title: Targeting pro-apoptotic trail receptors sensitizes HeLa cervical cancer cells to irradiation-induced apoptosis.
abstract: OBJECTIVE
  To investigate the potential of irradiation in combination with drugs targeting the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor (DR)4 and DR5 and their mechanism of action in a cervical cancer cell line.
  
  
  METHODS
  Recombinant human TRAIL (rhTRAIL) and the agonistic antibodies against DR4 and DR5 were added to irradiated HeLa cells. The effect was evaluated with apoptosis and cytotoxicity assays and at the protein level. Membrane receptor expression was measured with flow cytometry. Small-interfering RNA against p53, DR4, and DR5 was used to investigate their function on the combined effect.
  
  
  RESULTS
  rhTRAIL and the agonistic DR4 and DR5 antibodies strongly enhanced 10-Gy-induced apoptosis. This extra effect was 22%, 23%, and 29% for rhTRAIL, DR4, and DR5, respectively. Irradiation increased p53 expression and increased the membrane expression of DR5 and DR4. p53 suppression, as well as small-interfering RNA against DR5, resulted in a significant downregulation of DR5 membrane expression but did not affect apoptosis induced by irradiation and rhTRAIL. After small-interfering RNA against DR4, rhTRAIL-induced apoptosis and the additive effect of irradiation on rhTRAIL-induced apoptosis were abrogated, implicating an important role for DR4 in apoptosis induced through irradiation in combination with rhTRAIL.
  
  
  CONCLUSIONS
  Irradiation-induced apoptosis is strongly enhanced by targeting the pro-apoptotic TRAIL receptors DR4 or DR5. Irradiation results in a p53-dependent increase in DR5 membrane expression. The sensitizing effect of rhTRAIL on irradiation in the HeLa cell line is, however especially mediated through the DR4 receptor.
authors.affiliation: Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: John H
authors.initials: JH
authors.lastname: Maduro
authors.forename: Elisabeth G E
authors.initials: EG
authors.lastname: de Vries
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: Meersma
authors.forename: Brigitte M T
authors.initials: BM
authors.lastname: Hougardy
authors.forename: Ate G J
authors.initials: AG
authors.lastname: van der Zee
authors.forename: Steven
authors.initials: S
authors.lastname: de Jong
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D024161:Collagen Type XI / Q000378:metabolism; D003131:Combined Modality Therapy / Q000379:methods; D004354:Drug Screening Assays, Antitumor; D004789:Enzyme Activation; D005260:Female; D006367:HeLa Cells / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D009363:Neoplasm Proteins / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D034741:RNA, Small Interfering / Q000378:metabolism; D011829:Radiation Dosage; D011836:Radiation Tolerance; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D018124:Receptors, Tumor Necrosis Factor / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000532:radiotherapy*
chemical_list: C499319:COL11A2 protein, human; D024161:Collagen Type XI; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; D016159:Tumor Suppressor Protein p53; D053148:Caspase 3