title: Activation of tumor-promoting type 2 macrophages by EGFR-targeting antibody cetuximab.
abstract: OBJECTIVE
  In a recent randomized phase III clinical trial in metastatic colorectal cancer patients, the addition of the anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) cetuximab to bevacizumab and chemotherapy resulted in decreased progression-free survival, in particular for patients with the high-affinity FcγRIIIA.
  
  
  METHODS
  The presence of natural killer (NK) cells and type 2 (M2) macrophages in colorectal cancer was determined by immunohistochemistry, using antibodies to lineage-specific markers NKp46 and CD68 with CD163, respectively. Influence of tumor-bound cetuximab on M2 macrophages was carried out in vitro with EGFR-expressing tumor cells and short-term differentiated monocytes from blood donors, who were typed for the FcγRIIIA polymorphism (CD16).
  
  
  RESULTS
  Antibody-dependent cellular cytotoxicity by NK cells is generally proposed as one of the antitumor mechanisms of mAbs. We found that CD163-positive M2 macrophages are much more abundant in colorectal carcinomas. In vitro analysis of M2 macrophages revealed high levels of Fc-gamma receptors (FcγR) and PD-L1 and production of IL-10 and VEGF but not IL-12. These anti-inflammatory and tumor-promoting mediators were released upon coculture with EGFR-positive tumor cells loaded with low concentrations of cetuximab. Macrophage activation depended on EGFR expression on the tumor cells, FcγRs, target specificity of the mAb and mobility of antibody complexes. Cetuximab-induced macrophage responses were more pronounced for FCGR3A 158-Val (high-affinity) carriers.
  
  
  CONCLUSIONS
  These results suggest that tumor-promoting M2 macrophages are activated by the therapeutic mAb cetuximab in the local tumor microenvironment and argue that this immune mechanism should be taken into account for the application of therapeutic antibodies.
authors.affiliation: Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Pander
authors.forename: Moniek
authors.initials: M
authors.lastname: Heusinkveld
authors.forename: Tahar
authors.initials: T
authors.lastname: van der Straaten
authors.forename: Ekaterina S
authors.initials: ES
authors.lastname: Jordanova
authors.forename: Renée
authors.initials: R
authors.lastname: Baak-Pablo
authors.forename: Hans
authors.initials: H
authors.lastname: Gelderblom
authors.forename: Hans
authors.initials: H
authors.lastname: Morreau
authors.forename: Sjoerd H
authors.initials: SH
authors.lastname: van der Burg
authors.forename: Henk-Jan
authors.initials: HJ
authors.lastname: Guchelaar
authors.forename: Thorbald
authors.initials: T
authors.lastname: van Hall
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000920:Antibody-Dependent Cell Cytotoxicity; D015703:Antigens, CD / Q000276:immunology; D015214:Antigens, Differentiation, Myelomonocytic / Q000276:immunology; D000970:Antineoplastic Agents / Q000276:immunology / Q000494:pharmacology*; D060890:B7-H1 Antigen / Q000096:biosynthesis; D045744:Cell Line, Tumor; D000068818:Cetuximab; D015179:Colorectal Neoplasms / Q000276:immunology*; D066246:ErbB Receptors / Q000096:biosynthesis / Q000276:immunology; D006801:Humans; D016753:Interleukin-10 / Q000096:biosynthesis; D018664:Interleukin-12 / Q000096:biosynthesis; D007694:Killer Cells, Natural / Q000276:immunology; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D055627:Natural Cytotoxicity Triggering Receptor 1 / Q000276:immunology; D011956:Receptors, Cell Surface / Q000276:immunology; D017452:Receptors, IgG / Q000096:biosynthesis / Q000276:immunology; D059016:Tumor Microenvironment; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis; D000098902:CD163 Antigen; D000097382:CD68 Molecule
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000970:Antineoplastic Agents; D060890:B7-H1 Antigen; D000068818:Cetuximab; D066246:ErbB Receptors; D016753:Interleukin-10; D018664:Interleukin-12; D055627:Natural Cytotoxicity Triggering Receptor 1; D011956:Receptors, Cell Surface; D017452:Receptors, IgG; D042461:Vascular Endothelial Growth Factor A; D000098902:CD163 Antigen; C423236:CD274 protein, human; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C112260:NCR1 protein, human