Phosphorylation of dedicator of cytokinesis 1 (Dock180) at tyrosine residue Y722 by Src family kinases mediates EGFRvIII-driven glioblastoma tumorigenesis.
Glioblastoma, the most common primary malignant cancer of the brain, is characterized by rapid tumor growth and infiltration of tumor cells throughout the brain. These traits cause glioblastomas to be highly resistant to current therapies with a resultant poor prognosis. Although aberrant oncogenic signaling driven by signature genetic alterations, such as EGF receptor (EGFR) gene amplification and mutation, plays a major role in glioblastoma pathogenesis, the responsible downstream mechanisms remain less clear. Here, we report that EGFRvIII (also known as ΔEGFR and de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in human glioblastoma, promotes tumorigenesis through Src family kinase (SFK)-dependent phosphorylation of Dock180, a guanine nucleotide exchange factor for Rac1. EGFRvIII induces phosphorylation of Dock180 at tyrosine residue 722 (Dock180(Y722)) and stimulates Rac1-signaling, glioblastoma cell survival and migration. Consistent with this being causal, siRNA knockdown of Dock180 or expression of a Dock180(Y722F) mutant inhibits each of these EGFRvIII-stimulated activities. The SFKs, Src, Fyn, and Lyn, induce phosphorylation of Dock180(Y722) and inhibition of these SFKs by pharmacological inhibitors or shRNA depletion markedly attenuates EGFRvIII-induced phosphorylation of Dock180(Y722), Rac1 activity, and glioblastoma cell migration. Finally, phosphorylated Dock180(Y722) is coexpressed with EGFRvIII and phosphorylated Src(Y418) in clinical specimens, and such coexpression correlates with an extremely poor survival in glioblastoma patients. These results suggest that targeting the SFK-p-Dock180(Y722)-Rac1 signaling pathway may offer a novel therapeutic strategy for glioblastomas with EGFRvIII overexpression.
Department of Pathology, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
Haizhong
H
Feng
Bo
B
Hu
Michael J
MJ
Jarzynka
Yanxin
Y
Li
Susan
S
Keezer
Terrance G
TG
Johns
Careen K
CK
Tang
Ronald L
RL
Hamilton
Kristiina
K
Vuori
Ryo
R
Nishikawa
Jann N
JN
Sarkaria
Tim
T
Fenton
Tao
T
Cheng
Frank B
FB
Furnari
Webster K
WK
Cavenee
Shi-Yuan
SY
Cheng
D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002465:Cell Movement; D002470:Cell Survival; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D066246:ErbB Receptors / Q000378:metabolism*; D005909:Glioblastoma / Q000201:enzymology* / Q000473:pathology*; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011379:Prognosis; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*
C099818:DOCK1 protein, human; C410723:epidermal growth factor receptor VIII; D019000:Phosphotyrosine; D066246:ErbB Receptors; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein