In vitro activity of some flavonoid derivatives on human leukemic myeloid cells: evidence for aminopeptidase-N (CD13) inhibition, antiproliferative and cell death properties

Abstract

Leukemia cells from patients with acute myeloid leukemia (AML) display high proliferative capacity and are resistant to death. Membrane-anchored aminopeptidase-N/CD13 is a potential drug target in AML . Clinical research efforts are currently focusing on targeted therapies that induce death in AML cells. We previously developed a non-cytotoxic APN/CD13 inhibitor based on flavone-8-acetic acid scaffold, the 2',3-dinitroflavone-8-acetic acid (1) . In this context, among the variously substituted 113 compounds further synthesized and tested for evaluation of their effects on APN/CD13 activity, proliferation and survival in human AML U937 cells, eight flavonoid derivatives emerged: 2',3-dinitro-6-methoxy-flavone-8-acetic acid ( 2 ), four compounds ( 3 – 6 ) with the 3-chloro-2,3-dihydro-3-nitro-2-phenyl-4 H -1-benzopyran-4-one structure, and three ( 7 – 9 ) with the 3-chloro-3,4-dihydro-4-hydroxy-3-nitro-2-phenyl-2 H -1-benzopyran framework. Different structure-activity relationships were observed between APN/CD13 activity and growth/survival processes. We showed that compound 2 , but not benzopyran derivatives 3 – 9 , inhibited APN activity (although to a less degree than 1) . Both 1 and 2 did not affect AML cell proliferation and survival, indicating that CD13’s APN activity is not required for these processes. In contrast, benzopyran compounds 3 – 9 inhibited in a concentration-dependent manner the growth of U937 cells by inducing death as evidenced by phosphatidylserine externalization. Cell death was associated with the presence of geminal nitro group and chlorine at the 3-position of the 2 H -1-benzopyran scaffold. The presence of other substituents such as CH 2 COOH or CH 2 CH=CH 2 groups at the 8-position, NO 2 or I substituents at the 2'- or 3'-position, OCH 3 or OCH 2 C 6 H 5 groups at the 4'-position did not affect cell death. Importantly, the inhibitory effects evidenced with compounds 7 – 9 were not due to their potential decomposition into the corresponding ( Z )-(2chloro-2-nitroethenyl)benzene and salicylaldehyde. Based on these preliminary data, the 3-chloro,3-nitro-2 H -1-benzopyran derivatives could be classified as a new group of compounds with promising antitumor properties; this study therefore provides the opportunity to explore their potential efficiency in AML patients’ cells ex vivo .