title: Irradiation specifically sensitises solid tumour cell lines to TRAIL mediated apoptosis.
abstract: BACKGROUND
  TRAIL (tumor necrosis factor related apoptosis inducing ligand) is an apoptosis inducing ligand with high specificity for malignant cell systems. Combined treatment modalities using TRAIL and cytotoxic drugs revealed highly additive effects in different tumour cell lines. Little is known about the efficacy and underlying mechanistic effects of a combined therapy using TRAIL and ionising radiation in solid tumour cell systems. Additionally, little is known about the effect of TRAIL combined with radiation on normal tissues.
  
  
  METHODS
  Tumour cell systems derived from breast- (MDA MB231), lung--(NCI H460) colorectal--(Colo 205, HCT-15) and head and neck cancer (FaDu, SCC-4) were treated with a combination of TRAIL and irradiation using two different time schedules. Normal tissue cultures from breast, prostate, renal and bronchial epithelia, small muscle cells, endothelial cells, hepatocytes and fibroblasts were tested accordingly. Apoptosis was determined by fluorescence microscopy and western blot determination of PARP processing. Upregulation of death receptors was quantified by flow cytometry.
  
  
  RESULTS
  The combined treatment of TRAIL with irradiation strongly increased apoptosis induction in all treated tumour cell lines compared to treatment with TRAIL or irradiation alone. The synergistic effect was most prominent after sequential application of TRAIL after irradiation. Upregulation of TRAIL receptor DR5 after irradiation was observed in four of six tumour cell lines but did not correlate to tumour cell sensitisation to TRAIL. TRAIL did not show toxicity in normal tissue cell systems. In addition, pre-irradiation did not sensitise all nine tested human normal tissue cell cultures to TRAIL.
  
  
  CONCLUSIONS
  Based on the in vitro data, TRAIL represents a very promising candidate for combination with radiotherapy. Sequential application of ionising radiation followed by TRAIL is associated with an synergistic induction of cell death in a large panel of solid tumour cell lines. However, TRAIL receptor upregulation may not be the sole mechanism by which sensitation to TRAIL after irradiation is induced.
authors.affiliation: Department of Radiation Oncology, University of Tübingen, Experimental Radiation Oncology, Hoppe-Seyler-Str, 3, D-72076 Tübingen, Germany. patrizia.marini@uni-tuebingen.de
authors.forename: Patrizia
authors.initials: P
authors.lastname: Marini
authors.forename: Angelika
authors.initials: A
authors.lastname: Schmid
authors.forename: Verena
authors.initials: V
authors.lastname: Jendrossek
authors.forename: Heidrun
authors.initials: H
authors.lastname: Faltin
authors.forename: Peter T
authors.initials: PT
authors.lastname: Daniel
authors.forename: Wilfried
authors.initials: W
authors.lastname: Budach
authors.forename: Claus
authors.initials: C
authors.lastname: Belka
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003131:Combined Modality Therapy; D006801:Humans; D008562:Membrane Glycoproteins / Q000627:therapeutic use*; D009369:Neoplasms / Q000188:drug therapy / Q000532:radiotherapy / Q000628:therapy*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011839:Radiation, Ionizing; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000627:therapeutic use*
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D011065:Poly(ADP-ribose) Polymerases; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases