FN1 and breast cancer: Finally, Fn binding to cell surfaces via integrins also mediates clustering of growth factor receptors.164 Enhanced levels of VEGF41 are secreted by breast cancer cells (and/or fibroblasts subjected to paracrine signaling by breast cancer cells53 ) for tumor angiogenesis.31,48 An isoform of VEGF, VEGF165, increases breast cancer and endothelial cell migration in presence of Fn (and heparin).104 Specifically, Fn forms a complex with VEGF-receptor-2 and α5β178 to bind VEGF157 on the heparin II binding domain located on FnIII13–14.