The main advantages of exploiting proteases are that both therapeutics and assays can use specific chemical compounds that are far less expensive than antibodies.
FAP is predominantly associated with disease states, including liver and lung fibrosis, solid tumors, arthritis and atherosclerosis. Substrates of this protease include α-2-antiplasmin, collagen I and Neuropeptide Y. In a diet-induced obesity model, we have found that FAP gene knockout (gko) mice have improved glucose tolerance and liver histopathology, and less insulin resistance and fatty liver, compared R428 to wild type mice on this diet. FAP gko mice resist liver fibrosis. Using our recently published novel FAP activity assay (1), we observed that serum levels of FAP enzyme activity co-segregate with liver stiffness as a measure of fibrosis in two adult cohorts with NAFLD. Cohort 1 contained 108 patients with type 2 diabetes who had transient elastography and Cohort 2 contained 148 patients with morbid Vincristine research buy obesity with liver biopsies. In Cohort 1, serum FAP was an independent risk
factor for median liver stiffness ≥ 10.3 kPa. There was an 8-fold increased odds ratio of having a median liver stiffness of ≥10.3 kPa for those in the highest FAP tertile, compared with subjects in the lowest tertile (p = 0.01). A serum FAP level below 730 pmol AMC/min/mL had a negative Flavopiridol (Alvocidib) predictive value for significant fibrosis of 95%. In Cohort 2, the FAP level was added to the NAFLD fibrosis score (NFS) to correctly reclassify 49% of patients as low risk of severe fibrosis who by NFS had been classified as intermediate risk. Measuring FAP in serum is rapid and should thus become an inexpensive supplement to the NFS to avoid patients being sent for unnecessary further tests. Cell lines derived from FAP gko mice were engineered to express functional
FAP enzyme (FAPe+) vs inactive FAP (FAPe-). Proteomic analyses of these cells showed FAP-specific cleavage of many bioactive peptides. In vitro ‘wound healing’ found that cells with FAP activity exhibited greater cell migration but comparable proliferation and apoptosis. Conclusions: (1) FAP has an important role in glucose and lipid metabolism and in fibrosis progression. (2) Adding a FAP serum measurement to the existing clinical NFS algorithm may correctly diagnose as non-fibrotic about half of the patients who would otherwise receive an uncertain diagnosis and require further testing. (3) FAP enzyme activity causes increased cell migration and so may have roles in wound healing. 1. Keane FM, et al.