Going Rogue : How does a cancer spread to become metastatic?
Why do cells that are tightly packed or neatly arranged in rows (epithelia), come loose and become insidiously mobile? The answer lies in a basic developmental process known as EMT, short for epithelial to mesenchymal transition.
❑ During EMT, cells no longer know which way is up (i.e., lose their polarity), break off their cell-cell junctions and extend pseudopodia or foot-like processes that help them move. In the image below, colon cancer cells were caught in the act of rearranging their junctional proteins (in red and green) to become amorphous, drug-resistant and invasive. Even more dangerous, these cells acquire stem cell properties, allowing them to seed new cancers. In short, cells lose their mature, differentiated form and recapitulate their origins.
❑ But EMT, and its reverse process MET, are normal features of embryo development, leading to formation of the neural tube, heart valve and other organs. Also, during wound healing, skin cells at the edge of the wound undergo EMT, reverting back by MET after the wound is closed. Understanding what triggers these changes, and how they may be controlled, is key to cancer therapy.
❑ This explanation is in response to the more sensationalistic title, New theory uncovers cancer’s deep evolutionary roots , shared on G+. The theory “promises to transform the approach to cancer therapy, and to link the origin of cancer to the origin of life and the developmental processes of embryos”. Choose between breathless science (http://goo.gl/yDsys) or the rational explanation here 🙂
Wiki entry for EMT: http://goo.gl/2U806
Reference (open access): Chronic oxaliplatin resistance induces epithelial-to-mesenchymal transition in colorectal cancer cell lines. Yang et al. http://www.ncbi.nlm.nih.gov/pubmed/16857785