LAUSR

Arylamine N‐acetyltransferase 1 (NAT1) expression is reported to affect proliferation, invasiveness, and growth of cancer cells. MDA‐MB‐231 breast cancer cells were engineered such that NAT1 expression was elevated or suppressed, or treated with a small molecule inhibitor of NAT1. The MDA‐MB‐231 human breast cancer cell lines were engineered with a scrambled shRNA, a NAT1 specific shRNA or a NAT1 overexpression cassette stably integrated into a single flippase recognition target (FRT) site facilitating incorporation of these different genetic elements into the same genomic location. NAT1‐specific shRNA reduced NAT1 activity in vitro by 39%, increased endogenous acetyl coenzyme A levels by 35%, and reduced anchorage‐independent growth (sevenfold) without significant effects on cell morphology, growth rates, anchorage‐dependent colony formation, or invasiveness compared to the scrambled shRNA cell line. Despite 12‐fold overexpression of NAT1 activity in the NAT1 overexpression cassette transfected MDA‐MB‐231 cell line, doubling time, anchorage‐dependent cell growth, anchorage‐independent cell growth, and relative invasiveness were not changed significantly when compared to the scrambled shRNA cell line. A small molecule (5E)‐[5‐(4‐hydroxy‐3,5‐diiodobenzylidene)‐2‐thioxo‐1,3‐thiazolidin‐4‐one (5‐HDST) was 25‐fold more selective towards the inhibition of recombinant human NAT1 than N‐acetyltransferase 2. Incubation of MDA‐MB‐231 cell line with 5‐HDST resulted in 60% reduction in NAT1 activity and significant decreases in cell growth, anchorage‐dependent growth, and anchorage‐independent growth. In summary, inhibition of NAT1 activity by either shRNA or 5‐HDST reduced anchorage‐independent growth in the MDA‐MB‐231 human breast cancer cell line. These findings suggest that human NAT1 could serve as a target for the prevention and/or treatment of breast cancer.