title: Molecular and biochemical analyses of platelet-derived growth factor receptor (PDGFR) B, PDGFRA, and KIT receptors in chordomas.
abstract: OBJECTIVE
  We have previously shown the presence of an activated platelet-derived growth factor (PDGF) receptor (PDGFR) B and its ligand PDGFB in a limited number of patients with clinical and radiological responses to imatinib mesylate treatment. This article describes the results of comprehensive molecular/biochemical analyses of the three receptors targeted by the drug (PDGFRB, PDGFRA, and KIT) in a series of 31 chordoma patients.
  
  
  METHODS
  The presence and activation status of PDGFRB, PDGFRA, and KIT receptors were investigated by means of immunoprecipitation and Western blot analyses complemented by immunohistochemistry, their expression level was analyzed by means of real-time PCR, and the occurrence of activating point mutations was investigated by means of cDNA sequencing. The PDGFB, PDGFA, and stem cell factor cognate ligands were investigated by reverse transcription-PCR, and gene status was assessed by fluorescence in situ hybridization.
  
  
  RESULTS
  The results show that PDGFRB was highly expressed and phosphorylated, whereas PDGFRA and KIT were less expressed but phosphorylated and thus activated. These findings, together with the absence of gain-of-function mutations and the presence of the cognate ligands, strongly support the hypothesis that the activation mechanism is the autocrine/paracrine loop. No role seems to be played by gene amplification.
  
  
  CONCLUSIONS
  In the light of our findings, the clinical benefit observed in chordoma patients treated with imatinib seems to be attributable to the switching off of all three receptors.
authors.affiliation: Experimental Molecular Pathology, Department of Pathology, Fondazione IRCCS, Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Tamborini
authors.forename: Francesca
authors.initials: F
authors.lastname: Miselli
authors.forename: Tiziana
authors.initials: T
authors.lastname: Negri
authors.forename: M Stefania
authors.initials: MS
authors.lastname: Lagonigro
authors.forename: Samantha
authors.initials: S
authors.lastname: Staurengo
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Dagrada
authors.forename: Silvia
authors.initials: S
authors.lastname: Stacchiotti
authors.forename: Elisa
authors.initials: E
authors.lastname: Pastore
authors.forename: Alessandro
authors.initials: A
authors.lastname: Gronchi
authors.forename: Federica
authors.initials: F
authors.lastname: Perrone
authors.forename: Antonino
authors.initials: A
authors.lastname: Carbone
authors.forename: Marco A
authors.initials: MA
authors.lastname: Pierotti
authors.forename: Paolo G
authors.initials: PG
authors.lastname: Casali
authors.forename: Silvana
authors.initials: S
authors.lastname: Pilotti
mesh_terms: D000328:Adult; D000368:Aged; D015153:Blotting, Western; D002817:Chordoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA / Q000379:methods*
chemical_list: D012333:RNA, Messenger; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta