Epithelial-mesenchymal transition (EMT) is a complex process in which epithelial 
cells acquire the characteristics of invasive mesenchymal cells. EMT has been 
implicated in cancer progression and metastasis as well as the formation of many 
tissues and organs during development. Epithelial cells undergoing EMT lose 
cell-cell adhesion structures and polarity, and rearrange their cytoskeletons. 
Several oncogenic pathways such as transforming growth factor (TGF) -β, Wnt, and 
Notch signaling pathways, have been shown to induce EMT. These pathways have 
activated transcription factors including Snail, Slug, and the ZEB family which 
work as transcriptional repressors of E-cadherin, thereby making epithelial 
cells motile and resistant to apoptosis. Mounting evidence shows that EMT is 
associated with cell invasion and tumor progression.In this review, we summarize 
the characteristic features of EMT, pathways leading to EMT, and the role of EMT 
in cell invasion. Three topics are addressed in this review: (1) Definition of 
EMT, (2) Signaling pathways leading to EMT, (3) Role of EMT in cell invasion. 
Understanding the role of EMT in cell invasion will provide valuable information 
for establishing strategies to develop anti-metastatic therapeutics which 
modulate malignant cellular processes mediated by EMT.