title: The drug-resistance to gefitinib in PTEN low expression cancer cells is reversed by irradiation in vitro.
abstract: BACKGROUND
  Despite of the recent success of EGFR inhibitory agents, the primary drug-resistant becomes a major challenge for EGFR inhibitor therapies. PTEN gene is an important positive regulatory factor for response to EGFR inhibitor therapy. Low-expression of PTEN is clearly one of the important reasons why tumor cells resisted to tyrosine kinase inhibitors.
  
  
  METHODS
  To investigate the drug-resistance reversal to gefitinb and the mechanism in PTEN low expression cells which radiated with X-rays in vitro, We demonstrated that H-157 lung cancer cells (low-expression of PTEN but phospho-EGFR overexpressed tumor cells) exposed to X-rays. The PTEN expressions and radiosensitizing effects of tyrosine kinase inhibitor before and after irradiation were observed. The cell-survival rates were evaluated by colony-forming assays. The cell apoptosis was investigated using FCM. The expressions of phospho-EGFR and PTEN were determined by Western blot analysis.
  
  
  RESULTS
  The results showed that the PTEN expressions were significantly enhanced by X-rays. Moreover, the cell growth curve and survival curve were down-regulated in the gefitinib-treated groups after irradiation. Meanwhile, the radiation-induced apoptosis of tumor cells was increased by inhibition of the EGFR through up-regulation of PTEN.
  
  
  CONCLUSIONS
  These results suggested that PTEN gene is an important regulator on TKI inhibition, and the resistance to tyrosine kinase inhibitors might be reversed by irradiation in PTEN low expression cancer cells.
authors.affiliation: Department of Radiotherapy, Tianjin Medical University Cancer Institute and Hospital and Tianjin Key Laboratory of Cancer Prevention and Therapy, Tianjin, PR China. hongqingzh@163.com
authors.forename: Hong-Qing
authors.initials: HQ
authors.lastname: Zhuang
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Yuan
authors.forename: Lu-Jun
authors.initials: LJ
authors.lastname: Zhao
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.forename: Chang-Li
authors.initials: CL
authors.lastname: Wang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D000077156:Gefitinib; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000532:radiotherapy; D051059:PTEN Phosphohydrolase / Q000235:genetics* / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D015854:Up-Regulation; D014965:X-Rays
chemical_list: D000970:Antineoplastic Agents; D011799:Quinazolines; D066246:ErbB Receptors; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D000077156:Gefitinib