How do malignant cells invade and metastasize?

The genetic and molecular events that allow cells to invade and metastasize are a complex issue that is being studied in numerous laboratories. Malignant cells must be able to detach from adjacent cells (i.e., downregulate adhesion molecules), adhere to the adjacent matrix by the development of receptors to matrix molecules, such as fibronectin; lyse the extracellular matrix by the production of various enzymes; and migrate by the production of motility factors, such as hepatocyte growth factor. Once the tumor cells gain access to lymphatic spaces or blood vessels, they must be able to express adhesion molecules on their surface, which then allows them to attach to endothelial cells (e.g., CD44). There is also evidence that certain normal tissues produce chemoattractants that may attract tumor to a specific site.

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Nomura T, Katunuma N: Involvement of cathepsins in the invasion, metastasis, and proliferation of cancer cells, J Med Invest 52:1–9, 2005.