Proteases in invasion: matrix metalloproteinases

The role of proteases in general, and the matrix metalloproteinases in particular, in tumor invasion and metastasis is well established. However, the classic view that these enzymes simply provide a mechanism for the breakdown of connective tissue barriers has been challenged. This overview summarizes recent evidence to support the changing view of the role of matrix metalloproteinases in cancer progression. First we briefly review the central role of cell invasion in cancer progression and also the matrix metalloproteinase family members. We then focus on the emerging roles for these enzymes in cancer progression, including the role of matrix metalloproteinases in cell proliferation and release of growth factors, cell migration and in modification of the extracellular matrix to reveal cryptic sites that alter cell behaviour.