Reversibility of Epithelial-Mesenchymal Transition (EMT) Induced in Breast Cancer Cells by Activation of Urokinase Receptor-dependent Cell Signaling

• Published in: The Journal of biological chemistry 2009-08, Vol.284 (34), p.22825-22833
• Main Authors: Jo, Minji, Lester, Robin D., Montel, Valerie, Eastman, Boryana, Takimoto, Shinako, Gonias, Steven L.
• Format: Article
• Language: English
• Subjects: Animals; Calcium-Calmodulin-Dependent Protein Kinases - antagonists & inhibitors; Cell Hypoxia - physiology; Cell Line, Tumor; Cell Movement; Chick Embryo; Chickens; Chromones - pharmacology; Epithelium - drug effects; Epithelium - metabolism; Epithelium - pathology; Flavonoids - pharmacology; Humans; Immunoblotting; Mechanisms of Signal Transduction; Mesoderm - drug effects; Mesoderm - metabolism; Mesoderm - pathology; Microscopy, Fluorescence; Morpholines - pharmacology; Oxygen - pharmacology; Phosphoinositide-3 Kinase Inhibitors; Polymerase Chain Reaction; Receptors, Urokinase Plasminogen Activator - genetics; Receptors, Urokinase Plasminogen Activator - physiology; RNA, Small Interfering - genetics; RNA, Small Interfering - physiology; Signal Transduction - drug effects; Signal Transduction - genetics; Tubulin - genetics; Urokinase-Type Plasminogen Activator - genetics; Urokinase-Type Plasminogen Activator - physiology; Vimentin - genetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.023960

Hypoxia induces expression of the urokinase receptor (uPAR) and activates uPAR-dependent cell signaling in cancer cells. This process promotes epithelial-mesenchymal transition (EMT). uPAR overexpression in cancer cells also promotes EMT. In this study, we tested whether uPAR may be targeted to reverse cancer cell EMT. When MDA-MB 468 breast cancer cells were cultured in 1% O2, uPAR expression increased, as anticipated. Cell-cell junctions were disrupted, vimentin expression increased, and E-cadherin was lost from cell surfaces, indicating EMT. Transferring these cells back to 21% O2 decreased uPAR expression and reversed the signs of EMT. In uPAR-overexpressing MDA-MB 468 cells, EMT was reversed by silencing expression of endogenously produced urokinase-type plasminogen activator (uPA), which is necessary for uPAR-dependent cell signaling, or by targeting uPAR-activated cell signaling factors, including phosphatidylinositol 3-kinase, Src family kinases, and extracellular signal-regulated kinase. MDA-MB 231 breast cancer cells express high levels of uPA and uPAR and demonstrate mesenchymal cell morphology under normoxic culture conditions (21% O2). Silencing uPA expression in MDA-MB-231 cells decreased expression of vimentin and Snail, and induced changes in morphology characteristic of epithelial cells. These results demonstrate that uPAR-initiated cell signaling may be targeted to reverse EMT in cancer.