How exactly do tumors migrate to other parts of the body? This animation shows the journey these deadly cells travel to sow new tumors in parts of the body distant from where the original tumor took root. We call these “Sentinel Tumor Cells.”
This process starts with Primary Tumor Angiogenesis. Angio + Genesis literally means vessel creation. It is the pathological formation of new blood vessels from pre-existing blood vessels and is an essential process in the development of solid tumors, which need a blood supply to grow. Like nearly all aspects of cancer growth, malignant cells take over or “hijack” a normal and healthy function and use it to their advantage.
For example, the development of new blood vessels is a normal and healthy requirement of the human embryo and for wound healing. However, in cancer, this process is used to promote tumor growth.
The next phase in the process is called Epithelial to Mesenchymal Transition or EMT. The surface of a typical tumor is a collection of epithelial cells. Like the cells of your skin, these are tightly packed cells that need to remain in a large community in order to survive. They cannot survive alone. They have an electronic charge that makes them “sticky” so that they remain together to form membranes.
So how do these “social” cells manage to escape from a tumor, become loners and travel the bloodstream and begin new tumors elsewhere?
To do this, tumor cells must metamorphosize, in a sense. They do this through the EMT process. Mesenchymal cells are free agents. They are not polarized so they don’ stick together. They move around and don’t stay long in any one place. They are vascularized and receive nutrition from what is called the Extracellular Matrix (ECM), which is the non-cellular fluid that baths cells in the circulatory and lymphatic systems, as well as in spaces between cells and tissues. In other words, mesenchymal cells are ideal sentinels to establish new cancerous colonies in distant parts of the body.
When tightly packed and immobile tumor cells go through the EMT process and become individual free-floating cells, they enter the blood stream and begin to seek new sites for secondary tumors. While in the blood stream, these cells are “Sentinels” or early indicators, of the impending spread of a primary tumor. Detecting sentinel tumor cells in the bloodstream holds the promise of diagnosing “silent” tumors before they spread too far.
Tomorrow: New tumors take root and live on.