TLR3 agonists improve the immunostimulatory potential of cetuximab againstEGFR(+) head and neck cancer cells.

摘要

Toll-like receptor 3 (TLR3) agonists have been extensively used as adjuvants for anticancer vaccines. However, their immunostimulatory effects and precisemechanisms of action in the presence of antineoplastic monoclonal antibodies(mAbs) have not yet been evaluated. We investigated the effect of TLR3 agonistson cetuximab-mediated antibody-dependent cellular cytotoxicity (ADCC) againsthead and neck cancer (HNC) cells, as well as on dendritic cell (DC) maturationand cross-priming of epidermal growth factor receptor (EGFR)-specific CD8(+) Tcells. The cytotoxic activity of peripheral blood mononuclear cells (PBMCs) orisolated natural killer (NK) cells expressing polymorphic variants (at codon 158)of the Fcγ receptor IIIa (FcγIIIa) was determined in (51)Cr release assays uponincubation with the TLR3 agonist poly-ICLC. NK cell stimulation was measuredbased on activation and degranulation markers, while DC maturation in thepresence of poly-ICLC was assessed using flow cytometry. The DC-mediated crosspriming of EGFR-specific CD8(+) T cells was monitored upon in vitro stimulationwith tetramer-based flow cytometry. TLR3-stimulated, unfractionated PBMCs fromHNC patients mediated robust cetuximab-dependent ADCC, which was abrogated byNK-cell depletion. The cytolytic activity of TLR3-stimulated NK cells differedamong cells expressing different polymorphic variants of FcγRIIIa, and NK cellsexposed to both poly-ICLC and cetuximab expressed higher levels of CD107a andgranzyme B than their counterparts exposed to either stimulus alone. Poly-ICLCplus cetuximab also induced a robust upregulation of CD80, CD83 and CD86 on thesurface of DCs, a process that was partially NK-cell dependent. Furthermore, DCs matured in these conditions exhibited improved cross-priming abilities, resultingin higher numbers of EGFR-specific CD8(+) T cells. These findings suggest thatTLR3 agonists may provide a convenient means to improve the efficacy of mAb-basedanticancer regimens.