CD177 and neoplasm: Active targeting strategies are usually divided into two types of cellular targets: (1) specific cell surface receptors (such as folic acid, epidermal growth factor receptors, glycoprotein receptors, or overexpressed transferrin) and (2) specific receptors of tumor endothelium (such as vascular endothelial growth factor (VEGF), αvβ3 integrins, vascular cell adhesion molecule-1 (VCAM-1) or matrix metalloproteinases (MMP's)).