title: Emergence of Multiple EGFR Extracellular Mutations during Cetuximab Treatment in Colorectal Cancer.
abstract: OBJECTIVE
  Patients with colorectal cancer who respond to the anti-EGFR antibody cetuximab often develop resistance within several months of initiating therapy. To design new lines of treatment, the molecular landscape of resistant tumors must be ascertained. We investigated the role of mutations in the EGFR signaling axis on the acquisition of resistance to cetuximab in patients and cellular models.
  
  
  METHODS
  Tissue samples were obtained from 37 patients with colorectal cancer who became refractory to cetuximab. Colorectal cancer cells sensitive to cetuximab were treated until resistant derivatives emerged. Mutational profiling of biopsies and cell lines was performed. Structural modeling and functional analyses were performed to causally associate the alleles to resistance.
  
  
  RESULTS
  The genetic profile of tumor specimens obtained after cetuximab treatment revealed the emergence of a complex pattern of mutations in EGFR, KRAS, NRAS, BRAF, and PIK3CA genes, including two novel EGFR ectodomain mutations (R451C and K467T). Mutational profiling of cetuximab-resistant cells recapitulated the molecular landscape observed in clinical samples and revealed three additional EGFR alleles: S464L, G465R, and I491M. Structurally, these mutations are located in the cetuximab-binding region, except for the R451C mutant. Functionally, EGFR ectodomain mutations prevent binding to cetuximab but a subset is permissive for interaction with panitumumab.
  
  
  CONCLUSIONS
  Colorectal tumors evade EGFR blockade by constitutive activation of downstream signaling effectors and through mutations affecting receptor-antibody binding. Both mechanisms of resistance may occur concomitantly. Our data have implications for designing additional lines of therapy for patients with colorectal cancer who relapse upon treatment with anti-EGFR antibodies.
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy. Department of Oncology, University of Torino, Candiolo, Italy. FIRC Institute of Molecular Oncology (IFOM), Milano, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Arena
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain. Department of Pathology, Hospital del Mar, Barcelona, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Bellosillo
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy. Department of Oncology, University of Torino, Candiolo, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Siravegna
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain. Department of Medical Oncology, Hospital del Mar, Barcelona, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Martínez
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain.
authors.forename: Israel
authors.initials: I
authors.lastname: Cañadas
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy. Department of Oncology, University of Torino, Candiolo, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Lazzari
authors.affiliation: Computational Biophysics Laboratory (GRIB-IMIM), Pompeu Fabra University, PRBB, Barcelona, Spain.
authors.forename: Noelia
authors.initials: N
authors.lastname: Ferruz
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy. Department of Oncology, University of Torino, Candiolo, Italy.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Russo
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Misale
authors.affiliation: Department of Medical Oncology, Hospital del Mar, Barcelona, Spain.
authors.forename: Iria
authors.initials: I
authors.lastname: González
authors.affiliation: Department of Pathology, Hospital del Mar, Barcelona, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Iglesias
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Gavilan
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Corti
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy.
authors.forename: Sebastijan
authors.initials: S
authors.lastname: Hobor
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Crisafulli
authors.affiliation: Department of Pathology, Hospital del Mar, Barcelona, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Salido
authors.affiliation: Department of Radiology, Hospital del Mar, Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Sánchez
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain. Department of Pathology, Hospital del Mar, Barcelona, Spain.
authors.forename: Alba
authors.initials: A
authors.lastname: Dalmases
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Bellmunt
authors.affiliation: Computational Biophysics Laboratory (GRIB-IMIM), Pompeu Fabra University, PRBB, Barcelona, Spain. Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain.
authors.forename: Gianni
authors.initials: G
authors.lastname: De Fabritiis
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Rovira
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy. Department of Oncology, University of Torino, Candiolo, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Di Nicolantonio
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain. Department of Medical Oncology, Hospital del Mar, Barcelona, Spain. Pompeu Fabra University, Barcelona, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Albanell
authors.affiliation: Candiolo Cancer Institute-FPO, IRCCS, Candiolo, Italy. Department of Oncology, University of Torino, Candiolo, Italy. cmontagut@hospitaldelmar.cat alberto.bardelli@unito.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bardelli
authors.affiliation: Cancer Research Program, IMIM (Institut Hospital del Mar Investigacions Mediques), Hospital del Mar, Barcelona, Spain. Department of Medical Oncology, Hospital del Mar, Barcelona, Spain. cmontagut@hospitaldelmar.cat alberto.bardelli@unito.it.
authors.forename: Clara
authors.initials: C
authors.lastname: Montagut
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D015153:Blotting, Western; D045744:Cell Line, Tumor; D000068818:Cetuximab / Q000627:therapeutic use; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics*; D004252:DNA Mutational Analysis; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005110:Extracellular Space / Q000235:genetics; D005434:Flow Cytometry; D018773:Genes, erbB-1 / Q000235:genetics*; D006801:Humans; D009154:Mutation; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D000970:Antineoplastic Agents; D000068818:Cetuximab