title: Molecular characterization of pediatric gastrointestinal stromal tumors.
abstract: OBJECTIVE
  Pediatric gastrointestinal stromal tumors (GIST) are rare and occur preferentially in females as multifocal gastric tumors, typically lacking mutations in KIT and PDGFRA. As KIT oncoprotein is consistently overexpressed in pediatric GIST, we sought to investigate the activation of KIT downstream targets and alterations of KIT/PDGFRA gene copy number, mine novel therapeutic targets by gene expression, and test tyrosine kinase receptor activation by proteomic profiling.
  
  
  METHODS
  Seventeen pediatric GISTs were investigated for KIT/PDGFRA genotype and biochemical activation of KIT downstream targets. The transcriptional profile of 13 nodules from 8 pediatric patients was compared with 8 adult wild-type (WT) GISTs, including 3 young adults. The drug sensitivity of second-generation kinase inhibitors was tested in murine Ba/F3 cells expressing human WT KIT, as well as in short-term culture of explants of WT GIST cells.
  
  
  RESULTS
  A KIT/PDGFRA WT genotype was identified in all 12 female patients, whereas two of five males had either a KIT exon 11 or PDGFRA exon 18 mutation. KIT downstream targets were consistently activated. Pediatric GISTs showed a distinct transcriptional signature, with overexpression of BAALC, PLAG1, IGF1R, FGF4, and NELL1. In vitro studies showed that nilotinib, sunitinib, dasatinib, and sorafenib are more effective than imatinib against WT KIT.
  
  
  CONCLUSIONS
  Rare cases of pediatric GIST may occur in male patients and harbor activating KIT/PDGFRA mutations. Pediatric GISTs show distinct transcriptional signature, suggesting a different biology than WT GIST in adults. In vitro drug screening showed that second-generation kinase inhibitors may provide greater clinical benefit in pediatric GIST.
authors.affiliation: Department of Pathology, Sloan-Kettering Institute, New York, New York 10021, USA.
authors.forename: Narasimhan P
authors.initials: NP
authors.lastname: Agaram
authors.forename: Michael P
authors.initials: MP
authors.lastname: Laquaglia
authors.forename: Berrin
authors.initials: B
authors.lastname: Ustun
authors.forename: Tianhua
authors.initials: T
authors.lastname: Guo
authors.forename: Grace C
authors.initials: GC
authors.lastname: Wong
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Socci
authors.forename: Robert G
authors.initials: RG
authors.lastname: Maki
authors.forename: Ronald P
authors.initials: RP
authors.lastname: DeMatteo
authors.forename: Peter
authors.initials: P
authors.lastname: Besmer
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Antonescu
mesh_terms: D000293:Adolescent; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002648:Child; D004252:DNA Mutational Analysis; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000235:genetics* / Q000473:pathology; D018628:Gene Dosage; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D047468:Immunoprecipitation; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D009154:Mutation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012737:Sex Factors
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha