Dendritic cells (DCs) sense the microenvironment through several types of receptors recognizing pathogen-associated molecular patterns. In particular, C-type lectins, expressed by distinct subsets of DCs, recognize and internalize specific carbohydrate antigen in a Ca 2+ -dependent manner. Targeting of these receptors is becoming an efficient strategy of delivering antigens in DC-based anticancer immunotherapy. Here we investigated the role of the macrophage galactose type C-lectin receptor (MGL), expressed by immature DCs (iDCs), as a molecular target for α-N-acetylgalactosamine (GalNAc or Tn)-carrying tumor-associated antigens to improve DC performance. MGL expressed by ex vivo-generated iDCs from healthy donors was engaged by a 60-mer MUC1 9Tn -glycopeptide as a Tn-carrying tumor-associated antigen, and an anti-MGL antibody, as a specific MGL binder. We demonstrated that MGL engagement induced homotrimers and homodimers, triggering the phosphorylation of extracellular signal-regulated kinase 1,2 (ERK1,2) and nuclear factor-κB activation. Analysis of DC phenotype and function demonstrated that MGL engagement improved DC performance as antigen-presenting cells, promoting the upregulation of maturation markers, a decrease in phagocytosis, an enhancement of motility, and most importantly an increase in antigen-specific CD8 + T-cell activation. These results demonstrate that the targeting of MGL receptor on human DCs has an adjuvant effect and that this strategy can be used to design novel anticancer vaccines. Keywords: C-type lectins · Dendritic cells · Macrophage galactose-type C-type lectin (MGL) · MUC1 · Tn-tumor associated antigens IntroductionDendritic cells (DCs), as professional antigen-presenting cells (APCs), sense the microenvironment through different types of Correspondence: Prof. Marianna Nuti e-mail: marianna.nuti@uniroma1.it receptors to scan local environmental changes and eliminate incoming pathogens [1]. They play an essential role in the uptake of self-or pathogen-associated antigens, thus, steering and directing the immune response. After activation, DCs migrate to the draining lymph nodes, where they initiate specific immunity * These authors contributed equally to this work. The most important molecules from the CLR family include macrophage galactose type C-lectin (MGL), dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), the mannose receptor, DEC205, and Dectin-1. These receptors are able to trigger distinct signaling pathways that modulate DC functions through the expression of specific molecules and cytokines, determining the polarization of T cells [4]. These properties make this C-type lectin family an optimal tool for DC targeting in cancer vaccination. Human MGL (hMGL) is a type II C-type lectin, expressed in vitro by macrophages and monocyte derived DCs and in vivo by DCs of skin and lymph nodes [5,6]. Its carbohydrate recognition domains contain a QPD sequence that is responsible for recognition of α-or β-N-acetylgalactosamine (GalNAc, Tn) res...

C-type lectin receptors (CLRs) on antigen-presenting cells (APCs) facilitate uptake of carbohydrate antigens for antigen presentation, modulating the immune response in infection, homeostasis, autoimmunity, allergy, and cancer. In this review, we focus on the role of the macrophage galactose type C-type lectin (MGL) in the immune response against self-antigens, pathogens, and tumor associated antigens (TAA). MGL is a CLR exclusively expressed by dendritic cells (DCs) and activated macrophages (MØs), able to recognize terminal GalNAc residues, including the sialylated and nonsialylated Tn antigens. We discuss the effects on DC function induced throughout the engagement of MGL, highlighting the importance of the antigen structure in the modulation of immune response. Indeed modifying Tn-density, the length, and steric structure of the Tn-antigens can result in generating immunogens that can efficiently bind to MGL, strongly activate DCs, mimic the effects of a danger signal, and achieve an efficient presentation in HLA classes I and II compartments.

Abstract. Radiofrequency tumor ablation (RFA) is a therapeutic modality for liver cancer patients inducing localized tumor necrosis with maximal preservation of normal liver parenchyma. We investigated the immunomodulatory effects exerted by RFA treatment in liver cancer patients with metastatic liver lesions (13 patients) or hepatocellular carcinoma (HCC) (4 patients). Analysis of lymphocyte subsets by flow cytometry revealed that after RFA, CD3 + T cells, in particular CD4 + , were decreased in metastatic cancer patients, while no change was observed in HCC patients. Moreover, RFA induced trafficking of naïve and memory CD62L + T cells from circulation to tissues. When characterizing the function of T cells, proliferative response to PHA was strongly increased after 48 h from RFA in metastatic cancer patients. Furthermore, T cells produced IFN-γ in response to the tumor associated MUC1 antigen. In contrast, humoral immune responses against tumor antigens such as MUC1 and HCV proteins were unaffected by RFA treatment, although increase of circulating B cells was observed only in metastatic cancer patients. These results indicate that RFA application can exert an activating effect on the immune system in metastatic cancer patients, favouring trafficking of lymphocyte subsets and enhancing tumor antigen specific cellular immune responses.

Tyrosine kinase inhibitors (TKIs) target angiogenesis by affecting, for example, the VEGF receptors in tumors and have improved outcomes for patients with metastatic renal cell carcinoma (mRCC). Immune checkpoint inhibitors (ICIs) have also been proposed for treatment of mRCC with encouraging results. A better understanding of the activity of immune cells in mRCC, the immunomodulatory effects of TKIs, and the characteristics defining patients most likely to benefit from various therapies will help optimize immunotherapeutic approaches. In this study, we investigated the influence of the TKI pazopanib on dendritic cell (DC) performance and immune priming. Pazopanib improved DC differentiation and performance by promoting upregulation of the maturation markers HLA-DR, CD40, and CCR7; decreasing IL10 production and endocytosis; and increasing T-cell proliferation. PD-L1 expression was also downregulated. Our results demonstrate that pazopanib inhibits the Erk/b-catenin pathway, suggesting this pathway might be involved in increased DC activation. Similar results were confirmed in DCs differentiated from mRCC patients during pazopanib treatment. In treated patients pazopanib appeared to enhance a circulating CD4 þ T-cell population that expresses CD137 (4-1BB). These results suggest that a potentially exploitable immunomodulatory effect induced by pazopanib could improve responses of patients with mRCC in customized protocols combining TKIs with ICI immunotherapy. Cancer Immunol Res; 6(6); 711-22. Ó2018 AACR.