Matrix reloaded to circulation hits the tumor target

Proteolytic fragments of various components of the extracellular matrix exhibit antiangiogenic activity via interaction with endothelial cell surface integrins. Kalluri and coworkers (Hamano et al., 2003; this issue of Cancer Cell) use gene-targeted mice to show a physiological role for a carboxy-terminal fragment of collagen IV in the regulation of tumor angiogenesis.