title: Enhancing TRAIL-induced apoptosis by Bcl-X(L) siRNA.
abstract: We previously found that a change in the balance between mitochondrial pro- and anti-apoptotic proteins caused by ectopic expression of the Bax gene led to increased induction of apoptosis by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). To investigate whether a similar effect can be elicited by down-regulating Bcl-X(L), an anti-apoptotic protein, we tested the effects of a small interfering RNA (siRNA) specific for Bcl-X(L) in TRAIL-resistant cells. The down-regulation of Bcl-X(L) by siRNA inhibited cell proliferation and sensitized TRAIL-induced apoptosis in human cancer cells with both acquired and intrinsic TRAIL resistance. Combining the Bcl-X(L) siRNA with TRAIL protein treatment resulted in an increase in the percentage of apoptotic cells and increased cleavage of caspase-8, caspase-9, caspase-3 and PARP. Furthermore, the release of cytochrome c but not Smac from mitochondria was induced by Bcl-X(L) siRNA alone, and this release was dramatically amplified by combining the Bcl-X(L) siRNA and TRAIL protein treatment. Together, our data suggest that simultaneous triggering of the death receptor and mitochondrial apoptotic pathways leads to enhanced induction of apoptosis, which makes it potentially useful for the treatment of resistant cancers.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.forename: Lidong
authors.initials: L
authors.lastname: Zhang
authors.forename: John J
authors.initials: JJ
authors.lastname: Davis
authors.forename: Shuhong
authors.initials: S
authors.lastname: Wu
authors.forename: Fuminori
authors.initials: F
authors.lastname: Teraishi
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Cao
authors.forename: W Roy
authors.initials: WR
authors.lastname: Smythe
authors.forename: Bingliang
authors.initials: B
authors.lastname: Fang
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D024161:Collagen Type XI / Q000378:metabolism; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045304:Cytochromes c / Q000378:metabolism; D015536:Down-Regulation; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D008024:Ligands; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D008928:Mitochondria / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism / Q000494:pharmacology*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051020:bcl-X Protein / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C499319:COL11A2 protein, human; D024161:Collagen Type XI; D008024:Ligands; D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D045304:Cytochromes c; D020169:Caspases