Direct evidence for a role of beta-catenin/LEF-1 signaling pathway in induction of EMT.
Epithelial-mesenchymal transformation (EMT) is an important process in development that is characterized by loss of E-cadherin, beta-catenin relocalization, and acquisition of elongated cell shape and ability to invade ECM. beta-catenin has been shown to activate LEF-1 transcription during EMT induced in vitro by c-Fos. Here, we ask whether or not LEF-1 directly introduced into epithelial cells in an adenovirus construct can induce EMT. In normal epithelial cell lines, such as HCE and MDCK cells, that contain functional APC, nuclear beta-catenin induced by exogenous LEF-1 is rapidly exported and EMT is not induced. Leptomycin-B blocks beta-catenin nuclear export, but no EMT occurs due to toxicity. Addition of Wnt-1 to normal epithelial cell lines stabilizes cytoplasmic beta-catenin that LEF-1 then transports to nuclei, causing a small amount of EMT. Our experiments demonstrated, however, that overexpressed LEF-1 upregulates nuclear beta-catenin and promotes dramatic EMT in DLD-1 epithelial tumors that retain nuclear beta-catenin. This EMT is reversible if the LEF-1 virus is removed. Thus, our results demonstrate that LEF-1 can induce EMT directly when its transcription activity is activated by stable nuclear beta-catenin. Normal adult epithelial cells appear to use APC to keep beta-catenin out of the nucleus, thereby avoiding pathologies such as metastases due to LEF/beta-catenin-induced EMT.
Kim
Kwonseop
K
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Lu
Zifan
Z
Hay
Elizabeth D
ED
D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus; D000256:Adenoviridae; D000818:Animals; D002450:Cell Communication; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051180:Desmoplakins; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology; D005822:Genetic Vectors; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D051821:Lymphoid Enhancer-Binding Factor 1; D008648:Mesoderm / Q000502:physiology; D051379:Mice; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D051176:beta Catenin; D000097606:Exportin 1 Protein
D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D051180:Desmoplakins; D028884:Karyopherins; D051821:Lymphoid Enhancer-Binding Factor 1; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051176:beta Catenin; D000097606:Exportin 1 Protein; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; C497573:LEF1 protein, human; C497574:Lef1 protein, mouse