We used the lead compound C to

We used the lead compound C4 to demonstrate that small molecule ACL inhibitors can recapitulate ACL knockdown (KD) in modulation of cancer stemness. We have shown previously that ACL KD reduced the CSC population in multiple cancer cell lines. The E-snail cells are an established CSC model system. E-snail cells are derived from the HMLE (human mammary epithelial) cell line by overexpressing the transcription factor snail. Cell surface markers CD44 and CD24 are commonly used to distinguish cancer stem (CD44+/CD24−) and non-stem (CD44+/− and CD24+) cells. The E-snail cells were cultured in the absence (control) or the presence of inhibitor C4 (10 and 25μM) for 48 and then processed by FACS (fluorescence-activated cell sorting) analyses to separate the CD44+/CD24− and the CD44+/−/CD24+ cell populations. The control E-snail cells were dominated by the CD44+/CD24− stem cell population (A). In comparison, the ACL inhibitor C4 dose-dependently decreased the CSC (CD44+/CD24−) population as well as increased the non-CSC (CD44+/− and CD24+) population (B and C). This result is in agreement with the finding of ACL KD in E-snail cells, and supports the overall approach of targeting cancer stemness by inhibiting ACL activity. In summary, via docking analyses of 1947 furoic chemicals learn this here now derivatives, we identified 4 subtypes of (benzo)furan carboxylic acids that significantly and dose-dependently inhibited ACL activity. Our results expand the inhibitor chemical space for this important metabolic enzyme. We applied two docking algorithms to cross validate the hits and selected 24 virtual hits, each ranked in the top 10% of compounds by both algorithms, for determination of activity. Eleven (11) of the 24 compounds were confirmed as active hits according to our selection criteria (>20% inhibition at 10μM, and >80% at 100μM). The most potent lead (A1) showed an IC of 4.1μM in the ADP Glo ACL enzymatic assay. The IC values of two additional leads A3 and C4 were determined as 11.9 and 13.8μM, respectively. Furthermore, the identification of multiple hits in series A and C provides valuable preliminary SAR trends that will guide lead optimization studies. Acknowledgement This research was partially supported by a seed fund for the Center for Drug Discovery and Translational Research (LS) and a research grant by Fujifilm (VS and LS).
Introduction Acetyl coenzyme A (acetyl-CoA) is a high-energy metabolite that is a product of carbohydrate, amino acid, and lipid catabolism, and the precursor of numerous anabolic pathways (Oliver et al., 2009). Given its role at the ‘hub’ of cellular metabolism, a thorough understanding of acetyl-CoA biosynthesis is critical; this is especially true of eukaryotes, as acetyl-CoA is membrane-impermeable, and distinct biosynthetic mechanisms are therefore required in the various subcellular compartments, including mitochondria, chloroplasts, peroxisomes, and the cytosol (Oliver et al., 2009). In animals (Elshourbagy et al., 1990, Elshourbagy et al., 1992), land plants (Fatland et al., 2002), a glaucophyte alga (Ma et al., 2001), and filamentous fungi (Hynes and Murray, 2010, Son et al., 2011), the major cytosolic source of acetyl-CoA is ATP-citrate lyase (ACL; EC 2.3.3.8), an enzyme that catalyzes the ATP-dependent cleavage of citrate into oxaloacetate and acetyl-CoA. Typically, ACL’s substrate is mitochondrion-derived citrate; this enzyme therefore plays a role in the ‘citrate shuttle’ that effects the net transfer of acetyl-CoA equivalents to the cytosol for fatty acid biosynthesis. The acetyl-CoA generated by ACL is a key substrate of myriad other downstream anabolic processes in eukaryotes, including the biosynthesis of sterols, waxes, isoprenoids, and flavonoids (Oliver et al., 2009), and nuclear histone acetylation (Wellen et al., 2009). ACL is also encoded in the genomes of prokaryotes; however, it is sparsely distributed, and is found only in a few species belonging to ε-proteobacteria, Aquificae, Chlorobi, and Euryarchaeota, many of which are thermophiles living near deep-sea vents (Campbell and Cary, 2004). Although the chemical reaction catalyzed by ACL is the same as in eukaryotes, the physiological context is different: in prokaryotes, ACL is a component of the reverse TCA cycle, a reductive, carbon-fixing pathway that serves as an alternative to the Calvin–Benson–Bassham reductive pentose phosphate cycle (Buchanan and Arnon, 1990). Thus, there has been a functional modification in eukaryotes, with ACL shifting from a role in permitting autotrophic growth, to supplying a key intermediate in various eukaryotic anabolic processes (Fatland et al., 2002).