title: Impact of epidermal growth factor receptor (EGFR) cell surface expression levels on effector mechanisms of EGFR antibodies.
abstract: The epidermal growth factor receptor (EGFR) is a widely expressed Ag that is successfully targeted in tumor patients by mAbs or tyrosine kinase inhibitors. A clinical study in non-small cell lung cancer patients demonstrated a positive correlation between EGFR expression levels and the therapeutic efficacy of the EGFR mAb cetuximab. However, the impact of EGFR expression on the different mechanisms of action (MoAs) triggered by the EGFR mAb has not been defined. In this study, BHK-21 cells were stably transfected to express different EGFR levels, which were quantified by immunofluorescence and immunohistochemistry and compared with EGFR levels of clinical non-small cell lung cancer samples. These cells were used to systematically investigate the impact of target Ag expression levels on Fab- or Fc-mediated MoAs of EGFR mAb. A negative correlation between EGFR levels and potency of Fab-mediated MoA was observed. Interestingly, Ab-dependent cell-mediated cytotoxicity (ADCC) by NK cells, monocytes, or polymorphonuclear cells as well as complement-dependent cytotoxicity positively correlated with the number of EGFR molecules. In comparison with ADCC by mononuclear cells, polymorphonuclear cell-mediated ADCC and complement-dependent cytotoxicity required higher EGFR expression levels and higher mAb concentrations to trigger significant tumor cell killing. This correlation between EGFR expression levels and Fc-mediated MoA was confirmed in an independent panel of human tumor cell lines carrying diverse genetic alterations. Furthermore, RNA interference-induced knockdown experiments reinforced the impact of EGFR expression on tumor cell killing by EGFR mAb. In conclusion, these results suggest that EGFR expression levels may determine distinct patterns of MoAs that contribute to the therapeutic efficacy of EGFR mAb.
authors.affiliation: Division of Stem Cell Transplantation and Immunotherapy, 2nd Department of Medicine, Christian-Albrechts-University and University Hospital Schleswig-Holstein, 24105 Kiel, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Derer
authors.forename: Philip
authors.initials: P
authors.lastname: Bauer
authors.forename: Stefan
authors.initials: S
authors.lastname: Lohse
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Scheel
authors.forename: Sven
authors.initials: S
authors.lastname: Berger
authors.forename: Christian
authors.initials: C
authors.lastname: Kellner
authors.forename: Matthias
authors.initials: M
authors.lastname: Peipp
authors.forename: Thomas
authors.initials: T
authors.lastname: Valerius
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D000068818:Cetuximab; D003165:Complement System Proteins / Q000494:pharmacology; D006224:Cricetinae; D066246:ErbB Receptors / Q000235:genetics / Q000276:immunology*; D015870:Gene Expression / Q000276:immunology*; D055785:Gene Knockdown Techniques; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology*; D007141:Immunoglobulin Fc Fragments / Q000494:pharmacology*; D007694:Killer Cells, Natural / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000276:immunology; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D034741:RNA, Small Interfering; D003165:Complement System Proteins; C512478:EGFR protein, human; D066246:ErbB Receptors; D000068818:Cetuximab