Abstract
Gliomas are resistant to radiation therapy, as well as to TNFα induced killing. Radiation-induced TNFα triggers Nuclear factor κB (NFκB)-mediated radioresistance. As inhibition of NFκB activation sensitizes glioma cells to TNFα-induced apoptosis, we investigated whether TNFα modulates the responsiveness of glioma cells to ionizing radiation-mimetic Neocarzinostatin (NCS). TNFα enhanced the ability of NCS to induce glioma cell apoptosis. NCS-mediated death involved caspase-9 activation, reduction of mitochondrial copy number and lactate production. Death was concurrent with NFκB, Akt and Erk activation. Abrogation of Akt and NFκB activation further potentiated the death inducing ability of NCS in TNFα cotreated cells. NCS-induced p53 expression was accompanied by increase in TP53-induced glycolysis and apoptosis regulator (TIGAR) levels and ATM phosphorylation. siRNA-mediated knockdown of TIGAR abrogated NCS-induced apoptosis. While DN-IκB abrogated NCS-induced TIGAR both in the presence and absence of TNFα, TIGAR had no effect on NFκB activation. Transfection with TIGAR mutant (i) decreased apoptosis and γH2AX foci formation (ii) decreased p53 (iii) elevated ROS and (iv) increased Akt/Erk activation in cells cotreated with NCS and TNFα. Heightened TIGAR expression was observed in GBM tumors. While NCS induced ATM phosphorylation in a NFκB independent manner, ATM inhibition abrogated TIGAR and NFκB activation. Metabolic gene profiling indicated that TNFα affects NCS-mediated regulation of several genes associated with glycolysis. The existence of ATM-NFκB axis that regulate metabolic modeler TIGAR to overcome prosurvival response in NCS and TNFα cotreated cells, suggests mechanisms through which inflammation could affect resistance and adaptation to radiomimetics despite concurrent induction of death.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / metabolism
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Antibiotics, Antineoplastic / pharmacology*
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Apoptosis / drug effects*
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Apoptosis Regulatory Proteins
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Ataxia Telangiectasia Mutated Proteins
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Brain Neoplasms / metabolism
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Brain Neoplasms / pathology
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Caspase 9 / chemistry
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Caspase 9 / metabolism
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Cell Cycle Proteins / metabolism*
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Cell Line, Tumor
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DNA-Binding Proteins / metabolism*
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Glioma / metabolism
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Glioma / pathology
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Glycolysis
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Humans
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Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Lactic Acid / metabolism
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Microtubule-Associated Proteins / metabolism
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3 / metabolism
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NF-kappa B / metabolism*
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Phosphoric Monoester Hydrolases
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Phosphorylation
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Protein Serine-Threonine Kinases / metabolism*
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Proto-Oncogene Proteins c-akt / metabolism
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RNA Interference
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RNA, Small Interfering / metabolism
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Reactive Oxygen Species / metabolism
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Tumor Necrosis Factor-alpha / pharmacology*
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Tumor Suppressor Protein p53 / metabolism
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Tumor Suppressor Proteins / metabolism*
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Zinostatin / pharmacology*
Substances
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Antibiotics, Antineoplastic
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Apoptosis Regulatory Proteins
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Cell Cycle Proteins
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DNA-Binding Proteins
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Intracellular Signaling Peptides and Proteins
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MAP1LC3A protein, human
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Microtubule-Associated Proteins
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NF-kappa B
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RNA, Small Interfering
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Reactive Oxygen Species
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Tumor Necrosis Factor-alpha
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Tumor Suppressor Protein p53
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Tumor Suppressor Proteins
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Lactic Acid
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Adenosine Triphosphate
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Zinostatin
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ATM protein, human
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Ataxia Telangiectasia Mutated Proteins
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Phosphoric Monoester Hydrolases
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TIGAR protein, human
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Caspase 9