title: Pharmacological inhibition of nicotinamide phosphoribosyltransferase (NAMPT), an enzyme essential for NAD+ biosynthesis, in human cancer cells: metabolic basis and potential clinical implications.
abstract: Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the first rate-limiting step in converting nicotinamide to NAD(+), essential for cellular metabolism, energy production, and DNA repair. NAMPT has been extensively studied because of its critical role in these cellular processes and the prospect of developing therapeutics against the target, yet how it regulates cellular metabolism is not fully understood. In this study we utilized liquid chromatography-mass spectrometry to examine the effects of FK866, a small molecule inhibitor of NAMPT currently in clinical trials, on glycolysis, the pentose phosphate pathway, the tricarboxylic acid (TCA) cycle, and serine biosynthesis in cancer cells and tumor xenografts. We show for the first time that NAMPT inhibition leads to the attenuation of glycolysis at the glyceraldehyde 3-phosphate dehydrogenase step due to the reduced availability of NAD(+) for the enzyme. The attenuation of glycolysis results in the accumulation of glycolytic intermediates before and at the glyceraldehyde 3-phosphate dehydrogenase step, promoting carbon overflow into the pentose phosphate pathway as evidenced by the increased intermediate levels. The attenuation of glycolysis also causes decreased glycolytic intermediates after the glyceraldehyde 3-phosphate dehydrogenase step, thereby reducing carbon flow into serine biosynthesis and the TCA cycle. Labeling studies establish that the carbon overflow into the pentose phosphate pathway is mainly through its non-oxidative branch. Together, these studies establish the blockade of glycolysis at the glyceraldehyde 3-phosphate dehydrogenase step as the central metabolic basis of NAMPT inhibition responsible for ATP depletion, metabolic perturbation, and subsequent tumor growth inhibition. These studies also suggest that altered metabolite levels in tumors can be used as robust pharmacodynamic markers for evaluating NAMPT inhibitors in the clinic.
authors.affiliation: Translational Science and Technologies, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Tan
authors.forename: Debra A
authors.initials: DA
authors.lastname: Young
authors.forename: Zhao-Hai
authors.initials: ZH
authors.lastname: Lu
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Meier
authors.forename: Robert L
authors.initials: RL
authors.lastname: Shepard
authors.forename: Kenneth
authors.initials: K
authors.lastname: Roth
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhai
authors.forename: Karen
authors.initials: K
authors.lastname: Huss
authors.forename: Ming-Shang
authors.initials: MS
authors.lastname: Kuo
authors.forename: James
authors.initials: J
authors.lastname: Gillig
authors.forename: Saravanan
authors.initials: S
authors.lastname: Parthasarathy
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Burkholder
authors.forename: Michele C
authors.initials: MC
authors.lastname: Smith
authors.forename: Sandaruwan
authors.initials: S
authors.lastname: Geeganage
authors.forename: Genshi
authors.initials: G
authors.lastname: Zhao
mesh_terms: D000178:Acrylamides / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000172:deficiency / Q000378:metabolism; D000818:Animals; D002247:Carbon Isotopes; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002952:Citric Acid Cycle / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006019:Glycolysis / Q000187:drug effects; D006801:Humans; D007553:Isotope Labeling; D051379:Mice; D016513:Mice, SCID; D009243:NAD / Q000096:biosynthesis*; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology*; D054409:Nicotinamide Phosphoribosyltransferase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010427:Pentose Phosphate Pathway / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D012694:Serine / Q000096:biosynthesis; D023041:Xenograft Model Antitumor Assays
chemical_list: D000178:Acrylamides; D002247:Carbon Isotopes; D004791:Enzyme Inhibitors; C480543:N-(4-(1-benzoylpiperidin-4-yl)butyl)-3-(pyridin-3-yl)acrylamide; D010880:Piperidines; D009243:NAD; D012694:Serine; D000255:Adenosine Triphosphate; D054409:Nicotinamide Phosphoribosyltransferase