title: Increased TGF-α as a mechanism of acquired resistance to the anti-EGFR inhibitor cetuximab through EGFR-MET interaction and activation of MET signaling in colon cancer cells.
abstract: OBJECTIVE
  Although cetuximab, an anti-EGF receptor (EGFR) monoclonal antibody, is an effective treatment for patients with KRAS wild-type metastatic colorectal cancer (mCRC), its clinical use is limited by onset of resistance.
  
  
  METHODS
  We characterized two colorectal cancer models to study the mechanisms of acquired resistance to cetuximab.
  
  
  RESULTS
  Following chronic treatment of nude mice bearing cetuximab-sensitive human GEO colon xenografts, cetuximab-resistant GEO (GEO-CR) cells were obtained. In GEO-CR cells, proliferation and survival signals were constitutively active despite EGFR inhibition by cetuximab treatment. Whole gene expression profiling identified a series of genes involved in the hepatocyte growth factor (HGF)-MET-dependent pathways, which were upregulated in GEO-CR cells. Furthermore, activated, phosphorylated MET was detected in GEO-CR cells. A second colorectal cancer cell line with acquired resistance to cetuximab was obtained (SW48-CR). Inhibition of MET expression by siRNA restored cetuximab sensitivity in GEO-CR and SW48-CR cells, whereas exogenous activation of MET by HGF stimulation in cetuximab-sensitive GEO and SW48 cells induced resistance to cetuximab. Treatment of GEO-CR and SW48-CR cells with PHA665752, a selective MET inhibitor, inhibited cell growth, proliferation, and survival signals and impaired cancer cell migration. Overexpression of TGF-α, a specific EGFR ligand, was involved in the acquisition of cetuximab resistance in GEO-CR and SW48-CR cells. In fact, TGF-α overexpression induced the EGFR-MET interaction, with subsequent MET phosphorylation and activation of MET downstream effectors in GEO-CR and SW48-CR cells.
  
  
  CONCLUSIONS
  These results suggest that overexpression of TGF-α through induction of EGFR-MET interaction contributes to cetuximab resistance in colorectal cancer cells. The combined inhibition of EGFR and MET receptor could represent a strategy for preventing and/or overcoming cetuximab resistance in patients with colorectal cancer.
authors.affiliation: Authors' Affiliations: Oncologia Medica and Immunologia Clinica, Dipartimento Medico-Chirurgico di Internistica Clinica e Sperimentale F. Magrassi e A. Lanzara; Sezione di Farmacologia, Dipartimento di Medicina Sperimentale, Seconda Università degli Studi di Napoli; and Oncologia Medica, Dipartimento di Endocrinologia e Oncologia Molecolare e Clinica, Università di Napoli Federico II, Naples, Italy.
authors.forename: Teresa
authors.initials: T
authors.lastname: Troiani
authors.forename: Erika
authors.initials: E
authors.lastname: Martinelli
authors.forename: Stefania
authors.initials: S
authors.lastname: Napolitano
authors.forename: Donata
authors.initials: D
authors.lastname: Vitagliano
authors.forename: Loreta Pia
authors.initials: LP
authors.lastname: Ciuffreda
authors.forename: Sara
authors.initials: S
authors.lastname: Costantino
authors.forename: Floriana
authors.initials: F
authors.lastname: Morgillo
authors.forename: Anna
authors.initials: A
authors.lastname: Capasso
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Sforza
authors.forename: Anna
authors.initials: A
authors.lastname: Nappi
authors.forename: Raffaele
authors.initials: R
authors.lastname: De Palma
authors.forename: Elena
authors.initials: E
authors.lastname: D'Aiuto
authors.forename: Liberato
authors.initials: L
authors.lastname: Berrino
authors.forename: Roberto
authors.initials: R
authors.lastname: Bianco
authors.forename: Fortunato
authors.initials: F
authors.lastname: Ciardiello
mesh_terms: D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000068818:Cetuximab; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D017228:Hepatocyte Growth Factor / Q000096:biosynthesis; D006801:Humans; D051379:Mice; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis*
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D016211:Transforming Growth Factor alpha; D017228:Hepatocyte Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met; D000068818:Cetuximab