title: Anoxic induction of ATF-4 through HIF-1-independent pathways of protein stabilization in human cancer cells.
abstract: Hypoxia is a key factor in tumor development, contributing to angiogenesis and radiotherapy resistance. Hypoxia-inducible factor-1 (HIF-1) is a major transcription factor regulating the response of cancer cells to hypoxia. However, tumors also contain areas of more severe oxygen depletion, or anoxia. Mechanisms for survival under anoxia are HIF-1alpha independent in Caenorhabditis elegans and, thus, differ from the hypoxic response. Here we report a differential response of cancer cells to hypoxia and anoxia by demonstrating the induction of activating transcription factor-4 (ATF-4) and growth arrest DNA damage 153 (GADD153) protein specifically in anoxia and the lack of induction in hypoxia. By applying RNAi, ATF-4 induction in anoxia was shown to be independent of HIF-1alpha, and desferrioxamine mesylate (DFO) and cobalt chloride induced HIF-1alpha but not ATF-4 or GADD153. Furthermore, the inductive response of ATF-4 and GADD153 was not related to alterations in or arrest of mitochondrial respiration and was independent of von Hippel-Lindau (VHL) disease mutations. In reoxygenated anoxic cells, ATF-4 had a half-life of less than 5 minutes; adding the proteasome inhibitor to normoxic cells up-regulated ATF-4 protein. Extracts from primary human tumors demonstrated more ATF-4 expression in tumors near necrotic areas. Thus, this study demonstrates a novel HIF-1alpha-independent anoxic mechanism that regulates ATF-4 induction at the protein stability level in tumor cells.
authors: Cancer Research UK, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.
authors: Kurosh
authors: K
authors: Ameri
authors: Claire E
authors: CE
authors: Lewis
authors: Martin
authors: M
authors: Raida
authors: Heidi
authors: H
authors: Sowter
authors: Tsonwin
authors: T
authors: Hai
authors: Adrian L
authors: AL
authors: Harris
mesh_terms: D051701:Activating Transcription Factor 4; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D003035:Cobalt / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003676:Deferoxamine / Q000378:metabolism; D004579:Electron Transport; D005947:Glucose / Q000378:metabolism; D006801:Humans; D000860:Hypoxia; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015151:Immunoblotting; D007502:Iron Chelating Agents / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011190:Potassium Cyanide / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D013997:Time Factors; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: C497109:ATF4 protein, human; D022762:CCAAT-Enhancer-Binding Proteins; C497249:DDIT3 protein, human; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007502:Iron Chelating Agents; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D014415:Tunicamycin; D051701:Activating Transcription Factor 4; D051742:Transcription Factor CHOP; D003035:Cobalt; D012260:Ribonucleases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C018021:cobaltous chloride; D005947:Glucose; D003676:Deferoxamine; D011190:Potassium Cyanide; D010100:Oxygen