Basigin (BSG, CD147, EMPRIN) is a glycoprotein expressed on the surface of most tumor cells. It stimulates stromal cells to produce elevated levels of several matrix metalloproteinases (MMP), including interstitial collagenase (MMP1). MMPs have been implicated in several aspects of tumor progression, including invasion through basement membranes and interstitial matrices, angiogenesis, and tumor cell growth. Basigin not only stimulates the production of MMP1 but also forms a complex with MMP1 at the tumor cell surface. This interaction may be important in modifying the tumor cell pericellular matrix to promote invasion.