Glycan-Lectin Interactions in Cancer and Viral Infections and How to Disrupt Them

Effects of Chemical Fixatives on Kinetic Measurements of Biomolecular Interaction on Cell Membrane

Understanding the interaction between ligands and membrane proteins is important for drug design and optimization. Although investigation using live cells is desirable, it is not feasible in some circumstances and cell fixation is performed to reduce cell motion and degradation. This study compared the effects of five fixatives, i.e., formaldehyde vapor (FV), paraformaldehyde (PFA), acetone, methanol, and ethanol, on kinetic measurements via the LigandTracer method. We found that all five fixatives exerted insignificant effects on lectin-glycan interaction. However, antibody-receptor interaction is markedly perturbed by coagulant fixatives. The acetone fixation changed the binding of the anti-human epidermal growth factor receptor 2 (HER2) antibody to HER2 on the cell membrane from a 1:2 to a 1:1 binding model, while methanol and ethanol abolished the antibody binding possibly by removal of the HER2 receptors on the cell membrane. The capability of binding was retained when methanol fixation was performed at lower temperatures, albeit with a binding model of 1:1 instead. Moreover, whereas cell morphology does not exert a substantial impact on lectin-glycan interaction, it can indeed modify the binding model of antibody-receptor interaction. Our results provided insights into the selection of fixatives for cell-based kinetic studies.

Cell cross talk within the lymphoma tumor microenvironment: follicular lymphoma as a paradigm

ABSTRACT

Follicular lymphoma (FL) is an indolent yet incurable germinal center B-cell lymphoma retaining a characteristic follicular architecture. FL tumor B cells are highly dependent on direct and indirect interactions with a specific and complex tumor microenvironment (TME). Recently, great progress has been made in describing the heterogeneity and dynamics of the FL TME and in depicting how tumor clonal and functional heterogeneity rely on the integration of TME-related signals. Specifically, the FL TME is enriched for exhausted cytotoxic T cells, immunosuppressive regulatory T cells of various origins, and follicular helper T cells overexpressing B-cell and TME reprogramming factors. FL stromal cells have also emerged as crucial determinants of tumor growth and remodeling, with a key role in the deregulation of chemokines and extracellular matrix composition. Finally, tumor-associated macrophages play a dual function, contributing to FL cell phagocytosis and FL cell survival through long-lasting B-cell receptor activation. The resulting tumor-permissive niches show additional layers of site-to-site and kinetic heterogeneity, which raise questions about the niche of FL-committed precursor cells supporting early lymphomagenesis, clonal evolution, relapse, and transformation. In turn, FL B-cell genetic and nongenetic determinants drive the reprogramming of FL immune and stromal TME. Therefore, offering a functional picture of the dynamic cross talk between FL cells and TME holds the promise of identifying the mechanisms of therapy resistance, stratifying patients, and developing new therapeutic approaches capable of eradicating FL disease in its different ecosystems.

Lectin-conjugated nanotags with high SERS stability: selective probes for glycans

Surface-enhanced Raman scattering (SERS) nanotags functionalized with lectins as the biological recognition element can be used to target the carbohydrate portion of carbohydrate-carrying molecules (glycoconjugates). An investigation of the optical stability of such functionalized SERS nanotags is an essential initial step before future application and quantification of surface glycan biomarkers on cells and extracellular vesicles. Herein, we report an innovative approach to evaluate the SERS stability of lectin-conjugated nanotags by investigating any possible interfering lectin-lectin interactions in a mixture of different lectin-conjugated SERS nanotags, as well as an assessment of lectin-glycan interaction by mixing wheat germ agglutinin (WGA)-conjugated SERS nanotags with different glycoproteins. No lectin cross-reactivity was found in the mixture of lectin-conjugated SERS nanotags, evidenced by the constant SERS intensity. Additionally, the results showed that the lectins conjugated to SERS nanotags retain their ability to interact with glycans, as evidenced by the changes in the nanotag color and extinction spectra. Their SERS intensity remained constant as supported by finite-element method (FEM) simulation results, demonstrating a high SERS stability and selectivity of lectin-conjugated nanotags towards multiplex applications.

Cancer cells and viruses share common glycoepitopes: exciting opportunities toward combined treatments

Aberrant glycosylation patterns of glycoproteins and glycolipids have long been recognized as one the major hallmarks of cancer cells that has led to numerous glycoconjugate vaccine attempts. These abnormal glycosylation profiles mostly originate from the lack of key glycosyltransferases activities, mutations, over expressions, or modifications of the requisite chaperone for functional folding. Due to their relative structural simplicity, O-linked glycans of the altered mucin family of glycoproteins have been particularly attractive in the design of tumor associated carbohydrate-based vaccines. Several such glycoconjugate vaccine formulations have generated potent monoclonal anti-carbohydrate antibodies useful as diagnostic and immunotherapies in the fight against cancer. Paradoxically, glycoproteins related to enveloped viruses also express analogous N- and O-linked glycosylation patterns. However, due to the fact that viruses are not equipped with the appropriate glycosyl enzyme machinery, they need to hijack that of the infected host cells. Although the resulting N-linked glycans are very similar to those of normal cells, some of their O-linked glycan patterns often share the common structural simplicity to those identified on tumor cells. Consequently, given that both cancer cells and viral glycoproteins share both common N- and O-linked glycoepitopes, glycoconjugate vaccines could be highly attractive to generate potent immune responses to target both conditions.

Dielectrophoretic Capture of Cancer-Derived Small-Extracellular-Vesicle-Bound Janus Nanoparticles via Lectin-Glycan Interaction

Glycosylation is closely related to cellular metabolism and disease progression. In particular, glycan levels in cancer cells and tissues increase during cancer progression. This upregulation of glycosylation in cancer cells may provide a basis for the development of new biomarkers for the targeting and diagnosis of specific cancers. Here, they developed a detection technology for pancreatic cancer cell-derived small extracellular vesicles (PC-sEVs) based on lectin-glycan interactions. Lectins specific for sialic acids are conjugated to Janus nanoparticles to induce interactions with PC-sEVs in a dielectrophoretic (DEP) system. PC-sEVs are selectively bound to the lectin-conjugated Janus nanoparticles (lectin-JNPs) with an affinity comparable to that of conventionally used carbohydrate antigen 19-9 (CA19-9) antibodies. Furthermore, sEVs-bound Lectin-JNPs (sEVs-Lec-JNPs) are manipulated between two electrodes to which an AC signal is applied for DEP capture. In addition, the proposed DEP system can be used to trap the sEVs-Lec-JNP on the electrodes. Their results, which are confirmed by lectin-JNPs using the proposed DEP system followed by target gene analysis, provide a basis for the development of a new early diagnostic marker based on the glycan characteristics of PC-sEVs. In turn, these novel detection methods could overcome the shortcomings of commercially available pancreatic cancer detection techniques.

CLEC19A overexpression inhibits tumor cell proliferation/migration and promotes apoptosis concomitant suppression of PI3K/AKT/NF-κB signaling pathway in glioblastoma multiforme

BACKGROUND

GBM is the most frequent malignant primary brain tumor in humans. The CLEC19A is a member of the C-type lectin family, which has a high expression in brain tissue. Herein, we sought to carry out an in-depth analysis to pinpoint the role of CLEC19A expression in GBM.

METHODS

To determine the localization of CLEC19A, this protein was detected using Western blot, Immunocytochemistry/Immunofluorescence, and confocal microscopy imaging. CLEC19A expression in glioma cells and tissues was evaluated by qRT-PCR. Cell viability, proliferation, migration, and apoptosis were examined through MTT assay, CFSE assay, colony formation, wound healing assay, transwell test, and flow cytometry respectively after CLEC19A overexpression. The effect of CLEC19A overexpression on the PI3K/AKT/NF-κB signaling pathway was investigated using Western blot. An in vivo experiment substantiated the in vitro results using the glioblastoma rat models.

RESULTS

Our in-silico analysis using TCGA data and measuring CLEC19A expression level by qRT-PCR determined significantly lower expression of CLEC19A in human glioma tissues compared to healthy brain tissues. By employment of ICC/IF, confocal microscopy imaging, and Western blot we could show that CLEC19A is plausibly a secreted protein. Results obtained from several in vitro readouts showed that CLEC19A overexpression in U87 and C6 glioma cell lines is associated with the inhibition of cell proliferation, viability, and migration. Further, qRT-PCR and Western blot analysis showed CLEC19A overexpression could reduce the expression levels of PI3K, VEGFα, MMP2, and NF-κB and increase PTEN, TIMP3, RECK, and PDCD4 expression levels in glioma cell lines. Furthermore, flow cytometry results revealed that CLEC19A overexpression was associated with significant cell cycle arrest and promotion of apoptosis in glioma cell lines. Interestingly, using a glioma rat model we could substantiate that CLEC19A overexpression suppresses glioma tumor growth.

CONCLUSIONS

To our knowledge, this is the first report providing in-silico, molecular, cellular, and in vivo evidences on the role of CLEC19A as a putative tumor suppressor gene in GBM. These results enhance our understanding of the role of CLEC19A in glioma and warrant further exploration of CLEC19A as a potential therapeutic target for GBM.

Precision Glycan Supplementation Improves Gut Microbiota Diversity, Performance, and Disease Outbreak Resistance in Broiler Chickens

The poultry industry contributes significantly to the global meat industry but faces many production challenges like high-density housing, welfare issues, and pathogenic infections. While antibiotics have commonly been used to treat many of these issues, they are being removed from poultry production globally due to increased microbial resistance. Precision glycans offer a viable alternative to antibiotics by modulating microbial metabolic pathways. In this study, we investigated the effects of precision glycan supplementation on productivity and gut microbiota in broilers. The experiment was conducted in a commercial setting using 32,400 male Ross chickens randomly divided into three sheds with 10,800 birds each. One shed with 12 pen replicates of 900 birds was used as control, while the other two with an equal number of replicates and birds were assigned to precision glycan supplementation. The treatment significantly improved the average daily weight gain and feed conversion ratio, with a significant modification in the abundance of several bacterial taxa in the caecum, ileum, and ileum mucosa microbial communities. There was increased richness and diversity in the caecum, with a reduction in Proteobacteria and an increase in Firmicutes. Richness remained unchanged in the ileum, with an increase in diversity and reduction in pathogenic genera like Clostridium and Escherichia-Shigella. Ileum mucosa showed a lower abundance of mucin degraders and an increased presence of next-generation probiotics. Supplemented birds showed a high level of disease resistance when the farm experienced an outbreak of infectious bronchitis, evidenced by lower mortality. Histological analysis confirmed improvements in the ileum and liver health, where the precision glycan supplementation reduced the area of congested sinusoids compared to the control group in the liver and significantly improved ileum intestinal morphology by increasing crypt depth and surface area. These results collectively suggest that precision glycans offer substantial benefits in poultry production by improving productivity, gut health, and disease resistance.

The Importance of M1-and M2-Polarized Macrophages in Glioma and as Potential Treatment Targets

Glioma is the most common and malignant tumor of the central nervous system. Glioblastoma (GBM) is the most aggressive glioma, with a poor prognosis and no effective treatment because of its high invasiveness, metabolic rate, and heterogeneity. The tumor microenvironment (TME) contains many tumor-associated macrophages (TAMs), which play a critical role in tumor proliferation, invasion, metastasis, and angiogenesis and indirectly promote an immunosuppressive microenvironment. TAM is divided into tumor-suppressive M1-like (classic activation of macrophages) and tumor-supportive M2-like (alternatively activated macrophages) polarized cells. TAMs exhibit an M1-like phenotype in the initial stages of tumor progression, and along with the promotion of lysing tumors and the functions of T cells and NK cells, tumor growth is suppressed, and they rapidly transform into M2-like polarized macrophages, which promote tumor progression. In this review, we discuss the mechanism by which M1- and M2-polarized macrophages promote or inhibit the growth of glioblastoma and indicate the future directions for treatment.

Galectin-1: A Traditionally Immunosuppressive Protein Displays Context-Dependent Capacities

Galectin–Carbohydrate interactions are indispensable to pathogen recognition and immune response. Galectin-1, a ubiquitously expressed 14-kDa protein with an evolutionarily conserved β-galactoside binding site, translates glycoconjugate recognition into function. That galectin-1 is demonstrated to induce T cell apoptosis has led to substantial attention to the immunosuppressive properties of this protein, such as inducing naive immune cells to suppressive phenotypes, promoting recruitment of immunosuppressing cells as well as impairing functions of cytotoxic leukocytes. However, only in recent years have studies shown that galectin-1 appears to perform a pro-inflammatory role in certain diseases. In this review, we describe the anti-inflammatory function of galectin-1 and its possible mechanisms and summarize the existing therapies and preclinical efficacy relating to these agents. In the meantime, we also discuss the potential causal factors by which galectin-1 promotes the progression of inflammation.

Glycosylation in SARS-CoV-2 variants: A path to infection and recovery

Glycan is an essential molecule that controls and drives life in a precise direction. The paucity of research in glycobiology may impede the significance of its role in the pandemic guidelines. The SARS-CoV-2 spike protein is heavily glycosylated, with 22 putative N-glycosylation sites and 17 potential O-glycosylation sites discovered thus far. It is the anchor point to the host cell ACE2 receptor, TMPRSS2, and many other host proteins that can be recognized by their immune system; hence, glycosylation is considered the primary target of vaccine development. Therefore, it is essential to know how this surface glycan plays a role in viral entry, infection, transmission, antigen, antibody responses, and disease progression. Although the vaccines are developed and applied against COVID-19, the proficiency of the immunizations is not accomplished with the current mutant variations. The role of glycosylation in SARS-CoV-2 and its receptor ACE2 with respect to other putative cell glycan receptors and the significance of glycan in host cell immunity in COVID-19 are discussed in this paper. Hence, the molecular signature of the glycan in the coronavirus infection can be incorporated into the mainstream therapeutic process.

Targeting glycans for CAR therapy: The advent of sweet CARs

Chimeric antigen receptor (CAR) T cell therapy has created a paradigm shift in the treatment of hematologic malignancies but has not been as effective toward solid tumors. For such tumors, the primary obstacles facing CAR T cells are scarcity of tumor-specific antigens and the hostile and complex tumor microenvironment. Glycosylation, the process by which sugars are post-translationally added to proteins or lipids, is profoundly dysregulated in cancer. Abnormally glycosylated glycoproteins expressed on cancer cells offer unique targets for CAR T therapy as they are specific to tumor cells. Tumor stromal cells also express abnormal glycoproteins and thus also have the potential to be targeted by glycan-binding CAR T cells. This review will discuss the state of CAR T cells in the therapy of solid tumors, the cancer glycoproteome and its potential for use as a therapeutic target, and the landscape and future of glycan-binding CAR T cell therapy.

Seminal Plasma Glycoproteins as Potential Ligands of Lectins Engaged in Immunity Regulation

Environmental pollution, chronic stress, and unhealthy lifestyle are factors that negatively affect reproductive potential. Currently, 15-20% of couples in industrialized countries face the problem of infertility. This growing health and social problem prompts researchers to explore the regulatory mechanisms that may be important for successful fertilization. In recent years, more attention has been paid to male infertility factors, including the impact of seminal plasma components on regulation of the female immune response to allogenic sperm, embryo and fetal antigens. Directing this response to the tolerogenic pathway is crucial to achieve a healthy pregnancy. According to the fetoembryonic defense hypothesis, the regulatory mechanism may be associated with the interaction of lectins and immunomodulatory glycoepitopes. Such interactions may involve lectins of dendritic cells and macrophages, recruited to the cervical region immediately after intercourse. Carbohydrate binding receptors include C type lectins, such as DC-SIGN and MGL, as well as galectins and siglecs among others. In this article we discuss the expression of the possible lectin ligands, highly fucosylated and high mannose structures, which may be recognized by DC-SIGN, glycans of varying degrees of sialylation, which may differ in their interaction with siglecs, as well as T and Tn antigens in O-glycans.

Extracellular ST6GAL1 regulates monocyte-macrophage development and survival

Interaction of immune cells with the systemic environment is necessary for the coordinated development and execution of immune responses. Monocyte-macrophage lineage cells reside at the junction of innate and adaptive immunity. Previously we reported that the sialyltransferase ST6GAL1 in the extracellular milieu modulates B cell development and IgG production, granulocyte production, and attenuates acute airway inflammation to bacterial challenge in mouse models. Here, we report that extracellular ST6GAL1 also elicits profound responses in monocyte-macrophage lineage cells. We show that recombinant ST6GAL1 adheres to subsets of thioglycolate-elicited inflammatory cells in the mouse peritoneum and to cultured human monocyte THP-1 cells. Exposure of the inflammatory cells to recombinant ST6GAL1 elicited wholesale changes in the gene expression profile of primary mouse myeloid cells; most notable was the striking up-regulation of monocyte-macrophage and monocyte-derived dendritic cell development pathway signature genes and transcription factors PU.1, NFκB and their target genes, driving increased monocyte-macrophage population and survival ex vivo. In the cultured human monocyte cells, the essential cell surface receptor of the monocyte-macrophage lineage, the M-CSF receptor (M-CSF-R, Csfr1) was a target of extracellular ST6GAL1 catalytic activity. Extracellular ST6GAL1 activated the M-CSF-R and initiated intracellular signaling events, namely, the nuclear translocation of NFκB subunit p65, and phosphorylation of ERK 1/2 and AKT. The findings implicate extracellular ST6GAL1 in monocyte development by a mechanism initiated at the cell surface and support an emerging paradigm of an extracellular glycan-modifying enzyme as a central regulator coordinating immune hematopoietic cell development and function.

Glycan-Lectin Interactions as Novel Immunosuppression Drivers in Glioblastoma

Despite diagnostic and therapeutic improvements, glioblastoma (GB) remains one of the most threatening brain tumor in adults, underlining the urgent need of new therapeutic targets. Lectins are glycan-binding proteins that regulate several biological processes through the recognition of specific sugar motifs. Lectins and their ligands are found on immune cells, endothelial cells and, also, tumor cells, pointing out a strong correlation among immunity, tumor microenvironment and vascularization. In GB, altered glycans and lectins contribute to tumor progression and immune evasion, shaping the tumor-immune landscape promoting immunosuppressive cell subsets, such as myeloid-derived suppressor cells (MDSCs) and M2-macrophages, and affecting immunoeffector populations, such as CD8⁺ T cells and dendritic cells (DCs). Here, we discuss the latest knowledge on the immune cells, immune related lectin receptors (C-type lectins, Siglecs, galectins) and changes in glycosylation that are involved in immunosuppressive mechanisms in GB, highlighting their interest as possible novel therapeutical targets.