title: Response to imatinib mesylate of a gastrointestinal stromal tumor with very low expression of KIT.
abstract: More than 90% of gastrointestinal stromal tumors (GISTs) express the receptor tyrosine kinase KIT, and activating mutations of the KIT gene are detectable in the vast majority of these tumors. Imatinib mesylate (formerly STI571) is a potent inhibitor of KIT kinase activity and has been proven to be highly active in patients with unresectable or metastatic GIST expressing immunohistochemically detectable KIT protein. Here we report a patient with metastatic GIST who responded well to imatinib mesylate treatment despite the near absence of KIT expression in two different samples of his tumor. The tumor was morphologically typical for a GIST, stained positively for CD34, and harbored an in-frame deletion (WK 557-558) in KIT exon 11 that is common in GISTs. Our experience with this patient suggests that even GISTs with very low levels of KIT expression may respond to imatinib mesylate therapy.
authors.affiliation: Department of Internal Medicine (Cancer Research), University of Essen Medical School, Germany. sebastianbauer@uni-essen.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bauer
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Corless
authors.forename: Michael C
authors.initials: MC
authors.lastname: Heinrich
authors.forename: Olaf
authors.initials: O
authors.lastname: Dirsch
authors.forename: Gerald
authors.initials: G
authors.lastname: Antoch
authors.forename: Jörg
authors.initials: J
authors.lastname: Kanja
authors.forename: Siegfried
authors.initials: S
authors.lastname: Seeber
authors.forename: Jochen
authors.initials: J
authors.lastname: Schütte
mesh_terms: D000328:Adult; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001549:Benzamides; D004252:DNA Mutational Analysis; D016368:Frameshift Mutation; D005770:Gastrointestinal Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D000068877:Imatinib Mesylate; D007150:Immunohistochemistry; D008297:Male; D010879:Piperazines / Q000494:pharmacology*; D019009:Proto-Oncogene Proteins c-kit / Q000096:biosynthesis* / Q000235:genetics*; D011743:Pyrimidines / Q000494:pharmacology*; D017154:Stromal Cells
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit