Identification of Selective and Potent Inhibitors of Fibroblast Activation Protein and Prolyl Oligopeptidase

Abstract

Fibroblast activation protein (FAP) is a serine protease selectively expressed on reactive stromal fibroblasts of epithelial carcinomas. It is widely believed to play a role in tumor invasion and metastasis and therefore to represent a potential new drug target for cancer. Investigation into its biological function, however, has been hampered by the current unavailability of selective inhibitors. The challenge has been in identifying inhibitors that are selective for FAP over both the dipeptidyl peptidases (DPPs), with which it shares exopeptidase specificity, and prolyl oligopeptidase (PREP), with which it shares endopeptidase specificity. Here, we report the first potent FAP inhibitor with selectivity over both the DPPs and PREP, N-(pyridine-4-carbonyl)-d-Ala-boroPro (ARI-3099, 6). We also report a similarly potent and selective PREP inhibitor, N-(pyridine-3-carbonyl)-Val-boroPro (ARI-3531, 22). Both are boronic acid based inhibitors, demonstrating that high selectivity can be achieved using this electrophile. The inhibitors are stable, easy to synthesize, and should prove to be useful in helping to elucidate the biological functions of these two unique and interesting enzymes, as well as their potential as drug targets.

Pericyte-targeting prodrug overcomes tumor resistance to vascular disrupting agents

“…However, Z-GP-DAVLBH was resistant to hydrolysis by DPP-IV, the closest homolog of FAPα (Supplemental Figure 2). Interestingly, we found that prolyl endopeptidase (PEP), a cytosolic prolyl oligopeptidase that possesses FAPα-like endopeptidase activity (18), showed approximately 1/7 of the hydrolytic activity jci.org Volume 127 Number 10 October 2017…”

Molecular mechanism underlying the tumor-promoting functions of carcinoma-associated fibroblasts

“…(2) targeting the CAF-carcinoma cell interaction through CXCL12, CXCR4, CCL7, FGF, Gal-1, Smo, HGF, CCL2, IGF-II, CAIX, TN-C, POSTN, and TGF-β [76]; (3) targeting CAF-endothelial cell interactions through VEGF, FGFs, CXCL12, and PDGFs; (4) targeting the CAF-modulated ECM remodeling by inhibiting caveolin-1 and MMPs (and someone has tried to develop new techniques to alleviate solid stress or stiffness to increase tumor perfusion) [77]; (5) targeting CAF-induced inflammation and immune escape through CXCL1, CXCL2, CXCL12, CXCL14, COX-2, CCL2, CCL5, IL-1β, and TGF-β; (6) targeting CAFmediated anti-immune responses, the design of FAP-based therapeutic approaches to target CAFs has been developed, such as FAP neutralizing antibodies, inhibitors [78], prodrugs [79], and DNA vaccines [80]; and (7) targeting DNA methylation in CAFs may be another approach to preferentially block CAFs' function [34]. At present, two kinds of approaches targeting DNA methylation are available: methyl donor modifiers (folate, betaine, and choline) and methyltransferase inhibitors (nucleoside inhibitors: 5-azacytidine, 5-aza-2-deoxycytidine, and zebularine; and non-nucleoside inhibitors: procaine, procainamide, EGCG, and RG108) [81].…”

Fibroblast activation protein enzyme deficiency prevents liver steatosis, insulin resistance and glucose intolerance and increases fibroblast growth factor-21 in diet induced obese mice

“…These adipocytes were incubated with full-length or FAP-cleaved FGF-21 at 500 ng/mL. FGF-21 was pre-incubated with PBS or recombinant FAP (substrate: enzyme ratio = 5:1) for 2 h, with or without FAP-selective inhibitor ARI-3099 [32] at 5 µM. Immunoblots of FGF-21, Erk, phosphorylated Erk (p-Erk) ACC, p-ACC, PGC-1α and β-actin were performed on lysates of tissues or of cells.…”