Figure 3.

Schematic representation of the evolution of a carcinoma in situ into an invasive carcinoma. Invasion of cancer cells into the surrounding stroma involves a complex process by which they lose their epithelial characteristics and acquire instead a mesenchymal phenotype as part of the EMT. ZEB1 is not present in normal epithelial cells or at the center of well-differentiated carcinomas but is expressed by invasive cancer stem cells undergoing an active EMT at the tumor front of several types of carcinomas. ZEB1 also regulates several components of the basement membrane, which breakdown is required for cancer cells to invade the surrounding stroma.