FN1 and teratocarcinoma: In-vivo studies have found that teratocarcinomas derived from embryonic stem cells null for α5 integrin, a receptor promoting cellular attachment to fibronectin, expressed significantly fewer vascular structures in comparison to α5 integrin-expressing cells [10], further supporting a role for fibronectin in angiogenesis These results highlight the important role of fibronectin in directing vascular cell behaviors and angiogenic activities.