[HTML][HTML] β3Integrin and Src facilitate transforming growth factor-β mediated induction of epithelial-mesenchymal transition in mammary epithelial cells
AJ Galliher, WP Schiemann - Breast cancer research, 2006 - Springer
AJ Galliher, WP Schiemann
Breast cancer research, 2006•SpringerIntroduction Transforming growth factor (TGF)-β suppresses breast cancer formation by
preventing cell cycle progression in mammary epithelial cells (MECs). During the course of
mammary tumorigenesis, genetic and epigenetic changes negate the cytostatic actions of
TGF-β, thus enabling TGF-β to promote the acquisition and development of metastatic
phenotypes. The molecular mechanisms underlying this conversion of TGF-β function
remain poorly understood but may involve signaling inputs from integrins. Methods β 3 …
preventing cell cycle progression in mammary epithelial cells (MECs). During the course of
mammary tumorigenesis, genetic and epigenetic changes negate the cytostatic actions of
TGF-β, thus enabling TGF-β to promote the acquisition and development of metastatic
phenotypes. The molecular mechanisms underlying this conversion of TGF-β function
remain poorly understood but may involve signaling inputs from integrins. Methods β 3 …
Introduction
Transforming growth factor (TGF)-β suppresses breast cancer formation by preventing cell cycle progression in mammary epithelial cells (MECs). During the course of mammary tumorigenesis, genetic and epigenetic changes negate the cytostatic actions of TGF-β, thus enabling TGF-β to promote the acquisition and development of metastatic phenotypes. The molecular mechanisms underlying this conversion of TGF-β function remain poorly understood but may involve signaling inputs from integrins.
Methods
β3 Integrin expression or function in MECs was manipulated by retroviral transduction of active or inactive β3 integrins, or by transient transfection of small interfering RNA (siRNA) against β3 integrin. Altered proliferation, invasion, and epithelial-mesenchymal transition (EMT) stimulated by TGF-β in control and β3 integrin manipulated MECs was determined. Src involvement in β3 integrin mediated alterations in TGF-β signaling was assessed by performing Src protein kinase assays, and by interdicting Src function pharmacologically and genetically.
Results
TGF-β stimulation induced αvβ3 integrin expression in a manner that coincided with EMT in MECs. Introduction of siRNA against β3 integrin blocked its induction by TGF-β and prevented TGF-β stimulation of EMT in MECs. β3 integrin interacted physically with the TGF-β receptor (TβR) type II, thereby enhancing TGF-β stimulation of mitogen-activated protein kinases (MAPKs), and of Smad2/3-mediated gene transcription in MECs. Formation of β3 integrin:TβR-II complexes blocked TGF-β mediated growth arrest and increased TGF-β mediated invasion and EMT. Dual β3 integrin:TβR-II activation induced tyrosine phosphorylation of TβR-II, a phosphotransferase reaction mediated by Src in vitro. Inhibiting Src activity in MECs prevented the ability of β3 integrin to induce TβR-II tyrosine phosphorylation, MAPK activation, and EMT stimulated by TGF-β. Lastly, wild-type and D119A β3 integrin expression enhanced and abolished, respectively, TGF-β stimulation of invasion in human breast cancer cells.
Conclusion
We show that β3 integrin alters TGF-β signaling in MECs via Src-mediated TβR-II tyrosine phosphorylation, which significantly enhanced the ability of TGF-β to induce EMT and invasion. Our findings suggest that β3 integrin interdiction strategies may represent an innovative approach to re-establishing TGF-β mediated tumor suppression in progressing human breast cancers.
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