title: The metastasis suppressor, N-myc downstream-regulated gene 1 (NDRG1), inhibits stress-induced autophagy in cancer cells.
abstract: N-myc downstream regulated gene 1 (NDRG1) is a potent metastasis suppressor with an undefined role in the stress response. Autophagy is a pro-survival pathway and can be regulated via the protein kinase-like endoplasmic reticulum kinase (PERK)/eIF2α-mediated endoplasmic reticulum (ER) stress pathway. Hence, we investigated the role of NDRG1 in stress-induced autophagy as a mechanism of inhibiting metastasis via the induction of apoptosis. As thiosemicarbazone chelators induce stress and up-regulate NDRG1 to inhibit metastasis, we studied their effects on the ER stress response and autophagy. This was important to assess, as little is understood regarding the role of the stress induced by iron depletion and its role in autophagy. We observed that the chelator, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), which forms redox-active iron and copper complexes, effectively induced ER stress as shown by activation of the PERK/eIF2α pathway. Dp44mT also increased the expression of the autophagic marker, LC3-II, and this was dependent on activation of the PERK/eIF2α axis, as silencing PERK prevented LC3-II accumulation. The effect of Dp44mT on LC3-II expression was at least partially due to iron-depletion, as this effect was also demonstrated with the classical iron chelator, desferrioxamine (DFO), and was not observed for the DFO-iron complex. NDRG1 overexpression also inhibited basal autophagic initiation and the ER stress-mediated autophagic pathway via suppression of the PERK/eIF2α axis. Moreover, NDRG1-mediated suppression of the pro-survival autophagic pathway probably plays a role in its anti-metastatic effects by inducing apoptosis. In fact, multiple pro-apoptotic markers were increased, whereas anti-apoptotic Bcl-2 was decreased upon NDRG1 overexpression. This study demonstrates the role of NDRG1 as an autophagic inhibitor that is important for understanding its mechanism of action.
authors.affiliation: From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: Sumit
authors.initials: S
authors.lastname: Sahni
authors.forename: Dong-Hun
authors.initials: DH
authors.lastname: Bae
authors.forename: Darius J R
authors.initials: DJ
authors.lastname: Lane
authors.forename: Zaklina
authors.initials: Z
authors.lastname: Kovacevic
authors.forename: Danuta S
authors.initials: DS
authors.lastname: Kalinowski
authors.forename: Patric J
authors.initials: PJ
authors.lastname: Jansson
authors.forename: Des R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D001343:Autophagy; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor; D003300:Copper / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000235:genetics; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D013882:Thiosemicarbazones / Q000494:pharmacology; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism; D000099259:N-myc Downstream-Regulated Gene 1 Protein
chemical_list: D018797:Cell Cycle Proteins; D003300:Copper; D003676:Deferoxamine; D015852:Eukaryotic Initiation Factor-2; D047908:Intracellular Signaling Peptides and Proteins; D007501:Iron; D007502:Iron Chelating Agents; D008869:Microtubule-Associated Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013882:Thiosemicarbazones; D019892:eIF-2 Kinase; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C477012:MAP1LC3A protein, human; C539263:di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone; C460640:EIF2AK3 protein, human
keywords: Desferrioxamine; Dp44mT; Iron; Iron Chelators; Iron Metabolism; Iron-Protein Interactions; Ligand-Metal Interactions; Metastasis; Oxidative Stress; Stress