title: Response markers and the molecular mechanisms of action of Gleevec in gastrointestinal stromal tumors.
abstract: Gastrointestinal stromal tumors (GISTs), defined by the presence of constitutively activated KIT, are the most common gastrointestinal mesenchymal malignancies. This observation has been successfully exploited in clinical trials of Gleevec (also known as imatinib mesylate, STI-571) for patients with unresectable and/or metastatic GISTs. The biological mechanisms of Gleevec as well as its downstream molecular effects are generally unknown. We used a DNA microarray-based approach to identify gene expression patterns and signaling pathways that were altered in response to Gleevec in GIST cells. We identified a total of 148 genes or expressed sequence tags (of 10,367) that were differentially regulated; 7 known genes displayed a durable response after treatment. The significantly down-regulated genes were SPRY4A, FZD8, PDE2A, RTP801, FLJ20898, and ARHGEF2. The only up-regulated gene was MAFbx. On a functional level, we demonstrated that imatinib inhibited phosphorylation of KIT, AKT, and extracellular signal-regulated kinase 1/2 without affecting the total level of these proteins and that differential expression of these response genes involved activation of mitogen-activated protein kinase-dependent and -independent pathways. In an attempt to correlate these in vitro findings to clinical data, we examined GIST needle biopsy specimens taken from patients before and after Gleevec administration according to the CSTI571-B2222 Phase II trial and demonstrated that expression levels of the two gene transcripts evaluated correlated well with clinical response. This study emphasizes the potential value of an in vitro cell model to investigate GIST response to imatinib in vivo, for the purpose of identifying important genetic markers of clinical response, mechanisms of drug action, and possible therapeutic targets.
authors.affiliation: Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
authors.forename: Andrey
authors.initials: A
authors.lastname: Frolov
authors.forename: Santiago
authors.initials: S
authors.lastname: Chahwan
authors.forename: Michael
authors.initials: M
authors.lastname: Ochs
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Arnoletti
authors.forename: Zhong-Zong
authors.initials: ZZ
authors.lastname: Pan
authors.forename: Olga
authors.initials: O
authors.lastname: Favorova
authors.forename: Jonathan
authors.initials: J
authors.lastname: Fletcher
authors.forename: Margaret
authors.initials: M
authors.lastname: von Mehren
authors.forename: Burton
authors.initials: B
authors.lastname: Eisenberg
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Godwin
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001549:Benzamides; D001707:Biopsy, Needle; D002460:Cell Line; D015536:Down-Regulation; D005770:Gastrointestinal Neoplasms / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D018390:Gene Targeting; D005819:Genetic Markers; D000068877:Imatinib Mesylate; D009124:Muscle Proteins / Q000235:genetics; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D019009:Proto-Oncogene Proteins c-kit / Q000187:drug effects / Q000235:genetics; D011743:Pyrimidines / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D017154:Stromal Cells / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D005819:Genetic Markers; D009124:Muscle Proteins; D009363:Neoplasm Proteins; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; D019009:Proto-Oncogene Proteins c-kit