ENG and cancer: TGF-β signals via binding to both type I (ALK1 and ALK5) and type II receptors. In addition, TGF-β signaling in the vasculature involves coreceptors, e.g., endoglin (CD105), that act to modulate its effects. Endoglin is a membrane glycoprotein expressed by endothelial cells and placental syncytiotrophoblast. It has a crucial role in angiogenesis, therefore, making it an important protein for tumor growth, survival and metastasis of cancer cells to other locations in the body (Goumans et al., 2002; Shao et al., 2009).