Conversion of 2-deoxyglucose-induced growth inhibition to cell death in normoxic tumor cells

• Published in: Cancer chemotherapy and pharmacology 2013-07, Vol.72 (1), p.251-262
• Main Authors: Liu, Huaping, Kurtoglu, Metin, Cao, Yenong, Xi, Haibin, Kumar, Rakesh, Axten, Jeffrey M., Lampidis, Theodore J.
• Format: Article
• Language: English
• Subjects: Activating Transcription Factor 6 - antagonists & inhibitors; Activating Transcription Factor 6 - genetics; Activating Transcription Factor 6 - metabolism; Animals; Antimetabolites, Antineoplastic - pharmacology; Antineoplastic agents; Biological and medical sciences; Biomarkers - metabolism; Cancer Research; Cell death; Cell Death - drug effects; Cell Line, Tumor; Cell Proliferation - drug effects; Cells, Cultured; Deoxyglucose - pharmacology; eIF-2 Kinase - antagonists & inhibitors; eIF-2 Kinase - genetics; eIF-2 Kinase - metabolism; Glycosylation - drug effects; Humans; Medical sciences; Medicine; Medicine & Public Health; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Neoplasms - drug therapy; Neoplasms - metabolism; Oncology; Original Article; Pharmacology. Drug treatments; Pharmacology/Toxicology; Protein Kinase Inhibitors - pharmacology; Protein Processing, Post-Translational - drug effects; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; RNA Interference; Unfolded Protein Response - drug effects
• ISSN: 0344-5704; 1432-0843
• DOI: 10.1007/s00280-013-2193-y

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.