title: Inhibition of signal transducer and activator of transcription 3 and cyclooxygenase-2 is involved in radiosensitization of cepharanthine in HeLa cells.
abstract: OBJECTIVE
  To investigate the radiosensitizing effects of cepharanthine (CEP) in the human cervical adenocarcinoma HeLa cell line and to examine the underlying mechanisms.
  
  
  METHODS
  Survival of HeLa cells after treatment with or without ionizing radiation (IR) and CEP administration was investigated. MTT assays and apoptosis analysis were used to assess cytotoxicity. Nude mouse xenografts were established to evaluate the antitumor effects of CEP and IR in vivo. Expression of signal transducer and activator of transcription 3 (STAT3) and its downstream signaling molecules as well as cyclooxygenase-2 (COX-2) were examined by Western blot analysis.
  
  
  RESULTS
  Clonogenic assays showed that treatment with CEP and IR resulted in significant radiosensitization. Cepharanthine and IR treatment achieved maximum cytotoxic effects on HeLa cells with regard to apoptosis induction. Cepharanthine efficiently decreased IR-induced STAT3 and COX-2 activation. The STAT3 target genes, including the antiapoptotic Bcl-2 and the cell cycle regulator c-Myc, were decreased concomitantly. In vivo administration of CEP (20 mg/kg every 2 days) combined with radiation in HeLa xenografts enhanced tumor growth delay and apoptosis (indicated by activated caspase-3 Western blot analysis), with reduced expression of STAT3, Bcl-2, c-Myc, and COX-2.
  
  
  CONCLUSIONS
  Cepharanthine was shown to induce radiation sensitization in HeLa cells in vitro and in vivo. The inhibitory effects of CEP on STAT3 signaling pathway and COX-2 help us to better understand the radiosensitization of CEP.
authors: Department of Radiation Oncology, Peking University Third Hospital, Beijing, China.
authors: Zhen-hao
authors: ZH
authors: Fang
authors: Yan-jing
authors: YJ
authors: Li
authors: Zan
authors: Z
authors: Chen
authors: Jun-jie
authors: JJ
authors: Wang
authors: Li-hong
authors: LH
authors: Zhu
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D044182:Benzylisoquinolines / Q000494:pharmacology*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D011836:Radiation Tolerance / Q000187:drug effects*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D052117:Benzodioxoles
chemical_list: D044182:Benzylisoquinolines; D052246:Cyclooxygenase 2 Inhibitors; D011838:Radiation-Sensitizing Agents; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C006947:cepharanthine; D052117:Benzodioxoles