title: Cetuximab potentiates oxaliplatin cytotoxic effect through a defect in NER and DNA replication initiation.
abstract: Preclinical studies have demonstrated that the chemotherapeutic action of oxaliplatin, a third generation platinum derivative, is improved when combined with cetuximab, a monoclonal antibody inhibitor of epidermal growth factor receptors. To explore the mechanism of this synergistic benefit, we used HCT-8 and HCT-116, two human colon cancer cell lines, respectively, responsive and non-responsive to the oxaliplatin/cetuximab combination. We examined the effect of drug exposure on glutathione-S-transferase-mediated oxaliplatin detoxification, DNA-platinum adducts formation, cell cycle distribution, apoptosis, and the expression of multiple targets involved in DNA replication, recombination, and repair. The major changes we found in HCT-8 were a stimulation of oxaliplatin-DNA adduct formation associated with reduced expression of the key enzyme (excision repair cross complementation group1: ERCC1) in the key repair process of oxaliplatin-DNA platinum adduct, the nucleotide excision repair (NER), both at the mRNA and protein levels. We also observed a reduced expression of factors involved in DNA replication initiation, which correlates with an enrichment of cells in the G1 phase of the cell cycle as well as an acceleration of apoptosis. None of these changes occurred in the non-responsive HCT-116 cell that we used as a negative control. These findings support the fact that cetuximab potentiates the oxaliplatin-mediated cytotoxic effect as the result of inhibition of NER and also DNA replication initiation.
authors.affiliation: EA 3035 Laboratoire de Pharmacologie Clinique et Expérimentale des Médicaments Anticancéreux, Université Paul Sabatier, Toulouse, France.
authors.forename: D
authors.initials: D
authors.lastname: Balin-Gauthier
authors.forename: J-P
authors.initials: JP
authors.lastname: Delord
authors.forename: M-J
authors.initials: MJ
authors.lastname: Pillaire
authors.forename: P
authors.initials: P
authors.lastname: Rochaix
authors.forename: J-S
authors.initials: JS
authors.lastname: Hoffman
authors.forename: R
authors.initials: R
authors.lastname: Bugat
authors.forename: C
authors.initials: C
authors.lastname: Cazaux
authors.forename: P
authors.initials: P
authors.lastname: Canal
authors.forename: B C
authors.initials: BC
authors.lastname: Allal
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D061067:Antibodies, Monoclonal, Humanized; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D000068818:Cetuximab; D018736:DNA Adducts; D004260:DNA Repair / Q000187:drug effects*; D004261:DNA Replication / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004357:Drug Synergism; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D005982:Glutathione Transferase / Q000378:metabolism; D045325:HCT116 Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D009944:Organoplatinum Compounds / Q000008:administration & dosage; D000077150:Oxaliplatin; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018736:DNA Adducts; D004268:DNA-Binding Proteins; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin; D005982:Glutathione Transferase; D051057:Proto-Oncogene Proteins c-akt; C071447:ERCC1 protein, human; D004720:Endonucleases; D000068818:Cetuximab