title: Sequence-dependent antiproliferative effects of gefitinib and docetaxel on non-small cell lung cancer (NSCLC) cells and the possible mechanism.
abstract: OBJECTIVE
  Recent clinical trials showed that the sequential combination of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and chemotherapy could prolong the PFS and/or OS of advanced non-small cell lung cancer (NSCLC) patients with EGFR mutation. The aim of present study was to assess the optimal combination sequence and to explore its possible mechanism.
  
  
  METHODS
  PC-9 cells and A549 cells, the lung adenocarcinoma cells with mutant and wide-type EGFR respectively, were treated with docetaxel/gefitinib alone or in different combination schedules. The EGFR and K-ras gene status was determined by qPCR-HRM technique. Cell proliferation was detected by MTT assay. The expression and phosphorylation of EGFR, ERK, Akt and IGF-1R were detected by western blot. Cell cycle distribution was observed by flow cytometry.
  
  
  RESULTS
  Only sequential administration of docetaxel followed by gefitinib (D → G) induced significant synergistic effect in both cell lines (Combination Index<0.9). The reverse sequence (G → D) resulted in an antagonistic interaction in both cell lines (CI>1.1), whereas the concurrent administration (D+G) showed additive (0.9<CI<1.1)-synergistic effect in PC-9 cells and antagonistic-additive effect in A549 cells. Mechanism studies showed that docetaxel-induced phosphorylation of EGFR and ERK was repressed by subsequently used gefitinib, but not by concurrent exposure of gefitinib. The gefitinib-repressed phosphorylation of EGFR and ERK was reversed neither by concurrent nor by subsequent administration of docetaxel. D+G reinforced their inhibition on the phosphorylation of IGF-1R in PC-9 cells.
  
  
  CONCLUSIONS
  The cytotoxic drugs followed by EGFR-TKIs may be the optimal combination for antiproliferative effects in EGFR-mutant NSCLC cells, and the phosphorylation of EGFR and ERK might contribute to this effect.
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Bei
authors.initials: B
authors.lastname: Chen
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Jingxian
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Yunyun
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Baofeng
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Xie
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Jihua
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Oncology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou, Guangdong, China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000077143:Docetaxel; D004334:Drug Administration Schedule; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D000077156:Gefitinib; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011799:Quinazolines / Q000008:administration & dosage* / Q000494:pharmacology*; D043823:Taxoids / Q000008:administration & dosage* / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D043823:Taxoids; D000077143:Docetaxel; C512478:EGFR protein, human; D066246:ErbB Receptors; D000077156:Gefitinib