title: Peroxiredoxin 3 is a redox-dependent target of thiostrepton in malignant mesothelioma cells.
abstract: Thiostrepton (TS) is a thiazole antibiotic that inhibits expression of FOXM1, an oncogenic transcription factor required for cell cycle progression and resistance to oncogene-induced oxidative stress. The mechanism of action of TS is unclear and strategies that enhance TS activity will improve its therapeutic potential. Analysis of human tumor specimens showed FOXM1 is broadly expressed in malignant mesothelioma (MM), an intractable tumor associated with asbestos exposure. The mechanism of action of TS was investigated in a cell culture model of human MM. As for other tumor cell types, TS inhibited expression of FOXM1 in MM cells in a dose-dependent manner. Suppression of FOXM1 expression and coincidental activation of ERK1/2 by TS were abrogated by pre-incubation of cells with the antioxidant N-acetyl-L-cysteine (NAC), indicating its mechanism of action in MM cells is redox-dependent. Examination of the mitochondrial thioredoxin reductase 2 (TR2)-thioredoxin 2 (TRX2)-peroxiredoxin 3 (PRX3) antioxidant network revealed that TS modifies the electrophoretic mobility of PRX3. Incubation of recombinant human PRX3 with TS in vitro also resulted in PRX3 with altered electrophoretic mobility. The cellular and recombinant species of modified PRX3 were resistant to dithiothreitol and SDS and suppressed by NAC, indicating that TS covalently adducts cysteine residues in PRX3. Reduction of endogenous mitochondrial TRX2 levels by the cationic triphenylmethane gentian violet (GV) promoted modification of PRX3 by TS and significantly enhanced its cytotoxic activity. Our results indicate TS covalently adducts PRX3, thereby disabling a major mitochondrial antioxidant network that counters chronic mitochondrial oxidative stress. Redox-active compounds like GV that modify the TR2/TRX2 network may significantly enhance the efficacy of TS, thereby providing a combinatorial approach for exploiting redox-dependent perturbations in mitochondrial function as a therapeutic approach in mesothelioma.
authors: Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont, United States of America.
authors: Kheng
authors: K
authors: Newick
authors: Brian
authors: B
authors: Cunniff
authors: Kelsey
authors: K
authors: Preston
authors: Paul
authors: P
authors: Held
authors: Jack
authors: J
authors: Arbiser
authors: Harvey
authors: H
authors: Pass
authors: Brooke
authors: B
authors: Mossman
authors: Arti
authors: A
authors: Shukla
authors: Nicholas
authors: N
authors: Heintz
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism*; D008654:Mesothelioma / Q000378:metabolism*; D000086002:Mesothelioma, Malignant; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction; D061105:Peroxiredoxin III / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D013883:Thiostrepton / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000900:Anti-Bacterial Agents; C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; D013481:Superoxides; D061105:Peroxiredoxin III; D013883:Thiostrepton