Epithelial-Mesenchymal Transition

Epithelial-Mesenchymal Transition (EMT) is a natural cellular survival programme that is harnessed by cancer cells in response to a hostile tumour microenvironment. This hostile tumour microenvironment may be caused by inflammatory or immune responses, chemotherapeutics or the effect of more modern targeted therapeutic agents.

As a consequence many cancer cells will be killed; some however will engage survival mechanisms and transition from being epithelial to mesenchymal in character. This transition involves reprogramming many features of the cancer cell, which results in changes in the structure and shape of the cell, changes in the cell membrane, and changes in its metabolic cycles.

Mesenchymal cells can tolerate the hostile environment and can evade the body’s immune response. In solid cancers, these mesenchymal cells can also metastasize or re-locate to another site in the body where they either remain dormant or develop into secondary tumours.

Under normal circumstances, EMT is important during embryonic and vertebrate development. Epithelial cells gain phenotypic traits of mesenchymal cells, and in so doing they lose adhesion and basal polarity and gain the ability to migrate and enter the extracellular matrix. These cells can then migrate throughout the organism and give rise to many different structures and organs.

EMT is seldom activated in healthy adults, except in response to inflammation following injury or disease, when it plays a role in wound healing and tissue repair.

EMT also occurs during organ degenerative disease (e.g. fibrosis).