title: Conversion of 2-deoxyglucose-induced growth inhibition to cell death in normoxic tumor cells.
abstract: BACKGROUND
  Inhibition of glucose metabolism has recently become an attractive target for cancer treatment. Accordingly, since 2-deoxyglucose (2-DG) competes effectively with glucose, it has come under increasing scrutiny as a therapeutic agent. The initial response of tumor cells to 2-DG is growth inhibition, which is thought to conserve energy and consequently protect cells from its ATP-lowering effects as a glycolytic inhibitor. However, since 2-DG also mimics mannose and thereby interferes with N-linked glycosylation, the question is raised of how this sugar analog inhibits tumor cell growth and whether the mechanism by which it protects cells can be manipulated to convert 2-DG-induced growth inhibition to cell death.
  
  
  METHODS
  Cell growth and death were measured via counting viable and dead cells based on trypan blue exclusion. Markers of ATP reduction and the unfolded protein response (UPR) were detected by Western blot. Protein functions were manipulated through chemical compounds, siRNA and the use of gene-specific wild-type and knock-out mouse embryonic fibroblasts (MEFs).
  
  
  RESULTS
  At 2-DG concentrations that can be achieved in human plasma without causing significant side effects, we find (a) It induces growth inhibition predominantly by interference with glycosylation, which leads to accumulation of unfolded proteins in the endoplasmic reticulum activating the UPR; (b) Inhibition of PERK (but not ATF6 or IRE1), a major component of the UPR, leads to conversion of 2-DG-induced growth inhibition to cell death and (c) secondarily to PERK, inhibition of GCN2, a kinase that is activated in response to low intracellular glutamine, increases 2-DG's cytotoxic effects in PERK -/- MEFs.
  
  
  CONCLUSIONS
  Overall, these findings present a novel anticancer strategy that can be translated into therapeutic gain as they uncover the metabolic target PERK, and to a lesser degree GCN2, that when inhibited convert 2-DG's static effect to a toxic one in tumor cells growing under normoxia.
authors.affiliation: Department of Cell Biology and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL, USA. HLiu2@med.miami.edu
authors.forename: Huaping
authors.initials: H
authors.lastname: Liu
authors.forename: Metin
authors.initials: M
authors.lastname: Kurtoglu
authors.forename: Yenong
authors.initials: Y
authors.lastname: Cao
authors.forename: Haibin
authors.initials: H
authors.lastname: Xi
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Axten
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Lampidis
mesh_terms: D051702:Activating Transcription Factor 6 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D015415:Biomarkers / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000494:pharmacology*; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D056811:Unfolded Protein Response / Q000187:drug effects*; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D051702:Activating Transcription Factor 6; D000964:Antimetabolites, Antineoplastic; D015415:Biomarkers; D003847:Deoxyglucose; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D019892:eIF-2 Kinase; C497112:Atf6 protein, mouse; C486556:Ern2 protein, mouse; C070634:Eif2ak4 protein, mouse