Figure 1

Various factors that induce cancer cell Epithelial-Mesenchymal Transitions (EMT) in tumor microenvironment. Inflammatory cells and cytokines, increase of reactive oxygen species (ROS) in mitochondria induced by hypoxia, mesenchymal stem cells all can effectively lead the epithelial-to-mesenchymal transition (EMT) of tumor cells. EMT is a key event in the tumor invasion process whereby epithelial cell layers lose polarity together with cell-cell contacts and then undergo a dramatic remodeling of the cytoskeleton. EMT also causes disruption of cell-cell adherence, loss of apico-basal polarity, matrix remodeling, increased motility and invasiveness in promoting tumor metastasis. Once migrating to the suitable site, tumor cells re-express E-cadherin and other epithelial markers via a process that is sometimes referred to as "mesenchymal-to-epithelial transition (MET)".