tokens: However , it does induce chemotaxis , trans-Matrigel migration , and secretion of matrix metalloproteinase 9 ( MMP-9 ) and vascular endothelial growth factor ( VEGF ) by these cells , and both SDF-1 and TPO increase the adhesion of alpha ( IIb ) beta ( 3 ) ( + ) cells to fibrinogen and vitronectin .