Redefining the role(s) of endothelial αvβ3-integrin in angiogenesis

For nearly two decades now, the RGD (Arg-Gly-Asp)-binding αvβ3-integrin has been a focus of anti-angiogenic drug design. These inhibitors are well-tolerated, but have shown only limited success in patients. Over the years, studies in β3-integrin-knockout mice have shed some light on possible explanations for disappointing clinical outcomes. However, studying angiogenesis in β3-integrin-knockout mice is a blunt tool to investigate β3-integrin's role in pathological angiogenesis. Since establishing our laboratory at University of East Anglia (UEA), we have adopted more refined models of genetically manipulating the expression of the β3-integrin subunit. The present review will highlight some of our findings from these models and describe how data from them have forced us to rethink how targeting αvβ3-integrin expression affects tumour angiogenesis and cancer progression. Revisiting the fundamental biology behind how this integrin regulates tumour growth and angiogenesis, we believe, is the key not only to understanding how angiogenesis is normally co-ordinated, but also in success with drugs directed against it.