S100A4, a Mediator of Metastasis

The transition from benign tumor growth to malignancy is manifested by the ability of tumor cells to traverse tissue barriers and invade surrounding tissues. The traversal of basement membrane barriers is thought to be the critical event in the initiation of the metastatic cascade and, as described by the three-step hypothesis of metastasis, involves attachment to the extracellular matrix, local proteolysis, and subsequent migration (1). In recent years, a number of specific genes have been identified, the expressions of which correlate with tumorigenesis and/or metastatic potential.