Continuous de novo lipogenesis is a common feature of tumor cells and is required to meet the bioenergetic and biosynthetic demands of a growing tumor. The expression and activity of the fatty acid synthetic enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase are up-regulated in many types of cancer, where lipogenesis is essential for proliferation and tumor cell survival. These enzymes are therefore attractive targets for anti-neoplastic intervention. Inhibition of ACC results in inhibition of fatty acid synthesis (FASyn) and stimulation of fatty acid oxidation in cultured cells and in animals and has been shown to reduce cancer cell growth in vitro. Our efforts to develop novel ACC inhibitors have focused on the subunit dimerization site of the biotin carboxylase (BC) domain of the enzyme. This site also binds the inhibitory phosphopeptide of ACC phosphorylated by AMPK and the fungal metabolite Soraphen A, both of which suppress dimerization and inhibit enzymatic activity. Using state-of-the-art structure-based drug design and crystal structures of human ACC2 BC domain, we have identified a unique series of allosteric inhibitors with low nanomolar potency, represented by ND646, that bind to the Soraphen binding site, exhibit potent and selective activity in vitro and in vivo and show anti-neoplastic properties in cultured human non-small cell lung cancer (NSCLC) cells. The anti-proliferative action of ND646 in NSCLC cell lines A549, H460, and H358 was enhanced in delipidated media and attenuated by supplementation with palmitic acid, suggesting that the anti-proliferative effect of ND646 is induced by depletion of cellular fatty acids. Current efforts are focused on determining if the cell growth inhibitory actions of ND646 also possess apoptotic properties and on assessing the anti-neoplastic activity of ND646 in preclinical models of lung cancer. During the course of these studies, we also discovered that interaction of ND646 with the ACC phosphopeptide binding site markedly reduced the phosphorylation state of the enzyme in A549 cells, as determined by western blot analysis using anti-phosphoACC (pACC) antibody. Furthermore, in HepG2 cells, the reduction in pACC by the related analog ND630 (EC50 = 66 nM), which closely paralleled inhibition of FASyn (EC50 = 42 nM), resulted in complete loss of pACC at high doses. These observations, that were corroborated in hepatic tissue isolated from both ND646 and ND630 treated mice and in situ in tumors of genetically engineered mouse models of lung cancer dosed with ND646, suggest that assessment of pACC could provide a sensitive biomarker of target engagement for ACC inhibitors interacting in this region of the enzyme. Additional efforts are focused on examining the genetic contexts and optimal therapeutic combinations such that ACC inhibitors may find the greatest clinical utility as anti-neoplastic agents.
Citation Format: Robert Svensson, Geraldine Harriman, Jeremy Greenwood, Sathesh Bhat, H.James Harwood, Rosana Kapeller, Reuben Shaw. Acetyl-CoA carboxylase inhibition by ND646 reduces fatty acid synthesis and inhibits cell proliferation in human non-small cell lung cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2679. doi:10.1158/1538-7445.AM2014-2679