title: The pyrrolo-1,5-benzoxazepine, PBOX-15, enhances TRAIL‑induced apoptosis by upregulation of DR5 and downregulation of core cell survival proteins in acute lymphoblastic leukaemia cells.
abstract: Apoptotic defects are frequently associated with poor outcome in pediatric acute lymphoblastic leukaemia (ALL) hence there is an ongoing demand for novel strategies that counteract apoptotic resistance. The death ligand TRAIL (tumour necrosis factor-related apoptosis-inducing ligand) and its selective tumour receptor system has attracted exceptional clinical interest. However, many malignancies including ALL are resistant to TRAIL monotherapy. Tumour resistance can be overcome by drug combination therapy. TRAIL and its agonist antibodies are currently undergoing phase II clinical trials with established chemotherapeutics. Herein, we present promising therapeutic benefits in combining TRAIL with the selective anti-leukaemic agents, the pyrrolo-1,5-benzoxazepines (PBOXs) for the treatment of ALL. PBOX-15 synergistically enhanced apoptosis induced by TRAIL and a DR5-selective TRAIL variant in ALL-derived cells. PBOX-15 enhanced TRAIL-induced apoptosis by dual activation of extrinsic and intrinsic apoptotic pathways. The specific caspase-8 inhibitor, Z-IETD-FMK, identified the extrinsic pathway as the principal mode of apoptosis. We demonstrate that PBOX-15 can enhance TRAIL-induced apoptosis by upregulation of DR5, reduction of cellular mitochondrial potential, activation of the caspase cascade and downregulation of PI3K/Akt, c-FLIP, Mcl-1 and IAP survival pathways. Of note, the PI3K pathway inhibitor LY-294002 significantly enhanced the apoptotic potential of TRAIL and PBOX-15 validating the importance of Akt downregulation in the TRAIL/PBOX-15 synergistic combination. Considering the lack of cytotoxicity to normal cells and ability to downregulate several survival pathways, PBOX-15 may represent an effective agent for use in combination with TRAIL for the treatment of ALL.
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Seema-Maria
authors.initials: SM
authors.lastname: Nathwani
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Greene
authors.affiliation: European Research Centre for Drug Discovery and Development, University of Siena, Siena, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Butini
authors.affiliation: European Research Centre for Drug Discovery and Development, University of Siena, Siena, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Campiani
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: D Clive
authors.initials: DC
authors.lastname: Williams
authors.affiliation: Apoptosis Research Centre, Bioscience Research Building, National University of Ireland, Galway, Ireland.
authors.forename: Afshin
authors.initials: A
authors.lastname: Samali
authors.affiliation: Apoptosis Research Centre, Bioscience Research Building, National University of Ireland, Galway, Ireland.
authors.forename: Eva
authors.initials: E
authors.lastname: Szegezdi
authors.affiliation: School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Daniela M
authors.initials: DM
authors.lastname: Zisterer
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000096:biosynthesis; D053181:Caspase 8 / Q000096:biosynthesis; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000096:biosynthesis; D010077:Oxazepines / Q000008:administration & dosage*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D011758:Pyrroles / Q000008:administration & dosage*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage* / Q000235:genetics
chemical_list: C514160:4-acetoxy-5-(1-(naphthyl))naphtho(2,3-b)pyrrolo(2,1-d)(1,4)oxazepine; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010077:Oxazepines; D011758:Pyrroles; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C505639:TNFRSF10B protein, human; D019869:Phosphatidylinositol 3-Kinases; D053181:Caspase 8