Breaking away: matrix remodeling from the leading edge.

Substantial progress has been made in recent years toward understanding the molecular mechanisms by which tumor cells, and the supporting stroma, degrade confining matrix during migration. Significant attention has been focused on understanding the biology of several dynamic and distinct, but remarkably related, cell structures that include lamellipodia, focal adhesions (FAs), filopodia, podosomes, and invadopodia. How these invasive organelles assemble and function is a topic of intense study. Most exciting has been the recent progress made by combining advanced microscope technologies with a wide variety of different 3D matrices, tissue explants, or even living model organisms. From these approaches, it has become increasingly evident that the conventional definitions of these invasive structures may be less clear than was previously thought.