In silico screening for identification of fatty acid synthase inhibitors and evaluation of their antiproliferative activity using human cancer cell lines.

De novo lipogenesis (DNL) by upregulation of fatty acid synthase (FASN) is an important metabolic alteration of cancer cells. FASN is over-expressed in several cancers and is often associated with a high risk of recurrence and poor prognosis. Differential expression of FASN in cancer cells and their normal counterparts leads to the impression that FASN can be an attractive druggable target in cancer therapy. Present study focuses on identification of inhibitors against FASN ketoacyl synthase (KS) domain from Asinex Biodesign compound database using in silico tools. Virtual screening resulted in the identification of two hit compounds BDD27845077 and BDD27845082 with a common core structure. Molecular Docking studies showed that BDD27845077 and BDD27845082 bind at the substrate entry channel of KS domain with GScore -12.03 kcal/mol and -12.29 kcal/mol respectively. Molecular dynamics (MD) simulation of the protein-ligand complexes shows the binding stability of ligands with FASN-KS. In vitro validation of BDD27845082 demonstrated that the compound possesses antiproliferative activity in a panel of human cancer cell lines including MDA-MB-231 (breast cancer), HCT-116 (colon cancer) and HeLa (cervical cancer) with maximum sensitivity against HCT-116 (IC 50 = 25 µM). The study put forward two lead compounds against FASN with favorable pharmacokinetic profile as indicated by virtual screening tools for the development of cancer chemotherapeutics.

Natural fatty acid synthase inhibitors as potent therapeutic agents for cancers: A review.

Context Fatty acid synthase (FAS) is the only mammalian enzyme to catalyse the synthesis of fatty acid. The expression level of FAS is related to cancer progression, aggressiveness and metastasis. In recent years, research on natural FAS inhibitors with significant bioactivities and low side effects has increasingly become a new trend. Herein, we present recent research progress on natural fatty acid synthase inhibitors as potent therapeutic agents. Objective This paper is a mini overview of the typical natural FAS inhibitors and their possible mechanism of action in the past 10 years (2004-2014). Method The information was collected and compiled through major databases including Web of Science, PubMed, and CNKI. Results Many natural products induce cancer cells apoptosis by inhibiting FAS expression, with fewer side effects than synthetic inhibitors. Conclusion Natural FAS inhibitors are widely distributed in plants (especially in herbs and foods). Some natural products (mainly phenolics) possessing potent biological activities and stable structures are available as lead compounds to synthesise promising FAS inhibitors.

Progress in the development of fatty acid synthase inhibitors as anticancer targets.

Fatty acid synthase (E.C. 2.3.1.85; FASN) is a multifunctional enzyme system that catalyzes the formation of fatty acids from acetyl-CoA, malonyl-CoA, and NADPH and plays a central role in lipid biosynthesis. Two classes of FASN exist: FASN I in animals and fungi, and FASN II in plants and prokaryotes. Animal FASN I is a homodimeric protein found in the cytosol of lipogenic tissues such as the liver and brain. Many human carcinomas exhibit elevated levels of FASN I, though the benefit to cancer cells is still unclear. Inhibition of FASN I selectively effects apoptosis in cancer cells, and the role of FASN I in chemotherapy is a growing area of research with the use of natural products and small molecule inhibitors.

Crystal structure of the human fatty acid synthase enoyl-acyl carrier protein-reductase domain complexed with triclosan reveals allosteric protein-protein interface inhibition.

Human fatty acid synthase (FAS) is a large, multidomain protein that synthesizes long chain fatty acids. Because these fatty acids are primarily provided by diet, FAS is normally expressed at low levels; however, it is highly up-regulated in many cancers. Human enoyl-acyl carrier protein-reductase (hER) is one of the FAS catalytic domains, and its inhibition by drugs like triclosan (TCL) can increase cytotoxicity and decrease drug resistance in cancer cells. We have determined the structure of hER in the presence and absence of TCL. TCL was not bound in the active site, as predicted, but rather at the protein-protein interface (PPI). TCL binding induces a dimer orientation change that causes downstream structural rearrangement in critical active site residues. Kinetics studies indicate that TCL is capable of inhibiting the isolated hER domain with an IC50 of ∼ 55 µM. Given the hER-TCL structure and the inhibition observed in the hER domain, it seems likely that TCL is observed in the physiologically relevant binding site and that it acts as an allosteric PPI inhibitor. TCL may be a viable scaffold for the development of anti-cancer PPI FAS inhibitors.

Complete NMR assignments of undegraded asterosaponins from Asterias amurensis.

Four asterosaponins, thornasteroside A (1), versicoside A (2), anasteroside B (3), and asteronylpentaglycoside sulfate (4), were isolated from the predatory starfish Asterias amurensis Lütken. Unlike previous studies focusing on structure elucidation by degradation of the complex saponin molecules, complete nuclear magnetic resonance (NMR) assignment for the intact molecules was accomplished using 600 MHz high magnetic field NMR. The complete set of NMR assignments can help in the structure elucidation of asterosaponins isolated in low yields without resorting to chemical degradation. Furthermore, this approach can be extended to other complex steroidal saponins, which may accelerate the discovery of bioactive secondary metabolites from this invasive starfish species.

Bioassay-guided isolation of fatty acid synthase inhibitory diterpenoids from the roots of Salvia miltiorrhiza Bunge.

Fatty acid synthase (FAS) is considered as a novel drug target for the development of anticancer and anti-obesity agents. Bioassay-guided fractionation of a n-hexane-soluble extract prepared from the roots of Salvia miltiorrhiza Bunge (Labiatae), using an in vitro enzyme assay, led to the isolation of five abietane diterpenoids: 15,16-dihydrotanshinone I (1), cryptotanshinone (2), tanshinone I (3), tanshinone IIA (4), and dansenspiroketallactone (5). Compounds 1-5 were tested for their in vitro FAS inhibitory activity and, except for compound 5 (IC(50) > 100 µM), compounds 1-4 inhibited the enzyme activity with IC(50) values ranging from 12.0 to 30.3 µM. Our findings may be partially related to the anticancer activity of abietane diterpenoids from the plant, suggesting a further study on the anticancer potential of tanshinone derivatives.

Anti-cancer drugs targeting fatty acid synthase (FAS).

Fatty acid synthase (FAS) is a key enzyme of the fatty acid biosynthetic pathway which catalyzes de novo lipid synthesis. FAS expression in normal adult tissues is generally very low or undetectable as majority of fatty acids obtained are from dietary sources, whereas it is significantly upregulated in cancer cells despite adequate nutritional lipid supply. Activation of FAS provides rapidly proliferating tumor cells sufficient amount of lipids for membrane biogenesis and confers growth and survival advantage possibly acting as a metabolic oncogene. Importantly, inhibition of FAS in cancer cells using the pharmacological FAS inhibitors results in tumor cell death by apoptosis whereas normal cells are resistant. Due to this differential expression of FAS, the inhibitors of this enzyme are selectively toxic to tumor cells and therefore FAS is considered an attractive therapeutic target for cancer. Several FAS inhibitors are already patented and commercially available; however, the potential toxicity of these FAS inhibitors remains to be tested in clinical trials. In this review, we discuss some of the potent FAS inhibitors along with their patent information, the mechanism of anti-cancer effects and the development of more specific and potent FAS inhibitors with lower side effects that are expected to emerge as anti-cancer treatment in the near future.

Binding of triclosan to human serum albumin: insight into the molecular toxicity of emerging contaminant.

PURPOSE: The interaction between triclosan (TCS) and human serum albumin (HSA) was investigated in order to obtain the binding mechanism, binding constant, the type of binding force, the binding distance between the donor and acceptor, and the effect of TCS on the conformation change of HSA. METHODS: A HSA solution was added to the quartz cell and then titrated by successive addition of TCS. The fluorescence quenching spectra and synchronous spectra were recorded with the excitation and emission slits of the passage of band set at 10 and 20 nm. Three-dimensional fluorescence spectra of HSA were recorded before and after the addition of TCS. The capillary electrophoresis was conducted with the pressure injection mode at 0.5 psi for 5 s, separation under 25 kV, and detection at 214 nm. RESULTS: Fluorescence data indicated the fluorescence quenching of HSA by TCS was static quenching, and the quenching constants (K ( a )) were 1.14 × 10(5), 8.75 × 10(4), 6.67 × 10(4), and 5.00 × 10(4) at 293, 298, 303, and 309 K, respectively. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the interaction were calculated to be -37.9 kJ mol(-1) and 32.6 J mol(-1) K(-1). The binding distance between TCS and tryptophan residues of HSA was obtained to be 1.81 nm according to Fǒrster nonradioactive energy transfer theory. The UV-Vis absorption spectroscopy, the synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, and circular dichroism spectroscopy revealed the alterations of HSA secondary structure in the presence of TCS. Finally, the interaction between TCS and HSA was further confirmed by capillary electrophoresis. CONCLUSIONS: TCS was bound to HSA to form the TCS-HSA complex, with the binding distance of 1.81 nm. Hydrophobic interaction and hydrogen bond were dominated in the binding. TCS could change the secondary conformation of HSA. This work provides an insight into noncovalent interaction between emerging pollutants and protein, helping to elucidate the toxic mechanism of such pollutants.

Triclosan - an update.

The discovery in 1998 that triclosan has a site-specific action in the bacterial cell as an inhibitor of NADH- or NADPH-dependent enoyl-acyl carrier protein reductase led to a lively debate in the scientific press. The thesis of this debate was that such a mode of action may allow triclosan to induce resistance and cross-resistance in bacterial cells. The debate last saw review in 2004, and this paper aims at updating our knowledge in this area, given recent research on the topic.

Discovery and syntheses of "superbug challengers"-platensimycin and platencin.

Bacteria have developed resistance to almost all existing antibiotics known today and this has been a major issue over the last few decades. The search for a new class of antibiotics with a new mode of action to fight these multiply-drug-resistant strains, or "superbugs", allowed a team of scientists at Merck to discover two novel antibiotics, platensimycin and platencin using advanced screening strategies, as inhibitors of bacterial fatty acid biosynthesis, which is essential for the survival of bacteria. Though both these antibiotics are structurally related, they work by slightly different mechanisms and target different enzymes conserved in the bacterial fatty acid biosynthesis. This Focus Review summarizes the synthetic and biological aspects of these natural products and their analogues and congeners.

Transformation of Triclosan by Fe(III)-saturated montmorillonite.

Abiotic transformation of triclosan (TCS) was investigated by incubating TCS with Fe(III)- and Na-montmorillonite at 40% relative humidity and room temperature for up to 100 days. The TCS transformation products were characterized using LC/MS, GC/MS, and computational modeling and quantified using HPLC/UV and GC/MS. Within 1-5 days, depending on the initial TCS concentrations, about 55% of the TCS was rapidly transformed in the presence of Fe(III)-montmorillonite, producing 2,4-dichlorophenol, 3-chlorophenol, 2,4-dichlorophenol dimer, chlorophenoxy phenols, and TCS dimers and trimers. Computational modeling based on density functional theory confirmed the formation of four TCS dimer conformers and six TCS trimer conformers. The TCS phenoxy radicals, produced by Fe(III) oxidation of TCS, react with other TCS molecules to form TCS dimers. The TCS trimers were formed by attachment of TCS dimer phenoxy radicals, produced by Fe(III) oxidation of TCS dimers, with TCS molecules. Significantly smaller quantities of TCS transformation products were detected in the reactions with Na-montmorillonite compared to the reactions with Fe(III)-montmorillonite. Formation of a significant amount of 2,4-dichlorophenol, especially in reaction with Fe(III)-montmorillonite, may have negative impact on the environment because of its toxicity. However, mineral-facilitated TCS polymerization may reduce its mobility and bioavailability in soils.

Synthesis and biological activity of enantiomeric pairs of 5-(Alk-2-enyl)thiolactomycin and 5-[(E)-Cycloalk-2-enylidenemethyl]thiolactomycin congeners.

The title compounds were synthesized by the efficient route previously explored for the synthesis of enantiomeric pairs of thiolactomycin and its 3-demethyl derivative. These studies were carried out to prove the flexibility of the previously explored synthetic route to natural thiolactomycin (TLM) 1 and to examine the structure-activity relationship on the 5-position of 1. While all of the synthesized congeners lacked in vitro antibacterial activity, these studies led us to find 5-(alk-2-enyl)-TLM (ent-4d) which exhibits mammalian type I fatty acid synthase (FAS) inhibitory activity equal to that of C75, a potent inhibitor reported previously. It was also found that 5-[(E)-cycloalk-2-enylidenemethyl]-TLM (ent-5c) exhibited slightly less potent mammalian type I FAS inhibitory activity than C75.

Slow-onset inhibition of the FabI enoyl reductase from francisella tularensis: residence time and in vivo activity.

Francisella tularensis is a highly virulent and contagious Gram-negative intracellular bacterium that causes the disease tularemia in mammals. The high infectivity and the ability of the bacterium to survive for weeks in a cool, moist environment have raised the possibility that this organism could be exploited deliberately as a potential biological weapon. Fatty acid biosynthesis (FAS-II) is essential for bacterial viability and has been validated as a target for the discovery of novel antibacterials. The FAS-II enoyl reductase ftuFabI has been cloned and expressed, and a series of diphenyl ethers have been identified that are subnanomolar inhibitors of the enzyme with MIC90 values as low as 0.00018 microg mL(-1). The existence of a linear correlation between the Ki and MIC values strongly suggests that the antibacterial activity of the diphenyl ethers results from direct inhibition of ftuFabI within the cell. The compounds are slow-onset inhibitors of ftuFabI, and the residence time of the inhibitors on the enzyme correlates with their in vivo activity in a mouse model of tularemia infection. Significantly, the rate of breakdown of the enzyme-inhibitor complex is a better predictor of in vivo activity than the overall thermodynamic stability of the complex, a concept that has important implications for the discovery of novel chemotherapeutics that normally rely on equilibrium measurements of potency.

Surfactants, aromatic and isoprenoid compounds, and fatty acid biosynthesis inhibitors suppress Staphylococcus aureus production of toxic shock syndrome toxin 1.

Menstrual toxic shock syndrome is a rare but potentially life-threatening illness manifest through the actions of Staphylococcus aureus toxic shock syndrome toxin 1 (TSST-1). Previous studies have shown that tampon additives can influence staphylococcal TSST-1 production. We report here on the TSST-1-suppressing activity of 34 compounds that are commonly used additives in the pharmaceutical, food, and perfume industries. Many of the tested chemicals had a minimal impact on the growth of S. aureus and yet were potent inhibitors of TSST-1 production. The TSST-1-reducing compounds included surfactants with an ether, amide, or amine linkage to their fatty acid moiety (e.g., myreth-3-myristate, Laureth-3, disodium lauroamphodiacetate, disodium lauramido monoethanolamido, sodium lauriminodipropionic acid, and triethanolamine laureth sulfate); aromatic compounds (e.g. phenylethyl and benzyl alcohols); and several isoprenoids and related compounds (e.g., terpineol and menthol). The membrane-targeting and -altering effects of the TSST-1-suppressing compounds led us to assess the activity of molecules that are known to inhibit fatty acid biosynthesis (e.g., cerulenin, triclosan, and hexachlorophene). These compounds also reduced S. aureus TSST-1 production. This study suggests that more additives than previously recognized inhibit the production of TSST-1.

Phagocytic activity of macrophages against liposomes with conjugates of oxidized dextrans and isonicotinic acid hydrazide during modeling of phagocytosis disturbances in vitro.

We studied phagocytic activity of macrophages against molecular-liposome hybrid compositions consisting of liposomes (diameter 200-450 nm) containing oxidized dextrans with a molecular weight of 35 or 60 kDa conjugated with the basic antituberculosis preparation isonicotinic acid hydrazide (dextrazides) during modeling of various disturbances of endocytosis function of phagocytic cells in vitro. Preincubation of macrophages with trypsin, colchicine, or sodium azide did not change the parameters of adhesion of molecular-liposome hybrid compositions to macrophages. It was found that preincubation of cells with colchicine or sodium azide reduced parameters of phagocytosis of the molecular-liposome hybrid compositions; this reduction did not depend on the molecular weight of dextrans entering the composition of the molecular-liposome hybrid compositions.

Effects of molecular liposomal hybrid compositions with oxidized dextrans and isonicotinic acid hydrazide on production of granulocytic macrophage colony-stimulating factor by macrophages.

The effects of molecular liposomal hybrid compositions consisting of liposomes (200-450 nm) containing oxidized dextrans (dextranals; 35-60 kDa) conjugated with isonicotinic acid hydrazide (dextrazides), their components, and native dextrans on the production of granulocytic macrophage CSF by peritoneal macrophages were studied in vitro. Dextranals proved to be more potent inductors of granulocytic macrophage CSF than native dextrans. Conjugation of nicotinic acid hydrazide with dextranals did not modify their capacity to stimulate the production of granulocytic macrophage CSF. Liposomes in the molecular liposomal hybrid compositions did not attenuate the dextrazide capacity to stimulate the production of granulocytic macrophage CSF. Molecular liposomal compositions containing 60 kDa dextrazide exhibited the most potent stimulatory effect on macrophage production of granulocytic macrophage CSF.

cDNA microarray analysis of the expression profiles of Trichophyton rubrum in response to novel synthetic fatty acid synthase inhibitor PHS11A.

Trichophyton rubrum (T. rubrum) is a major pathogen responsible for dermatophytosis. Because of potential relapse of disease with current antifungal therapy protocols, there is a need for additional and/or alternative antifungal agents for the treatment of disease caused by T. rubrum. We synthesized a potent fungal fatty acid synthase inhibitor, PHS11A, based on the structure of fungal fatty acid synthase. The antifungal activities of PHS11A were tested against 38 clinical isolates of T. rubrum and compared with those of ketoconazole and terbinafine, the MIC(50) and MIC(90) of PHS11A on the isolates were 2 and 4 microg/ml, respectively. We evaluated the transcriptional response of T. rubrum hyphae exposed to PHS11A using 11,232-spot cDNA microarrays. PHS11A exposure increased transcription of fatty acid synthases (FASs) genes FAS1 and FAS2. PHS11A also affected transcription of some genes involved in lipid metabolism, cAMP and MAPK pathways, and multidrug resistance. Quantitative real-time PCR was performed for selected genes to verify the microarray results.