Enhanced expression of α2,3-linked sialic acids promotes gastric cancer cell metastasis and correlates with poor prognosis

When a negative (charge) is not a positive: sialylation and its role in cancer mechanics and progression

Sialic acids and sialoglycans are critical actors in cancer progression and metastasis. These terminal sugar residues on glycoproteins and glycolipids modulate key cellular processes such as immune evasion, cell adhesion, and migration. Aberrant sialylation is driven by overexpression of sialyltransferases, resulting in hypersialylation on cancer cell surfaces as well as enhancing tumor aggressiveness. Sialylated glycans alter the structure of the glycocalyx, a protective barrier that fosters cancer cell detachment, migration, and invasion. This bulky glycocalyx also increases membrane tension, promoting integrin clustering and downstream signaling pathways that drive cell proliferation and metastasis. They play a critical role in immune evasion by binding to Siglecs, inhibitory receptors on immune cells, which transmit signals that protect cancer cells from immune-mediated destruction. Targeting sialylation pathways presents a promising therapeutic opportunity to understand the complex roles of sialic acids and sialoglycans in cancer mechanics and progression, which is crucial for developing novel diagnostic and therapeutic strategies that can disrupt these processes and improve cancer treatment outcomes.

Adipose microenvironment promotes hypersialylation of ovarian cancer cells

Introduction

Ovarian and other peritoneal cancers have a strong tendency to metastasize into the surrounding adipose tissue. This study describes an effect of the adipose microenvironment on upregulation of sialic acid-containing glycans in ovarian cancer (OC). Heterogeneous populations of glycosylated OC tumors converged to a highly sialylated cell state that regulates tumorigenesis in an immune-dependent manner.

Methods

We modeled the adipose microenvironment by conditioning growth media with human patient-derived adipose tissue. OC cell lines grown in the presence vs. absence of adipose conditioned media (ACM) were characterized by transcriptomics, western blotting, and chemical biology glycan labeling methods. Fluorescence-activated cell sorting was used to separate adipose-driven upregulation of hypersialylated ("SNA-high") vs. hyposialylated ("SNA-low") OC subpopulations. The two subpopulations were characterized by further transcriptomic and quantitative polymerase chain reaction analyses, then injected into a syngeneic mouse model. Immune system involvement was implicated using wild type and athymic nude mice with a primary endpoint of overall survival.

Results

Adipose conditioning resulted in upregulation of sialyltransferases ST3GAL1, ST6GAL1, ST6GALNAC3, and ST8Sia1. In culture, OC cells displayed two distinct sialylated subpopulations that were stable for up to 9 passages, suggesting inherent heterogeneity in sialylation that is maintained throughout cell division and media changes. OC tumors that implanted in the omental adipose tissue exclusively reprogrammed to the highly sialylated subpopulation. In wild type C57BL/6 mice, only the hypersialylated SNA-high subpopulation implanted in the adipose, whereas the hyposialylated SNA-low subpopulation failed to be tumorigenic (p=0.023, n=5). In the single case where SNA-low established a tumor, post-mortem analysis revealed reprogramming of the tumor to the SNA-high state in vivo. In athymic nude mice, both subpopulations rapidly formed tumors, implicating a role of the adaptive immune system.

Conclusions

These findings suggest a model of glycan-dependent tumor evolution wherein the adipose microenvironment reprograms OC to a tumorigenic state that resists the adaptive immune system. Mechanistically, adipose factors upregulate sialyltransferases. To our knowledge, this is the first demonstration of the effect of adipose microenvironment on OC tumor sialylation. Our results set the stage for translational applications targeting sialic acid pathways in OC and other peritoneal cancer tumorigenesis and metastasis.

Adipose microenvironment promotes hypersialylation of ovarian cancer cells

Sialylation, the addition of negatively charged sialic acid sugars to terminal ends of glycans, is upregulated in most cancers. Hypersialylation supports multiple pro-tumor mechanisms such as enhanced migration and invasion, resistance to apoptosis and immune evasion. A current gap in knowledge is the lack of understanding on how the tumor microenvironment regulates cancer cell sialylation. The adipose niche is a main component of most peritoneal cancers' microenvironment. This includes ovarian cancer (OC), which causes most deaths from all gynecologic cancers. In this report, we demonstrate that the adipose microenvironment is a critical regulator of OC cell sialylation. In vitro adipose conditioning led to an increase in both ⍺2,3- and ⍺2,6-linked cell surface sialic acids in both human and mouse models of OC. Adipose-induced sialylation reprogramming was also observed in vivo from intra-peritoneal OC tumors seeded in the adipose-rich omentum. Mechanistically, we observed upregulation of at least three sialyltransferases, ST3GAL1, ST6GAL1 and ST3GALNAC3. Hypersialylated OC cells consistently formed intra-peritoneal tumors in both immune-competent mice and immune-compromised athymic nude mice. In contrast, hyposiaylated OC cells persistently formed tumors only in athymic nude mice demonstrating that sialylation impacts OC tumor formation in an immune dependent manner. To our knowledge, this is the first demonstration of the effect of adipose microenvironment on OC tumor sialylation. Our results set the stage for translational applications targeting sialic acid pathways in OC and other peritoneal cancers.

The underlying mechanism of nuclear and mitochondrial DNA damages in triggering cancer incidences: Insights into proteomic and genomic sciences

The attempt of this review article is to determine the impact of nuclear and mitochondrial damages on the propagation of cancer incidences. This review has advanced our understanding to altered genes and their relevant cancerous proteins. The progressive raising effects of free reactive oxygen species ROS and toxicogenic compounds contributed to significant mutation in nuclear and mitochondrial DNA where the incidence of gastric cancer is found to be linked with down regulation of some relevant genes and mutation in some important cellular proteins such as AMP-18 and CA-11. Thereby, the resulting changes in gene mutations induced the apparition of newly polymorphisms eventually leading to unusual cellular expression to mutant proteins. Reduction of these apoptotic growth factors and nuclear damages is increasingly accepted by cell reactivation effect, enhanced cellular signaling and DNA repairs. Acetylation, glycation, pegylation and phosphorylation are among the molecular techniques used in DNA repair for rectifying mutation incidences. In addition, the molecular labeling based fluorescent materials are currently used along with the bioconjugating of signal molecules in targeting disease translocation site, particularly cancers and tumors. These strategies would help in determining relevant compounds capable in overcoming problems of down regulating genes responsible for repair mechanisms. These issues of course need interplay of both proteomic and genomic studies often in combination of molecular engineering to cible the exact expressed gene relevant to these cancerous proteins.

Structural and functional analysis of a novel galactose-binding lectin derived from Chlorella sorokiniana MW769776

A freshwater green microalgal strain was isolated and the lectin was identified in it by a strong hemagglutination activity (HA) assay. Characterization of the algal strain was found to be Chlorella sorokiniana (MW769776). A single step affinity chromatographic technique was developed to purify Chlorella sorokiniana lectin (CSL) using guar gum as the affinity matrix. The precipitate showed a single active peak with a titer value of 1024 HU, with a concentration of 1111 U, and a purification fold of 9. The purified protein exhibited a single band in SDS-PAGE with a molecular weight of 16 kDa. Analysis by liquid chromatography-electrospray ionization-quadrupole-time of flight mass spectrometry (LC-ESI-Q-TOF-MS) of tryptic-digested purified lectin showed that it was a monomeric protein. A multiple sequence alignment analysis revealed that the peptide sequences of CSL exhibited similarity with the H-type lectin domain of Micractinium conductrix. The structure of CSL was studied by FTIR and homology modeling methods, indicating the presence of α-helix as well as β-sheet in its secondary structure. Whereas the 3D structure exhibited the similarity with the core protein of light-harvesting reaction center complex of photosystem I. The significance of this study suggests that the characteristics of CSL are consistent with its identification as a hemagglutinin, a type of novel lectin, which suggests its candidature for various biological purposes.Communicated by Ramaswamy H. Sarma.

Recent advances in the development of sialyltransferase inhibitors to control cancer metastasis: A comprehensive review

Metastasis accounts for the majority of cancer-associated mortalities, representing a huge health and economic burden. One of the mechanisms that enables metastasis is hypersialylation, characterized by an overabundance of sialylated glycans on the tumor surface, which leads to repulsion and detachment of cells from the original tumor. Once the tumor cells are mobilized, sialylated glycans hijack the natural killer T-cells through self-molecular mimicry and activatea downstream cascade of molecular events that result in inhibition of cytotoxicity and inflammatory responses against cancer cells, ultimately leading to immune evasion. Sialylation is mediated by a family of enzymes known as sialyltransferases (STs), which catalyse the transfer of sialic acid residue from the donor, CMP-sialic acid, onto the terminal end of an acceptor such as N-acetylgalactosamine on the cell-surface. Upregulation of STs increases tumor hypersialylation by up to 60% which is considered a distinctive hallmark of several types of cancers such as pancreatic, breast, and ovarian cancer. Therefore, inhibiting STs has emerged as a potential strategy to prevent metastasis. In this comprehensive review, we discuss the recent advances in designing novel sialyltransferase inhibitors using ligand-based drug design and high-throughput screening of natural and synthetic entities, emphasizing the most successful approaches. We analyse the limitations and challenges of designing selective, potent, and cell-permeable ST inhibitors that hindered further development of ST inhibitors into clinical trials. We conclude by analysing emerging opportunities, including advanced delivery methods which further increase the potential of these inhibitors to enrich the clinics with novel therapeutics to combat metastasis.

Sialyl-Tn Antigen-Imprinted Dual Fluorescent Core-Shell Nanoparticles for Ratiometric Sialyl-Tn Antigen Detection and Dual-Color Labeling of Cancer Cells

Sialyl-Tn (STn or sialyl-Thomsen-nouveau) is a carbohydrate antigen expressed by more than 80% of human carcinomas. We here report a strategy for ratiometric STn detection and dual-color cancer cell labeling, particularly, by molecularly imprinted polymers (MIPs). Imprinting was based on spectroscopic studies of a urea-containing green-fluorescent monomer 1 and STn-Thr-Na (sodium salt of Neu5Acα2-6GalNAcα-O-Thr). A few-nanometer-thin green-fluorescent polymer shell, in which STn-Thr-Na was imprinted with 1, other comonomers, and a cross-linker, was synthesized from the surface of red-emissive carbon nanodot (R-CND)-doped silica nanoparticles, resulting in dual fluorescent STn-MIPs. Dual-color labeling of cancer cells was achieved since both red and green emissions were detected in two separate channels of the microscope and an improved accuracy was obtained in comparison with single-signal MIPs. The flow cytometric cell analysis showed that the binding of STn-MIPs was significantly higher (p < 0.001) than that of non-imprinted polymer (NIP) control particles within the same cell line, allowing to distinguish populations. Based on the modularity of the luminescent core-fluorescent MIP shell architecture, the concept can be transferred in a straightforward manner to other target analytes.

Sialyltransferase Inhibitor Ac53FaxNeu5Ac Reverts the Malignant Phenotype of Pancreatic Cancer Cells, and Reduces Tumor Volume and Favors T-Cell Infiltrates in Mice

Hypersialylation is a feature of pancreatic ductal adenocarcinoma (PDA) and it has been related to tumor malignancy and immune suppression. In this work, we have evaluated the potential of the sialyltransferase inhibitor, Ac₅3F_axNeu5Ac, to decrease tumor sialoglycans in PDA and to revert its malignant phenotype. Sialoglycans on PDA cells were evaluated by flow cytometry, and the functional impact of Ac₅3F_axNeu5Ac was assessed using E-selectin adhesion, migration, and invasion assays. PDA tumors were generated in syngeneic mice from KC cells and treated with Ac₅3F_axNeu5Ac to evaluate tumor growth, mice survival, and its impact on blocking sialic acid (SA) and on the tumor immune component. Ac₅3F_axNeu5Ac treatment on human PDA cells decreased α2,3-SA and sialyl-Lewis^x, which resulted in a reduction in their E-selectin adhesion, and in their migratory and invasive capabilities. Subcutaneous murine tumors treated with Ac₅3F_axNeu5Ac reduced their volume, their SA expression, and modified their immune component, with an increase in CD8⁺ T-lymphocytes and NK cells. In conclusion, Ac₅3F_axNeu5Ac treatment weakened PDA cells' malignant phenotype, thereby reducing tumor growth while favoring anti-tumor immune surveillance. Altogether, these results show the positive impact of reducing SA expression by inhibiting cell sialyltransferases and open the way to use sialyltransferase inhibitors to target this dismal disease.

Loss of GNE Predicts Lymph Node Metastasis in Early Gastric Cancer

Endoscopic surgery is increasingly utilized for the treatment of early gastric cancer (EGC) worldwide, whereas lymph node metastasis (LNM) remains a critical risk factor for the relapse of EGC after endoscopic surgery. Therefore, identifying potential predictive factors and understanding the molecular mechanisms are urgently needed for improving the outcome of EGC patients with LNM. UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) is the key enzyme in the process of biosynthesis of CMP-Neu5Ac from UDP-N-acetylglucosamine (UDP-GlcNAc), which acts as a substrate for several reactions in glycan metabolism. In this study, we found that GNE was down-regulated in EGC patients with LNM. GNE expression as well as localization, tumor size, intravascular tumor thrombi and Lauren's classification were further identified as independent predictive factors for LNM. Combining GNE expression with traditional risk factors, including tumor size and differentiation degrees, could generate a better model for predicting LNM in EGC patients. Overall, our study implies that low GNE expression is a potential predictor of LNM in EGC.

Serum α2,6-sialylated glycoform of serotransferrin as a glycobiomarker for diagnosis and prediction of clinical severity in cholangiocarcinoma

BACKGROUND

Glycoprotein sialylation changes are associated with severe development of various cancers. We previously discovered the sialylation of serotransferrin (TF) in cholangiocarcinoma (CCA) using glycoproteomics approach. However, a simple and reliable method for validating sialylation of a specific glycobiomarker is urgently needed.

METHODS

We identified the altered glycosylation in CCA tissues by glycoproteomics approach using mass spectrometry. An enzyme-linked lectin assay (ELLA) was developed for determining the serum levels of sialylated TF in CCA, hepatocellular carcinoma (HCC) and healthy controls in training and validation cohorts.

RESULTS

The nine highly sialylated glycoforms of TF were markedly abundant in CCA tumor tissues than in control. Serum SNA-TF and MAL1-TF were significantly higher in CCA patients. Under receiver operating characteristic curve, serum SNA-TF concentrations significantly differentiated CCA from healthy control. Higher SNA-TF were significantly correlated with severe tumor stages and lymph node metastasis. The combined SNA-TF, MAL1-TF, and CA19-9 as a novel glycobiomarkers panel demonstrated the highest specificity (96.2%) for distinguishing CCA from HCC patients. In CCA patients with low CA19-9 levels, SNA-TF in combination with CA19-9 achieved in 97% diagnostic accuracy.

CONCLUSIONS

Sialylated serotransferrin glycoforms could be used as a novel glycobiomarker for diagnosis and prediction of clinical severity in CCA patients.

Role of a Disease-associated ST3Gal-4 in Non-small Cell Lung Cancer

Sialylation promotes tumorigenesis by affecting various cancer-related events, including apoptosis inhibition, cell growth, invasion, migration, metastasis, chemo-resistance, and immunomodulation in favor of tumor progression. An altered expression of sialyltransferase enzymes is responsible for synthesizing various tumor-associated sialylated structures. In the present study, our findings have revealed a significant up-regulation of ST3Gal-4 transcript in the two major subtypes of NSCLC cell lines [squamous cell carcinoma cell line (NCI-H520) and adenocarcinoma cell line (A549)]. Thus, the role of the ST3Gal-4 gene was assessed on cancer-associated signal transduction pathways in these cells in view of proliferation, invasion, and migration. ST3Gal-4 was silenced by transfection of both the cell lines with esi-ST3Gal-4-RNA, which RT-PCR and western immunoblotting confirmed. Silencing of ST3Gal-4 resulted in a decreased expression of MAL-I interacting membrane-HSP60, identified earlier as an α2,3-sialylated glycoprotein, thus pointing towards the possible role of ST3Gal-4 in its sialylation. The proliferation, invasion, and migration of both types of NSCLC cells were reduced significantly in the ST3Gal-4 silenced cells. Our findings were substantiated by the down-regulation of β-catenin and E-cadherin, a reduced expression of activated AKT1, ERK1/2, and NF-ƙB in these cells. We propose that ST3Gal-4 may be the disease-associated sialyltransferase involved in α2,3 sialylation of the membrane proteins, including HSP60 of the NSCLC cells. This may lead to the conformational alteration of these proteins, required for the activation of E-cadherin/β-catenin, AKT, and ERK/NF-ƙB mediated signal transduction pathways in these cells, resulting in their proliferation, invasion, and migration.

Sialic acids: An Avenue to Target Cancer Progression, Metastasis, and Resistance to Therapy

Background

Sialic acids are alpha-keto acids with nine carbons that are commonly present in the terminal sugars of glycans on glycoproteins and glycolipids on the cell surface. Sialic acids have a role in a variety of physiological and pathological processes by interacting with carbohydrates and proteins, communicating between cells, and acting as cell surface receptors for viruses and bacteria. Several studies have shown the aberrant pattern of sialic acids on cancer cells due to change in their glycosylation status. This pattern may be attributed to various physiological and pathological changes occurring in tumour cells. Hypersialylation in tumours, its involvement in tumour growth, immune evasion and escape from the apoptotic pathway, metastasis formation, and therapeutic resistance have all been fairly well investigated.

Methods

A PubMed search was conducted and published articles in different studies from 2000 to 2020 were included and reviewed. Here, we discuss current outcomes that emphasize the unfavourable effects of hypersialylation on multiple aspects of tumour genesis, immune evasion, metastasis and resistance to therapy.

Conclusion

These recent investigations have found that aberrant sialylation is an essential process for tumour cells to evade immune surveillance and maintain their malignancy. Together, these noteworthy views provide a solid platform for designing and developing therapeutic approaches that target hypersialylation of cancer cells.

The Distinct Roles of Sialyltransferases in Cancer Biology and Onco-Immunology

Aberrant glycosylation is a key feature of malignant transformation. Hypersialylation, the enhanced expression of sialic acid-terminated glycoconjugates on the cell surface, has been linked to immune evasion and metastatic spread, eventually by interaction with sialoglycan-binding lectins, including Siglecs and selectins. The biosynthesis of tumor-associated sialoglycans involves sialyltransferases, which are differentially expressed in cancer cells. In this review article, we provide an overview of the twenty human sialyltransferases and their roles in cancer biology and immunity. A better understanding of the individual contribution of select sialyltransferases to the tumor sialome may lead to more personalized strategies for the treatment of cancer.

Pathological features in 'humanized' neonatal pig

Cytidine monophosphate-Nacetylneuraminic acid (Neu5Ac) hydroxylase (CMAH) and glycoprotein, alpha1, 3-galactosyltransferase (GGTA1) double knockout (DKO) pig models were produced to reduce immune reaction for xenotransplantation. However, the role of Neu5Gc and α-Gal in pigs has not been fully elucidated and it is necessary to consider the after-effect of inactivation of GGTA1 and CMAH in pigs. Hematological profiles of DKO pigs were analyzed through complete blood count (CBC). Histology of liver and spleen of DKO were investigated, and lectin blotting and mass spectrometry (MS) were performed to explore glycosylation changes in red blood cell (RBC) membranes of DKO pigs. DKO pigs showed common clinical signs such as weakness (100%), dyspnea (90%) and constipation (65%). DKO pigs revealed a significant decrease in RBC, hemoglobin (HGB) and hematocrit (HGB), and an increase in white blood cell (WBC), lymphocyte (LYM), monocyte (MON), and erythrocyte mean corpuscular volume (MCV). DKO piglets showed swollen liver and spleen, and exhibited raised deposition of hemosiderin and severe bleeding. Lectin assay and MS proved variations in glycosylation on RBC membranes. GGTA1/CMAH DKO pigs developed pathological features which are similar to anemic symptoms, and the variations in glycosylation on RBC membranes of DKO pigs may be attributed to the pathologies observed.

Aberrant Sialylation in Cancer: Biomarker and Potential Target for Therapeutic Intervention?

Simple Summary

Sialylation is a post-translational modification that consists in the addition of sialic acid to growing glycan chains on glycoproteins and glycolipids. Aberrant sialylation is an established hallmark of several types of cancer, including breast, ovarian, pancreatic, prostate, colorectal and lung cancers, melanoma and hepatocellular carcinoma. Hypersialylation can be the effect of increased activity of sialyltransferases and results in an excess of negatively charged sialic acid on the surface of cancer cells. Sialic acid accumulation contributes to tumor progression by several paths, including stimulation of tumor invasion and migration, and enhancing immune evasion and tumor cell survival. In this review we explore the mechanisms by which sialyltransferases promote cancer progression. In addition, we provide insights into the possible use of sialyltransferases as biomarkers for cancer and summarize findings on the development of sialyltransferase inhibitors as potential anti-cancer treatments.

Abstract

Sialylation is an integral part of cellular function, governing many biological processes including cellular recognition, adhesion, molecular trafficking, signal transduction and endocytosis. Sialylation is controlled by the levels and the activities of sialyltransferases on glycoproteins and lipids. Altered gene expression of these enzymes in cancer yields to cancer-specific alterations of glycoprotein sialylation. Mounting evidence indicate that hypersialylation is closely associated with cancer progression and metastatic spread, and can be of prognostic significance in human cancer. Aberrant sialylation is not only a result of cancer, but also a driver of malignant phenotype, directly impacting key processes such as tumor cell dissociation and invasion, cell-cell and cell-matrix interactions, angiogenesis, resistance to apoptosis, and evasion of immune destruction. In this review we provide insights on the impact of sialylation in tumor progression, and outline the possible application of sialyltransferases as cancer biomarkers. We also summarize the most promising findings on the development of sialyltransferase inhibitors as potential anti-cancer treatments.

ST3Gal IV Mediates the Growth and Proliferation of Cervical Cancer Cells In Vitro and In Vivo Via the Notch/p21/CDKs Pathway

ST3Gal IV is one of the principal sialyltransferases responsible for the biosynthesis of α2, 3-sialic acid to the termini N-glycans or O-glycans of glycoproteins and glycolipids. It has been reported that ST3Gal IV expression is associated with gastric carcinoma, pancreatic adenocarcinoma and breast cancer. While the expression and functions of ST3Gal IV in cervical cancer are still poorly understood. In this study, we found that ST3Gal IV was downregulated in human cervical cancer tissues compared to normal cervix tissues, and ST3Gal IV expression was negatively associated with the pathological grade of cervical cancer. ST3Gal IV upregulation inhibited the growth and proliferation of cervical cancer HeLa and SiHa cells in vitro and in vivo. Furthermore, ST3Gal IV overexpression enhanced the expression of several Notch pathway components such as Jagged1, Notch1, Hes1 and Hey1, while cell cycle protein expression like Cyclin D1, Cyclin E1, CDK2 and CDK4 were decreased. These results indicate that expression of ST3Gal IV is reduced in cervical cancer and plays a negative role in cell proliferation via Notch/p21/CDKs signaling pathway. Thus, sialyltransferase ST3Gal IV might be a target for the diagnosis and therapy of cervical cancer.

Insights into the role of sialylation in cancer progression and metastasis

Upregulation of sialyltransferases—the enzymes responsible for the addition of sialic acid to growing glycoconjugate chains—and the resultant hypersialylation of up to 40–60% of tumour cell surfaces are established hallmarks of several cancers, including lung, breast, ovarian, pancreatic and prostate cancer. Hypersialylation promotes tumour metastasis by several routes, including enhancing immune evasion and tumour cell survival, and stimulating tumour invasion and migration. The critical role of enzymes that regulate sialic acid in tumour cell growth and metastasis points towards targeting sialylation as a potential new anti-metastatic cancer treatment strategy. Herein, we explore insights into the mechanisms by which hypersialylation plays a role in promoting metastasis, and explore the current state of sialyltransferase inhibitor development.

Knockdown of α2,3-Sialyltransferases Impairs Pancreatic Cancer Cell Migration, Invasion and E-selectin-Dependent Adhesion

Aberrant sialylation is frequently found in pancreatic ductal adenocarcinoma (PDA). α2,3-Sialyltransferases (α2,3-STs) ST3GAL3 and ST3GAL4 are overexpressed in PDA tissues and are responsible for increased biosynthesis of sialyl-Lewis (sLe) antigens, which play an important role in metastasis. This study addresses the effect of α2,3-STs knockdown on the migratory and invasive phenotype of PDA cells, and on E-selectin-dependent adhesion. Characterization of the cell sialome, the α2,3-STs and fucosyltransferases involved in the biosynthesis of sLe antigens, using a panel of human PDA cells showed differences in the levels of sialylated determinants and α2,3-STs expression, reflecting their phenotypic heterogeneity. Knockdown of ST3GAL3 and ST3GAL4 in BxPC-3 and Capan-1 cells, which expressed moderate to high levels of sLe antigens and α2,3-STs, led to a significant reduction in sLe^x and in most cases in sLe^a, with slight increases in the α2,6-sialic acid content. Moreover, ST3GAL3 and ST3GAL4 downregulation resulted in a significant decrease in cell migration and invasion. Binding and rolling to E-selectin, which represent key steps in metastasis, were also markedly impaired in the α2,3-STs knockdown cells. Our results indicate that inhibition of ST3GAL3 and ST3GAL4 may be a novel strategy to block PDA metastasis, which is one of the reasons for its dismal prognosis.

Identification of LCA-binding Glycans as a Novel Biomarker for Esophageal Cancer Metastasis using a Lectin Array-based Strategy

Esophageal cancer (EC) is a unique and heterogeneous disease diagnosed mostly at advanced stages. Altered glycans presented on cell surfaces are involved in the occurrence and development of malignancy. However, the effects of glycans on EC progression are largely unexplored. Here, a lectin array was utilized to detect the glycan profiling of the normal esophageal mucosal epithelial cell line and two EC cell lines. The binding of Lens culinaris lectin (LCA) to EC cells was found to be stronger than that of the normal cells. Lectin immunohistochemical staining revealed that LCA-binding glycans were markedly elevated in EC tissues compared to adjacent non-cancerous tissues. LCA staining was significantly associated with lymph node metastasis, depth of invasion, TNM stage and poor overall survival of EC patients. Added LCA to block LCA recognized glycans could inhibit the migration and invasion of EC cells. Further analysis revealed that blocking the biosynthesis of LCA-binding glycans by tunicamycin attenuated cellular migratory and invasive abilities. Additionally, a membrane glycoprotein CD147 was recognized as a binder of LCA. There was a positive correlation between LCA-binding glycans and CD147 expression in clinical samples. Interestingly, CD147 inhibition also reduced cell migration and invasion. These findings indicated that LCA-binding glycans may function as a novel indicator to predict metastasis for patients with EC.

Lectin microarrays for glycoproteomics: an overview of their use and potential

Introduction: Glycoproteomics is an important subdiscipline of proteomics, focusing on the role of protein glycosylation in various biological processes. Protein glycosylation is the enzymatic addition of sugars or oligosaccharides to proteins. Altered glycosylation often occurs in the early stages of disease development, for example, certain tumor-associated glycans have been shown to be expressed in precursor lesions of different types of cancer, making them powerful early diagnostic markers. Lectin microarrays have become a powerful tool for both the study of glycosylation and the diagnosis of various diseases including cancer.Areas covered: This review will discuss the most useful features of lectin microarrays, such as their technological advances, their capability for parallel/high-throughput analysis for the important glycopatterns of glycoprotein, and an overview of their use for glycosylation analysis of various complex protein samples, as well as their diagnostic potential in various diseases.Expert opinion: Lectin microarrays have proved to be useful in studying multiple lectin-glycan interactions in a single experiment and, with the advances made in the field, hold a promise of enabling glycopatterns of diseases in a fast and efficient manner. Lectin microarrays will become increasingly powerful early diagnostic tool for a variety of conditions.

Biological Functions and Analytical Strategies of Sialic Acids in Tumor

Sialic acids, a subset of nine carbon acidic sugars, often exist as the terminal sugars of glycans on either glycoproteins or glycolipids on the cell surface. Sialic acids play important roles in many physiological and pathological processes via carbohydrate-protein interactions, including cell-cell communication, bacterial and viral infections. In particular, hypersialylation in tumors, as well as their roles in tumor growth and metastasis, have been widely described. Recent studies have indicated that the aberrant sialylation is a vital way for tumor cells to escape immune surveillance and keep malignance. In this article, we outline the present state of knowledge on the metabolic pathway of human sialic acids, the function of hypersialylation in tumors, as well as the recent labeling and analytical techniques for sialic acids. It is expected to offer a brief introduction of sialic acid metabolism and provide advanced analytical strategies in sialic acid studies.

Increase of MAL-II Binding Alpha2,3-Sialylated Glycan Is Associated with 5-FU Resistance and Short Survival of Cholangiocarcinoma Patients

Background and objectives: Sialylation plays important roles in tumor progression. Our present study aimed to demonstrate the alteration of sialylation and its role in cholangiocarcinoma (CCA). Materials and Methods: The α2,3- and α2,6-sialylation in CCA tissue was analyzed by lectin-histochemistry using Maackia amurensis lectin-II (MAL-II) and Sambucus nigra agglutinin (SNA). CCA cell lines were treated with the pan-sialylation inhibitor 3Fax-peracetyl-Neu5Ac (3F-Sia) followed by proliferation and chemosensitivity assays. Results: MAL-II binding α2,3-Sialylated Glycan (MAL-SG) and SNA binding α2,6-Sialylated Glycan (SNA-SG) were both elevated in CCA compared with hyperplastic/dysplastic (HP/DP) and normal bile ducts (NBD). The positive staining for MAL-SG or SNA-SG were found in 82% (61/74) of the CCA cases. Higher expression of MAL-SG in CCA was associated with shorter survival of the patients. The median survival of patients with high and low MAL-SG were 167 and 308 days, respectively, with overall survival of 233 days, suggesting the involvement of MAL-SG in CCA progression. MAL-SG expression of CCA cell lines was markedly decreased after treatment with 3F-Sia for 48 to 72 h. While proliferation of CCA cells were not affected by 3F-Sia treatment, their susceptibility to 5-fluorouracil (5-FU) was significantly enhanced. These results suggest that sialylation is involved in the development of 5-FU resistance and the sialylation inhibitor 3F-Sia can be used as a chemosensitizer for CCA. Conclusions: Sialylation is critically involved in the development of chemoresistance of CCA, and sialylation inhibitors may be used as a chemosensitizer in CCA treatment.

Integrated Glycome Strategy for Characterization of Aberrant LacNAc Contained N-Glycans Associated With Gastric Carcinoma

Aberrant glycosylation is not only a feature of malignant cell transformation, but also plays an important role in metastasis. In the present study, an integrated strategy combining the lectin microarrays and lectin cytochemistry was employed to investigate and verify the altered glycopatterns in gastric cancer (GC) cell lines as well as resected tumor specimens from matched tissue sets of 46 GC patients. Subsequently, lectin-mediated affinity capture glycoproteins, and MALDI-TOF/TOF-MS were employed to further acquire precise structural information of the altered glycans. According to the results, the glycopatterns recognized by 10 (e.g., ACA, MAL-I, and ConA) and 3 lectins (PNA, MAL-I, and VVA) showed significantly variations in GC cells and tissue compared to their corresponding controls, respectively. Notably, the relative abundance of Galβ-1,4GlcNAc (LacNAc) recognized by MAL-I exhibited a significant increase in GC cells (p < 0.001) and tissue from patients at stage II and III (p < 0.05), and a significant increase in lymph node positive tumor cases, compared with lymph node negative tumor cases (p < 0.05). More LacNAc contained N-glycans were characterized in tumor sample with advanced stage compared to corresponding control. Moreover, there were 10 neo-LacNAc-contained N-glycans (e.g., m/z 1625.605, 1803.652, and 1914.671) only presented in GC tissue with advanced stage. Among these, six N-glycans were modified with sialic acid or fucose based on LacNAc to form sialylated N-glycans or lewis antigens, respectively. Our results revealed that the aberrant expression of LacNAc is a characteristic of GC, and LacNAc may serve as a scaffold to be further modified with sialic acid or fucose. Our findings provided useful information for us to understand the development of GC.

Two-Step Isolation, Purification, and Characterization of Lectin from Zihua Snap Bean (Phaseolus vulgaris) Seeds

A two-step method based on an aqueous two-phase system and Sephadex G-75 was used to separate and purify lectin from the seeds of the Zihua snap bean. The preliminary properties and bioactivity of the Zihua snap bean lectin were characterized by different instrumental methods, such as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE), liquid chromatography-nano electrospray ionization mass spectrometry (Nano LC-ESI-MS/MS), and Fourier transform infrared spectroscopy (FTIR). The hemagglutinating activity of the Zihua snap bean lectin could not be inhibited by glucose, N-acetyl-d-glucosamine, d-galactose, N-acetyl-d-galactosamine, fructose, sucrose, d-maltose, d-trehalose, and lactose. It was found that the hemagglutinating activity of the lectin showed strong dependence on Mn²⁺ and Ca²⁺. The thermal and pH stability of the Zihua snap bean lectin was studied by FTIR and fluorescence spectroscopy. Relatively good stability was observed when the temperature was not higher than 70 °C, as well as in the pH range of 2.0 to 10.0. Digestive stability in vitro was investigated. The untreated lectin was relatively stable to pepsin and trypsin activity, but heat treatment could significantly reduce the digestive stability in vitro. Moreover, the lectin showed an inhibitory effect on the tested bacteria (Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Bacillus subtilis (B. subtilis)), and it also showed a certain inhibitory effect on the growth of Phytophthora infestans (P. infestans) at higher concentrations.

Integrin β1 regulates the invasion and radioresistance of laryngeal cancer cells by targeting CD147

Background

Increased expression of integrin β1 has been reported to correlate with progression and therapy resistance in many types of cancers. The aim of this study was to investigate the effects of integrin β1 on the invasion and radioresistance of laryngeal cancer cells.

Methods

The expression of integrin β1 in the tumor specimens of laryngeal cancer patients was assessed by immunohistochemical assays. The invasion ability of laryngeal cancer cells was detected by transwell and wound healing assays. The radiosensitivity of laryngeal cancer cells was evaluated by flow cytometry and colony formation assays.

Results

High expression of integrin β1 was significantly associated with lymph node metastasis, TNM stage and poor clinical outcomes (all p < 0.05). Knockdown of integrin β1 in laryngeal cancer cells inhibited invasion and increased radiosensitivity. Mechanistically, these effects were caused by suppression of the downstream focal adhesion kinase (FAK)/cortactin pathway. In addition, integrin β1 could interact with CD147 and the antibody blockade of CD147 led to the deactivation of FAK/cortactin signaling. Further studies revealed that the interaction between integrin β1 and CD147 relied on intact lipid rafts. Disruption of lipid rafts by methyl beta cyclodextrin in laryngeal cancer cells was able to reverse integrin β1-mediated malignant phenotypes.

Conclusions

Integrin β1 has potential as a therapeutic target in prevention and treatment of laryngeal cancer.

Serum sialylation changes in cancer

Cancer is a major cause of death in both developing and developed countries. Early detection and efficient therapy can greatly enhance survival. Aberrant glycosylation has been recognized to be one of the hallmarks of cancer as glycans participate in many cancer-associated events. Cancer-associated glycosylation changes often involve sialic acids which play important roles in cell-cell interaction, recognition and immunological response. This review aims at giving a comprehensive overview of the literature on changes of sialylation in serum of cancer patients. Furthermore, the methods available to measure serum and plasma sialic acids as well as possible underlying biochemical mechanisms involved in the serum sialylation changes are surveyed. In general, total serum sialylation levels appear to be increased with various malignancies and show a potential for clinical applications, especially for disease monitoring and prognosis. In addition to overall sialic acid levels and the amount of sialic acid per total protein, glycoprofiling of specific cancer-associated glycoproteins, acute phase proteins and immunoglobulins in serum as well as the measurements of sialylation-related enzymes such as sialidases and sialyltransferases have been reported for early detection of cancer, assessing cancer progression and improving prognosis of cancer patients. Moreover, sialic-acid containing glycan antigens such as CA19-9, sialyl Lewis X and sialyl Tn on serum proteins have also displayed their value in cancer diagnosis and management whereby increased levels of these factors positively correlated with metastasis or poor prognosis.

Altered O-glycosylation is associated with inherent radioresistance and malignancy of human laryngeal carcinoma

Radioresistance (inherent or acquired) remains a major obstacle affecting the clinical outcome of radiotherapy for laryngeal carcinoma. Results from our laboratory and other groups suggest that aberrant glycosylation contributes to cancer acquired radioresistance. However, the role of glycosylation in inherent radioresistance of laryngeal carcinoma has not been fully uncovered. In this study, we investigated the glycan profiling of the inherent radioresistant (Hep-2max) and radiosensitive (Hep-2min) cell lines using lectin microarray analysis. The results revealed that the radioresistant cell line Hep-2max presented higher core 1-type O-glycans than the sensitive one. Further analysis of the O-glycan regulation by benzyl-α-GalNAc application in Hep-2max cells showed partial inhibition of the O-glycan biosynthesis and increased radiosensitivity. In addition, core 1 β1, 3-galactosyltransferase (C1GALT1) overexpression in Hep-2min cells enhanced cell migration, invasion, and radioresistance. Conversely, knockdown of C1GALT1 in Hep-2max cells was able to suppress these malignant phenotypes. Moreover, mechanistic investigations showed that C1GALT1 modified the O-glycans on integrin β1 and regulated its activity. The glycosylation-mediated radioresistance was further inhibited by anti-integrin β1 blocking antibody. Importantly, we also observed that core 1-type O-glycans expression was correlated with advanced tumor stage, metastasis, and poor survival of laryngeal carcinoma patients. These findings suggest that altered O-glycosylation can lead to the inherent radioresistance and progression, and therefore may be important for enhancing the efficacy of radiotherapy in laryngeal carcinoma.

Legume Lectins: Proteins with Diverse Applications

Lectins are a diverse class of proteins distributed extensively in nature. Among these proteins; legume lectins display a variety of interesting features including antimicrobial; insecticidal and antitumor activities. Because lectins recognize and bind to specific glycoconjugates present on the surface of cells and intracellular structures; they can serve as potential target molecules for developing practical applications in the fields of food; agriculture; health and pharmaceutical research. This review presents the current knowledge of the main structural characteristics of legume lectins and the relationship of structure to the exhibited specificities; provides an overview of their particular antimicrobial; insecticidal and antitumor biological activities and describes possible applications based on the pattern of recognized glyco-targets.