Epidermal growth factor-induced tumor cell invasion and metastasis initiated by dephosphorylation and downregulation of focal adhesion kinase.
Upregulated epidermal growth factor (EGF) receptor (EGFR) expression and EGFR-induced signaling have been correlated with progression to invasion and metastasis in a wide variety of carcinomas, but the mechanism behind this is not well understood. We show here that, in various human carcinoma cells that overexpress EGFR, EGF treatment induced rapid tyrosine dephosphorylation of focal adhesion kinase (FAK) associated with downregulation of its kinase activity. The downregulation of FAK activity was both required and sufficient for EGF-induced refractile morphological changes, detachment of cells from the extracellular matrix, and increased tumor cell motility, invasion, and metastasis. Tumor cells with downregulated FAK activity became less adherent to the extracellular matrix. However, once cells started reattaching, FAK activity was restored by activated integrin signaling. Moreover, this process of readhesion and spreading could not be abrogated by further EGF stimulation. Interruption of transforming growth factor alpha-EGFR autocrine regulation with an EGFR tyrosine kinase inhibitor led to a substantial increase in FAK tyrosine phosphorylation and inhibition of tumor cell invasion in vitro. Consistent with this, FAK tyrosine phosphorylation was reduced in cells from tumors growing in transplanted, athymic, nude mice, which have an intact autocrine regulation of the EGFR. We suggest that the dynamic regulation of FAK activity, initiated by EGF-induced downregulation of FAK leading to cell detachment and increased motility and invasion, followed by integrin-dependent reactivation during readhesion, plays a role in EGF-associated tumor invasion and metastasis.
Lu
Z
Z
Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA.
Jiang
G
G
Blume-Jensen
P
P
Hunter
T
T
D016475:3T3 Cells; D020087:Alu Elements; D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D009362:Neoplasm Metastasis / Q000503:physiopathology*; D051419:Paxillin; D010641:Phenotype; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D014407:Tumor Cells, Cultured
D003598:Cytoskeletal Proteins; D017931:DNA Primers; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D011506:Proteins; C496062:Pxn protein, mouse; D050717:Retinoblastoma-Like Protein p130; D004815:Epidermal Growth Factor; C113183:FAK-related nonkinase; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse