VCAM1 and cancer: Two distinguishing paths have been explored by 1) targeting to cancer cells due to the overexpression of transferrin, folate, epidermal growth factor, or glycoproteins etc. and 2) targeting to the tumor endothelium due to the overexpression of the vascular endothelial growth factors (VEGF), αvβ3 integrins, the vascular cell adhesion molecule-1 (VCAM-1) or matrix metalloproteinases (MMP) etc. (11, 19).