Intravenous liposomal delivery of the snake venom disintegrin contortrostatin limits breast cancer progression

Abstract

Despite significant research in this area, metastatic breast cancer remains a disease with a poor prognosis. Until an effective therapy is developed, it is imperative that new treatment modalities be investigated. In this report, we describe an effective method for delivery of a novel snake venom disintegrin, contortrostatin (CN), in an orthotopic, xenograft model of human mammary cancer in immunodeficient mice. CN (Mr 13,500) is a homodimeric disintegrin isolated from venom of the Southern Copperhead snake. The homodimer possesses two Arg-Gly-Asp sites, which modulate its interaction with integrins on tumor cells and angiogenic vascular endothelial cells. Although our laboratory has previously described the antitumor activity of CN in a mouse model of human mammary cancer, the method of delivery, daily intratumor injection, was not translatable to clinical application. We now describe a clinically relevant method of administering CN, liposomal delivery (LCN). A unique liposomal system has been designed for i.v. administration of a biologically active protein with full retention of biological activity. Pharmacokinetics, biodistribution, platelet reactivity, and immunogenicity of LCN were determined and compared with similar characteristics of native, unencapsulated CN. There are several advantages to liposomal delivery of CN: (1) LCN has a significantly prolonged circulatory half-life compared with native CN; (2) LCN is passively accumulated in the tumor; (3) LCN has no platelet reactivity; and (4) LCN is not recognized by the immune system. Finally, antiangiogenic activity is an important component of CN's mechanism of antitumor action. We have demonstrated that i.v. delivery of LCN leads to potent antiangiogenic activity in the orthotopic, xenograft human mammary tumor model.

Multimeric Disintegrin Protein Polymer Fusions That Target Tumor Vasculature

“…12 Unlike free RGD peptides, the disintegrin specificity and affinity is enhanced by the tertiary structure of the disulfide framework and the amino acid chain at the carboxy terminus of the disintegrin. 8,13−15 Although the pharmacological properties of the disintegrin CN have made it an intriguing molecule for potential anticancer therapeutic strategies, 16,17 it is produced in small quantities from snake venom (∼0.01%). To overcome this obstacle, a recombinant disintegrin was designed by the Markland laboratory, vicrostatin (VCN), which can be produced through heterologous expression in E. coli.…”

“…20−22 Previously Swenson et al determined the circulatory half-life of CN and liposomal CN, and it was observed that liposomal CN is cleared slowly compared to "naked" CN with a circulatory half-life of 19 and 0.5 h, respectively. 16 As an alternative to conventional macromolecular carriers, protein polymers are under investigation for transport and delivery of imaging and therapeutic agents. 23−25 These bioconjugates are typically large hydrophilic molecules linked to a therapeutic agent, which can target tumors either passively through enhanced permeability and retention or actively through affinity toward a molecular target.…”

“…Although the pharmacological properties of the disintegrin CN have made it an intriguing molecule for potential anticancer therapeutic strategies, , it is produced in small quantities from snake venom (∼0.01%). To overcome this obstacle, a recombinant disintegrin was designed by the Markland laboratory, vicrostatin (VCN), which can be produced through heterologous expression in E.…”

Strategies To Inhibit Tumor Associated Integrin Receptors: Rationale for Dual and Multi-Antagonists

“…The echistatin/contortrostatin chimera vicrostatin can be reliably produced recombinantly, avoiding difficulties in supplying contortrostatin in large quantities, 136 and contortrostatin itself has been produced recombinantly 137 and formulated as liposomes to improve half-life and facilitate intravenous administration. 138 Preclinical experiments with disintegrins indicate that multiantagonists of the RGD-binding integrins are effective, and generally safe, anticancer agents. Knowledge of disintegrin structures, specifically the conformation of the loop containing the recognition motif, and the nature of the amino acids flanking the RGD tripeptide will provide inspiration for small molecule development.…”

“…Naturally produced supply is limited, expensive, and hazardous to collect, whereas recombinant disintegrins may have different properties compared to the naturally sourced material. The echistatin/contortrostatin chimera vicrostatin can be reliably produced recombinantly, avoiding difficulties in supplying contortrostatin in large quantities, and contortrostatin itself has been produced recombinantly and formulated as liposomes to improve half-life and facilitate intravenous administration …”