Proteasome Inhibitors Enhance TRAIL-Induced Apoptosis through the Intronic Regulation of DR5: Involvement of NF-κB and Reactive Oxygen Species-Mediated p53 Activation
Journal
Journal of Immunology
Journal Volume
180
Journal Issue
12
Pages
8030-8039
Date Issued
2008
Author(s)
Abstract
Manipulation of TRAIL receptor 2 (DR5) pathway is a promising therapeutic strategy to overcome TRAIL-resistant lung cancer cells. Preclinical studies have shown that proteasome inhibitors enhance TRAIL-induced apoptosis in lung cancer cells, but the underlying mechanism has not been fully elucidated. In this study, we demonstrated the enhancement of TRAIL-mediated apoptosis in human alveolar epithelial cells by proteasome inhibitors that up-regulate DR5 expression. This effect was blocked by DR5-neutralizing Ab. Using reporter assay, we demonstrated that the p53 and NF-κB elements on the DR5 first intron region were involved in proteasome inhibitor-induced DR5 expression. Both p53 small interfering RNA and NF-κB inhibitor suppressed DR5 expression, strengthening the significance of p53 and NF-κB in DR5 transcription. The protein stability, Ser392 phosphorylation and Lys373/ Lys382 acetylation of p53 were enhanced by MG132. In addition to p53, IκBα degradation and NF-κB translocation was also observed. Moreover, the binding of p53 and p65 to the first intron of DR5 was demonstrated by DNA affinity protein-binding and chromatin immunoprecipitation assays. Jntraceliular reactive oxygen species (ROS) generation after MG132 treatment contributed to p53, but not p65 nuclear translocation and DNA-binding activity. ROS scavenger dramatically inhibited the apoptosis induced by proteasome inhibitors plus TRAIL. The p53-null H1299 cells were resistant to proteasome inhibitor-induced DR5 up-regulation and enhancement of TRAIL-induced apoptosis. These findings reveal that proteasome inhibitor-mediated NF-κB and ROS-dependent p53 activation are contributed to intronic regulation of DR5 transcription, and resulted in the subsequent enhancement of TRAIL-induced apoptosis in human lung cancer cells. Copyright ? 2008 by The American Association of Immunologists, Inc.
Other Subjects
benzyloxycarbonylleucylleucylleucinal; death receptor 5; I kappa B; I kappa B alpha; immunoglobulin enhancer binding protein; neutralizing antibody; proteasome inhibitor; protein p53; reactive oxygen metabolite; small interfering RNA; tumor necrosis factor related apoptosis inducing ligand; antiserum; benzyloxycarbonylleucyl leucyl leucine aldehyde; benzyloxycarbonylleucyl-leucyl-leucine aldehyde; cysteine proteinase inhibitor; immunoglobulin enhancer binding protein; leupeptin; protein p53; reactive oxygen metabolite; scavenger; TNFSF10 protein, human; tumor necrosis factor related apoptosis inducing ligand; tumor necrosis factor related apoptosis inducing ligand receptor; apoptosis; article; controlled study; gene activation; gene control; gene expression; gene translocation; genetic transcription; human; human cell; intron; lung alveolus epithelium; priority journal; protein binding; protein degradation; protein phosphorylation; protein stability; apoptosis; cell line; cell strain HCT116; cytology; drug antagonism; drug effect; drug resistance; gene expression regulation; genetics; immunology; intron; metabolism; pathology; physiology; respiratory tract mucosa; signal transduction; upregulation; Apoptosis; Cell Line; Cysteine Proteinase Inhibitors; Drug Resistance, Neoplasm; Free Radical Scavengers; Gene Expression Regulation, Neoplastic; HCT116 Cells; Humans; Immune Sera; Introns; Leupeptins; NF-kappa B; Protein Binding; Reactive Oxygen Species; Receptors, TNF-Related Apoptosis-Inducing Ligand; Respiratory Mucosa; Signal Transduction; TNF-Related Apoptosis-Inducing Ligand; Tumor Suppressor Protein p53; Up-Regulation
Type
journal article