title: Synthetic lethal interaction of cetuximab with MEK1/2 inhibition in NRAS-mutant metastatic colorectal cancer.
abstract: KRAS mutations are an established predictor of lack of response to EGFR-targeted therapies in patients with metastatic colorectal cancer (mCRC). However, little is known about the role of the rarer NRAS mutations as a mechanism of primary resistance to the anti-EGFR monoclonal antibody cetuximab in wild-type KRAS mCRC. Using isogenic mCRC cells with a heterozygous knock-in of the NRAS activating mutation Q61K, we aimed to elucidate the mechanism(s) by which mutant NRAS blocks cetuximab from inhibiting mCRC growth. NRASQ61K/+ cells were refractory to cetuximab-induced growth inhibition. Pathway-oriented proteome profiling revealed that cetuximab-unresponsive ERK1/2 phosphorylation was the sole biomarker distinguishing cetuximab-refractory NRASQ61K/+ from cetuximab-sensitive NRAS+/+ cells. We therefore employed four representative MEK1/2 inhibitors (binimetinib, trametinib, selumetinib, and pimasertib) to evaluate the therapeutic value of MEK/ERK signaling in cetuximab-refractory NRAS mutation-induced mCRC. Co-treatment with an ineffective dose of cetuximab augmented, up to more than 1,300-fold, the cytotoxic effects of pimasertib against NRASQ61K/+ cells. Simultaneous combination of MEK1/2 inhibitors with cetuximab resulted in extremely high and dose-dependent synthetic lethal effects, which were executed, at least in part, by exacerbated apoptotic cell death. Dynamic monitoring of real-time cell growth rates confirmed that cetuximab synergistically sensitized NRASQ61K/+ cellsto MEK1/2 inhibition. Our discovery of a synthetic lethal interaction of cetuximab in combination with MEK1/2 inhibition for the NRAS mutant subgroup of mCRC underscores the importance of therapeutic intervention both in the MEK-ERK and EGFR pathways to achieve maximal therapeutic efficacy against NRAS-mutant mCRC tumors.
authors.affiliation: Department of Medical Oncology, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Girona Biomedical Research Institute, Girona, Catalonia, Spain.|Department of Medical Sciences, Medical School, University of Girona, Girona, Spain.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Queralt
authors.affiliation: Girona Biomedical Research Institute, Girona, Catalonia, Spain.|ProCURE (Program Against Cancer Therapeutic Resistance), Metabolism & Cancer Group, Catalan Institute of Oncology, Girona, Catalonia, Spain.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Cuyàs
authors.affiliation: Department of Medical Oncology, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Girona Biomedical Research Institute, Girona, Catalonia, Spain.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Bosch-Barrera
authors.affiliation: Biochemistry and Molecular Biology Unit, Department of Biology, University of Girona, Girona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Massaguer
authors.affiliation: Biochemistry and Molecular Biology Unit, Department of Biology, University of Girona, Girona, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: de Llorens
authors.affiliation: Girona Biomedical Research Institute, Girona, Catalonia, Spain.|Unit of Clinical Research, Catalan Institute of Oncology, Girona, Catalonia, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: Martin-Castillo
authors.affiliation: Department of Medical Oncology, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Girona Biomedical Research Institute, Girona, Catalonia, Spain.|Department of Medical Sciences, Medical School, University of Girona, Girona, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Brunet
authors.affiliation: Department of Medical Oncology, Catalan Institute of Oncology, Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, Barcelona, Spain.
authors.forename: Ramon
authors.initials: R
authors.lastname: Salazar
authors.affiliation: Girona Biomedical Research Institute, Girona, Catalonia, Spain.|ProCURE (Program Against Cancer Therapeutic Resistance), Metabolism & Cancer Group, Catalan Institute of Oncology, Girona, Catalonia, Spain.
authors.forename: Javier A
authors.initials: JA
authors.lastname: Menendez
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001562:Benzimidazoles / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000068818:Cetuximab / Q000494:pharmacology*; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004357:Drug Synergism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000235:genetics*; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation; D009536:Niacinamide / Q000031:analogs & derivatives / Q000494:pharmacology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D040901:Proteomics / Q000379:methods; D011728:Pyridones / Q000494:pharmacology; D011744:Pyrimidinones / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
chemical_list: C517975:AZD 6244; D001562:Benzimidazoles; D008565:Membrane Proteins; C550600:N-(2,3-dihydroxypropyl)-1-((2-fluoro-4-iodophenyl)amino)isonicotinamide; D047428:Protein Kinase Inhibitors; D011728:Pyridones; D011744:Pyrimidinones; C581313:binimetinib; D009536:Niacinamide; C560077:trametinib; C482128:MAP2K2 protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human; D000068818:Cetuximab
keywords: KRAS; MEK1/2; NRAS; cetuximab; colon cancer