title: Modulation of cellular redox state underlies antagonism between oxaliplatin and cetuximab in human colorectal cancer cell lines.
abstract: OBJECTIVE
  Oxaliplatin is the first platinum-based compound effective in the treatment of colorectal cancer. Oxaliplatin combined with cetuximab for metastatic colorectal cancer is under evaluation. The preliminary results seem controversial, particularly for the use of cetuximab in K-Ras mutated patients. K-Ras mutation is known to affect redox homeostasis. Here we evaluated how the efficacy of oxaliplatin alone or combined with cetuximab varied according to the Ras mutation and redox status in a panel of colorectal tumour cell lines.
  
  
  METHODS
  Viability was evaluated by methylthiazoletetrazolium assay, reactive oxygen species production by DCFDA and lucigenin on HT29-D4, Caco-2, SW480 and SW620 cell lines.
  
  
  RESULTS
  Combination of oxaliplatin and cetuximab was less cytotoxic than oxaliplatin alone in colorectal cells harbouring wild-type Ras and membrane expression of receptors for epidermal growth factor receptor (EGFR), such as HT29-D4 and Caco-2 cells. In contrast, cetuximab did not affect oxaliplatin efficiency in cells harbouring K-Ras(V12) mutation, irrespective of membrane EGFR expression (SW620 and SW480 cells). Transfection of HT29-D4 with K-Ras(V12) decreased oxaliplatin IC(50) and impaired cetuximab sensitivity, without affecting expression of membrane EGFR compared with HT29-D4 control. Oxaliplatin efficacy relies on endogenous production of H(2)O(2). Cetuximab inhibits H(2)O(2) production inhibiting the EGFR/Nox1 NADPH oxidase pathway. Oxaliplatin efficacy was impaired by short hairpin RNA for Nox1 and by catalase (H(2)O(2) scavenger).
  
  
  CONCLUSIONS
  Cetuximab limited oxaliplatin efficiency by affecting the redox status of cancer cells through Nox1. Such combined therapy might be improved by controlling H(2)O(2) elimination.
authors.affiliation: UMR INSERM 911, Centre de Recherche en Oncologie Biologique et Oncopharmacologie, Faculté de Pharmacie, Aix Marseille Université, Marseille, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Dahan
authors.forename: Amine
authors.initials: A
authors.lastname: Sadok
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Formento
authors.forename: Jean François
authors.initials: JF
authors.lastname: Seitz
authors.forename: Hervé
authors.initials: H
authors.lastname: Kovacic
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000068818:Cetuximab; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics; D004336:Drug Antagonism; D066246:ErbB Receptors / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D020128:Inhibitory Concentration 50; D009154:Mutation; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases / Q000378:metabolism; D009944:Organoplatinum Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D000077150:Oxaliplatin; D010084:Oxidation-Reduction / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin; D006861:Hydrogen Peroxide; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases; C402799:NOX1 protein, human; D066246:ErbB Receptors; D000068818:Cetuximab