title: Imatinib inhibits various types of activating mutant kit found in gastrointestinal stromal tumors.
abstract: Mutations of proto-oncogene c-KIT in gastrointestinal stromal tumors (GISTs) are considered to cause a constitutive activation of KIT responsible for their oncogenesis. Imatinib has therapeutic potential for GISTs because of its inhibitory effect on KIT kinase activity. To investigate the effect of Imatinib on various c-KIT mutations found in GISTs, we examined kinase activity of KIT, cell proliferation and tumorigenicity of transfectants with various c-KIT mutations. Murine lymphoid Ba/F3 cells transfected with one of the three types of mutants (KIT(del559-560), KIT(642Glu), and KIT(820Tyr)) or wild-type KIT were used for the experiments. Phosphorylation of KIT, mitogen-activated protein (MAP) and Akt was studied by immunoblotting with or without immunoprecipitation. In vitro studies on cell proliferation using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylcetrazolium bromide colorimetric assay and in vivo tumorigenicity assay using nude mice were also carried out. Imatinib could inhibit the KIT, MAP and Akt phosphorylation of all the transfectants but had a weaker effect on KIT(820Tyr). Imatinib potently inhibited the proliferation of cells transfected with KIT(820Tyr) at the concentration of 10 microM whereas it inhibited the other 3 types at 1 microM. Moreover, Imatinib could inhibit the tumor formation in nude mice transplanted with transfectants. In various types of activating mutant KIT, Imatinib could inhibit the constitutive activation of KIT signal transduction and cell proliferation both in vitro and in vivo although the effect of Imatinib on KIT(820Tyr) was weaker than that on KIT(del559-560) or KIT(642Glu).
authors.affiliation: Department of Internal Medicine and Molecular Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Koji
authors.initials: K
authors.lastname: Isozaki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kinoshita
authors.forename: Akiko
authors.initials: A
authors.lastname: Ohashi
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Shinomura
authors.forename: Yuji
authors.initials: Y
authors.lastname: Matsuzawa
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Kitamura
authors.forename: Seiichi
authors.initials: S
authors.lastname: Hirota
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001549:Benzamides; D002455:Cell Division; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005770:Gastrointestinal Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D000068877:Imatinib Mesylate; D015151:Immunoblotting; D020935:MAP Kinase Signaling System; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011233:Precipitin Tests; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit