title: EIF2A-dependent translational arrest protects leukemia cells from the energetic stress induced by NAMPT inhibition.
abstract: BACKGROUND
  Nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in NAD(+) biosynthesis from nicotinamide, is one of the major factors regulating cancer cells metabolism and is considered a promising target for treating cancer. The prototypical NAMPT inhibitor FK866 effectively lowers NAD(+) levels in cancer cells, reducing the activity of NAD(+)-dependent enzymes, lowering intracellular ATP, and promoting cell death.
  
  
  RESULTS
  We show that FK866 induces a translational arrest in leukemia cells through inhibition of MTOR/4EBP1 signaling and of the initiation factors EIF4E and EIF2A. Specifically, treatment with FK866 is shown to induce 5'AMP-activated protein kinase (AMPK) activation, which, together with EIF2A phosphorylation, is responsible for the inhibition of protein synthesis. Notably, such an effect was also observed in patients' derived primary leukemia cells including T-cell Acute Lymphoblastic Leukemia. Jurkat cells in which AMPK or LKB1 expression was silenced or in which a non-phosphorylatable EIF2A mutant was ectopically expressed showed enhanced sensitivity to the NAMPT inhibitor, confirming a key role for the LKB1-AMPK-EIF2A axis in cell fate determination in response to energetic stress via NAD(+) depletion.
  
  
  CONCLUSIONS
  We identified EIF2A phosphorylation as a novel early molecular event occurring in response to NAMPT inhibition and mediating protein synthesis arrest. In addition, our data suggest that tumors exhibiting an impaired LBK1- AMPK- EIF2A response may be especially susceptible to NAMPT inhibitors and thus become an elective indication for this type of agents.
authors.affiliation: Laboratory of Genomic Screening, CIBIO, University of Trento, Trento, Italy. chiara.zucal@unitn.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Zucal
authors.affiliation: Laboratory of Genomic Screening, CIBIO, University of Trento, Trento, Italy. vito.dagostino@unitn.it.
authors.forename: Vito G
authors.initials: VG
authors.lastname: D'Agostino
authors.affiliation: Laboratory of Molecular Virology, CIBIO, University of Trento, Trento, Italy. antonio.casini@unitn.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: Casini
authors.affiliation: Laboratory of Genomic Screening, CIBIO, University of Trento, Trento, Italy. barbara.mantelli@unitn.it.
authors.forename: Barbara
authors.initials: B
authors.lastname: Mantelli
authors.affiliation: Laboratory of Genomic Screening, CIBIO, University of Trento, Trento, Italy. natthakan.thongon@unitn.it.
authors.forename: Natthakan
authors.initials: N
authors.lastname: Thongon
authors.affiliation: Laboratory of Translational Networks, CIBIO, University of Trento, Trento, Italy. soncini.debora@gmail.com.
authors.forename: Debora
authors.initials: D
authors.lastname: Soncini
authors.affiliation: Department of Internal Medicine, University of Genoa, Genoa, Italy. irene.caffa@libero.it.
authors.forename: Irene
authors.initials: I
authors.lastname: Caffa
authors.affiliation: Department of Internal Medicine, University of Genoa, Genoa, Italy. michele.cea@unige.it.
authors.forename: Michele
authors.initials: M
authors.lastname: Cea
authors.affiliation: Department of Internal Medicine, University of Genoa, Genoa, Italy. aballestrero@unige.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Ballestrero
authors.affiliation: Laboratory of Translational Networks, CIBIO, University of Trento, Trento, Italy. alessandro.quattrone@unitn.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Quattrone
authors.affiliation: Istituto Oncologico Veneto IOV-IRCCS, Padova, Italy. stefano.indraccolo@unipd.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Indraccolo
authors.affiliation: Department of Internal Medicine, University of Genoa, Genoa, Italy. alessio.nencioni@unige.it.
authors.forename: Alessio
authors.initials: A
authors.lastname: Nencioni
authors.affiliation: Laboratory of Genomic Screening, CIBIO, University of Trento, Trento, Italy. alessandro.provenzani@unitn.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Provenzani
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000178:Acrylamides / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000037:antagonists & inhibitors*; D019008:Drug Resistance, Neoplasm; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D007938:Leukemia / Q000235:genetics* / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D054409:Nicotinamide Phosphoribosyltransferase / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D010880:Piperidines / Q000494:pharmacology; D014176:Protein Biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D000178:Acrylamides; D016207:Cytokines; D015852:Eukaryotic Initiation Factor-2; D039561:Eukaryotic Initiation Factor-4E; C480543:N-(4-(1-benzoylpiperidin-4-yl)butyl)-3-(pyridin-3-yl)acrylamide; D010880:Piperidines; D009243:NAD; D000255:Adenosine Triphosphate; D054409:Nicotinamide Phosphoribosyltransferase; C085455:nicotinamide phosphoribosyltransferase, human; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D020169:Caspases