title: Oxaliplatin sensitizes human colon cancer cells to TRAIL through JNK-dependent phosphorylation of Bcl-xL.
abstract: OBJECTIVE
  Oxaliplatin sensitizes drug-resistant colon cancer cell lines to tumor necrosis factor-related apoptosis inducing ligand (TRAIL), a death receptor ligand that is selective for cancer cells. We investigated the molecular mechanisms by which oxaliplatin sensitizes cancer cells to TRAIL-induced apoptosis.
  
  
  METHODS
  We incubated the colon cancer cell lines HT29 and V9P, which are resistant to TRAIL, with TRAIL or with oxaliplatin for 2 hours, followed by TRAIL. Annexin V staining was used to measure apoptosis; RNA silencing and immunoblot experiments were used to study the roles of apoptosis-related proteins. Site-directed mutagenesis experiments were used to determine requirements for phosphorylation of Bcl-xL; co-immunoprecipitation experiments were used to analyze the interactions among Bcl-xL, Bax, and Bak, and activation of Bax.
  
  
  RESULTS
  Oxaliplatin-induced sensitivity to TRAIL required activation of the mitochondrial apoptotic pathway; reduced expression of Bax, Bak, and caspase-9, and stable overexpression of Bcl-xL, reduced TRAIL-induced death of cells incubated with oxaliplatin. Mitochondrial priming was induced in cells that were sensitized by oxaliplatin and required signaling via c-Jun N-terminal kinase and phosphorylation of Bcl-xL. Mimicking constitutive phosphorylation of Bcl-xL by site-directed mutagenesis at serine 62 restored sensitivity of cells to TRAIL. Co-immunoprecipitation experiments showed that oxaliplatin-induced phosphorylation of Bcl-xL disrupted its ability to sequestrate Bax, allowing Bax to interact with Bak to induce TRAIL-mediated apoptosis.
  
  
  CONCLUSIONS
  Oxaliplatin facilitates TRAIL-induced apoptosis in colon cancer cells by activating c-Jun N-terminal kinase signaling and phosphorylation of Bcl-xL. Oxaliplatin-induced sensitivity to TRAIL might be developed as an approach to cancer therapy.
authors.affiliation: INSERM U865, University of Lyon, Faculté Laënnec, Lyon, France.
authors.forename: Zineb
authors.initials: Z
authors.lastname: El Fajoui
authors.forename: Florent
authors.initials: F
authors.lastname: Toscano
authors.forename: Guillaume
authors.initials: G
authors.lastname: Jacquemin
authors.forename: Jacques
authors.initials: J
authors.lastname: Abello
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Scoazec
authors.forename: Olivier
authors.initials: O
authors.lastname: Micheau
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Saurin
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism / Q000502:physiology; D053181:Caspase 8 / Q000378:metabolism / Q000502:physiology; D053453:Caspase 9 / Q000378:metabolism / Q000502:physiology; D003110:Colonic Neoplasms / Q000188:drug therapy*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D019073:HT29 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000187:drug effects* / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D009944:Organoplatinum Compounds / Q000494:pharmacology* / Q000627:therapeutic use; D000077150:Oxaliplatin; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology* / Q000627:therapeutic use*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism / Q000502:physiology; D051028:bcl-2-Associated X Protein / Q000378:metabolism / Q000502:physiology; D051020:bcl-X Protein / Q000378:metabolism / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D053221:TNF-Related Apoptosis-Inducing Ligand; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D000077150:Oxaliplatin; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9