Inhibitor-Decorated Polymer Conjugates Targeting Fibroblast Activation Protein

Abstract

Proteases are directly involved in cancer pathogenesis. Expression of fibroblast activation protein (FAP) is upregulated in stromal fibroblasts in more than 90% of epithelial cancers and is associated with tumor progression. FAP expression is minimal or absent in most normal adult tissues, suggesting its promise as a target for the diagnosis or treatment of various cancers. Here, we report preparation of a polymer conjugate (an iBody) containing a FAP-specific inhibitor as the targeting ligand. The iBody inhibits both human and mouse FAP with low nanomolar inhibition constants but does not inhibit close FAP homologues dipeptidyl peptidase IV, dipeptidyl peptidase 9, and prolyl oligopeptidase. We demonstrate the applicability of this iBody for the isolation of FAP from cell lysates and blood serum as well as for its detection by ELISA, Western blot, flow cytometry, and confocal microscopy. Our results show the iBody is a useful tool for FAP targeting in vitro and potentially also for specific anticancer drug delivery.

Inhibitor-conjugated harmonic nanoparticles targeting fibroblast activation protein

“…Conjugation of this inhibitory scaffold to N-(2-hydroxypropyl)methacrylamide copolymer was previously used to vizualize and isolate FAP from cell lysates. 63 Interestingly, derivatization with a PEG spacer delivered Biotin-PEG 3 -FAPi which displayed effective binding to FAP (K i ¼ 3.8 AE 0.20 nM), high specic discrimination between FAP and its closely related proteases DPP IV and PREP (selectivity indexes above 10 000), and good biocompatibility with the human 3D tissue model MucilAir™-HF. 56 Combination of a N-acyl-Gly-Pro fragment with a (4-quinolinoyl)glycyl-2-cyanopyrrolidine moiety and a polar PEG spacer resulted in sharp specicity toward FAP.…”

Tris-(Nitrilotriacetic Acid)-Decorated Polymer Conjugates as Tools for Immobilization and Visualization of His-Tagged Proteins

“…Catalysts 2019, 9,1011 3 of 11 which corresponds to 50 reactive groups per polymer chain on average. We prepared two versions of anti-polyHis iBodies (Figure 1) differing in the conjugated fluorescent probe to provide distinct means of detection.…”

“…The low stability inherent to proteins, difficulty of introducing chemical modifications, and often-unreliable batch-to-batch consistency and target specificity are among the major limitations that can adversely affect the quality of research [6,7]. The fairly young field of antibody mimetics aims to develop alternative, more reliable strategies.Recently, we described antibody mimetics based on synthetic polymer conjugates, so-called iBodies [8][9][10]. In the present work, we tailored this polymer-based flexible system to provide a substitute for anti-His antibodies in applications involving His-tag.…”

“…Recently, we described antibody mimetics based on synthetic polymer conjugates, so-called iBodies [8][9][10]. In the present work, we tailored this polymer-based flexible system to provide a substitute for anti-His antibodies in applications involving His-tag.…”

Targeting fibroblast activation protein (FAP): Next generation PET radiotracers using squaramide coupled bifunctional DOTA and DATA5m chelators

“…It is related to the dipeptidyl peptidases (DPPs) DPP2, DPP4, DPP8 and DPP9 and furthermore related to the endopeptidase prolyl oligopeptidase (PREP). [1,2] FAP combines DPP and endopeptidase activities. [3][4][5][6] With respect to FAP's endopeptidase activity, a remarkable preference is present for cleavage after Gly-Pro motifs in peptides.…”