title: Patient-derived glioblastoma cells show significant heterogeneity in treatment responses to the inhibitor-of-apoptosis-protein antagonist birinapant.
abstract: BACKGROUND
  Resistance to temozolomide (TMZ) greatly limits chemotherapeutic effectiveness in glioblastoma (GBM). Here we analysed the ability of the Inhibitor-of-apoptosis-protein (IAP) antagonist birinapant to enhance treatment responses to TMZ in both commercially available and patient-derived GBM cells.
  
  
  METHODS
  Responses to TMZ and birinapant were analysed in a panel of commercial and patient-derived GBM cell lines using colorimetric viability assays, flow cytometry, morphological analysis and protein expression profiling of pro- and antiapoptotic proteins. Responses in vivo were analysed in an orthotopic xenograft GBM model.
  
  
  RESULTS
  Single-agent treatment experiments categorised GBM cells into TMZ-sensitive cells, birinapant-sensitive cells, and cells that were insensitive to either treatment. Combination treatment allowed sensitisation to therapy in only a subset of resistant GBM cells. Cell death analysis identified three principal response patterns: Type A cells that readily activated caspase-8 and cell death in response to TMZ while addition of birinapant further sensitised the cells to TMZ-induced cell death; Type B cells that readily activated caspase-8 and cell death in response to birinapant but did not show further sensitisation with TMZ; and Type C cells that showed no significant cell death or moderately enhanced cell death in the combined treatment paradigm. Furthermore, in vivo, a Type C patient-derived cell line that was TMZ-insensitive in vitro and showed a strong sensitivity to TMZ and TMZ plus birinapant treatments.
  
  
  CONCLUSIONS
  Our results demonstrate remarkable differences in responses of patient-derived GBM cells to birinapant single and combination treatments, and suggest that therapeutic responses in vivo may be greatly affected by the tumour microenvironment.
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.|National Centre for Neurosurgery, Beaumont Hospital, Dublin 9, Ireland.
authors.forename: Z
authors.initials: Z
authors.lastname: Zakaria
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: A
authors.initials: A
authors.lastname: Tivnan
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: L
authors.initials: L
authors.lastname: Flanagan
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: D W
authors.initials: DW
authors.lastname: Murray
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Salvucci
authors.affiliation: Brain Cancer Research Unit, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: B W
authors.initials: BW
authors.lastname: Stringer
authors.affiliation: Brain Cancer Research Unit, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: B W
authors.initials: BW
authors.lastname: Day
authors.affiliation: Brain Cancer Research Unit, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: A W
authors.initials: AW
authors.lastname: Boyd
authors.affiliation: Experimental Neurosurgery, Neuroscience Center, Frankfurt University Hospital, Frankfurt am Main, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Kögel
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Rehm
authors.affiliation: National Centre for Neurosurgery, Beaumont Hospital, Dublin 9, Ireland.
authors.forename: D F
authors.initials: DF
authors.lastname: O'Brien
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: A T
authors.initials: AT
authors.lastname: Byrne
authors.affiliation: Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: J H M
authors.initials: JH
authors.lastname: Prehn
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000473:pathology*; D053181:Caspase 8 / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005434:Flow Cytometry; D005909:Glioblastoma / Q000473:pathology*; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008858:Microscopy, Phase-Contrast; D009368:Neoplasm Transplantation; D000077204:Temozolomide; D023041:Xenograft Model Antitumor Assays
chemical_list: D004151:Dipeptides; D007211:Indoles; D051034:Inhibitor of Apoptosis Proteins; C582429:birinapant; D003606:Dacarbazine; C505530:CASP8 protein, human; D053181:Caspase 8; D000077204:Temozolomide