Cetuximab-Activated Natural Killer and Dendritic Cells Collaborate to Trigger Tumor Antigen-Specific T-cell Immunity in Head and Neck Cancer Patients

Purpose: Tumor antigen-specific monoclonal antibodies (mAb) block oncogenic signaling and induce Fc gamma receptor (Fc gamma R)-mediated cytotoxicity. However, the role of CD8(+) CTL and Fc gamma R in initiating innate and adaptive immune responses in mAb-treated human patients with cancer is still emerging. Experimental Design: Fc gamma RIIIa codon 158 polymorphism was correlated with survival in 107 cetuximab-treated patients with head and neck cancer (HNC). Flow cytometry was carried out to quantify EGF receptor (EGFR)-specific T cells in cetuximab-treated patients with HNC. The effect of cetuximab on natural killer (NK) cell, dendritic cell (DC), and T-cell activation was measured using IFN-gamma release assays and flow cytometry. Results: Fc gamma RIIIa polymorphism did not predict clinical outcome in cetuximab-treated patients with HNC; however, elevated circulating EGFR(853-861)-specific CD8(+) T cells were found in cetuximab-treated patients with HNC (P < 0.005). Cetuximab promoted EGFR-specific cellular immunity through the interaction of EGFR(+) tumor cells and FcgRIIIa on NK cells but not on the polymorphism per se. Cetuximab-activated NK cells induced IFN-gamma-dependent expression of DC maturation markers, antigen processing machinery components such as TAP-1/2 and T-helper cell (T(H)1) chemokines through NKG2D/MICA binding. Cetuximab initiated adaptive immune responses via NK cell-induced DC maturation, which enhanced cross-presentation to CTL specific for EGFR as well as another tumor antigen, MAGE-3. Conclusion: Cetuximab-activated NK cells promote DC maturation and CD8(+) T-cell priming, leading to tumor antigen spreading and T(H)1 cytokine release through NK-DC cross-talk. Fc gamma RIIIa polymorphism did not predict clinical response to cetuximab but was necessary for NK-DC interaction and mAb-induced cross-presentation. EGFR-specific T cells in cetuximab-treated patients with HNC may contribute to clinical response. Clin Cancer Res; 19(7); 1858-72. (C)2013 AACR.