Engineering of a disulfide loop instead of a Zn binding loop restores the anti-proliferative, anti-angiogenic and anti-tumor activities of the N-terminal fragment of endostatin: Mechanistic and therapeutic insights

• Published in: Vascular pharmacology 2015-09, Vol.72, p.73-82
• Main Authors: Chamani, Reyhane, Asghari, S. Mohsen, Alizadeh, Ali Mohammad, Eskandari, Sedigheh, Mansouri, Kamran, Khodarahmi, Reza, Taghdir, Majid, Heidari, Zahra, Gorji, Ali, Aliakbar, Alireza, Ranjbar, Bijan, Khajeh, Khosro
• Format: Article
• Language: English
• Subjects: Angiogenesis; Angiogenesis Inhibitors - chemistry; Angiogenesis Inhibitors - pharmacology; Anti-breast tumor activity; Antineoplastic Agents - chemistry; Antineoplastic Agents - pharmacology; Binding Sites; Cardiovascular; Cell Line; Cell Proliferation - drug effects; Disulfide loop; Disulfides - chemistry; Endostatin; Endostatins - chemistry; Endostatins - pharmacology; Human Umbilical Vein Endothelial Cells; Humans; Integrin alphaVbeta3 - metabolism; Neoplasms - drug therapy; Neoplasms - metabolism; Peptide design; Peptides - metabolism; Platelet Endothelial Cell Adhesion Molecule-1 - metabolism; Protein Structure, Secondary; Signal Transduction - drug effects; Zinc - chemistry
• ISSN: 1537-1891; 1879-3649
• DOI: 10.1016/j.vph.2015.07.006

Abstract Although considerable effort has been devoted to understanding the molecular mechanism of endostatin's anti-cancer activity, the role of its Zn bound N-terminal loop has not been completely clarified. To investigate whether Zn binding or the N-terminal loop is involved in the anti-cancer properties of endostatin, we compared the structure and biological activity of a native Zn binding endostatin peptide (ES-Zn) with three variants: a Zn free variant (ES), a variant containing both a Zn binding site and a disulfide bond (ES-SSZn), and a variant including a disulfide loop but incapable of Zn binding (ES-SS). Spectroscopic studies indicated that ES-Zn and ES-SS consist of random coil and β structures, whereas ES-SSZn and ES fold into random coils. Theoretical analysis proposed that ES-Zn and ES-SS have a similar binding site to αV β3 integrin. The anti-proliferative activity of endostatin was retained by all peptides except ES, and the in vitro anti-angiogenic property was preserved in ES-Zn and ES-SS. Remarkably, breast tumor growth and CD31 activity were inhibited more effectively by ES-SS than by ES-Zn. Therefore, a correlation exists between the N-terminal loop and anti-cancer properties of endostatin fragment and a disulfide loop may be more promising than a Zn binding loop for inhibiting tumor growth.