title: Excessive MET signaling causes acquired resistance and addiction to MET inhibitors in the MKN45 gastric cancer cell line.
abstract: The clinical efficacy of MET tyrosine kinase inhibitors (MET-TKIs) is hindered by the emergence of acquired resistance, presenting an obstacle to drug discovery. To clarify the mechanisms underlying acquired resistance to MET-TKIs, we established resistance models by continuous exposure of the MET-amplified gastric cancer cell line MKN45 to MET-TKIs, PHA665752 (MKN45-PR) and GSK1363089 (MKN45-GR). Baseline expression and phosphorylation of MET were elevated in MKN45-PR and MKN45-GR compared to MKN45 cells, and higher concentrations of MET-TKIs were required to inhibit MET phosphorylation compared to parental cells. Alterations in MET previously associated with resistance to MET-TKIs were observed in resistant cells, including elevated MET copy number, observed in both resistant lines compared to MKN45 cells, and the Y1230H mutation, detected in MKN45-PR cells. Notably, the growth of resistant lines was lower in the absence of MET-TKIs, suggesting "addiction" to inhibitors. While MKN45-PR cells exhibited a higher S-phase fraction in the absence of PHA665752, bromodeoxyuridine (BrdU) uptake was identical. Baseline phosphorylation of ATR, Chk1 and p53 and p21(waf1/Cip1) expression was higher in MKN45-PR compared to MKN45 cells, and levels were reduced to those observed in untreated MKN45 cells following PHA665752 treatment. Furthermore, targeted knockdown of MET enhanced the growth of MKN45-PR cells. These findings suggest that alterations in MET leading to acquired MET-TKI resistance, may cause excessive MET signaling, subsequent replication stress and DNA damage response, and intra-S-phase arrest in the absence of MET-TKIs. Thus, partial MET inhibition is necessary for resistant cells to proliferate, a phenomenon we refer to as MET-TKI "addiction".
authors.affiliation: Division of Medical Oncology/Hematology, Department of Medicine, Kobe University Hospital and Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Funakoshi
authors.forename: Toru
authors.initials: T
authors.lastname: Mukohara
authors.forename: Hideo
authors.initials: H
authors.lastname: Tomioka
authors.forename: Roudy Chiminch
authors.initials: RC
authors.lastname: Ekyalongo
authors.forename: Yu
authors.initials: Y
authors.lastname: Kataoka
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Inui
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Kawamori
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: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004249:DNA Damage; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D013274:Stomach Neoplasms; D013450:Sulfones / Q000494:pharmacology*
chemical_list: C480541:5-((2,6-dichlorobenzyl)sulfonyl)-3-((3,5-dimethyl-4-((2-(pyrrolidin-1-ylmethyl)pyrrolidin-1-yl)carbonyl)-1H-pyrrol-2-yl)methylene)-1,3-dihydro-2H-indol-2-one; D000970:Antineoplastic Agents; D007211:Indoles; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D013450:Sulfones; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met