title: Regulation of tumor cell sensitivity to TRAIL-induced apoptosis by the metastatic suppressor Raf kinase inhibitor protein via Yin Yang 1 inhibition and death receptor 5 up-regulation.
abstract: Raf-1 kinase inhibitor protein (RKIP) has been implicated in the regulation of cell survival pathways and metastases, and is poorly expressed in tumors. We have reported that the NF-kappaB pathway regulates tumor resistance to apoptosis by the TNF-alpha family via inactivation of the transcription repressor Yin Yang 1 (YY1). We hypothesized that RKIP overexpression may regulate tumor sensitivity to death ligands via inhibition of YY1 and up-regulation of death receptors (DRs). The TRAIL-resistant prostate carcinoma PC-3 and melanoma M202 cell lines were examined. Transfection with CMV-RKIP, but not with control CMV-EV, sensitized the cells to TRAIL-mediated apoptosis. Treatment with RKIP small interfering RNA (siRNA) inhibited TRAIL-induced apoptosis. RKIP overexpression was paralleled with up-regulation of DR5 transcription and expression; no change in DR4, decoy receptor 1, and decoy receptor 2 expression; and inhibition of YY1 transcription and expression. Inhibition of YY1 by YY1 siRNA sensitized the cells to TRAIL apoptosis concomitantly with DR5 up-regulation. RKIP overexpression inhibited several antiapoptotic gene products such as X-linked inhibitor of apoptosis (XIAP), c-FLIP long, and Bcl-x(L) that were accompanied with mitochondrial membrane depolarization. RKIP overexpression in combination with TRAIL resulted in the potentiation of these above effects and activation of caspases 8, 9, and 3, resulting in apoptosis. These findings demonstrate that RKIP overexpression regulates tumor cell sensitivity to TRAIL via inhibition of YY1, up-regulation of DR5, and modulation of apoptotic pathways. We suggest that RKIP may serve as an immune surveillance cancer gene, and its low expression or absence in tumors allows the tumor to escape host immune cytotoxic effector cells.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095, USA.
authors.forename: Stavroula
authors.initials: S
authors.lastname: Baritaki
authors.forename: Alina
authors.initials: A
authors.lastname: Katsman
authors.forename: Devasis
authors.initials: D
authors.lastname: Chatterjee
authors.forename: Kam C
authors.initials: KC
authors.lastname: Yeung
authors.forename: Demetrios A
authors.initials: DA
authors.lastname: Spandidos
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bonavida
mesh_terms: D000230:Adenocarcinoma / Q000276:immunology / Q000473:pathology; D017209:Apoptosis / Q000276:immunology*; D001859:Bone Neoplasms / Q000276:immunology / Q000473:pathology / Q000556:secondary; D045744:Cell Line, Tumor; D006801:Humans; D008297:Male; D008545:Melanoma / Q000276:immunology / Q000473:pathology / Q000556:secondary; D049488:Phosphatidylethanolamine Binding Protein / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011471:Prostatic Neoplasms / Q000276:immunology* / Q000473:pathology; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis* / Q000502:physiology; D015398:Signal Transduction / Q000276:immunology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology*; D019139:Tumor Escape / Q000276:immunology; D025521:Tumor Suppressor Proteins / Q000502:physiology*; D015854:Up-Regulation / Q000276:immunology*; D050986:YY1 Transcription Factor / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: D049488:Phosphatidylethanolamine Binding Protein; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D025521:Tumor Suppressor Proteins; D050986:YY1 Transcription Factor