Angiopoietin 1 is a 70-kDa secreted glycoprotein generated from vascular mural cells, pericytes, and certain other cells. Angiopoietin 1 participates in vascular differentiation through angiogenesis, which is the process of the growth and remodelling of existing vessels. Angiopoietin 1 is also involved in the maintenance and turnover of blood vessels in mature animals. Angiopoietin1 binds to and activates the TEK/TIE2 receptor by inducing its dimerization and tyrosine phosphorylation, playing an important role in the regulation of angiogenesis. Overexpression of Angiopoietin1 has been proven to occur in malignant glioblastoma, neuroblastoma, non-small cell lung cancer and other tumors.