Figure 1.

EMT and MET mediate dynamic and reversible changes along a spectrum of intermediate epithelial–mesenchymal phenotypes. Mature epithelial cells (yellow) are characterized by apicobasal polarity, lateral cell–cell junctions such as adherens junctions, gap junctions or tight junctions, and adhesion to a basement membrane (brown). Mesenchymal cells (blue) exhibit front–rear polarity, lack cell–cell adhesions and migrate individually following detachment from the basement membrane. Cells with intermediate phenotypes, induced via partial EMT, can simultaneously possess both mesenchymal and epithelial features, and often migrate as a collective owing to the retention of intercellular adhesion. This diagram acts as an exemplar for the continuum of EMT states, but will differ between tissue contexts in vivo depending on the maturity of epithelial cells, junctional arrangements, basal adhesion and modulation of the EMT programme.