CD44 and its partners in metastasis.

The establishment of metastasis requires that tumor cells acquire new adhesion and migration properties to emigrate from primary sites and colonize distant organs. CD44 is a cell membrane protein often overexpressed on tumor cells and, being both a cell-cell and cell-extracellular matrix adhesion protein, is well positioned to contribute to this process. Furthermore the interaction of CD44 with other cellular proteins involved in motogenesis and proteolysis is a determinant factor in cell migration and invasion. This review summarizes current knowledge on the role of CD44 in metastasis, as well as the challenges on understanding how this process operates.