C-type Lectin Receptors for Tumor Eradication: Future Directions

Targeting the "Sweet Side" of Tumor with Glycan-Binding Molecules Conjugated-Nanoparticles: Implications in Cancer Therapy and Diagnosis

Nanotechnology is in the spotlight of therapeutic innovation, with numerous advantages for tumor visualization and eradication. The end goal of the therapeutic use of nanoparticles, however, remains distant due to the limitations of nanoparticles to target cancer tissue. The functionalization of nanosystem surfaces with biological ligands is a major strategy for directing the actions of nanomaterials specifically to tumor cells. Cancer formation and metastasis are accompanied by profound alterations in protein glycosylation. Hence, the detection and targeting of aberrant glycans are of great value in cancer diagnosis and therapy. In this review, we provide a brief update on recent progress targeting aberrant glycosylation by functionalizing nanoparticles with glycan-binding molecules (with a special focus on lectins and anti-glycan antibodies) to improve the efficacy of nanoparticles in cancer targeting, diagnosis, and therapy and outline the challenges and limitations in implementing this approach. We envision that the combination of nanotechnological strategies and cancer-associated glycan targeting could remodel the field of cancer diagnosis and therapy, including immunotherapy.

Enhanced Immune Response Against the Thomsen-Friedenreich Tumor Antigen Using a Bivalent Entirely Carbohydrate Conjugate

The Thomsen-Friedenreich (TF) antigen is a key target for the development of anticancer vaccines, and this ongoing challenge remains relevant due to the poor immunogenicity of the TF antigen. To overcome this challenge, we adopted a bivalent conjugate design which introduced both the TF antigen and the Thomsen-nouveau (Tn) antigen onto the immunologically relevant polysaccharide A1 (PS A1). The immunological results in C57BL/6 mice revealed that the bivalent, Tn-TF-PS A1 conjugate increased the immune response towards the TF antigen as compared to the monovalent TF-PS A1. This phenomenon was first observed with enzyme-linked immunosorbent assay (ELISA) where the bivalent conjugate generated high titers of IgG antibodies where the monovalent conjugate generated an exclusive IgM response. Fluorescence-activated cell sorting (FACS) analysis also revealed increased binding events to the tumor cell lines MCF-7 and OVCAR-5, which are consistent with the enhanced tumor cell lysis observed in a complement dependent cytotoxicity (CDC) assay. The cytokine profile generated by the bivalent construct revealed increased pro-inflammatory cytokines IL-17 and IFN-γ. This increase in cytokine concentration was matched with an increase in cytokine producing cells as observed by ELISpot. We hypothesized the mechanisms for this phenomenon to involve the macrophage galactose N-acetylgalactosamine specific lectin 2 (MGL2). This hypothesis was supported by using biotinylated probes and recombinant MGL2 to measure carbohydrate-protein interactions.

Overexpression of dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin-related protein in cervical cancer and correlation with squamous cell carcinoma antigen

Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin-related protein (DC-SIGNR) is a type II transmembrane protein that has been reported to bind to various pathogens and participate in immunoregulation and tumorigenesis. However, further research is required to investigate whether the level of DC-SIGNR and cervical cancer are associated. The present study aimed to explore the clinical diagnostic significance of DC-SIGNR in cervical cancer. Immunohistochemical staining of DC-SIGNR was performed in samples from 25 patients with early stage cervical cancer, 14 patients with cervical intraepithelial neoplasia (CIN) and cervical polyp samples from 15 individuals. DC-SIGNR expression in cervical cancer tissue was significantly higher compared with that in CIN and cervical polyp tissue (P=0.0184 and P=0.0236, respectively). However, there was no significant difference in DC-SIGNR expression between CIN and cervical polyp tissue (P=0.8103). Additionally, the serum DC-SIGNR levels in 84 cervical cancer patients and 69 healthy female individuals were measured using an ELISA. Serum (s)DC-SIGNR levels were significantly higher in cervical cancer patients compared with healthy female individuals (P<0.0001). A sDC-SIGNR level of 93.7 ng/ml was revealed by receiver operating characteristic curve analysis to predict the presence of cervical cancer with 69.57% sensitivity and 66.67% specificity (area under the curve, 0.6989; P<0.0001). Levels of sDC-SIGNR in cervical cancer patients were also correlated with serum levels of squamous cell carcinoma antigen (r=0.2583; P=0.0348). The results of the present study demonstrate that DC-SIGNR is overexpressed in cervical cancer tissue, and suggest that DC-SIGNR could serve as a biomarker for the early diagnosis of cervical cancer. Nevertheless, further studies are required to demonstrate what role DC-SIGNR serves in cervical cancer.

Pros and Cons of Antigen-Presenting Cell Targeted Tumor Vaccines

In therapeutic antitumor vaccination, dendritic cells play the leading role since they decide if, how, when, and where a potent antitumor immune response will take place. Since the disentanglement of the complexity and merit of different antigen-presenting cell subtypes, antitumor immunotherapeutic research started to investigate the potential benefit of targeting these subtypes in situ. This review will discuss which antigen-presenting cell subtypes are at play and how they have been targeted and finally question the true meaning of targeting antitumor-based vaccines.

Glycobiology of immune responses

Unlike their protein "roommates" and their nucleic acid "cousins," carbohydrates remain an enigmatic arm of biology. The central reason for the difficulty in fully understanding how carbohydrate structure and biological function are tied is the nontemplate nature of their synthesis and the resulting heterogeneity. The goal of this collection of expert reviews is to highlight what is known about how carbohydrates and their binding partners-the microbial (non-self), tumor (altered-self), and host (self)-cooperate within the immune system, while also identifying areas of opportunity to those willing to take up the challenge of understanding more about how carbohydrates influence immune responses. In the end, these reviews will serve as specific examples of how carbohydrates are as integral to biology as are proteins, nucleic acids, and lipids. Here, we attempt to summarize general concepts on glycans and glycan-binding proteins (mainly C-type lectins, siglecs, and galectins) and their contributions to the biology of immune responses in physiologic and pathologic settings.