title: Inhibition of Yin Yang 1-dependent repressor activity of DR5 transcription and expression by the novel proteasome inhibitor NPI-0052 contributes to its TRAIL-enhanced apoptosis in cancer cells.
abstract: TRAIL promotes apoptotic tumor cell death; however, TRAIL-resistant tumors need to be sensitized to reverse resistance. Proteasome inhibitors potentiate TRAIL apoptosis in vitro and in vivo and correlate with up-regulation of death receptor 5 (DR5) via an unknown mechanism. We hypothesized that the proteasome inhibitor NPI-0052 inhibits the transcription repressor Yin Yang 1 (YY1) which regulates TRAIL resistance and negatively regulates DR5 transcription. Treatment of PC-3 and Ramos cells with NPI-0052 (</=2.5 nM) and TRAIL sensitizes the tumor cells to TRAIL-induced apoptosis. By comparison to bortezomib, a 400-fold less concentration of NPI-0052 was used. NPI-0052 up-regulated DR5 reporter activity and both surface and total DR5 protein expression. NPI-0052-induced inhibition of NF-kappaB activity was involved in TRAIL sensitization as corroborated by the use of the NF-kappaB inhibitor dehydroxymethylepoxyquinomicin. NPI-0052 inhibited YY1 promoter activity as well as both YY1 mRNA and protein expression. The direct role of NPI-0052-induced inhibition of YY1 and up-regulation of DR5 in the regulation of TRAIL sensitivity was demonstrated by the use of YY1 small interfering RNA. The NPI-0052-induced sensitization to TRAIL involved activation of the intrinsic apoptotic pathway and dysregulation of genes that regulate apoptosis. The NPI-0052 concentrations used for TRAIL sensitization were not toxic to human hematopoetic stem cells. The present findings demonstrate, for the first time, the potential mechanism by which a proteasome inhibitor, like NPI-0052, inhibits the transcription repressor YY1 involved in TRAIL resistance and DR5 regulation. The findings also suggest the therapeutic application of subtoxic NPI-0052 concentrations in combination with TRAIL/agonist DR4/DR5 mAbs in the treatment of TRAIL-resistant tumors.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, Division of Surgical Oncology, David Geffen School of Medicine, University of California-Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
authors.forename: Stavroula
authors.initials: S
authors.lastname: Baritaki
authors.forename: Eriko
authors.initials: E
authors.lastname: Suzuki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Umezawa
authors.forename: Demetrios A
authors.initials: DA
authors.lastname: Spandidos
authors.forename: James
authors.initials: J
authors.lastname: Berenson
authors.forename: Tracy R
authors.initials: TR
authors.lastname: Daniels
authors.forename: Manuel L
authors.initials: ML
authors.lastname: Penichet
authors.forename: Ali R
authors.initials: AR
authors.lastname: Jazirehi
authors.forename: Michael
authors.initials: M
authors.lastname: Palladino
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bonavida
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D007783:Lactones / Q000009:adverse effects / Q000494:pharmacology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011480:Protease Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology; D011758:Pyrroles / Q000009:adverse effects / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis* / Q000235:genetics; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects*; D050986:YY1 Transcription Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D001897:Boronic Acids; D007783:Lactones; D016328:NF-kappa B; D011480:Protease Inhibitors; D011719:Pyrazines; D011758:Pyrroles; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D050986:YY1 Transcription Factor; D000069286:Bortezomib; C475865:marizomib