More Evidence That the Biology of Embryogenesis Explains Metastasis

Epithelial tissue is the most common source of human cancers. When epithelial cancer cells metastasize, they sever their connections to adjacent cells, burrow through tissue and enter a blood or lymphatic vessel, survive in the circulation, exit the circulation and enter a distant organ, and then grow. As researchers first noted nearly a decade ago, each of these steps is similar to what happens in embryogenesis when an epithelial cell turns into a mesenchymal cell (cells of the connective tissue, largely derived from mesoderm). This switch is called the epithelial-to-mesenchymal transition, or EMT (JW Gen Med Aug 24 2004).

Two new studies expand this story. Once mesenchymal-like metastatic cells have entered a distant organ, they need to tr…