title: Loss of XIAP protein expression by RNAi and antisense approaches sensitizes cancer cells to functionally diverse chemotherapeutics.
abstract: Stable expression of short-hairpin RNAs (shRNAs) directed against the X-linked inhibitor of apoptosis (XIAP) resulted in the generation of three MDA-MB-231 cell lines (XIAP shRNA cells) with reductions in XIAP mRNA and protein levels > 85% relative to MDA-MB-231 cells stably transfected with the U6 RNA polymerase III promoter alone (U6 cells). This RNA interference (RNAi) approach dramatically sensitized these cells to killing by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Importantly, loss of XIAP also sensitized the cells to killing by taxanes but had no additional effects on killing by carboplatin and doxorubicin. The increased sensitivity of the XIAP shRNA cells to killing by TRAIL and taxanes correlated with enhanced caspase cleavage and activation, including caspase-8, and robust processing of poly(ADP-ribose) polymerase and BID compared to U6 cells. Additionally, increasing XIAP levels by adenovirus-mediated expression protected both XIAP shRNA and U6 cells from TRAIL killing in a dose-dependent manner. The effects observed by stable RNAi with respect to TRAIL sensitization were also achieved following downregulation of XIAP in Panc-1 cells treated with a second-generation, mixed-backbone antisense oligonucleotide, AEG 35156/GEM640. These data indicate that reducing XIAP protein expression by either RNAi or antisense approaches increases cancer cell susceptibility to functionally diverse chemotherapeutic agents and supports the notion that downregulation of XIAP in vivo may synergize with disease-relevant chemotherapeutic regimes, including TRAIL and taxanes, to increase the effectiveness of antineoplastic agents.
authors.affiliation: Aegera Oncology Inc., University of Ottawa and Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada K1H 8L1.
authors.forename: Dan C
authors.initials: DC
authors.lastname: McManus
authors.forename: Charles A
authors.initials: CA
authors.lastname: Lefebvre
authors.forename: Gabriele
authors.initials: G
authors.lastname: Cherton-Horvat
authors.forename: Martine
authors.initials: M
authors.lastname: St-Jean
authors.forename: Ekambar R
authors.initials: ER
authors.lastname: Kandimalla
authors.forename: Sudhir
authors.initials: S
authors.lastname: Agrawal
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Morris
authors.forename: Jon P
authors.initials: JP
authors.lastname: Durkin
authors.forename: Eric C
authors.initials: EC
authors.lastname: Lacasse
mesh_terms: D016375:Antisense Elements (Genetics) / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D009369:Neoplasms / Q000188:drug therapy*; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D034622:RNA Interference; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D051636:X-Linked Inhibitor of Apoptosis Protein
chemical_list: D016375:Antisense Elements (Genetics); D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D011506:Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D016899:Interferon-beta; D020169:Caspases