DAAP, double anti-angiogenic protein, as a novel therapeutic protein for tumor and ocular angiogenesis

Abstract

Angiogenesis has a crucial role in normal development and in pathological conditions such as tumors and ocular diseases. Vascular endothelial growth factors (VEGF) are the key molecules promoting endothelial cell growth, migration, and survival through VEGFR2 activation. Angiopoietins are also critical for blood vessel stabilization and sprouting by binding to their receptor Tie2. VEGF-A and angiopoietin-2 (Ang2) are highly upregulated during tumorigenesis and retinal neovascularization suggesting that these are critical molecules for pathological angiogenesis. Several studies about anti-angiogenic therapy targeting VEGFR2 or Tie2 pathways have shown to be efficacious against tumor and retinopathy. It is possible that simultaneous blockades of both signal pathways can enhance antiangiogenic and antitumor effects. A novel protein capable of simultaneous binding to both VEGF-A and Ang2 was developed and named as “double anti-angiogenic protein (DAAP)”. DAAP inhibited not only VEGFR2 phosphorylation induced by VEGF-A, but also Tie2 phosphorylation induced by Ang2. To test the anti-angiogenic effects of this protein as therapeutic applications, PBS, Fc, VEGF-Trap or Tie2-Fc were used for negative and positive controls in Lewis lung carcinoma tumor implantation experiment and retinopathy of prematurity (ROP) model. Tumor growth was significantly attenuated by DAAP and VEGF-Trap treatment. Immunohistochemical analysis revealed that DAAP reduced tumor vessel diameter and induced vessel pruning resulting in a decrease in vascular density. DAAP also exhibited significantly reduced metastasis into lung and distant lymph node. ROP induced vascular micro-tufts in the retinal vessels and blood vessel tortuosity were markedly reduced by DAAP treatment. These results suggest that DAAP can be therapeutically useful as VEGF and angiopoietin-associated pathological conditions such as cancer and retinopathy.