title: Loss of an EGFR-amplified chromosome 7 as a novel mechanism of acquired resistance to EGFR-TKIs in EGFR-mutated NSCLC cells.
abstract: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) show notable effects against non-small cell lung cancers (NSCLCs) harboring EGFR-activating mutations. However, almost all patients eventually acquire resistance to EGFR-TKIs. In this study, we established novel erlotinib resistant NSCLC cells and examined their resistant mechanisms. Resistant cells were established in 14, 3, and 0 wells exposed to 0.1, 1, and 10 μM erlotinib, respectively. The IC(50) values of these cells were 47- to 1209-fold higher than that of the parent cells. No secondary T790M mutation was detected in any resistant cells. However, in 13/17 resistant cells, EGFR copy number was reduced less than approximately one-eighth of parent cells, and in one resistant cell (B10), >99.99% of the population was EGFR-unamplified cells. Most (97.5%) parent cells showed EGFR amplification, but 2.5% of the population comprised EGFR-unamplified cells. An EGFR-unamplified clone (4D8) isolated from parent cells in erlotinib-free normal medium also showed erlotinib resistance comparable to the resistant B10 cells. Loss of an EGFR-amplified chromosome 7 (EGFR-ampch7) was observed in 4D8 and B10 cells. EGFR-unamplified cells were constantly maintained as a minor population of the parent cells under normal cell culture conditions. In conclusion, loss of an EGFR-ampch7 causes acquired resistance in EGFR-mutated HCC827 cells exposed to a relatively low concentration of erlotinib, but a high concentration prevents the emergence of resistance.
authors.affiliation: Product Research Department, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Japan.
authors.forename: Koh
authors.initials: K
authors.lastname: Furugaki
authors.affiliation: Product Research Department, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Iwai
authors.affiliation: Product Research Department, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Japan. Electronic address: moriyayui@chugai-pharm.co.jp.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Moriya
authors.affiliation: Product Research Department, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Harada
authors.affiliation: Product Research Department, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Fujimoto-Ouchi
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics; D045744:Cell Line, Tumor; D002869:Chromosome Aberrations; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D000069347:Erlotinib Hydrochloride; D005784:Gene Amplification; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011799:Quinazolines / Q000627:therapeutic use*
chemical_list: D011799:Quinazolines; D000069347:Erlotinib Hydrochloride; C512478:EGFR protein, human; D066246:ErbB Receptors
keywords: EGFR-TKI; Erlotinib; Mutation; NSCLC; Non-small cell lung cancer; Resistance