title: [Ionizing Radiation Reduces TKI Resistance Caused by T790M Mutation in NSCLC Cell Lines].
abstract: OBJECTIVE
  Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI), which targets EGFR, plays an important role in non-small cell lung cancer (NSCLC) treatment. Patients with somatic activating mutations in the EGFR gene exhibit significant initial response but eventually develop resistance to TKI. The second mutation (T790M) of the EGFR gene is the possible main cause of drug resistance. The aim of this study is to investigate the effect of ionizing radiation on EGFR-TKI resistance caused by T790M mutation in NSCLC cell lines.
  
  
  METHODS
  We selected H1975 and H3255 as research subjects and tested the mutation states by real-time PCR analysis. Radiosensitivity was determined by clone-forming test, and drug resistance was detected in different groups by MTT assay.
  
  
  RESULTS
  H1975 is an EGFR double mutant (L858R plus T790M), whereas H3255 is an EGFR single mutant (L858R). The cell survival fractions of H1975 and H3255 did not vary in different treatment groups (P=0.952). Thus, T790M mutation did not affect the radiosensitivity of NSCLC cell lines. The IC50 of H1975 in the 2.5 Gy group [(0.678; 2±0.373) μmol/L] was statistically significant compared with that in the 0 Gy normal control group [(3.520±0.821) μmol/L] (P=0.008). The drug tolerance of the H1975 cell line by 89.5 dropped to 39.2 times.
  
  
  CONCLUSIONS
  Ionizing radiation can reduce TKI resistance caused by T790M mutation in NSCLC cell lines. Our results provide a research basis for future in vivo and clinical studies. Radiotherapy combined with EGFR-TKI treatment can be a promising strategy to overcome T790M-mediated drug resistance. .
authors: Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
authors: Jing
authors: J
authors: Li
authors: Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
authors: Xinhu
authors: X
authors: Wu
authors: Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
authors: Zhen
authors: Z
authors: Wang
authors: Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
authors: Zetian
authors: Z
authors: Shen
authors: Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
authors: Ni
authors: N
authors: Sun
authors: Department of Radiation Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
authors: Xixu
authors: X
authors: Zhu
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D009154:Mutation; D011839:Radiation, Ionizing
chemical_list: D004791:Enzyme Inhibitors