Activity screening and structure-activity relationship of the hit compounds targeting APN/CD13.

Aminopeptidase N (APN) plays an important role in tumor progression, which participates in the progress such as proliferation, attachment, angiogenesis, and tumor invasion. All of this makes APN as a good chemical therapeutic anti-tumor target. In this study, a series of chemically synthesized APN inhibitors were tested for the anti-tumor activities, and three most effective compounds were chosen according to the MTT assay. Then, the enzyme inhibitory, anti-tumor, specificity, angiogenesis, and invasion were determined to evaluate the activity of these three compounds. All compounds can markedly inhibit the enzyme activity of APN, angiogenesis of endothelial cells, and the invasion of ES-2 cells. And it had little effect on the viability of K562 which express low level of APN. This data indicated that the tested compounds were APN hit compounds. We also did kinetic assay to determine the inhibition constant and constructed a three-dimensional quantitative structure-activity relationship model to analyze the structure-activity relationship to direct the further design of novel APN inhibitors as anti-tumor agents. These data demonstrate that the tested compounds can be developed as novel candidates of anticancer agent.