Matrix metalloproteinases and oral cancer.
For tumours to invade and metastasise, neoplastic cells must be capable of degrading the extracellular matrix (ECM), and accessing blood vessels and lymphatics. This process is mediated in the pericellular environment and is a highly controlled cascade of events utilising the same mechanisms that normal cells use for migrating through tissue barriers, for example, in development and wound healing. Proteolytic enzymes from several families, including matrix metalloproteinases (MMPs), are involved in ECM remodelling. Increased production of these enzymes has been associated with the invasive and/or metastatic phenotype in many tumours. Several MMPs have been shown to play a role in the invasion and metastasis of oral carcinoma, and it is increasingly apparent that tumour cells, as well as producing endogenous MMP, are capable of utilising MMP produced by tumour stromal cells, indicating an active role for stroma in tumour invasion. It is not clear whether a particular invasive system is favoured by oral carcinoma, but it is likely that further understanding of the interactions between carcinoma and stromal cells will provide an opportunity to refine the therapeutic interventions that are currently being tested.