Synthetic Integrin-Targeting Dextran-Fc Hybrids Efficiently Inhibit Tumor Proliferation In Vitro.

Hendrik Schneider,Jorge Alberto Lerma Romero,Harald Kolmar,Simon Englert,Arturo Macarrón Palacios,Ataurehman Ali,Olga Avrutina

doi:10.3389/fchem.2021.693097

Abstract

Herein, we present the design, synthesis, and biological evaluation of novel integrin-targeting molecular hybrids combining RGD peptides and a potent cytotoxin presented on dextran polysaccharides. Based on an aglycosylated Fc as a centerpiece, endosomal-cleavable cytotoxic agent monomethyl auristatin E (MMAE) and dextran as multimerization site were covalently connected by two bioorthogonal enzyme-mediated reactions site-specifically. Decoration of dextran with cyclic RGD peptides, introduced by copper “click” reaction, resulted in the final constructs with the potential to kill integrin-overexpressing tumor cells. We found that these modifications had little impact on the stability of the Fc scaffold and the RGD-bearing construct showed good binding properties of αvβ3-expressing U87MG cells. Furthermore, the construct showed a remarkable antiproliferative activity. These results demonstrate the general capability of our design to provoke receptor-mediated endocytosis upon binding to the cellular surface, followed by endosomal cleavage of the linkage between Fc-dextran and MMAE and its subsequent release. Our approach opens new avenues to transcribe small molecule binders into tailor-made multimeric molecular hybrids with antitumor potential.

Highlights

Over the last decades, specific targeting of cancer cells has become an increasingly important issue in the development of novel approaches to antitumor therapy
Dextran 9 was conjugated to Fc-monomethyl auristatin E (MMAE) 3 using transglutaminase (Figure 2), an enzyme catalyzing the formation of isopeptide bonds between suited glutamine residues and amine counterparts
Peptides incorporating the RGD-motif have proven their efficacy as integrin binders in numerous publications, whereby their potency was even further enhanced by multimerization

Summary

Introduction

Specific targeting of cancer cells has become an increasingly important issue in the development of novel approaches to antitumor therapy. Antibody–drug conjugates (ADCs) became popular as vehicles relying on immunoglobins, which bind to overexpressed antigens on cancer cells and facilitate the delivery of cytotoxic agents (Khongorzul et al, 2020). Besides these large and complex architectures, targeting modules based on small molecules and peptides have been developed (Krall et al, 2013). Being the key actors in cell–cell and extracellular matrix communication, integrins are important regulators of cellular processes such as adhesion, proliferation, apoptosis, and migration (Humphries et al, 2006; Nieberler et al, 2017) These glycosylated transmembrane proteins are heterodimers; a pool of 18 α-subunits and 8 β-subunits results in at least 24 variants in humans (Yousefi et al, 2021). Expression levels of several integrin subtypes, most prominently αvβ, have been reported to be elevated in solid tumors, for example, melanoma, breast, pancreatic cancer, and glioblastoma, as well

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