IgG isotype, glycosylation, and EGFR expression determine the induction of antibody-dependent cellular cytotoxicity in vitro by cetuximab

Hum Antibodies. 2010;19(4):89-99. doi: 10.3233/HAB-2010-0232.


Purpose: To evaluate the antibody-dependent cellular cytotoxicity (ADCC) of cetuximab, an anti-epidermal growth factor receptor (EGFR) IgG1 antibody, in vitro.

Methods: Binding to human Fc receptors was measured by ELISA. ADCC against a panel of tumor cell lines was evaluated using peripheral blood mononuclear cells or NK cells as effectors and lactate dehydrogenase release as a marker of cell killing. Cetuximab was compared with two glycan variants of cetuximab and with panitumumab, an anti-EGFR IgG2.

Results: Cetuximab bound with high affinity to FcγRI (EC50 = 0.13 nM) and FcγRIIIa (EC50 = 6 nM) and effectively induced ADCC across multiple tumor cell lines. Panitumumab and aglycosylated cetuximab did not bind to FcγRI or FcγRIIIa nor have ADCC activity even at high effector-target cell ratios, even though the EGFR-binding affinity of cetuximab and panitumumab were shown to be comparable (KD = 87 pM and 83 pM, respectively). The extent of cetuximab-elicited ADCC was associated with the level of EGFR expression on tumor cells.

Conclusions: Cetuximab elicits effective ADCC activity against a wide range of tumor cells in vitro. This activity is dependent on antibody glycosylation and IgG1 isotype as well as tumor-cell EGFR expression. These findings suggest that ADCC may contribute to the antitumor activity of cetuximab.

MeSH terms

  • Antibodies, Monoclonal / immunology*
  • Antibodies, Monoclonal / metabolism
  • Antibodies, Monoclonal, Humanized
  • Antibody-Dependent Cell Cytotoxicity*
  • Antineoplastic Agents / immunology*
  • Antineoplastic Agents / metabolism
  • Cell Line, Tumor
  • Cetuximab
  • Dose-Response Relationship, Drug
  • Enzyme-Linked Immunosorbent Assay
  • ErbB Receptors / immunology
  • ErbB Receptors / metabolism*
  • Glycosylation
  • Humans
  • Immunoglobulin G / immunology*
  • Immunoglobulin Isotypes
  • Killer Cells, Natural / immunology
  • L-Lactate Dehydrogenase / metabolism
  • Leukocytes, Mononuclear / immunology
  • Panitumumab


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • Immunoglobulin G
  • Immunoglobulin Isotypes
  • Panitumumab
  • L-Lactate Dehydrogenase
  • ErbB Receptors
  • Cetuximab