ELAM-1 mediates cell adhesion by recognition of a carbohydrate ligand, sialyl-Lex

Characterization of isomeric glycan structures by LC-MS/MS

The characterization of glycosylation is critical for obtaining a comprehensive view of the regulation and functions of glycoproteins of interest. Due to the complex nature of oligosaccharides, stemming from variable compositions and linkages, and ion suppression effects, the chromatographic separation of glycans, including isomeric structures, is necessary for exhaustive characterization by MS. This review introduces the fundamental principles underlying the techniques in LC utilized by modern day glycomics researchers. Recent advances in porous graphitized carbon, reverse phase, ion exchange, and hydrophilic interaction LC utilized in conjunction with MS, for the characterization of protein glycosylation, are described with an emphasis on methods capable of resolving isomeric glycan structures.

Radiation-induced changes in the glycome of endothelial cells with functional consequences

As it is altered by ionizing radiation, the vascular network is considered as a prime target in limiting normal tissue damage and improving tumor control in radiation therapy. Irradiation activates endothelial cells which then participate in the recruitment of circulating cells, especially by overexpressing cell adhesion molecules, but also by other as yet unknown mechanisms. Since protein glycosylation is an important determinant of cell adhesion, we hypothesized that radiation could alter the glycosylation pattern of endothelial cells and thereby impact adhesion of circulating cells. Herein, we show that ionizing radiation increases high mannose-type N-glycans and decreases glycosaminoglycans. These changes stimulate interactions measured under flow conditions between irradiated endothelial cells and monocytes. Targeted transcriptomic approaches in vitro in endothelial cells and in vivo in a radiation enteropathy mouse model confirm that genes involved in N- and O-glycosylation are modulated by radiation, and in silico analyses give insight into the mechanism by which radiation modifies glycosylation. The endothelium glycome may therefore be considered as a key therapeutic target for modulating the chronic inflammatory response observed in healthy tissues or for participating in tumor control by radiation therapy.

Pathologic evaluation of tumor-associated macrophage density and vessel inflammation in invasive breast carcinomas

Tumor-associated macrophages (TAMs) are major constituents of the tumor microenvironment in solid tumors and have been implicated as mediators of tumor progression, invasion and metastasis. Correspondingly, accumulation of TAMs is associated with unfavorable clinical outcomes in numerous types of solid tumors. E-selectin is a hallmark of inflammation and a key adhesion molecule that accommodates the initial contact of circulating immune cells with the inflamed vessel surface. Currently, the association between E-selectin and TAMs is not fully elucidated; therefore, the present study investigated the association between vessel inflammation, TAM infiltration, and clinical outcome in breast cancer. A total of 53 procedure-naïve invasive breast cancer cases were immunohistochemically analyzed for the presence of cluster of differentiation (CD)68⁺ TAMs, E-selectin⁺ vessels and tumor inflammation. The association between CD68 and E-selectin expression, and tumor inflammation as well as overall survival was evaluated using Kaplan-Meier survival curves and multivariable Cox's proportional hazards regression analysis. The abundance of TAMs was identified to be positively associated with tumor inflammation, estrogen receptor and E-selectin expression levels. A greater prevalence of TAMs and tumor inflammation was significantly associated with shorter overall survival times. E-selectin expression levels were significantly higher in tumor vessels among elderly patients, but were not associated with overall survival. The abundance of TAMs was associated with the presence of E-selectin-expressing inflamed tumor vessels and tumor inflammation, as well as overall survival in patients with invasive breast carcinoma.

Expression of Lewis-a glycans on polymorphonuclear leukocytes augments function by increasing transmigration

PMN-expressed fucosylated glycans from the Lewis glycan family, including Lewis-x (Le^x) and sialyl Lewis-x (sLe^x), have previously been implicated in the regulation of important PMN functions, including selectin-mediated trafficking across vascular endothelium. Although glycans, such as Le^x and sLe^x, which are based on the type 2 sequence (Galβ1-4GlcNAc-R), are abundant on PMNs, the presence of type 1 Galβ1-3GlcNAc-R glycans required for PMN expression of the closely related stereoisomer of Le^x, termed Lewis-A (Le^a), has not, to our knowledge, been reported. Here, we show that Le^a is abundantly expressed by human PMNs and functionally regulates PMN migration. Using mAbs whose precise epitopes were determined using glycan array technology, Le^a function was probed using Le^a-selective mAbs and lectins, revealing increased PMN transmigration across model intestinal epithelia, which was independent of epithelial-expressed Le^a Analyses of glycan synthetic machinery in PMNs revealed expression of β1-3 galactosyltransferase and α1-4 fucosyltransferase, which are required for Le^a synthesis. Specificity of functional effects observed after ligation of Le^a was confirmed by failure of anti-Le^a mAbs to enhance migration using PMNs from individuals deficient in α1-4 fucosylation. These results demonstrate that Le^a is expressed on human PMNs, and its specific engagement enhances PMN migration responses. We propose that PMN Le^a represents a new target for modulating inflammation and regulating intestinal, innate immunity.

Cell-Specific Variation in E-Selectin Ligand Expression among Human Peripheral Blood Mononuclear Cells: Implications for Immunosurveillance and Pathobiology

Both host defense and immunopathology are shaped by the ordered recruitment of circulating leukocytes to affected sites, a process initiated by binding of blood-borne cells to E-selectin displayed at target endothelial beds. Accordingly, knowledge of the expression and function of leukocyte E-selectin ligands is key to understanding the tempo and specificity of immunoreactivity. In this study, we performed E-selectin adherence assays under hemodynamic flow conditions coupled with flow cytometry and Western blot analysis to elucidate the function and structural biology of glycoprotein E-selectin ligands expressed on human PBMCs. Circulating monocytes uniformly express high levels of the canonical E-selectin binding determinant sialyl Lewis X (sLe^X) and display markedly greater adhesive interactions with E-selectin than do circulating lymphocytes, which exhibit variable E-selectin binding among CD4⁺ and CD8⁺ T cells but no binding by B cells. Monocytes prominently present sLe^X decorations on an array of protein scaffolds, including P-selectin glycoprotein ligand-1, CD43, and CD44 (rendering the E-selectin ligands cutaneous lymphocyte Ag, CD43E, and hematopoietic cell E-selectin/L-selectin ligand, respectively), and B cells altogether lack E-selectin ligands. Quantitative PCR gene expression studies of glycosyltransferases that regulate display of sLe^X reveal high transcript levels among circulating monocytes and low levels among circulating B cells, and, commensurately, cell surface α(1,3)-fucosylation reveals that acceptor sialyllactosaminyl glycans convertible into sLe^X are abundantly expressed on human monocytes yet are relatively deficient on B cells. Collectively, these findings unveil distinct cell-specific patterns of E-selectin ligand expression among human PBMCs, indicating that circulating monocytes are specialized to engage E-selectin and providing key insights into the molecular effectors mediating recruitment of these cells at inflammatory sites.

Sialylation of N-glycans: mechanism, cellular compartmentalization and function

Sialylated N-glycans play essential roles in the immune system, pathogen recognition and cancer. This review approaches the sialylation of N-glycans from three perspectives. The first section focuses on the sialyltransferases that add sialic acid to N-glycans. Included in the discussion is a description of these enzymes' glycan acceptors, conserved domain organization and sequences, molecular structure and catalytic mechanism. In addition, we discuss the protein interactions underlying the polysialylation of a select group of adhesion and signaling molecules. In the second section, the biosynthesis of sialic acid, CMP-sialic acid and sialylated N-glycans is discussed, with a special emphasis on the compartmentalization of these processes in the mammalian cell. The sequences and mechanisms maintaining the sialyltransferases and other glycosylation enzymes in the Golgi are also reviewed. In the final section, we have chosen to discuss processes in which sialylated glycans, both N- and O-linked, play a role. The first part of this section focuses on sialic acid-binding proteins including viral hemagglutinins, Siglecs and selectins. In the second half of this section, we comment on the role of sialylated N-glycans in cancer, including the roles of β1-integrin and Fas receptor N-glycan sialylation in cancer cell survival and drug resistance, and the role of these sialylated proteins and polysialic acid in cancer metastasis.

Leukocyte-borne α(1,3)-fucose is a negative regulator of β2-integrin-dependent recruitment in lung inflammation

Leukocyte recruitment in inflammation is a multistep, sequential cascade where the initial step is the selectin-dependent tethering, followed by the formation of firmer integrin-mediated adhesive forces leading to extravasation. The α(1,3)-fucose-containing sialyl-Lewis X (sLe^X) is the archetypical ligand on leukocyte surfaces mediating selectin interactions. Canonically, disruption of α(1,3)-fucose formation ablates selectin-mediated adhesion, dramatically reducing trafficking. We report a paradoxical response to α(1,3)-fucose deficiency in which the loss exacerbated rather than attenuated leukocyte recruitment in a murine model of acute airway inflammation. The architecture of the capillary-dominated vasculature in the lung minimized the importance of the selectin dependent step, and we observed that α(1,3)-fucose deficiency augmented CXCR2-mediated Rap1-GTP signaling to enhance the β₂-integrin-ICAM-1-binding axis. The data disclose a previously unknown function for α(1,3)-fucose, in which this structure negatively regulates the integrin activation step in leukocyte recruitment.

A New Route for the Synthesis of 1-Amino-3,6,9,12-Tetraoxapentadecan-15-Oic Acid

1-Amino-3,6,9,12-tetraoxapentadecan-15-oic acid 8 was synthesised from tetraethylene glycol through a 7 step sequence including esterification, mesylation, azide substitution with subsequent reduction followed by hydrolysis. The structure of product 8 was identified by 1H and 13C NMR spectroscopy, elemental analysis and electrospray ionisation mass spectrometry (ESI-MS). All reaction conditions were optimised and easy to control. The key advantages of this process are the high yields of products and a new route to synthesise 1-amino-3,6,9,12-tetraoxapentadecan-15-oic acid.

"Siglec"ting the allergic response for therapeutic targeting

As a physician-scientist, I have pursued research related to translational immunology with the goal of improving our ability to diagnose and treat allergic, immunologic and other diseases involving eosinophils, basophils and mast cells. We have tried to delineate novel mechanisms of human disease, working whenever possible with primary human cells and tissues, attempting to identify targets that might be amenable to the development of new therapies. As a general strategy, we have compared eosinophils, basophils, mast cells and neutrophils to look for pathways in inflammation that were unique to distinct subsets of these cells. In doing so, the concepts of glycobiology did not enter my mind until we began noticing some intriguing functional differences involving selectins and their ligands among these cell types. One simple observation, that neutrophils were coated with a glycan that allowed them to interact with an endothelial adhesion molecule while eosinophils lacked this structure, pried open the glyco-door for me. Fruitful collaborations with card-carrying glycobiologists soon followed that have forever positively influenced our science, and have enhanced our hypotheses, experimental design, research opportunities and discoveries. Within a few years, we helped to discover Siglec-8, an I-type lectin expressed only on human eosinophils, basophils, mast cells. This receptor, together with its closest mouse counterpart Siglec-F, has been the primary focus of our work now for over a decade. If not for those in the fields of glycobiology and glycoimmunology, my lab would not have made much progress toward the goal of leveraging Siglec-8 for therapeutic purposes.

Convergent synthesis of oligosaccharides on the gram-scale using cetyl thioglycoside based on a hydrophobically assisted switching phase method

A hydrophobically assisted switching phase (HASP) method is an efficient strategy for the synthesis of carrier-loaded oligosaccharides.

Porifera Lectins: Diversity, Physiological Roles and Biotechnological Potential

An overview on the diversity of 39 lectins from the phylum Porifera is presented, including 38 lectins, which were identified from the class of demosponges, and one lectin from the class of hexactinellida. Their purification from crude extracts was mainly performed by using affinity chromatography and gel filtration techniques. Other protocols were also developed in order to collect and study sponge lectins, including screening of sponge genomes and expression in heterologous bacterial systems. The characterization of the lectins was performed by Edman degradation or mass spectrometry. Regarding their physiological roles, sponge lectins showed to be involved in morphogenesis and cell interaction, biomineralization and spiculogenesis, as well as host defense mechanisms and potentially in the association between the sponge and its microorganisms. In addition, these lectins exhibited a broad range of bioactivities, including modulation of inflammatory response, antimicrobial and cytotoxic activities, as well as anticancer and neuromodulatory activity. In view of their potential pharmacological applications, sponge lectins constitute promising molecules of biotechnological interest.

Efficient assembly of oligomannosides using the hydrophobically assisted switching phase method

The hydrophobically assisted switching phase (HASP) method was applied in the assembly of oligomannosides. A new mannosyl donor with high reactivity was selected after a series of optimization studies, which was suitable for the synthesis of oligomannosides via the HASP method. The practicability of the HASP method towards the synthesis of branched oligosaccharides was explored and two branched penta-mannosides were assembled efficiently.

E-selectin ligand complexes adopt an extended high-affinity conformation

E-selectin is a cell-adhesion molecule of the vascular endothelium that promotes essential leukocyte rolling in the early inflammatory response by binding to glycoproteins containing the tetrasaccharide sialyl Lewis(x) (sLe(x)). Efficient leukocyte recruitment under vascular flow conditions depends on an increased lifetime of E-selectin/ligand complexes under tensile force in a so-called catch-bond binding mode. Co-crystal structures of a representative fragment of the extracellular E-selectin region with sLe(x) and a glycomimetic antagonist thereof reveal an extended E-selectin conformation, which is identified as a high-affinity binding state of E-selectin by molecular dynamics simulations. Small-angle X-ray scattering experiments demonstrate a direct link between ligand binding and E-selectin conformational transition under static conditions in solution. This permits tracing a series of concerted structural changes connecting ligand binding to conformational stretching as the structural basis of E-selectin catch-bond-mediated leukocyte recruitment. The detailed molecular view of the binding site paves the way for the design of a new generation of selectin antagonists. This is of special interest, since their therapeutic potential was recently demonstrated with the pan-selectin antagonists GMI-1070 (Rivipansel).

Efficient Chemoenzymatic Synthesis of an N-glycan Isomer Library

Quantification, characterization and biofunctional studies of N-glycans on proteins remain challenging tasks due to complexity, diversity and low abundance of these glycans. The availability of structurally defined N-glycans (especially isomers) libraries is essential to help on solving these tasks. We reported herein an efficient chemoenzymatic strategy, namely Core Synthesis/Enzymatic Extension (CSEE), for rapid production of diverse N-glycans. Starting with 5 chemically prepared building blocks, 8 N-glycan core structures containing one or two terminal N-acetyl-D-glucosamine (GlcNAc) residue(s) were chemically synthesized via consistent use of oligosaccharyl thioethers as glycosylation donors in the convergent fragment coupling strategy. Each of these core structures was then extended to 5 to 15 N-glycan sequences by enzymatic reactions catalyzed by 4 robust glycosyltransferases. Success in synthesizing N-glycans with Neu5Gc and core-fucosylation further expanded the ability of enzymatic extension. High performance liquid chromatography with an amide column enabled rapid and efficient purification (>98% purity) of N-glycans in milligram scales. A total of 73 N-glycans (63 isomers) were successfully prepared and characterized by MS² and NMR. The CSEE strategy provides a practical approach for "mass production" of structurally defined N-glycans, which are important standards and probes for Glycoscience.

Protein glycosylation in cancer

Neoplastic transformation results in a wide variety of cellular alterations that impact the growth, survival, and general behavior of affected tissue. Although genetic alterations underpin the development of neoplastic disease, epigenetic changes can exert an equally significant effect on neoplastic transformation. Among neoplasia-associated epigenetic alterations, changes in cellular glycosylation have recently received attention as a key component of neoplastic progression. Alterations in glycosylation appear to not only directly impact cell growth and survival but also facilitate tumor-induced immunomodulation and eventual metastasis. Many of these changes may support neoplastic progression, and unique alterations in tumor-associated glycosylation may also serve as a distinct feature of cancer cells and therefore provide novel diagnostic and even therapeutic targets.

Safety evaluation of intravenously administered mono-thioated aptamer against E-selectin in mice

The medical applications of aptamers have recently emerged. We developed an antagonistic thioaptamer (ESTA) against E-selectin. Previously, we showed that a single injection of ESTA at a dose of 100μg inhibits breast cancer metastasis in mice through the functional blockade of E-selectin. In the present study, we evaluated the safety of different doses of intravenously administered ESTA in single-dose acute and repeat-dose subacute studies in ICR mice. Our data indicated that intravenous administration of up to 500μg ESTA did not result in hematologic abnormality in either study. Additionally, intravenous injection of ESTA did not affect the levels of plasma cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, GM-CSF, IFN-γ, and TNF-α) or complement split products (C3a and C5a) in either study. However, repeated injections of ESTA slightly increased plasma ALT and AST activities, in accordance with the appearance of small necrotic areas in the liver. In conclusion, our data demonstrated that intravenous administration of ESTA does not cause overt hematologic, organs, and immunologic responses under the experimental conditions.

Molecular pathogenicity of Streptococcus anginosus

Streptococcus anginosus and the closely related species Streptococcus constellatus and Streptococcus intermedius, are primarily commensals of the mucosa. The true pathogenic potential of this group has been under-recognized for a long time because of difficulties in correct species identification as well as the commensal nature of these species. In recent years, streptococci of the S. anginosus group have been increasingly found as relevant microbial pathogens in abscesses and blood cultures and they play a pathogenic role in cystic fibrosis. Several international studies have shown a surprisingly high frequency of infections caused by the S. anginosus group. Recent studies and a genome-wide comparative analysis suggested the presence of multiple putative virulence factors that are well-known from other streptococcal species. However, very little is known about the molecular basis of pathogenicity in these bacteria. This review summarizes our current knowledge of pathogenicity factors and their regulation in S. anginosus.

Tumor-associated neutrophils as a new prognostic factor in cancer: a systematic review and meta-analysis

Purpose

Tumor-associated neutrophils (TAN) have been reported in a variety of malignancies. We conducted an up-to-date meta-analysis to evaluate the prognostic role of TAN in cancer.

Method

Pubmed, Embase and web of science databases were searched for studies published up to April 2013. Pooled hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs) were calculated. The impact of neutrophils localization and primary antibody were also assessed.

Results

A total of 3946 patients with various solid tumors from 20 studies were included. High density of intratumoral neutrophils were independently associated with unfavorable survival; the pooled HRs were 1.68 (95%CI: 1.36–2.07, I² = 55.8%, p<0.001) for recurrence-free survival (RFS)/disease-free survival (DFS), 3.36 (95%CI: 2.08–5.42, I² = 0%, p<0.001) for cancer-specific survival (CSS) and 1.66 (95%CI: 1.37–2.01, I² = 70.5%, p<0.001) for overall survival (OS). Peritumoral and stromal neutrophils were not statistically significantly associated with survival. When grouped by primary antibody, the pooled HRs were 1.80 (95%CI: 1.47–2.22, I² = 67.7%, p<0.001) for CD66b, and 1.44 (95%CI: 0.90–2.30, I² = 45.9%, p = 0.125) for CD15, suggesting that CD66b positive TAN might have a better prognostic value than CD15.

Conclusion

High levels of intratumoral neutrophils are associated with unfavorable recurrence-free, cancer-specific and overall survival.

Rapid assays for lectin toxicity and binding changes that reflect altered glycosylation in mammalian cells

Glycosylation engineering is used to generate glycoproteins, glycolipids, or proteoglycans with a more defined complement of glycans on their glycoconjugates. For example, a mammalian cell glycosylation mutant lacking a specific glycosyltransferase generates glycoproteins, and/or glycolipids, and/or proteoglycans with truncated glycans missing the sugar transferred by that glycosyltransferase, as well as those sugars that would be added subsequently. In some cases, an alternative glycosyltransferase may then use the truncated glycans as acceptors, thereby generating a new or different glycan subset in the mutant cell. Another type of glycosylation mutant arises from gain-of-function mutations that, for example, activate a silent glycosyltransferase gene. In this case, glycoconjugates will have glycans with additional sugar(s) that are more elaborate than the glycans of wild type cells. Mutations in other genes that affect glycosylation, such as nucleotide sugar synthases or transporters, will alter the glycan complement in more general ways that usually affect several types of glycoconjugates. There are now many strategies for generating a precise mutation in a glycosylation gene in a mammalian cell. Large-volume cultures of mammalian cells may also generate spontaneous mutants in glycosylation pathways. This article will focus on how to rapidly characterize mammalian cells with an altered glycosylation activity. The key reagents for the protocols described are plant lectins that bind mammalian glycans with varying avidities, depending on the specific structure of those glycans. Cells with altered glycosylation generally become resistant or hypersensitive to lectin toxicity, and have reduced or increased lectin or antibody binding. Here we describe rapid assays to compare the cytotoxicity of lectins in a lectin resistance test, and the binding of lectins or antibodies by flow cytometry in a glycan-binding assay. Based on these tests, glycosylation changes expressed by a cell can be revealed, and glycosylation mutants classified into phenotypic groups that may reflect a loss-of-function or gain-of-function mutation in a specific gene involved in glycan synthesis.

Extract from Acanthopanax senticosus prevents LPS-induced monocytic cell adhesion via suppression of LFA-1 and Mac-1

A crude extract from Acanthopanax senticosus (AS) has drawn increased attention because of its potentially beneficial activities, including anti-fatigue, anti-stress, anti-gastric-ulcer, and immunoenhancing effects. We previously reported that AS crude extract exerts anti-inflammatory activity through blockade of monocytic adhesion to endothelial cells. However, the underlying mechanisms remained unknown, and so this study was designed to investigate the pathways involved. It was confirmed that AS extract inhibited lipopolysaccharide (LPS)-induced adhesion of monocytes to endothelial cells, and we found that whole extract was superior to eleutheroside E, a principal functional component of AS. A series of PCR experiments revealed that AS extract inhibited LPS-induced expression of genes encoding lymphocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1) in THP-1 cells. Consistently, protein levels and cell surface expression of LFA-1 and Mac-1 were noticeably reduced upon treatment with AS extract. This inhibitory effect was mediated by the suppression of LPS-induced degradation of IκB-α, a known inhibitor of nuclear factor-κB (NF-κB). In conclusion, AS extract exerts anti-inflammatory activity via the suppression of LFA-1 and Mac-1, lending itself as a potential therapeutic galenical for the prevention and treatment of various inflammatory diseases.

High expression of sLex associated with poor survival in Argentinian colorectal cancer patients

AIM

Colorectal cancer (CRC) is one of the most prevalent malignancies in Argentina with 11,043 new cases and 6,596 deaths estimated to have occurred in 2008. The present study was developed to clarify the differential expression of MUC1, MUC2, sLex, and sLea in colorectal cancer patients and their relationship with survival and clinical and histological features.

METHODS

Ninety primary tumor samples and 43 metastatic lymph nodes from CRC patients were studied; follow-up was documented. Twenty-six adenoma and 68 histological normal mucosa specimens were analyzed. An immunohistochemical approach was applied and statistical analysis was performed.

RESULTS

In tumor samples, MUC1, sLea, and sLex were highly expressed (94%, 67%, and 91%, respectively); also, we found a significantly increased expression of the 3 antigens in primary tumors and metastatic lymph nodes compared with normal mucosa and adenomas. MUC2 was expressed in 52% of both normal mucosa and CRC samples; this reactivity significantly decreased in metastatic lymph nodes (p<0.05). A multiple comparison analysis showed that MUC1 and sLex discriminated among 3 groups: normal, adenoma, and CRC tissues. The increase of sLex expression showed an association with recurrence, and survival analysis showed that a high sLex staining was significantly associated with a poor survival. By multivariate analysis MUC1 inmunoreactivity correlated positively and significantly with tumor size, while MUC2 expression showed the opposite correlation.

CONCLUSIONS

The correlation of sLex overexpression in primary tumors and metastatic lymph nodes, the discrimination among the normal, adenoma, and CRC groups based on sLex expression, as well as its association with recurrence and survival, all suggest a prognostic role of sLex in Argentinian CRC patients.

Nitric oxide inhibits hetero-adhesion of cancer cells to endothelial cells: restraining circulating tumor cells from initiating metastatic cascade

Adhesion of circulating tumor cells (CTCs) to vascular endothelial bed becomes a crucial starting point in metastatic cascade. We hypothesized that nitric oxide (NO) may prevent cancer metastasis from happening by its direct vasodilation and inhibition of cell adhesion molecules (CAMs). Here we show that S-nitrosocaptopril (CAP-NO, a typical NO donor) produced direct vasorelaxation that can be antagonized by typical NO scavenger hemoglobin and guanylate cyclase inhibitor. Cytokines significantly stimulated production of typical CAMs by the highly-purified human umbilical vein endothelial cells (HUVECs). CAP-NO inhibited expression of the stimulated CAMs (particularly VCAM-1) and the resultant hetero-adhesion of human colorectal cancer cells HT-29 to the HUVECs in a concentration-dependent manner. The same concentration of CAP-NO, however, did not significantly affect cell viability, cell cycle and mitochondrial membrane potential of HT-29, thus excluding the possibility that inhibition of the hetero-adhesion was caused by cytotoxicity by CAP-NO on HT-29. Hemoglobin reversed the inhibition of CAP-NO on both the hetero-adhesion between HT-29 and HUVECs and VCAM-1 expression. These data demonstrate that CAP-NO, by directly releasing NO, produces vasorelaxation and interferes with hetero-adhesion of cancer cells to vascular endothelium via down-regulating expression of CAMs. The study highlights the importance of NO in cancer metastatic prevention.

Total synthesis of a sialyl Lewis(x) derivative for the diagnosis of cancer

The total synthesis of aminoethyl glycoside of sialyl Lewis(x) (sLe(x)) is described. A galactose donor was condensed with a diol of glucosamine to afford regioselectively a β1,4 linked disaccharide, which was further stereoselectively fucosylated to provide a protected Lewis(x) trisaccharide. After chemical modification, the trisaccharide was sialylated to give regio- and stereoselectively an azidoethyl glycoside of sLe(x). Finally, deprotection and azide reduction afforded the target compound. This compound will be coupled with protein and then be used to conduct further preclinical studies for the diagnosis of cancer.

Human multipotent adult progenitor cells transcriptionally regulate fucosyltransferase VII

BACKGROUND AIMS

Targeted recruitment of leukocytes to sites of inflammation is a crucial event in normal host defense against pathogens, and attachment to and rolling on activated endothelial cells is a prerequisite first step for eventual leukocyte extravasation into sites of inflammation. These key events are mediated by interactions between glycosylated ligands expressed on leukocytes and selectins expressed on activated endothelium. Cell surface expression of selectin ligands on leukocytes is regulated by the rate-limiting enzyme fucosyltransferase VII (Fut7), and in its absence extravasation of leukocytes is severely inhibited. Multipotent adult progenitor cells (MAPCs) are an adherent cell population isolated from adult bone marrow. Intravenous administration of MAPCs provided functional improvement in multiple pre-clinical models of injury or disease, but the mechanisms by which these outcomes were achieved remain poorly understood.

METHODS

In vitro cell analysis studies including fluorescence-activated cell sorting, messenger RNA analysis, T-cell proliferation assays and endothelial cell binding assays were performed.

RESULTS

The in vitro cell analysis studies characterized the ability of MAPCs to secrete factors that transcriptionally attenuate expression of Fut7 in T cells, blocking the terminal fucosylation event in the biosynthesis of selectin ligands and reducing T-cell binding to endothelial cells.

CONCLUSIONS

This study presents the first example of a distinct regulatory mechanism involving transcriptional down-regulation of Fut7 by MAPCs that could modulate the trafficking behavior of T cells in vivo.

Serum glycan markers for evaluation of disease activity and prediction of clinical course in patients with ulcerative colitis

BACKGROUND

The aims of this study were to determine the change of whole-serum N-glycan profile in ulcerative colitis (UC) patients and to investigate its clinical utility.

METHODS

We collected serum from 75 UC patients at the time of admission and the same number of age/sex-matched healthy volunteers. Serum glycan profile was measured by comprehensive quantitative high-throughput glycome analysis and was compared with disease activity and prognosis.

RESULTS

Out of 61 glycans detected, 24 were differentially expressed in UC patients. Pathway analysis demonstrated that highly sialylated multi-branched glycans and agalactosyl bi-antennary glycans were elevated in UC patients; in addition, the glycan ratio m/z 2378/1914, which also increased in UC, showed the highest Area under Receiver Operating Characteristic curve (0.923) for the diagnosis of UC. Highly sialylated multi-branched glycans and the glycan ratio m/z 2378/1914 were higher in the patients with total colitis, Clinical Activity Index >10, Mayo endoscopic score 3, or a steroid-refractory status. In particular, the glycan ratio m/z 2378/1914 (above median) was an independent prognostic factor for the need for an operation (hazard ratio, 2.67; 95% confidence interval, 1.04-7.84).

CONCLUSIONS

Whole-serum glycan profiles revealed that the glycan ratio m/z 2378/1914 and highly sialylated multi-branched glycans increase in UC patients, and are correlated with disease activity. The glycan ratio m/z 2378/1914 was an independent predictive factor of the prognosis of UC.

Design of glycosyltransferase inhibitors: pyridine as a pyrophosphate surrogate

A series of ten glycosyltransferase inhibitors has been designed and synthesized by using pyridine as a pyrophosphate surrogate. The series was prepared by conjugation of carbohydrate, pyridine, and nucleoside building blocks by using a combination of glycosylation, the Staudinger-Vilarrasa amide-bond formation, and azide-alkyne click chemistry. The compounds were evaluated as inhibitors of five metal-dependent galactosyltransferases. Crystallographic analyses of three inhibitors complexed in the active site of one of the enzymes confirmed that the pyridine moiety chelates the Mn(2+) ion causing a slight displacement (2 Å) from its original position. The carbohydrate head group occupies a different position than in the natural uridine diphosphate (UDP)-Gal substrate with little interaction with the enzyme.

Total serum glycan analysis is superior to lectin-FLISA for the early detection of hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is a primary cancer of the liver that is predominantly the result of infection with a hepatotropic virus such as hepatitis B virus or hepatitis C virus. As liver cancer is often asymptomatic, the development of sensitive noninvasive biomarkers is needed for early detection and improved survival.

EXPERIMENTAL DESIGN

We have previously identified alterations in the N-linked glycosylation of serum proteins with the development of HCC and identified many of the proteins that contained the altered glycosylation. In the current study, we compared the ability of the identified proteins to diagnose HCC with the total serum glycan analysis.

RESULTS

Surprisingly, glycan analysis of total serum had the greatest ability to distinguish HCC from cirrhosis with an AUROC of 0.851, a sensitivity of 73% at a specificity of 88%. When total glycan sequencing was combined with alpha-fetoprotein (AFP), the sensitivity increased to 95% at a specificity of 90%.

CONCLUSION AND CLINICAL RELEVANCE

Changes in glycosylation as detected in whole serum could be used to diagnose HCC with greater sensitivity and specificity than that observed through the analysis of specific protein glycoforms or protein levels. Such an assay could have value in the management of those at risk for the development of HCC.

Stabilization of branched oligosaccharides: Lewis(x) benefits from a nonconventional C-H···O hydrogen bond

Although animal lectins usually show a high degree of specificity for glycan structures, their single-site binding affinities are typically weak, a drawback which is often compensated in biological systems by an oligovalent presentation of carbohydrate epitopes. For the design of monovalent glycomimetics, structural information regarding solution and bound conformation of the carbohydrate lead represents a valuable starting point. In this paper, we focus on the conformation of the trisaccharide Le(x) (Gal[Fucα(1-3)]β(1-4)GlcNAc). Mainly because of the unfavorable tumbling regime, the elucidation of the solution conformation of Le(x) by NMR has only been partially successful so far. Le(x) was therefore attached to a (13)C,(15)N-labeled protein. (13)C,(15)N-filtered NOESY NMR techniques at ultrahigh field allowed increasing the maximal NOE enhancement, resulting in a high number of distance restraints per glycosidic bond and, consequently, a well-defined structure. In addition to the known contributors to the conformational restriction of the Le(x) structure (exoanomeric effect, steric compression induced by the NHAc group adjacent to the linking position of L-fucose, and the hydrophobic interaction of L-fucose with the β-face of D-galactose), a nonconventional C-H···O hydrogen bond between H-C(5) of L-fucose and O(5) of D-galactose was identified. According to quantum mechanical calculations, this C-H···O hydrogen bond is the most prominent factor in stabilization, contributing 40% of the total stabilization energy. We therefore propose that the nonconventional hydrogen bond contributing to a reduction of the conformational flexibility of the Le(x) core represents a novel element of the glycocode. Its relevance to the stabilization of related branched oligosaccharides is currently being studied.

The Expression of CD10 and CD15 Is Progressively Increased during Colorectal Cancer Development

Background

The aim of this study was to examine the expression of CD10 and CD15 in tumor cells, stromal cells and infiltrating inflammatory cells during colorectal carcinoma (CRC) development and to investigate their expression levels between the tumor center and invasive front and compare them to clinicopathological parameters in invasive CRC.

Methods

We performed immunohistochemical staining for CD10, CD15, and E-cadherin in 42 cases of CRC, 49 of tubular adenoma, 15 of hyperplastic polyp, and 17 of non-neoplastic colon.

Results

CD10 was expressed in tumor cells (tCD10), stromal cells (sCD10) and infiltrating inflammatory cells (iCD10), and CD15 was expressed in tumor cells (tCD15) and infiltrating inflammatory cells (iCD15). Their expressions were progressively increased during CRC development and the iCD10 expression level was significantly correlated with the iCD15 expression level in invasive CRC. Invasive front revealed a higher expression level of iCD10 and iCD15 than the tumor center. Moreover, the iCD15 expression level of invasive front was significantly correlated with the degree of tumor budding and tCD15 in whole tissue sections was closely associated with tumor depth.

Conclusions

The present study suggests that the expression of CD10 and CD15 is associated with the development and progression of CRC.

Heterogenic endothelial responses to inflammation: role for differential N-glycosylation and vascular bed of origin

BACKGROUND

Endothelial cell responses during inflammation are heterogeneous and key for selectivity in how leukocytes hone in on specific sites and why vascular diseases are highly bed specific. However, mechanisms for this specificity remain unclear.

METHODS AND RESULTS

Here, we exposed human endothelial cells isolated from 5 systemic arterial beds from 1 donor (to overcome donor-to-donor genetic/epigenetic differences), the umbilical vein, and pulmonary microvasculature to TNF-α, LPS, and IL-1β and assessed acute (ERK1/2 and p65) and chronic (ICAM-1, VCAM-1 total and surface expression) signaling responses and assessed changes in surface N-glycans and monocyte adhesion. Significant diversity in responses was evident by disparate changes in ERK1/2 and p65 NF-κB phosphorylation, which varied up to 5-fold between different cells and in temporal and magnitude differences in ICAM-1 and VCAM-1 expression (maximal VCAM-1 induction typically being observed by 4 hours, whereas ICAM-1 expression was increased further at 24 hours relative to 4 hours). N-glycan profiles both basally and with stimulation were also bed specific, with hypoglycosylated N-glycans correlating with increased THP-1 monocyte adhesion. Differences in surface N-glycan expression tracked with dynamic up- or downregulation of α-mannosidase activity during inflammation.

CONCLUSIONS

These results demonstrate a critical role for the vascular bed of origin in controlling endothelial responses and function to inflammatory stimuli and suggest that bed-specific expression of N-linked sugars may provide a signature for select leukocyte recruitment.

E- and p-selectins are essential for repopulation of chronic myelogenous and chronic eosinophilic leukemias in a scid mouse xenograft model

In chronic myelogenous (CML) and chronic eosinophilic leukemia (CEL), neoplastic cells spread via the circulation into various extramedullary organs. As E- and P-selectin constitute the starting point for the leucocyte adhesion/invasion cascade, and CEL and CML cells share many properties with normal granulocytes, we investigated the role of these selectins in CEL and CML cell expansion and organ invasion in a xenotransplantation model using scid mice. Using two human leukemic cell lines (EOL-1 and K562), we were able to show that E- and P-selectins mediate leukemia cell tethering and adherence in a laminar flow assay. While E-selectin binding depended on sialylated carbohydrate moieties, P-selectin binding was completely (K562) or partially (EOL-1) independent of these carbohydrates indicating the involvement of non-canonical selectin ligands. In a xenograft model in scid mice, both cell lines invaded the bone marrow and other organs, formed chloromas, and ultimately produced an overt leukemia. In contrast, in E- and P-selectin knockout scid mice, the cells failed to show engraftment in 8 out of 10 animals and even if they did engraft, they produced only little organ invasion and chloroma formation. Together, these data suggest that E- and P-selectins play an important role in leukemic dissemination in CML and CEL.

Regulation of the metastatic cell phenotype by sialylated glycans

Tumor cells exhibit striking changes in cell surface glycosylation as a consequence of dysregulated glycosyltransferases and glycosidases. In particular, an increase in the expression of certain sialylated glycans is a prominent feature of many transformed cells. Altered sialylation has long been associated with metastatic cell behaviors including invasion and enhanced cell survival; however, there is limited information regarding the molecular details of how distinct sialylated structures or sialylated carrier proteins regulate cell signaling to control responses such as adhesion/migration or resistance to specific apoptotic pathways. The goal of this review is to highlight selected examples of sialylated glycans for which there is some knowledge of molecular mechanisms linking aberrant sialylation to critical processes involved in metastasis.

Nanomolar E-selectin antagonists with prolonged half-lives by a fragment-based approach

Selectins, a family of C-type lectins, play a key role in inflammatory diseases (e.g., asthma and arthritis). However, the only millimolar affinity of sialyl Lewis(x) (sLe(x)), which is the common tetrasaccharide epitope of all physiological selectin ligands, has been a major obstacle to the development of selectin antagonists for therapeutic applications. In a fragment-based approach guided by NMR, ligands binding to a second site in close proximity to a sLe(x) mimic were identified. A library of antagonists obtained by connecting the sLe(x) mimic to the best second-site ligand via triazole linkers of different lengths was evaluated by surface plasmon resonance. Detailed analysis of the five most promising candidates revealed antagonists with K(D) values ranging from 30 to 89 nM. In contrast to carbohydrate-lectin complexes with typical half-lives (t(1/2)) in the range of one second or even less, these fragment-based selectin antagonists show t1/2 of several minutes. They exhibit a promising starting point for the development of novel anti-inflammatory drugs.

Distinct glycosyltransferases synthesize E-selectin ligands in human vs. mouse leukocytes

The binding of selectins to carbohydrate epitopes expressed on leukocytes is the first step in a multi-step cell adhesion cascade that controls the rate of leukocyte recruitment at sites of inflammation. The glycans that function as selectin-ligands are post-translationally synthesized by the serial action of Golgi resident enzymes called glycosyltransferases (glycoTs). Whereas much of our current knowledge regarding the role of glycoTs in constructing selectin-ligands comes from reconstituted biochemical investigations or murine models, tools to assess the impact of these enzymes on the human ligands are relatively underdeveloped. This is significant since the selectin-ligands, particularly those that bind E-selectin, vary between different leukocyte cell populations and they are also different in humans compared with mice. To address this shortcoming, a recent study by Buffone et al. (2013) outlines a systematic strategy to knockdown upto three glycoTs simultaneously in human leukocytes. The results suggest that the fucosyltransferases (FUTs) regulating selectin-ligand synthesis may be species-specific. In particular, they demonstrate that FUT9 plays a significant role during human, but not mouse, leukocyte-endothelial interactions. Overall, this article discusses the relative roles of the FUTs during human L-, E-, and P-selectin-ligand biosynthesis, and the potential that the knockdown strategy outlined here may assess the role of other glycoTs in human leukocytes also.

N-glycomic biomarkers of biological aging and longevity: a link with inflammaging

Glycosylation is a frequent co/post-translational modification of proteins which modulates a variety of biological functions. The analysis of N-glycome, i.e. the sugar chains N-linked to asparagine, identified new candidate biomarkers of aging such as N-glycans devoid of galactose residues on their branches, in a variety of human and experimental model systems, such as healthy old people, centenarians and their offspring and caloric restricted mice. These agalactosylated biantennary structures mainly decorate Asn297 of Fc portion of IgG (IgG-G0), and are present also in patients affected by progeroid syndromes and a variety of autoimmune/inflammatory diseases. IgG-G0 exert a pro-inflammatory effect through different mechanisms, including the lectin pathway of complement, binding to Fcγ receptors and formation of autoantibody aggregates. The age-related accumulation of IgG-G0 can contribute to inflammaging, the low-grade pro-inflammatory status that characterizes elderly, by creating a vicious loop in which inflammation is responsible for the production of aberrantly glycosylated IgG which, in turn, would activate the immune system, exacerbating inflammation. Moreover, recent data suggest that the N-glycomic shift observed in aging could be related not only to inflammation but also to alteration of important metabolic pathways. Thus, altered N-glycans are both powerful markers of aging and possible contributors to its pathogenesis.

Endothelial heterogeneity and adhesion molecules N-glycosylation: implications in leukocyte trafficking in inflammation

Inflammation is a major contributing element to a host of diseases with the interaction between leukocytes and the endothelium being key in this process. Much is understood about the nature of the adhesion molecule proteins expressed on any given leukocyte and endothelial cell that modulates adhesive interactions. Although it is appreciated that these proteins are heavily glycosylated, relatively little is known about the roles of these posttranslational modifications and whether they are regulated, and if so how during inflammation. Herein, we suggest that a paucity in this understanding is one major reason for the lack of successful therapies to date for modulating leukocyte-endothelial interactions in human inflammatory disease and discuss developing paradigms of (i) how endothelial adhesion molecule glycosylation (with a focus on N-glycosylation) maybe a critical element in understanding endothelial heterogeneity between different vascular beds and species, (ii) how adhesion molecule N-glycosylation may be under distinct, and as yet, unknown modes of regulation during inflammatory stress to affect the inflammatory response in a vascular bed- and disease-specific manner (analogous to a "zip code" for inflammation) and finally (iii) to underscore the concept that a fuller appreciation of the role of adhesion molecule glycoforms is needed to provide foundations for disease and tissue-specific targeting of inflammation.

Glycoengineering of host mimicking type-2 LacNAc polymers and Lewis X antigens on bacterial cell surfaces

Bacterial carbohydrate structures play a central role in mediating a variety of host-pathogen interactions. Glycans can either elicit protective immune response or lead to escape of immune surveillance by mimicking host structures. Lipopolysaccharide (LPS), a major component on the surface of Gram-negative bacteria, is composed of a lipid A-core and the O-antigen polysaccharide. Pathogens like Neisseria meningitidis expose a lipooligosaccharide (LOS), which outermost glycans mimick mammalian epitopes to avoid immune recognition. Lewis X (Galβ1-4(Fucα1-3)GlcNAc) antigens of Helicobacter pylori or of the helminth Schistosoma mansoni modulate the immune response by interacting with receptors on human dendritic cells. In a glycoengineering approach we generate human carbohydrate structures on the surface of recombinant Gram-negative bacteria, such as Escherichia coli and Salmonella enterica sv. Typhimurium that lack O-antigen. A ubiquitous building block in mammalian N-linked protein glycans is Galβ1-4GlcNAc, referred to as a type-2 N-acetyllactosamine, LacNAc, sequence. Strains displaying polymeric LacNAc were generated by introducing a combination of glycosyltransferases that act on modified lipid A-cores, resulting in efficient expression of the carbohydrate epitope on bacterial cell surfaces. The poly-LacNAc scaffold was used as an acceptor for fucosylation leading to polymers of Lewis X antigens. We analysed the distribution of the carbohydrate epitopes by FACS, microscopy and ELISA and confirmed engineered LOS containing LacNAc and Lewis X repeats by MALDI-TOF and NMR analysis. Glycoengineered LOS induced pro-inflammatory response in murine dendritic cells. These bacterial strains can thus serve as tools to analyse the role of defined carbohydrate structures in different biological processes.

Tumor-associated glycans and their role in gynecological cancers: accelerating translational research by novel high-throughput approaches

Glycans are important partners in many biological processes, including carcinogenesis. The rapidly developing field of functional glycomics becomes one of the frontiers of biology and biomedicine. Aberrant glycosylation of proteins and lipids occurs commonly during malignant transformation and leads to the expression of specific tumor-associated glycans. The appearance of aberrant glycans on carcinoma cells is typically associated with grade, invasion, metastasis and overall poor prognosis. Cancer-associated carbohydrates are mostly located on the surface of cancer cells and are therefore potential diagnostic biomarkers. Currently, there is increasing interest in cancer-associated aberrant glycosylation, with growing numbers of characteristic cancer targets being detected every day. Breast and ovarian cancer are the most common and lethal malignancies in women, respectively, and potential glycan biomarkers hold promise for early detection and targeted therapies. However, the acceleration of research and comprehensive multi-target investigation of cancer-specific glycans could only be successfully achieved with the help of a combination of novel high-throughput glycomic approaches.