title: EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180.
abstract: Glioblastomas (GBMs), the most common and malignant brain tumors, are highly resistant to current therapies. The failure of targeted therapies against aberrantly activated oncogenic signaling, such as that of the EGFR-PI3K/Akt pathway, underscores the urgent need to understand alternative downstream pathways and to identify new molecular targets for the development of more effective treatments for gliomas. Here, we report that EGFRvIII (ΔEGFR/de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in clinical GBM tumors, promotes glioma growth and invasion through protein kinase A (PKA)-dependent phosphorylation of Dock180, a bipartite guanine nucleotide exchange factor (GEF) for Rac1. We demonstrate that EGFRvIII induces serine phosphorylation of Dock180, stimulates Rac1 activation and glioma cell migration. Treatments of glioma cells using the PKA inhibitors H-89 and KT5720, overexpression of a PKA inhibitor (PKI), and in vitro PKA kinase assays show that EGFRvIII induction of serine phosphorylation of Dock180 is PKA-dependent. Significantly, PKA induces phosphorylation of Dock180 at amino acid residue S1250 that resides within its Rac1-activating DHR-2 domain. Expression of the Dock180(S1250L) mutant, but not wild type Dock180(WT), protein in EGFRvIII-expressing glioma cells inhibited receptor-stimulated cell proliferation, survival, migration in vitro and glioma tumor growth and invasion in vivo. Together, our findings describe a novel mechanism by which EGFRvIII drives glioma tumorigenesis and invasion through PKA-dependent phosphorylation of Dock180, thereby suggesting that targeting EGFRvIII-PKA-Dock180-Rac1 signaling axis could provide a novel pathway to develop potential therapeutic strategies for malignant gliomas.
authors.affiliation: 1] Department of Neurology, Northwestern Brain Tumor Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [2] Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [3] The Robert H Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [4] Stem Cell Research Center, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: H
authors.initials: H
authors.lastname: Feng
authors.affiliation: 1] Department of Neurology, Northwestern Brain Tumor Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [2] Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [3] The Robert H Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: B
authors.initials: B
authors.lastname: Hu
authors.affiliation: Sanford-Burnham Medical Research Institute, La Jolla, CA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Vuori
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, MN, USA.
authors.forename: J N
authors.initials: JN
authors.lastname: Sarkaria
authors.affiliation: Ludwig Institute for Cancer Research, University of California-San Diego, School of Medicine, La Jolla, CA, USA.
authors.forename: F B
authors.initials: FB
authors.lastname: Furnari
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, MN, USA.
authors.forename: W K
authors.initials: WK
authors.lastname: Cavenee
authors.affiliation: 1] Department of Neurology, Northwestern Brain Tumor Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [2] Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA [3] The Robert H Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: S-Y
authors.initials: SY
authors.lastname: Cheng
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D057809:HEK293 Cells; D064593:Heterografts; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C099818:DOCK1 protein, human; C410723:epidermal growth factor receptor VIII; D012694:Serine; D066246:ErbB Receptors; D017868:Cyclic AMP-Dependent Protein Kinases; D020744:rac GTP-Binding Proteins