ICAM1 and neoplasm: Interaction of endothelial VCAM-1 with tumor cell VLA-4 and/or endothelial ICAM-1 with platelet αIIbß3 triggers an “outside-in” signaling cascade in endothelial cells that induces the digestion of tight junctions, cytoskeletal rearrangement, and endothelial retraction (199, 200).