title: Regulation of MET kinase inhibitor resistance by copy number of MET in gastric carcinoma cells.
abstract: We previously established acquired resistant models for MET-tyrosine kinase inhibitors (TKIs) by continuously exposing the MET-amplified gastric cancer cell line MKN45 to MET-TKIs, PHA665752 (MKN45-PR), or GSK1363089 (MKN45-GR). We found resistant mechanisms caused by increased copy number of MET in both lines and Y1230H mutation in MKN45-PR. We also found that excessive MET signaling caused by these MET alterations resulted in intra-S-phase arrest in the absence of MET-TKIs, so that cells grew faster in the presence of MET-TKIs, a phenomenon referred to as "addiction." In this study, to investigate reversibility of the acquired resistance and "addiction" to MET-TKIs and their causative MET alterations, we sequentially cultured MKN45-PR and MKN45-GR in decreasing concentrations of MET-TKIs until they were able to grow in a drug-free condition. These "revertant" cell lines (designated MKN45-PR-RE and MKN45-GR-RE) were comparatively analyzed. Growth assay showed that both MKN45-PR-RE and MKN45-GR-RE partially lost the property of "addiction" to MET-TKIs. MKN45-GR-RE lost the property of resistance to GSK1363089, but MKN45-PR-RE retained resistance to PHA665752. Copy numbers and expression and phosphorylation of MET protein reduced in both MKN45-PR-RE and MKN45-GR-RE compared with MKN45-PR and MKN45-GR, respectively, but Y1230H mutation and biochemical resistance to PHA665752 remained in MKN45-PR-RE. The "addiction" to MET-TKIs appeared attributable to increased copy number, and the property and the MET alteration were reversible. The Y1230H mutation appeared enough in itself to keep cells resistant to MET-TKIs and was irreversible.
authors.affiliation: Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Funakoshi
authors.forename: Toru
authors.initials: T
authors.lastname: Mukohara
authors.forename: Roudy Chiminch
authors.initials: RC
authors.lastname: Ekyalongo
authors.forename: Hideo
authors.initials: H
authors.lastname: Tomioka
authors.forename: Yu
authors.initials: Y
authors.lastname: Kataoka
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shimono
authors.forename: Naoko
authors.initials: N
authors.lastname: Chayahara
authors.forename: Masanori
authors.initials: M
authors.lastname: Toyoda
authors.forename: Naomi
authors.initials: N
authors.lastname: Kiyota
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: Hironobu
authors.initials: H
authors.lastname: Minami
mesh_terms: D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004252:DNA Mutational Analysis; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D018628:Gene Dosage; D006801:Humans; D009154:Mutation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors* / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism
chemical_list: D047428:Protein Kinase Inhibitors; D019859:Proto-Oncogene Proteins c-met