title: Acquired resistance to imatinib in gastrointestinal stromal tumor occurs through secondary gene mutation.
abstract: Most gastrointestinal stromal tumors (GIST) have an activating mutation in either KIT or PDGFRA. Imatinib is a selective tyrosine kinase inhibitor and achieves a partial response or stable disease in about 80% of patients with metastatic GIST. It is now clear that some patients with GIST develop resistance to imatinib during chronic therapy. To identify the mechanism of resistance, we studied 31 patients with GIST who were treated with imatinib and then underwent surgical resection. There were 13 patients who were nonresistant to imatinib, 3 with primary resistance, and 15 with acquired resistance after initial benefit from the drug. There were no secondary mutations in KIT or PDGFRA in the nonresistant or primary resistance groups. In contrast, secondary mutations were found in 7 of 15 (46%) patients with acquired resistance, each of whom had a primary mutation in KIT exon 11. Most secondary mutations were located in KIT exon 17. KIT phosphorylation was heterogeneous and did not correlate with clinical response to imatinib or mutation status. That acquired resistance to imatinib in GIST commonly occurs via secondary gene mutation in the KIT kinase domain has implications for strategies to delay or prevent imatinib resistance and to employ newer targeted therapies.
authors.affiliation: Department of Pathology, Sloan-Kettering Institute, New York, New York, USA. antonesc@mskcc.org
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Antonescu
authors.forename: Peter
authors.initials: P
authors.lastname: Besmer
authors.forename: Tianhua
authors.initials: T
authors.lastname: Guo
authors.forename: Knarik
authors.initials: K
authors.lastname: Arkun
authors.forename: Glory
authors.initials: G
authors.lastname: Hom
authors.forename: Beata
authors.initials: B
authors.lastname: Koryotowski
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Leversha
authors.forename: Philip D
authors.initials: PD
authors.lastname: Jeffrey
authors.forename: Diann
authors.initials: D
authors.lastname: Desantis
authors.forename: Samuel
authors.initials: S
authors.lastname: Singer
authors.forename: Murray F
authors.initials: MF
authors.lastname: Brennan
authors.forename: Robert G
authors.initials: RG
authors.lastname: Maki
authors.forename: Ronald P
authors.initials: RP
authors.lastname: DeMatteo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D001549:Benzamides; D015153:Blotting, Western; D004252:DNA Mutational Analysis; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D005838:Genotype; D006801:Humans; D000068877:Imatinib Mesylate; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D010879:Piperazines / Q000494:pharmacology / Q000627:therapeutic use*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology / Q000627:therapeutic use*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha