title: Differential roles of RelA (p65) and c-Rel subunits of nuclear factor kappa B in tumor necrosis factor-related apoptosis-inducing ligand signaling.
abstract: Apo-2L/TRAIL (tumor-necrosis factor-related apoptosis-inducing ligand) is a member of the tumor necrosis factor superfamily and has recently been shown to induce apoptosis through engagement of the death receptors TRAIL-R1 (DR4) and TRAIL-R2 (DR5). The transcription factor nuclear factor (NF)-kappa B regulates the expression of genes involved in cancer cell invasion, metastasis, and resistance to chemotherapy. In normal unstimulated cells, NF-kappa B is maintained in the cytoplasm with its inhibitor protein I kappa B, whereas in cancer cells, NF-kappa B is in the nucleus and constitutively activates target genes. To understand the function of NF-kappa B in TRAIL-induced apoptosis, we have analyzed the specific roles of NF-kappa B subunits. Overexpression of a transdominant-negative mutant of the inhibitory protein I kappa B alpha results in down-regulation of constitutively active NF-kappa B, induction of DR5, and tumor necrosis factor receptor (TNFR) 1-associated death domain expression and enhancement of TRAIL sensitivity. Overexpression of RelA or a transcriptional-deficient mutant of c-Rel inhibits TRAIL-induced apoptosis. Depletion of RelA in mouse embryonic fibroblasts increases cytokine-induced apoptosis, whereas depletion of c-Rel blocks this process. Overexpression of RelA subunit inhibits caspase-8 and DR4 and DR5 expression and enhances expression of cIAP1 and c-IAP2 after TRAIL treatment. By comparison, overexpression of c-Rel enhances DR4, DR5, and Bcl-X(s) and inhibits cIAP1, cIAP2, and survivin after TRAIL treatment. These results suggest that the RelA subunit acts as a survival factor by inhibiting expression of DR4/DR5 and caspase-8 and up-regulating cIAP1 and cIAP2. The dual function of NF-kappa B, as an inhibitor or activator of apoptosis, depends on the relative levels of RelA and c-Rel subunits. Thus, NF-kappa B activity may play an important role in tumor progression, and down-regulation of RelA or up-regulation of c-Rel represents a possible therapeutic target for the treatment of cancer.
authors.affiliation: Department of Pharmaceutical Sciences, Molecular and Cellular Biology Program, Greenebaum Cancer Center, University of Maryland, Baltimore, Maryland 21201-1180, USA.
authors.forename: Xufeng
authors.initials: X
authors.lastname: Chen
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Kandasamy
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Srivastava
mesh_terms: D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D008562:Membrane Glycoproteins / Q000494:pharmacology / Q000502:physiology*; D016328:NF-kappa B / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D020569:Proto-Oncogene Proteins c-rel / Q000172:deficiency / Q000502:physiology*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand; D051996:Transcription Factor RelA; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D020569:Proto-Oncogene Proteins c-rel; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; C505653:TNFSF10 protein, human; C505640:Tnfrsf10b protein, mouse; C505654:Tnfsf10 protein, mouse; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases