title: Analysis of phosphotyrosine signaling in glioblastoma identifies STAT5 as a novel downstream target of ΔEGFR.
abstract: An in-frame deletion mutation in Epidermal Growth Receptor (EGFR), ΔEGFR is a common and potent oncogene in glioblastoma (GBM), promoting growth and survival of cancer cells. This mutated receptor is ligand independent and constitutively active. Its activity is low in intensity and thought to be qualitatively different from acutely ligand stimulated wild-type receptor implying that the preferred downstream targets of ΔEGFR play a significant role in malignancy. To understand the ΔEGFR signal, we compared it to that of a kinase-inactivated mutant of ΔEGFR and wild-type EGFR with shotgun phosphoproteomics using an electron-transfer dissociation (ETD) enabled ion trap mass spectrometer. We identified and quantified 354 phosphopeptides corresponding to 249 proteins. Among the ΔEGFR-associated phosphorylations were the previously described Gab1, c-Met and Mig-6, and also novel phosphorylations including that of STAT5 on Y694/9. We have confirmed the most prominent phosphorylation events in cultured cells and in murine xenograft models of glioblastoma. Pathway analysis of these proteins suggests a preference for an alternative signal transduction pathway by ΔEGFR compared to wild-type EGFR. This understanding will potentially benefit the search for new therapeutic targets for ΔEGFR expressing tumors.
authors.affiliation: Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Chumbalkar
authors.forename: Khatri
authors.initials: K
authors.lastname: Latha
authors.forename: YeoHyeon
authors.initials: Y
authors.lastname: Hwang
authors.forename: Rebecca
authors.initials: R
authors.lastname: Maywald
authors.forename: Lauren
authors.initials: L
authors.lastname: Hawley
authors.forename: Raymond
authors.initials: R
authors.lastname: Sawaya
authors.forename: Lixia
authors.initials: L
authors.lastname: Diao
authors.forename: Keith
authors.initials: K
authors.lastname: Baggerly
authors.forename: Webster K
authors.initials: WK
authors.lastname: Cavenee
authors.forename: Frank B
authors.initials: FB
authors.lastname: Furnari
authors.forename: Oliver
authors.initials: O
authors.lastname: Bogler
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism*; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D010748:Phosphopeptides / Q000032:analysis; D019000:Phosphotyrosine / Q000378:metabolism*; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D010748:Phosphopeptides; D050799:STAT5 Transcription Factor; D019000:Phosphotyrosine; D066246:ErbB Receptors