title: MEK inhibitors reverse resistance in epidermal growth factor receptor mutation lung cancer cells with acquired resistance to gefitinib.
abstract: Lung adenocarcinoma cells harboring epidermal growth factor receptor (EGFR) mutations are sensitive to EGFR tyrosine kinase inhibitors (TKIs), including gefitinib. Acquired resistance to EGFR-TKIs develops after prolonged treatments. The study was prompt to explore effective strategies against resistance to EGFR-TKIs. We established gefitinib resistant PC-9 cells which harbor EGFR exon 19 deletion. Known mechanisms for intrinsic or acquired EGFR-TKI resistance, including KRAS mutation, HER2 mutation, EGFR T790M mutation and MET gene amplification, were studied, and we did not observe any known mechanisms for intrinsic or acquired resistance to EGFR-TKIs in the resistant cells. In the parental PC-9 cells, labeled as PC-9/wt, gefitinib completely inhibited EGF-induced phosphorylation of EGFR, AKT and ERK. Gefitinib inhibited EGFR phosphorylation, but was unable to block EGF-induced phosphorylation of ERK in resistant cells, labeled as PC-9/gef cells, including PC-9/gefB4, PC-9/gefE3, and PC-9/gefE7 subclones. We detected NRAS Q61K mutation in the PC-9/gef cells but not the PC-9/wt cells. MEK inhibitors, either AZD6244 or CI1040, inhibited ERK phosphorylation and sensitized gefitinib-induced cytotoxicity in PC-9/gef cells. Whereas MEK inhibitors or gefitinib alone did not activate caspases in PC-9/gef cells, combination of gefitinib and AZD6244 or CI1040 induced apoptosis. Our in vivo studies showed that gefitinib inhibited growth of PC-9/wt xenografts but not PC-9/gef xenografts. Furthermore, combination of a MEK inhibitor and gefitinib inhibited growth of both PC-9/wt xenografts and PC-9/gefB4 xenografts. To conclude, persistent activation of ERK pathway contributes to the acquired gefitinib-resistance. Combined treatment of gefitinib and MEK inhibitors may be therapeutically useful for acquired gefitinib-resistance lung adenocarcinoma cells harboring EGFR mutations.
authors.affiliation: Graduate Institute of Oncology and Cancer Research Center, National Taiwan University, Taipei, Taiwan.
authors.forename: Ming-Hung
authors.initials: MH
authors.lastname: Huang
authors.forename: Jih-Hsiang
authors.initials: JH
authors.lastname: Lee
authors.forename: Ya-Ju
authors.initials: YJ
authors.lastname: Chang
authors.forename: Hsin-Hui
authors.initials: HH
authors.lastname: Tsai
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Lin
authors.forename: Anya Maan-Yuh
authors.initials: AM
authors.lastname: Lin
authors.forename: James Chih-Hsin
authors.initials: JC
authors.lastname: Yang
mesh_terms: D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066246:ErbB Receptors / Q000235:genetics*; D020558:GTP Phosphohydrolases / Q000235:genetics; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D011799:Quinazolines / Q000627:therapeutic use*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D018631:ras Proteins / Q000235:genetics
chemical_list: D001562:Benzimidazoles; D004791:Enzyme Inhibitors; D066246:ErbB Receptors; D020558:GTP Phosphohydrolases; D000077156:Gefitinib; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D016283:Proto-Oncogene Proteins p21(ras); D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D018631:ras Proteins; C517975:AZD 6244; C117307:KRAS protein, human; C508053:ERBB2 protein, human; C579846:NRAS protein, human