title: Hydrogen peroxide induces cell death in human TRAIL-resistant melanoma             through intracellular superoxide generation.
abstract: Intracellular reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O2()) are thought to mediate apoptosis induced by death receptor ligands, including tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). However, the role of H(2)O(2) is controversial, since some evidence suggests that H(2)O(2) acts as an anti-apoptotic factor. Here, we show that exogenously applied H(2)O(2) (30-100 µM) induces cell death in TRAIL-resistant human melanoma cells via intracellular superoxide (O(2)-) generation. H(2)O(2) induced apoptotic or necrotic cell death, depending on the concentration of the oxidant applied; low concentrations of H(2)O(2) preferentially activated the caspase-dependent apoptotic pathway, while high concentrations of H(2)O(2) induced apoptotic and necrotic cell death in a caspase-independent manner. The H(2)O(2)-induced cell death was associated with increased mitochondrial membrane potential collapse and caspase-3/7 activation and ER stress responses including caspase-12 and X-box-binding protein-1 (XBP-1) activation. H(2)O(2) induced intracellular O2- generation even within the mitochondria, while TRAIL did not. The superoxide dismutase mimetic antioxidant MnTBaP [Mn (III) tetrakis (4-benzonic acid) porphyrin chloride] inhibited the H(2)O(2)-induced O(2)- generation, apoptosis and XBP-1 and caspase-12 activation at comparable concentrations. Importantly, H(2)O(2) treatment caused minimal O(2)- generation and apoptosis in normal primary melanocytes. These data show that H(2)O(2) induces endoplasmic reticulum-associated cell death via intracellular O(2)- generation and that malignant melanoma cells are more susceptible than normal cells to this oxidative cell death. The findings suggest that H(2)O(2) has therapeutic potential in the treatment of TRAIL-resistant melanoma.
authors: Division of Molecular Cell Immunology and Allergology, Department                     of Biomedical Sciences, Nihon University School of Medicine, Tokyo, Japan.
authors: Mizuki
authors: M
authors: Tochigi
authors: Toshio
authors: T
authors: Inoue
authors: Miki
authors: M
authors: Suzuki-Karasaki
authors: Toyoko
authors: T
authors: Ochiai
authors: Chisei
authors: C
authors: Ra
authors: Yoshihiro
authors: Y
authors: Suzuki-Karasaki
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053454:Caspase 12 / Q000187:drug effects / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D004789:Enzyme Activation; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008545:Melanoma / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial; D008665:Metalloporphyrins / Q000494:pharmacology; D009336:Necrosis; D000071701:Regulatory Factor X Transcription Factors; D013481:Superoxides / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D000071717:X-Box Binding Protein 1
chemical_list: D004268:DNA-Binding Proteins; D016166:Free Radical Scavengers; D008665:Metalloporphyrins; D000071701:Regulatory Factor X Transcription Factors; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; D013481:Superoxides; D006861:Hydrogen Peroxide; D053454:Caspase 12; D053148:Caspase 3; D053179:Caspase 7