title: [Cetuximab in combination with icotinib overcomes the acquired resistance caused by EGFR T790M mutation in non-small cell lung cancer].
abstract: OBJECTIVE
  The aim of this study was to investigate the effects of combination of icotinib and cetuximab on the acquired drug resistance caused by T790M mutation of EGFR in NSCLC, and provide experimental evidence for rational treatment of NSCLC.
  
  
  METHODS
  The effects of these two agents on cell proliferation, apoptosis, and EGFR-dependent signaling were evaluated using 3-(4, 5-dimethylthiazol-2-yl)- 5-diphenyltetrazolium bromide (MTT) assay, annexin V staining, and Western blotting. The expression of molecular markers of tumor proliferation PCNA and Ki-67 protein was further examined by immunohistochemistry, and the expression of EGFR-signaling-related proteins in tissue sections taken from H1975 tumor xenografts was assessed by Western blot assay. Sensitivity to EGFR inhibitors was detected in human H1975 tumor xenograft in nude mice.
  
  
  RESULTS
  The in vitro experiment showed that the proliferative ability of H1975 cells was inhibited in a dose-dependent manner, along with the increasing doses of cetuximab and icotinib, and the combination of cetuximab with icotinib resulted in a more pronounced growth inhibition of the H1975 cells. The apoptosis rate of H1975 cells after treatment with 0.5 µmol/L icotinib and 1 µg/ml cetuximab was (22.03 ± 2.41)% and that after treatment with 5 µmol/L icotinib and 10 µg/ml cetuximab was (42.75 ± 2.49)%, both were significantly higher than that after treatment with the same dose of icotinib or cetuximab alone (P < 0.05). The nude mouse experiment showed that the transplanted tumor was growing to (614.5 ± 10.8) mm(3) in the blank control group and to (611.2 ± 8.7) mm(3) at 28 days after icotinib treatment, but (30.8 ± 2.0) mm(3) in the cetuximab treatment group and 0 mm(3) in the cetuximab combined with icotinib group. There was a significantly decreased expression of Ki-67 and PCNA proteins and down-regulation of phosphorylation of EGFR signaling-related proteins in the cetuximab combined with icotinib group.
  
  
  CONCLUSIONS
  The combination of icotinib with cetuximab can exert synergistic inhibitory effect on the acquired drug resistance caused by T790M mutation of EGFR in NSCLC H1975 cells, interrupts the EGFR-downstream signaling pathway, and enhances the anticancer activity of chemotherapeutic drugs. Our results provide further experimental evidence for the clinical studies of combination of icotinib with cetuximab in the treatment of NSCLC patients associated with secondary drug resistance caused by T790M mutation of EGFR.
authors.affiliation: Department of Lung Cancer, Cancer Institute & Hospital, Tianjin Medical University, Key Laboratory of Cancer Prevention and Therapy Tianjin, Tianjin 300060, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Lung Cancer, Cancer Institute & Hospital, Tianjin Medical University, Key Laboratory of Cancer Prevention and Therapy Tianjin, Tianjin 300060, China.
authors.forename: Lianmin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Lung Cancer, Cancer Institute & Hospital, Tianjin Medical University, Key Laboratory of Cancer Prevention and Therapy Tianjin, Tianjin 300060, China.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Lung Cancer, Cancer Institute & Hospital, Tianjin Medical University, Key Laboratory of Cancer Prevention and Therapy Tianjin, Tianjin 300060, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Lung Cancer, Cancer Institute & Hospital, Tianjin Medical University, Key Laboratory of Cancer Prevention and Therapy Tianjin, Tianjin 300060, China.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Lung Cancer, Cancer Institute & Hospital, Tianjin Medical University, Key Laboratory of Cancer Prevention and Therapy Tianjin, Tianjin 300060, China. Email: ezxwm@163.com.
authors.forename: Changli
authors.initials: C
authors.lastname: Wang
mesh_terms: D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000068818:Cetuximab; D043844:Crown Ethers / Q000008:administration & dosage / Q000627:therapeutic use; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors; D018773:Genes, erbB-1 / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D011799:Quinazolines / Q000008:administration & dosage / Q000627:therapeutic use; D015398:Signal Transduction
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D043844:Crown Ethers; D011799:Quinazolines; C531470:icotinib; D066246:ErbB Receptors; D000068818:Cetuximab