title: Epidermal growth factor receptor dynamics influences response to epidermal growth factor receptor targeted agents.
abstract: Analysis of gene expression of cancer cell lines exposed to erlotinib, a small molecule inhibitor of the epidermal growth factor receptor (EGFR), showed a marked increase in EGFR mRNA in resistant cell lines but not in susceptible ones. Because cetuximab induces EGFR down-regulation, we explored the hypothesis that treatment with cetuximab would interfere with erlotinib-induced EGFR up-regulation and result in antitumor effects. Exposure of the resistant biliary tract cancer cell line HuCCT1 but not the susceptible A431 epidermoid cell line to erlotinib induced EGFR mRNA and protein expression. Combined treatment with cetuximab blunted the erlotinib-induced EGFR up-regulation and resulted in inhibition of cell proliferation and apoptosis in the HuCCT1 cells. Blockage of erlotinib-induced EGFR synthesis in HuCCT1 cells by small interfering RNA resulted in identical antitumor effects as cetuximab, providing mechanistic specificity. In mice xenografted with A431, HuCCT1, and the pancreatic cancer cell line Panc430, maximal growth arrest and decrease in Ki67 proliferation index were documented with combined therapy, and EGFR down-regulation was observed in cetuximab-treated tumors. These results may indicate that resistance to EGFR kinase inhibition may be, at least in part, mediated by a highly dynamic feedback loop consisting of up-regulation of the EGFR upon exposure to EGFR kinase inhibitors. Abrogation of this response by small interfering RNA-mediated EGFR mRNA down-regulation and/or by cetuximab-mediated protein clearance induced tumor arrest across several cancer models with different EGFR expression levels, suggesting that resistance and sensitivity are dynamic events where proportional decrease in the target rather than absolute content dictates outcome.
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
authors.forename: Antonio
authors.initials: A
authors.lastname: Jimeno
authors.forename: Belen
authors.initials: B
authors.lastname: Rubio-Viqueira
authors.forename: Maria L
authors.initials: ML
authors.lastname: Amador
authors.forename: Darin
authors.initials: D
authors.lastname: Oppenheimer
authors.forename: Nadia
authors.initials: N
authors.lastname: Bouraoud
authors.forename: Peter
authors.initials: P
authors.lastname: Kulesza
authors.forename: Valeria
authors.initials: V
authors.lastname: Sebastiani
authors.forename: Anirban
authors.initials: A
authors.lastname: Maitra
authors.forename: Manuel
authors.initials: M
authors.lastname: Hidalgo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001661:Biliary Tract Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D045744:Cell Line, Tumor; D000068818:Cetuximab; D018281:Cholangiocarcinoma / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D000069347:Erlotinib Hydrochloride; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011799:Quinazolines / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D000068818:Cetuximab