N-cadherin is a calcium-dependent endothelial cell adhesion molecule. It promotes cell adhesion by a homophilic mechanism. The first extracellular domain of this integral membrane glycoprotein contains the cell adhesion recognition sequence, His-Ala-Val (HAV). Linear and cyclic peptides containing this sequence have been shown to inhibit N-cadherin-mediated cell adhesion. Exherin™ (ADH-1) is a cyclic peptide containing the HAV motif (N-Ac-CHAVC-NH2) that is capable of acting as an N-cadherin antagonist (J. Biol. Chem., 2000, 275, 4007). We have previously shown that ADH-1 causes apoptosis of murine capillary endothelial H5V cells and bovine capillary endothelial cells (Exp. Cell Res., 2004, 294, 366). In addition, ADH-1 has been shown to cause tumor blood vessel rupture in animal model systems without affecting normal blood vessels. ADH-1 is currently in Phase I clinical trials and has shown anti-tumor activity. We have conducted additional studies to explore the ability of ADH-1 to affect endothelial cell adhesion and blood vessel formation. Treatment of confluent cultures of either human umbilical vein endothelial cells (HUVEC) or human microvascular endothelial cells (HMVEC) for 24 hr with ADH-1 (1 mg/ml) results in a loss of adhesion, followed by apoptosis. We subsequently examined the ability of ADH-1 and a negative control cyclic peptide (N-Ac-CVAHC-NH2) to block angiogenesis utilizing the chick chorioallantoic membrane assay at a concentration of 3 μg/mesh for 24 hr in the presence or absence of 0.01 mM VEGF. In the presence of VEGF, ADH-1 and the control peptide inhibited angiogenesis by 46% and 7%, respectively. In the absence of VEGF, ADH-1 and the control peptide inhibited angiogenesis by 12% and 0%, respectively. Finally, we assessed the ability of ADH-1 to reduce tumor microvessel density and inhibit Lewis Lung carcinoma growth rate in nude mice. Tumor cells were injected into the mouse footpad, followed 24 hr later by daily IP injections of ADH-1 (200 mg/kg) for 21 days. By the end of the study, ADH-1 reduced microvessel density by 45% (p<0.05) compared to the vehicle control group. Furthermore, ADH-1 reduced the tumor growth rate by 50% after 21 days of treatment when compared to the vehicle control group. Collectively, these observations suggest that ADH-1 is capable of acting as an anti-angiogenic agent and reducing tumor growth in vivo.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]