title: Metabolic shifts induced by fatty acid synthase inhibitor orlistat in non-small cell lung carcinoma cells provide novel pharmacodynamic biomarkers for positron emission tomography and magnetic resonance spectroscopy.
abstract: OBJECTIVE
  Abnormal fatty acid (FA) synthesis is one of the common features of cancer. Fatty acid synthase (FASN), a multifunctional enzyme playing a key role in biosynthesis of FA, is up-regulated in prostate, breast, and lung carcinomas. Orlistat is a FDA-approved anti-obesity drug that inhibits the thioesterase domain of FASN, interferes with cellular FA synthesis, can arrest tumor cell proliferation, and induces tumor cell apoptosis. The current study was aimed to investigate the metabolic changes associated with FASN inhibition by orlistat and to understand the molecular mechanisms behind the observed metabolic changes in non-small cell lung carcinoma (NSCLC) cell lines.
  
  
  METHODS
  Changes in metabolite pools in four NSCLC cell lines (H441, H1975, H3255, and PC14) with different mutational profiles were studied using NMR spectroscopy before and after in vitro incubation with sub-toxic concentration of orlistat and [1-(13)C]D-glucose or [1,2-(13)C2]choline. In vitro radiotracer accumulation assays in cells were performed with [(3)H]acetate, [(14)C]fluoroacetate, and 2-deoxy-2-[(18)F]fluoro-D-glucose. In parallel, microarray profiling of genes involved in the regulation of carbohydrate and lipid metabolism was performed.
  
  
  RESULTS
  In orlistat-treated NSCLC cells, FASN inhibition results in characteristic changes in intermediary metabolites (FAs, choline, phospholipids, and TCA cycle metabolites) as observed by magnetic resonance spectroscopy. Further, FASN inhibition by orlistat induces multiple adaptive changes in FA synthetic pathway and associated metabolic pathways, including induction of ketone metabolism and glutaminolysis, as well as the up-regulation of 5' adenosine monophosphate-activated protein kinase.
  
  
  CONCLUSIONS
  These observed changes in metabolic pools in orlistat-treated cells demonstrate the critical role of fatty acid de novo synthesis and metabolism for cellular energy production, especially in tumor cells with low glycolytic activity, which goes beyond the widely accepted concept that FA synthesis is important for cell membrane biosynthesis in rapidly proliferating tumor cells.
authors.affiliation: Department of Experimental Diagnostic Imaging, The University of Texas M D Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Madhuri
authors.initials: M
authors.lastname: Sankaranarayanapillai
authors.forename: Nianxiang
authors.initials: N
authors.lastname: Zhang
authors.forename: Keith A
authors.initials: KA
authors.lastname: Baggerly
authors.forename: Juri G
authors.initials: JG
authors.lastname: Gelovani
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000032:analysis; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D016000:Cluster Analysis; D064429:Fatty Acid Synthases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007783:Lactones / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D000077403:Orlistat; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals / Q000032:analysis / Q000493:pharmacokinetics; D059467:Transcriptome / Q000187:drug effects
chemical_list: D014408:Biomarkers, Tumor; D002250:Carbon Radioisotopes; D007783:Lactones; D019275:Radiopharmaceuticals; D000077403:Orlistat; D064429:Fatty Acid Synthases