Tumors Established with Cell Lines Selected for Oxaliplatin Resistance Respond to Oxaliplatin if Combined with Cetuximab

• Published in: Clinical cancer research 2007-12, Vol.13 (24), p.7432-7440
• Main Authors: PREWETT, Marie, DEEVI, Dhanvanthri S, BASSI, Rajiv, FAN FAN, ELLIS, Lee M, HICKLIN, Daniel J, TONRA, James R
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Monoclonal - administration & dosage; Antibodies, Monoclonal, Humanized; Antineoplastic agents; Antineoplastic Combined Chemotherapy Protocols - pharmacology; Biological and medical sciences; biological therapeutic agents; Blotting, Western; Cell Line, Tumor; Cetuximab; Colorectal Neoplasms - drug therapy; Colorectal Neoplasms - metabolism; combined modality therapies; DNA Adducts - drug effects; DNA damage and repair mechanisms; DNA Repair - drug effects; DNA-Binding Proteins - drug effects; Drug Resistance, Neoplasm - drug effects; Drug Resistance, Neoplasm - physiology; EGFR; Extracellular Signal-Regulated MAP Kinases - drug effects; Flow Cytometry; gastrointestinal cancers: colorectal; Humans; Medical sciences; Mice; Mice, Nude; monoclonal antibody; Neoplasms, Experimental - drug therapy; Neoplasms, Experimental - metabolism; Organoplatinum Compounds - administration & dosage; oxaliplatin; Pharmacology. Drug treatments; Proto-Oncogene Proteins c-akt - drug effects; Receptor, Epidermal Growth Factor - biosynthesis; X-ray Repair Cross Complementing Protein 1; Xenograft Model Antitumor Assays; xenografts
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-07-1768

Purpose: To establish whether cetuximab, a chimeric IgG1 antibody targeting epidermal growth factor receptor, has the potential to restore responsiveness to oxaliplatin in preclinical cancer models, as has been shown with irinotecan in irinotecan refractory metastatic colorectal cancer patients. Experimental Design: The effects of cetuximab and oxaliplatin, alone or in combination, were tested in vitro and in vivo using human colorectal cancer cell lines selected for oxaliplatin resistance, as well as parental control cell lines. Evaluations were made of subcutaneous xenograft tumor growth in nu/nu athymic mice, as well as activation of mitogen-activated protein kinase (extracellular signal-regulated kinase 1/2) and AKT, expression of DNA repair genes, density of apurinic/apyrimidinic DNA damage, and accumulation of platinum-DNA adducts in vitro . Results: Oxaliplatin + cetuximab efficacy in murine subcutaneous xenograft models was greater than that of monotherapies and independent of the responsiveness to oxaliplatin monotherapy. In vitro , cetuximab reduced expression of excision repair cross-complementation group 1 and XPF, which are key components of the nucleotide excision repair pathway involved in the excision of platinum-DNA adducts. In addition, cetuximab reduced expression of XRCC1, a component of the base excision repair pathway responsible for the repair of apurinic/apyrimidinic sites. Effects of cetuximab on DNA repair protein levels were downstream to effects on mitogen-activated protein kinase and AKT pathway activation. In line with effects on DNA repair protein expression, cetuximab increased the accumulation of platinum and apurinic/apyrimidinic sites on DNA during oxaliplatin treatment. Conclusions: Cetuximab has the potential to salvage the benefits of oxaliplatin in oxaliplatin-resistant colorectal cancer patients by reducing DNA repair capacity.