2-Deoxy-d-glucose activates autophagy via endoplasmic reticulum stress rather than ATP depletion

Haibin Xi, Metin Kurtoglu, Huaping Liu, Medhi Wangpaichitr, Min You, Xiongfei Liu, Niramol Savaraj, Theodore J. Lampidis

Research output: Contribution to journalArticle

107 Scopus citations

Abstract

Purpose: The glucose analog and glycolytic inhibitor 2-deoxy-d-glucose (2-DG), which is currently under clinical evaluation for targeting cancer cells, not only blocks glycolysis thereby reducing cellular ATP, but also interferes with N-linked glycosylation, which leads to endoplasmic reticulum (ER) stress and an unfolded protein response (UPR). Both bioenergetic challenge and ER stress have been shown to activate autophagy, a bulk cellular degradation process that plays either a pro- or anti-death role. Here, we investigate which pathway 2-DG interferes with that activates autophagy and the role of this process in modulating 2-DG-induced toxicity. Methods: Pancreatic cancer cell line 1420, melanoma cell line MDA-MB-435 and breast cancer cell line SKBR3 were used to investigate the relationship between induction by 2-DG treatment of ER stress/UPR, ATP reduction and activation of autophagy. ER stress/UPR (Grp78 and CHOP) and autophagy (LC3B II) markers were assayed by immunoblotting, while ATP levels were measured using the CellTiter-Glo Luminescent Cell Viability Assay. Autophagy was also measured by immunofluorescence utilizing LC3B antibody. Cell death was detected with a Vi-Cell cell viability analyzer using trypan blue exclusion. Results: In the three different cancer cell lines described earlier, we find that 2-DG upregulates autophagy, increases ER stress and lowers ATP levels. Addition of exogenous mannose reverses 2-DG-induced autophagy and ER stress but does not recover the lowered levels of ATP. Moreover, under anaerobic conditions where 2-DG severely depletes ATP, autophagy is diminished rather than activated, which correlates with lowered levels of the ER stress marker Grp78. Additionally, when autophagy is blocked by siRNA, cell sensitivity to 2-DG is increased corresponding with upregulation of ER stress-mediated apoptosis. Similar increased toxicity is observed with 3-methyladenine, a known autophagy inhibitor. In contrast, rapamycin which enhances autophagy reduces 2-DG-induced toxicity. Conclusions: Overall, these results indicate that the major mechanism by which 2-DG stimulates autophagy is through ER stress/UPR and not by lowering ATP levels. Furthermore, autophagy plays a protective role against 2-DG-elicited cell death apparently by relieving ER stress. These data suggest that combining autophagy inhibitors with 2-DG may be useful clinically.

Original languageEnglish (US)
Pages (from-to)899-910
Number of pages12
JournalCancer Chemotherapy And Pharmacology
Volume67
Issue number4
DOIs
StatePublished - Apr 1 2011

Keywords

  • 2-Deoxy-d-glucose
  • ATP
  • Autophagy
  • Cell death
  • ER stress

ASJC Scopus subject areas

  • Cancer Research
  • Oncology
  • Pharmacology
  • Pharmacology (medical)
  • Toxicology

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