Identification and Characterization of Novel Arylamine NAcetyltransferase Small Molecule Inhibitors

Abstract

Many environmental arylamines play a vital role in the etiology of cancer and require metabolic activation by acetylation. Arylamine N‐acetyltransferase 1 (NAT1), a xenobiotic metabolizing enzyme, catalyzes the N‐acetylation or O‐acetylation of arylamine carcinogens. O‐acetylation, which is preceded by cytochrome P450 N‐hydroxylation, results in nitrenium ions that form DNA adducts. If unrepaired, these adducts can lead to mutagenesis and initiate cancer. Molecular epidemiology studies suggest that NAT1 expression and genetic polymorphisms play an important role in individual risk for many cancers, including breast cancer. Studies also suggest that NAT1 may play an important role in cell growth and survival, as well as in cell invasion, which is a hallmark of metastatic cancer. The purpose of this study is to use NAT1 as a molecular target for the development of small molecule inhibitors for cancer prevention. We utilized in silico screening of 17 million compounds to identify those that interact with NAT active sites. A total of 150 lead compounds were identified, scored and ranked based on their active site association. Sixty of these compounds were tested for their ability to inhibit recombinant human NAT1. The IC50 values of the most efficacious inhibitors (2, 10, 11 and 16 ) of human NAT1 in vitro were >2 mM, and 0.75, 191, and 202 μM, respectively. The most potent inhibitor (10 ) was further tested for inhibition of N‐acetylation in situ in Chinese hamster ovary cells. The IC50 values of inhibitor 10 were 118 μM and 81.6 μM towards the N‐acetylation of p‐aminobenzoic acid and the arylamine carcinogen 4‐aminobiphenyl. We report the in silico identification and verification of compound 10 as a potential new small molecule for cancer prevention. [NIH/NIEHS (T32‐ ES011564) and UofL Clinical and Translational Sciences Program]