Effect of Non-Competitive Inhibitors of Aminopeptidase N on Viability of Human and Murine Tumor Cells

Abstract Cancer is the second leading cause of death worldwide. Peptidases participate in tumor development and growth. Mammalian neutral aminopeptidase (APN, EC 3.4.11.2, M1 family) catalyzes the cleavage of neutral and basic amino acids from the N-terminus of substrates. APN expression is dysregulated in several types of cancer, being a target for the development of new anticancer agents. Recently, we identified three new non-competitive inhibitors of soluble porcine APN (pAPN) by virtual screening (BTB11079, JFD00064, BTB07018, from Maybridge). In the present contribution we assayed their effect on the activity of APN in a microsomal preparation of porcine kidney cortex, a model of the physicochemical environment of the enzyme. These classical inhibitors had an IC50 value of 3–5 µM. Additionally, using a kinetic approach and a specific substrate, we quantified APN activity on the cell surface of human and murine lung, colon, prostate, and skin tumor cells. APN inhibitors reduced tumor cells viability, more efficiently in the higher APN activity tumor cell lines, but not in non-tumoral cells. BTB11079, JFD00064, BTB07018 effects on cell viability were stronger than that of bestatin, a positive control. Thus, these non-competitive APN inhibitors may be useful tools for cancer treatment.