title: TRAIL-induced programmed necrosis as a novel approach to eliminate tumor cells.
abstract: BACKGROUND
  The cytokine TRAIL represents one of the most promising candidates for the apoptotic elimination of tumor cells, either alone or in combination therapies. However, its efficacy is often limited by intrinsic or acquired resistance of tumor cells to apoptosis. Programmed necrosis is an alternative, molecularly distinct mode of programmed cell death that is elicited by TRAIL under conditions when the classical apoptosis machinery fails or is actively inhibited. The potential of TRAIL-induced programmed necrosis in tumor therapy is, however, almost completely uncharacterized. We therefore investigated its impact on a panel of tumor cell lines of wide-ranging origin.
  
  
  METHODS
  Cell death/viability was measured by flow cytometry/determination of intracellular ATP levels/crystal violet staining. Cell surface expression of TRAIL receptors was detected by flow cytometry, expression of proteins by Western blot. Ceramide levels were quantified by high-performance thin layer chromatography and densitometric analysis, clonogenic survival of cells was determined by crystal violet staining or by soft agarose cloning.
  
  
  RESULTS
  TRAIL-induced programmed necrosis killed eight out of 14 tumor cell lines. Clonogenic survival was reduced in all sensitive and even one resistant cell lines tested. TRAIL synergized with chemotherapeutics in killing tumor cell lines by programmed necrosis, enhancing their effect in eight out of 10 tested tumor cell lines and in 41 out of 80 chemotherapeutic/TRAIL combinations. Susceptibility/resistance of the investigated tumor cell lines to programmed necrosis seems to primarily depend on expression of the pro-necrotic kinase RIPK3 rather than the related kinase RIPK1 or cell surface expression of TRAIL receptors. Furthermore, interference with production of the lipid ceramide protected all tested tumor cell lines.
  
  
  CONCLUSIONS
  Our study provides evidence that TRAIL-induced programmed necrosis represents a feasible approach for the elimination of tumor cells, and that this treatment may represent a promising new option for the future development of combination therapies. Our data also suggest that RIPK3 expression may serve as a potential predictive marker for the sensitivity of tumor cells to programmed necrosis and extend the previously established role of ceramide as a key mediator of death receptor-induced programmed necrosis (and thus as a potential target for future therapies) also to the tumor cell lines examined here.
authors: Susann
authors: S
authors: Voigt
authors: Stephan
authors: S
authors: Philipp
authors: Parvin
authors: P
authors: Davarnia
authors: Supandi
authors: S
authors: Winoto-Morbach
authors: Christian
authors: C
authors: Röder
authors: Christoph
authors: C
authors: Arenz
authors: Anna
authors: A
authors: Trauzold
authors: Dieter
authors: D
authors: Kabelitz
authors: Stefan
authors: S
authors: Schütze
authors: Holger
authors: H
authors: Kalthoff
authors: Institut für Immunologie, Christian-Albrechts-Universität, Michaelisstrasse 5, 24105 Kiel, Germany. dadam@email.uni-kiel.de.
authors: Dieter
authors: D
authors: Adam
mesh_terms: D000970:Antineoplastic Agents / Q000506:poisoning; D017209:Apoptosis / Q000235:genetics*; D015153:Blotting, Western; D016923:Cell Death / Q000235:genetics; D005434:Flow Cytometry / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D009336:Necrosis / Q000473:pathology / Q000517:prevention & control; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis / Q000235:genetics* / Q000506:poisoning*; D020298:U937 Cells
chemical_list: D000970:Antineoplastic Agents; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human