The basement membrane matrix in malignancy.

Cancer is the second most common cause of death among Americans, although for several age groups it ranks first. Most of these deaths are not due to the primary tumour but rather to tumour cell metastases to distant organs. There are many steps that lead to metastasis, all of which are being studied with the goal of preventing these fatalities. Normally, cells attach to the extracellular matrix to maintain tissue integrity. During cancer progression, cells become more motile and acquire invasive qualities. Tumour cells move along blood and lymph vessels or invade into them to travel to distant sites. Then, the tumour cells must attach to the vessel wall, extravasate from the vessel, invade the new tissue, proliferate, and form a secondary tumour. Angiogenesis, the formation of new blood vessels, is critical to survival of these cells at the new site and is also important for primary tumour growth and spread. Tumour cell metastasis is a complex cascade of sequential steps, each of which is not yet fully understood. Progress has been made in identifying several key activators, one of which is the extracellular matrix. A major tumour promoter is the glycoprotein laminin, which is predominantly found in the extracellular matrix produced by endothelial and epithelial cells. This review will follow the metastatic process with particular attention to the effect of laminin on tumour cells. Copyright 2003 John Wiley & Sons, Ltd.