NK cell-dependent antibody-mediated immunotherapy is improved in vitro and in vivo when combined with agonists for toll-like receptor 2 in head and neck cancer models

The immunosuppressive character of head and neck cancers may explain the relatively low response rates to antibody therapy targeting a tumor antigen, such as cetuximab, and anti-PD-1 checkpoint inhibition. Immunostimulatory agents that overcome tumor-derived inhibitory signals could augment therapeutic efficacy, thereby enhancing tumor elimination and improving patient survival. Here, we demonstrate that cetuximab treatment combined with immunostimulatory agonists for Toll-like receptor (TLR) 2 induces profound immune responses. Natural killer (NK) cells, isolated from healthy individuals or patients with head and neck cancer, harbored enhanced cytotoxic capacity and increased tumor-killing potential in vitro. Additionally, combination treatment increased the release of several pro-inflammatory cytokines and chemokines by NK cells. Tumor-bearing mice that received cetuximab and the TLR2 ligand Pam3CSK4 showed increased infiltration of immune cells into the tumors compared to mice that received cetuximab monotherapy, resulting in a significant delay in tumor growth or even complete tumor regression. Moreover, combination treatment resulted in improved overall survival in vivo. In conclusion, combining tumor-targeting antibody-based immunotherapy with TLR stimulation represents a promising treatment strategy to improve the clinical outcomes of cancer patients. This treatment could well be applied together with other therapeutic strategies such as anti-PD-(L)1 checkpoint inhibition to further overcome immunosuppression.Transplantation and immunomodulatio

Ins and outs of the IgA receptor, FcαRI

The interaction between immunoglobulins and Fc receptors has been recognized as a key element of the body's natural defense, and play a crucial role in FcR-mediated immunotherapy. FcαRI, the receptor for IgA, represents a transmembrane receptor consisting of two extracellular Ig-like domains, a 19 amino acid transmembrane region and a short (41 amino acid) cytoplasmic tail devoid of any recognized signaling motifs. Notably, most FcαRI research has focussed on the receptors found in complex with the ITAM (immunoreceptor tyrosine-based activation motif)-bearing FcR γ-chains, which was found crucial for coupling FcR to cellular activation, including phagocytosis, antigen presentation, ADCC, superoxide production and cytokine release. Cytokine induced inside-out signaling refers to the ability of cytokines to increase the binding capacity of FcαRI for IgA-immune complexes without effects on receptor expression levels, a process critically dependent on the FcαRI intracellular domain but not on the FcR γ-chains. In the present thesis, the emphasis was placed on the biological role of the FcαRI α-chain, which lead to a better insight in IgA receptor complex formation, FcαRI protein turn-over and cytokine-induced FcαRI activation, a critical step in FcαRI functioning. We addressed the molecular basis of the FcαRI-FcR γ-chain transmembrane interaction important for cellular activation, identified new mediators in FcαRI signaling for which two showed their functional importance in regulating the molecular switch for FcαRI activation. The third novel identified protein displayed its role in modulation of FcαRI-FcR γ-chain complex formation on protein levels. Last, we investigated the contribution of receptor avidity but also affinity in IgA immune complex binding. Thorough understanding of the role of IgA and its receptor will contribute to our insight in both normal and pathological immunity. These novel findings and future work contributing to the IgA receptor biology may furthermore unravel FcαRI signaling and regulation, and may well catalyze the development of novel strategies to modulate FcαRI function for immunotherapy

Fc receptors on neutrophils: two sides of the same coin?

Proteomic

Fc receptors on neutrophils: two sides of the same coin?

Proteomic

Protein 4.1G binds to a unique motif within the Fc gamma RI cytoplasmic tail

The C-terminal domain of protein 4.1G was identified to interact with the cytosolic tail of the high affinity IgG receptor, Fc gamma RI, in yeast two-hybrid screens. Proteins of the 4.1 family have previously been found to mediate receptor/cytoskeleton interactions. In the study presented here, we show an alternatively spliced 4.1G product to be associated with increased Fc gamma RI binding in yeast two-hybrid assays, and to be selectively enriched in most immune cells at the transcript level. In addition, a detailed analysis of the 4.1G 'docking site' within Fc gamma RI is provided by examining Fc gamma RI-CY-truncated and alanine-substituted mutants. These pointed to an Fc gamma RI membrane-proximal core motif of HxxBxxxBB (H represents hydrophobic residues, B basic residues and x represents any residue), followed by hydrophobic and (potentially) negatively charged residues to be central for interaction with protein 4.1G

Targeting Fc alpha RI on Polymorphonuclear Cells Induces Tumor Cell Killing through Autophagy

Neutrophils are the most abundant circulating FcR-expressing WBCs with potent cytotoxic ability. Currently, they are recognized as promising effector cells for Ab-mediated immunotherapy of cancer, because their capacity to kill tumor cells is greatly enhanced by tumor Ag-specific mAbs. The Fc alpha RI represents the most potent FcR on neutrophils for induction of Ab-mediated tumor cell killing. However, the mechanisms of cell death that are induced are poorly understood. Because these mechanisms can be used for modulation of anticancer treatment, we investigated the tumor cell death induced by neutrophil-mediated Ab-dependent killing via Fc alpha RI. Human mammary carcinoma cells were efficiently killed when incubated with human neutrophils and tumor-specific Fc alpha RI bispecific or IgA Abs. Interestingly, we observed characteristics of autophagy such as autophagic structures by electron microscopy and LC3B(+) autophagosomes in different human epithelial carcinoma cells, which resulted in tumor cell death. To a lesser extent, necrotic features, such as cellular membrane breakdown and spillage of intracellular content, were found. By contrast, apoptotic features including fragmented nuclei, Annexin V-positivity, and presence of cleaved caspase-3 were not observed. These findings indicate that neutrophils mainly facilitate autophagy to induce tumor cell death rather than the more commonly recognized apoptotic cell death mechanisms induced by NK cells or cytotoxic T cells. This knowledge not only reveals the type of tumor cell death induced in neutrophil-mediated, Ab-dependent cellular cytotoxicity, but importantly opens up additional perspectives for modulation of anticancer therapy in, for example, apoptosis-resistant tumor cells. The Journal of Immunology, 2011, 187: 726-732