Retro-inverso Urokinase Receptor Antagonists for the Treatment of Metastatic Sarcomas

Maria Vincenza Carriero,Susan Costantini,Gennaro Ciliberto,Gerardo Botti,Domenica Rea,Vincenzo Ingangi,Katia Bifulco,Michele Minopoli,Maria Letizia Motti,Giovanni Botti,Antonello Pessi,Concetta Ragone,Claudio Arra,Giosuè Scognamiglio

doi:10.1038/s41598-017-01425-9

Abstract

The development of metastases is a multistep process that requires the activation of physiological and biochemical processes that govern migration, invasion and entry of metastatic cells into blood vessels. The urokinase receptor (uPAR) promotes cell migration by interacting with the Formyl Peptide Receptors (FPRs). Since both uPAR and FPR1 are involved in tumor progression, the uPAR-FPR1 interaction is an attractive therapeutic target. We previously described peptide antagonists of the uPAR-FPR1 interaction that inhibited cell migration and angiogenesis. To develop enzyme-resistant analogues, we applied here the Retro-Inverso (RI) approach, whereby the topology of the side chains is maintained by inverting the sequence of the peptide and the chirality of all residues. Molecular dynamics suggests that peptide RI-3 adopts the turn structure typical of uPAR-FPR1 antagonists. Accordingly, RI-3 is a nanomolar competitor of N-formyl-Met-Leu-Phe for binding to FPR1 and inhibits migration, invasion, trans-endothelial migration of sarcoma cells and VEGF-triggered endothelial tube formation. When sarcoma cells were subcutaneously injected in nude mice, tumor size, intra-tumoral microvessel density, circulating tumor cells and pulmonary metastases were significantly reduced in animals treated daily with 6 mg/Kg RI-3 as compared to animals treated with vehicle only. Thus, RI-3 represents a promising lead for anti-metastatic drugs.

Highlights

Despite significant progress in therapy, patients affected by solid tumors frequently die for systemic spread of the disease to distant sites
We developed a series of linear peptides that inhibit the Urinary Plasminogen Activator Receptor (uPAR)/FPR type 1 (FPR1) interaction and reduce to basal levels directional cell migration, invasion and angiogenesis[37,38,39,40]
We have previously shown that, upon exposure to uPAR84–95, endothelial cells form cord-like structures on matrigel and that peptide inhibitors of the uPAR/FPR1 interaction inhibit angiogenesis in vitro and in vivo[27, 39, 40]

Summary

Introduction

Despite significant progress in therapy, patients affected by solid tumors frequently die for systemic spread of the disease to distant sites. When expressed on cell surface, uPAR promotes cell-associated proteolysis by binding to Urokinase Plasminogen Activator (uPA), which locally converts plasminogen into active plasmin, favoring tissue invasion and metastasis[7, 8]. Plasmin generated by uPA or uPA itself can cleave intact uPAR (DI-DIII), releasing DI, while the remaining GPI-anchored DII‒DIII can remain on cell surface or be secreted in the extracellular milieu following cleavage of the anchor[9]. Besides being responsible for focusing urokinase-mediated plasminogen activation on cell surface[11], uPAR promotes www.nature.com/scientificreports/. Despite significant effort, no uPAR-targeted therapeutics are in clinical evaluation to date. This supports the relevance of innovative, therapeutic approaches devoted to interfering with uPAR/co-receptor interactions

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Results

Conclusion