title: Distinct Afatinib Resistance Mechanisms Identified in Lung Adenocarcinoma Harboring an EGFR Mutation.
abstract: EGFR tyrosine kinase inhibitors (TKI) are associated with significant responses in non-small cell lung cancer (NSCLC) patients harboringEGFR-activating mutations. However, acquired resistance to reversible EGFR-TKIs remains a major obstacle. In particular, although the second-generation irreversible EGFR-TKI afatinib is currently used for treating NSCLC patients, the mechanisms underlying acquired afatinib resistance remain poorly understood. Here, heterogeneous mechanisms of acquired resistance were identified following long-term exposure to increasing doses of afatinib in EGFR-mutant lung adenocarcinoma PC-9 cells. Notably, three resistant cell lines, PC-9AFR1, PC-9AFR2, and PC-9AFR3 (AFR1, AFR2, and AFR3, respectively) employed distinct mechanisms for avoiding EGFR inhibition, with increasedEGFRexpression being detected in all resistant cell lines. Moreover, an activatingEGFRmutation was partially lost in AFR1 and AFR2 cells. AFR1 cells exhibited afatinib resistance as a result of wild-type KRAS amplification and overexpression; however, these cells showed a progressive decrease and eventual loss of the acquired KRAS dependence, as well as resensitization to afatinib, following a drug holiday. Meanwhile, AFR2 cells exhibited increased expression of insulin-like growth factor-binding protein 3 (IGFBP3), which promoted insulin-like growth factor 1 receptor (IGF1R) activity and subsequent AKT phosphorylation, thereby indicating a potential bypass signaling pathway associated with IGFR1. Finally, AFR3 cells harbored the secondary EGFR mutation T790M. Our findings constitute the first report showing acquired wild-type KRAS overexpression and attenuation of afatinib resistance following a drug holiday.Implications:The heterogeneous mechanisms of afatinib resistance should facilitate the development of more effective therapeutic strategies for NSCLC patients.Mol Cancer Res; 15(7); 915-28. ©2017 AACR.
authors.affiliation: Institute of Molecular Oncology, Showa University, Tokyo, Japan. yamaoka.t@med.showa-u.ac.jp.
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Yamaoka
authors.affiliation: Institute of Molecular Oncology, Showa University, Tokyo, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Ohmori
authors.affiliation: Institute of Molecular Oncology, Showa University, Tokyo, Japan.
authors.forename: Motoi
authors.initials: M
authors.lastname: Ohba
authors.affiliation: Institute of Molecular Oncology, Showa University, Tokyo, Japan.|Center for Biotechnology, Showa University, Tokyo, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Arata
authors.affiliation: Division of Allergology and Respiratory Medicine, Department of Medicine, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Murata
authors.affiliation: Division of Allergology and Respiratory Medicine, Department of Medicine, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Sojiro
authors.initials: S
authors.lastname: Kusumoto
authors.affiliation: Division of Allergology and Respiratory Medicine, Department of Medicine, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Ando
authors.affiliation: Division of Clinical Oncology, Department of Medicine, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Hiroo
authors.initials: H
authors.lastname: Ishida
authors.affiliation: Division of Allergology and Respiratory Medicine, Department of Medicine, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Ohnishi
authors.affiliation: Division of Clinical Oncology, Department of Medicine, Showa University School of Medicine, Tokyo, Japan.
authors.forename: Yasutsuna
authors.initials: Y
authors.lastname: Sasaki
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D000077192:Adenocarcinoma of Lung; D000077716:Afatinib; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D051379:Mice; D009154:Mutation; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000009:adverse effects; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D011799:Quinazolines / Q000008:administration & dosage* / Q000009:adverse effects; D017526:Receptor, IGF Type 1; D017451:Receptors, Somatomedin / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: C000597236:IGF1R protein, human; C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; C117307:KRAS protein, human; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D017451:Receptors, Somatomedin; D000077716:Afatinib; C512478:EGFR protein, human; D066246:ErbB Receptors; D017526:Receptor, IGF Type 1; D016283:Proto-Oncogene Proteins p21(ras)