmentation of radiation-induced apoptosis and inhibition of the PI3K/Akt pathway.
abstract: OBJECTIVE
  To investigate the radiosensitizing effect and mechanism of action by the natural product Paeonol on lung adenocarcinoma both in vitro and in vivo.
  
  
  METHODS
  Two lung adenocarcinoma cell lines (human lung adenocarcinoma cell line A549 and mouse Lewis lung carcinoma (LLC) cell line) were chosen for this research. In order to select the experimental concentrations of Paeonol, cytotoxicity was determined using a MTT (3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide) assay. A clonogenic assay was performed to measure the radiosensitizing effects. Apoptosis was determined by the Tunel (terminal deoxynucleotidyl transferase-mediated dUTP nick and labeling) assay and flow cytometry. Protein expression was analyzed by Western blotting. To test the radiosensitizing effect in vivo, a transplanted tumor model was established.
  
  
  RESULTS
  The MTT assay showed that Paeonol inhibited proliferation of cells. Paeonol concentration ranged from an IC5 (5% inhibiting concentration) to an IC20 and was used at non-toxic concentrations for subsequent experiments. The clonogenic assay showed that Paeonol enhanced the radiosensitivity of cells. Data from the Tunel assay and flow cytometry verified that Paeonol enhanced radiation-induced apoptosis. Paeonol inhibited the activation of the PI3K/AKT (Phosphatidylinositol 3-kinase/ Protein Kinase B) pathway and down-regulated the expression of COX-2 (Cyclooxygenase-2) and Survivin. Paeonol (1718 mg/kg) combined with 10 Gy irradiation inhibited the growth of a transplanted tumor model in vivo, resulting in the longest tumor growth time, tumor growth delay and the highest inhibition ratio when compared with the radiotherapy alone group.
  
  
  CONCLUSIONS
  It is reported for the first time that Paeonol has a radiosensitizing effect on lung adenocarcinoma both in vitro and in vivo. This effect could be related to the augmentation of radiation-induced apoptosis and the inhibition of the PI3K/Akt signalling pathway and its downstream proteins: COX-2 and Survivin.
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Anhui Medical University , Hefei.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lei
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Li
authors.forename: Wen-Sen
authors.initials: WS
authors.lastname: Jin
authors.forename: Wan-Ren
authors.initials: WR
authors.lastname: Peng
authors.forename: Cong-Jun
authors.initials: CJ
authors.lastname: Zhang
authors.forename: Li-Jia
authors.initials: LJ
authors.lastname: Bu
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Du
authors.forename: Tai
authors.initials: T
authors.lastname: Ma
authors.forename: Guo-Ping
authors.initials: GP
authors.lastname: Sun
mesh_terms: D000098:Acetophenones / Q000494:pharmacology*; D000230:Adenocarcinoma / Q000188:drug therapy* / Q000532:radiotherapy*; D000818:Animals; D017209:Apoptosis; D018827:Carcinoma, Lewis Lung; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D051546:Cyclooxygenase 2 / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D015398:Signal Transduction; D000077022:Survivin; D014410:Tumor Stem Cell Assay
chemical_list: D000098:Acetophenones; C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D011838:Radiation-Sensitizing Agents; D000077022:Survivin; C013638:paeonol; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D019869:Phosphatidylinositol 3-Kinases; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt