Cetuximab Enhanced the Cytotoxic Activity of Immune Cells during Treatment of Colorectal Cancer

Background/Aims: Cetuximab is a chimeric IgG1 monoclonal antibody which targets the extracellular domain of epidermal growth factor receptor. This antibody is widely used for colorectal cancer (CRC) treatment but its influence on the immune system is incompletely understood. Methods: The immune influence of cetuximab therapy in CRC patients was investigated by analyzing peripheral blood mononuclear cells using flow cytometry. We undertook in vitro cytotoxicity and cytokine-profile assays to ascertain the immunomodulatory effect of cetuximab treatment. Results: The number of CD3 + T, CD8 + T, and natural killer (NK) cells was increased significantly and T-regulatory cells reduced gradually after cetuximab treatment. Percentage of CD4 + T, natural killer T (NKT)-like, invariant NKT, and dendritic cells was similar between baseline patients and cetuximab patients. Expression of CD137 on NK and CD8 + T cells was increased significantly after 4 weeks of cetuximab therapy. In vitro cetuximab treatment markedly increased expression of CD137 and CD107a on NK and CD8 + T cells. Cetuximab treatment promoted the cytotoxic activity of NK and CD8 + T cells against tumor cells. Conclusion: Cetuximab treatment promotes activation of the immune response but alleviates immunosuppression: this might be the underlying anti-CRC effect of cetuximab.