Glycomic and glycoproteomic analysis of serum from patients with stomach cancer reveals potential markers arising from host defense response mechanisms

Deep learning enhanced the diagnostic merit of serum glycome for multiple cancers

Protein glycosylation is associated with the pathogenesis of various cancers. The utilization of certain glycans in cancer diagnosis models holds promise, yet their accuracy is not always guaranteed. Here, we investigated the utility of deep learning techniques, specifically random forests combined with transfer learning, in enhancing serum glycome's discriminative power for cancer diagnosis (including ovarian cancer, non-small cell lung cancer, gastric cancer, and esophageal cancer). We started with ovarian cancer and demonstrated that transfer learning can achieve superior performance in data-disadvantaged cohorts (AUROC >0.9), outperforming the approach of PLS-DA. We identified a serum glycan-biomarker panel including 18 serum N-glycans and 4 glycan derived traits, most of which were featured with sialylation. Furthermore, we validated advantage of the transfer learning scheme across other cancer groups. These findings highlighted the superiority of transfer learning in improving the performance of glycans-based cancer diagnosis model and identifying cancer biomarkers, providing a new high-fidelity cancer diagnosis venue.

Mapping of the gene network that regulates glycan clock of ageing

Glycans are an essential structural component of immunoglobulin G (IgG) that modulate its structure and function. However, regulatory mechanisms behind this complex posttranslational modification are not well known. Previous genome-wide association studies (GWAS) identified 29 genomic regions involved in regulation of IgG glycosylation, but only a few were functionally validated. One of the key functional features of IgG glycosylation is the addition of galactose (galactosylation), a trait which was shown to be associated with ageing. We performed GWAS of IgG galactosylation (N=13,705) and identified 16 significantly associated loci, indicating that IgG galactosylation is regulated by a complex network of genes that extends beyond the galactosyltransferase enzyme that adds galactose to IgG glycans. Gene prioritization identified 37 candidate genes. Using a recently developed CRISPR/dCas9 system we manipulated gene expression of candidate genes in the in vitro IgG expression system. Upregulation of three genes, EEF1A1, MANBA and TNFRSF13B, changed the IgG glycome composition, which confirmed that these three genes are involved in IgG galactosylation in this in vitro expression system.

Circulating Proteins as Diagnostic Markers in Gastric Cancer

Gastric cancer (GC) is a highly malignant disease affecting humans worldwide and has a poor prognosis. Most GC cases are detected at advanced stages due to the cancer lacking early detectable symptoms. Therefore, there is great interest in improving early diagnosis by implementing targeted prevention strategies. Markers are necessary for early detection and to guide clinicians to the best personalized treatment. The current semi-invasive endoscopic methods to detect GC are invasive, costly, and time-consuming. Recent advances in proteomics technologies have enabled the screening of many samples and the detection of novel biomarkers and disease-related signature signaling networks. These biomarkers include circulating proteins from different fluids (e.g., plasma, serum, urine, and saliva) and extracellular vesicles. We review relevant published studies on circulating protein biomarkers in GC and detail their application as potential biomarkers for GC diagnosis. Identifying highly sensitive and highly specific diagnostic markers for GC may improve patient survival rates and contribute to advancing precision/personalized medicine.

IgG glycans in health and disease: Prediction, intervention, prognosis, and therapy

Immunoglobulin (IgG) glycosylation is a complex enzymatically controlled process, essential for the structure and function of IgG. IgG glycome is relatively stable in the state of homeostasis, yet its alterations have been associated with aging, pollution and toxic exposure, as well as various diseases, including autoimmune and inflammatory diseases, cardiometabolic diseases, infectious diseases and cancer. IgG is also an effector molecule directly involved in the inflammation processes included in the pathogenesis of many diseases. Numerous recently published studies support the idea that IgG N-glycosylation fine-tunes the immune response and plays a significant role in chronic inflammation. This makes it a promising novel biomarker of biological age, and a prognostic, diagnostic and treatment evaluation tool. Here we provide an overview of the current state of knowledge regarding the IgG glycosylation in health and disease, and its potential applications in pro-active prevention and monitoring of various health interventions.

IgG glycomic profiling identifies potential biomarkers for diagnosis of echinococcosis

Echinococcosis caused by larval stage of the genus Echinococcus, is a serious and potentially fatal parasitic zoonosis distributed globally. The two types of the disease in human are cystic echinococcosis (CE) and alveolar echinococcosis (AE). As the biological and encysting characteristics of the parasite, early diagnosis remains to address. In the present study, we demonstrate the value of Immunoglobulin G (IgG) glycome as a potential diagnostic biomarker for echinococcosis. Serum IgG glycome profiles were analyzed by ultra-performance liquid chromatography in a cohort comprised of 127 echinococcosis patients, of them 98 were diagnosed as CE and 29 as AE. IgG N-glycome analysis in pretreatment serum of echinococcosis patients presents 25 glycans and 64 derived traits. Compared with IgG glycans of healthy control group, neutral glycans, fucosylation and agalactosylated N-glycans increased while sialylation and galactosylation decreased in echinococcosis patients. Combined with a machine-learning-based approach, we built three biomarker combinations to distinguish CE, AE and healthy controls. Meanwhile, galactosylation, sialylation and A2BG2S1 in IgG glycan profiles were evidently associated with different types of CE (from CE1 to CE5). Our findings suggest that the alterations in IgG N-glycome may be of value in CE and AE diagnosis and follow-up CE disease progress. The role of IgG N-glycans as diagnostic biomarker remains to be verified in future study.

In-depth investigation of altered glycosylation in human haptoglobin associated cancer by mass spectrometry

Serum haptoglobin (Hp), a highly sialylated biomolecule with four N-glycosylation sites, is a positive acute-phase response glycoprotein that acts as an immunomodulator. Hp has gained considerable attention due to its potential as a signature molecule that exhibits aberrant glycosylation in inflammatory disorders and malignancies. Its glycosylation can be analyzed qualitatively and quantitatively by various methods using mass spectrometry. In this review, we have provided a brief overview of Hp structure and biological function and described mass spectrometry-based techniques for analyzing glycosylation ranging from macroheterogeneity to microheterogeneity of Hp in diseases and cancer. The sugars on haptoglobin can be a sweet bridge to link the potential of cancer-specific biomarkers to clinically relevant applications.

Three Major Gastrointestinal Cancers Could Be Distinguished through Subclass-Specific IgG Glycosylation

Esophageal cancer (EC), gastric cancer (GC), and colorectal cancer (CRC) are three major digestive tract tumors with higher morbidity and mortality due to significant molecular heterogeneity. Altered IgG glycosylation has been observed in inflammatory activities and disease progression, and the IgG glycome profile could be used for disease stratification. However, IgG N-glycome profiles in these three cancers have not been systematically investigated. Herein, subclass-specific IgG glycosylation in CRC, GC, and EC was comprehensively characterized by liquid chromatography-tandem mass spectrometry. It was found that IgG1 sialylation was decreased in all three cancers, and the alterations in CRC and EC may be subclass-specific. IgG4 mono-galactosylation was increased in all three cancers, which was a subclass-specific change in all of them. Additionally, glycopeptides of IgG1-H5N5, IgG2-H4N3F1, and IgG4-H4N4F1 could distinguish all three cancer groups from controls with fair diagnostic performance. Furthermore, bioinformatics verified the differential expression of relevant glycosyltransferase genes in cancer progression. Significantly, those three gastrointestinal cancers could be distinguished from each other using subclass-specific IgG glycans. These findings demonstrated the spatial and temporal diversity of IgG N-glycome among digestive cancers, increasing our understanding of the molecular mechanisms of EC, GC, and CRC pathogenesis.

Nomograms Based on Serum N-glycome for Diagnosis of Papillary Thyroid Microcarcinoma and Prediction of Lymph Node Metastasis

Non-invasive biomarkers for the diagnosis and prognosis of papillary thyroid microcarcinoma (PTMC) are still urgently needed. We aimed to characterize the N-glycome of PTMC, and establish nomograms for the diagnosis of PTMC and the prediction of lymph node metastasis (LNM). N-glycome of PTMC (LNM vs. non-LNM, capsular invasion (CI) vs. non-CI (NCI)) and matched healthy controls (HC) were quantitatively analyzed based on mass spectrometry. N-glycan traits associated with PTMC/LNM were used to create binomial logistic regression models and were visualized as nomograms. We found serum N-glycome differed between PTMC and HC in high-mannose, complexity, fucosylation, and bisection, of which, four N-glycan traits (TM, CA1, CA4, and A2Fa) were significantly associated with PTMC. The nomogram based on four traits achieved good performance for the identification of PTMC. Two N-glycan traits (CA4 and A2F0S0G) showed strong associations with LNM. The nomogram based on two traits showed relatively good performance in predicting LNM. We also found differences between CI and NCI in several N-glycan traits, which were not the same as that associated with LNM. This study reported serum N-glycosylation signatures of PTMC for the first time. Nomograms constructed from aberrant glycans could be useful tools for PTMC diagnosis and stratification.

Association of immunoglobulin G N-glycosylation with carotid atherosclerotic plaque phenotypes and actual clinical cardiovascular events: a study protocol for a longitudinal prospective cohort study

INTRODUCTION

Immune-inflammatory response plays a key role in the pathogenesis of atherosclerosis. IgG N-glycosylation is reported to be associated with the 10-year atherosclerotic cardiovascular disease risk score and subclinical atherosclerosis. However, the relationship of IgG glycosylation with actual clinical cardiovascular disease (CVD) events and plaque phenotypes has rarely been investigated. Therefore, this study aims to understand whether IgG glycosylation traits are correlated with actual clinical CVD events and plaque phenotypes.

METHODS AND ANALYSIS

Designed to verify the efficacy of IgG glycosylation as a risk for CVD events and screen potential biomarkers of CVD to prevent atherosclerosis occurrence, this longitudinal prospective cohort study will be conducted at the First Affiliated Hospital of Shantou University Medical College, China. In total, 2720 participants routinely examined by carotid ultrasound will be divided into different groups according to plaque phenotype characteristics. Ultra-performance liquid chromatography will be performed to separate and detect IgG N-glycans in serum collected at baseline and at the end of the first, second and third years. The primary outcome is the actual clinical CVD composite events, including non-fatal myocardial infarction, death due to coronary heart disease, and fatal or non-fatal stroke.

ETHICS AND DISSEMINATION

The Clinical Ethics Committee of the First Affiliated Hospital of Shantou University Medical College approved this study (number: B-2021-127). Findings of this study will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCTR2100048740.

Increased levels of acidic free-N-glycans, including multi-antennary and fucosylated structures, in the urine of cancer patients

We recently reported increased levels of urinary free-glycans in some cancer patients. Here, we focused on cancer related alterations in the levels of high molecular weight free-glycans. The rationale for this study was that branching, elongation, fucosylation and sialylation, which lead to increases in the molecular weight of glycans, are known to be up-regulated in cancer. Urine samples from patients with gastric cancer, pancreatic cancer, cholangiocarcinoma and colorectal cancer and normal controls were analyzed. The extracted free-glycans were fluorescently labeled with 2-aminopyridine and analyzed by multi-step liquid chromatography. Comparison of the glycan profiles revealed increased levels of glycans in some cancer patients. Structural analysis of the glycans was carried out by performing chromatography and mass spectrometry together with enzymatic or chemical treatments. To compare glycan levels between samples with high sensitivity and selectivity, simultaneous measurements by reversed-phase liquid chromatography-selected ion monitoring of mass spectrometry were also performed. As a result, three lactose-core glycans and 78 free-N-glycans (one phosphorylated oligomannose-type, four sialylated hybrid-type and 73 bi-, tri- and tetra-antennary complex-type structures) were identified. Among them, glycans with α1,3-fucosylation ((+/− sialyl) Lewis X), triply α2,6-sialylated tri-antennary structures and/or a (Man3)GlcNAc1-core displayed elevated levels in cancer patients. However, simple α2,3-sialylation and α1,6-core-fucosylation did not appear to contribute to the observed increase in the level of glycans. Interestingly, one tri-antennary free-N-glycan that showed remarkable elevation in some cancer patients contained a unique Glcβ1-4GlcNAc-core instead of the common GlcNAc2-core at the reducing end. This study provides further insights into free-glycans as potential tumor markers and their processing pathways in cancer.

IgG N-glycans

Glycosylation, one of the most common post-translational modifications in mammalian cells, impacts many biological processes such as cell adhesion, proliferation and differentiation. As the most abundant glycoprotein in human serum, immunoglobulin G (IgG) plays a vital role in immune response and protection. There is a growing body of evidence suggests that IgG structure and function are modulated by attached glycans, especially N-glycans, and aberrant glycosylation is associated with disease states. In this chapter, we review IgG glycan repertoire and function, strategies for profiling IgG N-glycome and recent studies. Mass spectrometry (MS) based techniques are the most powerful tools for profiling IgG glycome. IgG glycans can be divided into high-mannose, biantennary complex and hybrid types, modified with mannosylation, core-fucosylation, galactosylation, bisecting GlcNAcylation, or sialylation. Glycosylation of IgG affects antibody half-life and their affinity and avidity for antigens, regulates crystallizable fragment (Fc) structure and Fcγ receptor signaling, as well as antibody effector function. Because of their critical roles, IgG N-glycans appear to be promising biomarkers for various disease states. Specific IgG glycosylation can convert a pro-inflammatory response to an anti-inflammatory activity. Accordingly, IgG glycoengineering provides a powerful approach to potentially develop effective drugs and treat disease. Based on the understanding of the functional role of IgG glycans, the development of vaccines with enhanced capacity and long-term protection are possible in the near future.

Advances in the discovery of novel biomarkers for cancer: spotlight on protein N-glycosylation

Progress on glycosylation and tumor markers has not been extensively reported. Glycosylation plays an important part in post-translational modification. Previous research on glycosylation-modified biomarkers has lagged behind due to insufficient understanding of glycosylation-related regulations. However, some new methods and ideas illustrated in recent research may provide new inspirations in the field. This article aims to review current advances in revealing relationship between tumors and abnormal N-glycosylation and discuss leading-edge applications of N-glycosylation in developing novel tumor biomarkers.

2-Dimensional ultra-high performance liquid chromatography and DMT-MM derivatization paired with tandem mass spectrometry for comprehensive serum N-glycome characterization

Glycosylation is a prominent co- and post-translational modification which contributes to a variety of important biological functions. Protein glycosylation characteristics, particularly N-glycosylation, are influenced by changes in one's pathological state, such as through the presence of disease, and as such, there is great interest in N-glycans as potential disease biomarkers. Human serum is an attractive source for N-glycan based biomarker studies as circulatory proteins are representative of one's physiology, with many serum proteins containing N-glycosylation. The difficulty in comprehensively characterizing the serum N-glycome arises from the absence of a biosynthetic template resulting in great structural heterogeneity and complexity. To help overcome these challenges we developed a 2-dimensional liquid chromatography platform which utilizes offline weak anion exchange (WAX) chromatography in the first dimension and hydrophilic interaction liquid chromatography (HILIC) in the second dimension to separate N-glycans by charge, corresponding to degree of sialylation, and size, respectively. Performing these separations offline enables subsequent derivatization with 4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) for sialic acid linkage determination and the identification of sialic acid linkage isomers. Subsequent tandem mass spectrometry analysis revealed the identification of 212 complete and partial N-glycan structures including low abundant N-glycans containing acetyl and sulphate modifications. The identifications obtained through this platform were then applied to N-glycans released from a set of stage 3 gastric cancer serum samples obtained from patients before (pre-op) and after (post-op) tumour resection to investigate how the serum N-glycome can facilitate differentiation between the two pathological states.

Diagnostic Potential of Plasma IgG N-glycans in Discriminating Thyroid Cancer from Benign Thyroid Nodules and Healthy Controls

Background

Novel biomarkers are urgently needed to distinguish between benign and malignant thyroid nodules and detect thyroid cancer in the early stage. The associations between serum IgG N-glycosylation and thyroid cancer risk have been revealed. We aimed to explore the potential of IgG N-glycan traits as biomarkers in the differential diagnosis of thyroid cancer.

Methods

Plasma IgG N-glycome analysis was applied to a discovery cohort followed by independent validation. IgG N-glycan profiles were obtained using a robust quantitative strategy based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. IgG N-glycans were relatively quantified, and classification performance was evaluated based on directly detected and derived glycan traits.

Results

Four directly detected glycans were significantly changed in thyroid cancer patients compared to that in non-cancer controls. Derived glycan traits and a classification glycol-panel were generated based on the directly detected glycan traits. In the discovery cohort, derived trait BN (bisecting type neutral N-glycans) and the glyco-panel showed potential in distinguishing between thyroid cancer and non-cancer controls with AUCs of 0.920 and 0.917, respectively. The diagnostic potential was further validated. Derived trait BN and the glycol-panel displayed “accurate” performance (AUC>0.8) in discriminating thyroid cancer from benign thyroid nodules and healthy controls in the validation cohort. Meanwhile, derived trait BN and the glycol-panel also showed diagnostic potential in detecting early-stage thyroid cancer.

Conclusions

IgG N-glycome analysis revealed N-glycomic differences that allow classification of thyroid cancer from non-cancer controls. Our results suggested that derived trait BN and the classification glyco-panel rather than single N-glycans may serve as candidate biomarkers for further validation.

Detection of Aberrant Glycosylation of Serum Haptoglobin for Gastric Cancer Diagnosis Using a Middle-Up-Down Glycoproteome Platform

Gastric cancer is a frequently occurring cancer and is the leading cause of cancer-related deaths. Recent studies have shown that aberrant glycosylation of serum haptoglobin is closely related to gastric cancer and has enormous potential for use in diagnosis. However, there is no platform with high reliability and high reproducibility to comprehensively analyze haptoglobin glycosylation covering microheterogeneity to macroheterogeneity for clinical applications. In this study, we developed a middle-up-down glycoproteome platform for fast and accurate monitoring of haptoglobin glycosylation. This platform utilizes an online purification of LC for sample desalting, and an in silico haptoglobin glycopeptide library constructed by combining peptides and N-glycans to readily identify glycopeptides. In addition, site-specific glycosylation with glycan heterogeneity can be obtained through only a single MS analysis. Haptoglobin glycosylation in clinical samples consisting of healthy controls (n = 47) and gastric cancer patients (n = 43) was extensively investigated using three groups of tryptic glycopeptides: GP1 (including Asn184), GP2 (including Asn207 and Asn211), and GP3 (including Asn241). A total of 23 individual glycopeptides were determined as potential biomarkers (p < 0.00001). In addition, to improve diagnostic efficacy, we derived representative group biomarkers with high AUC values (0.929 to 0.977) through logistic regression analysis for each GP group. It has been found that glycosylation of haptoglobin is highly associated with gastric cancer, especially the glycosite Asn241. Our assay not only allows to quickly and easily obtain information on glycosylation heterogeneity of a target glycoprotein but also makes it an efficient tool for biomarker discovery and clinical diagnosis.

Glycosylation of Anti-Thyroglobulin IgG1 and IgG4 Subclasses in Thyroid Diseases

OBJECTIVE

Thyroglobulin antibodies (TgAb), principally comprising immunoglobulin G (IgG), are frequently found in healthy individuals. Previously, we showed that the glycosylation levels of TgAb IgG differed across various thyroid diseases, suggesting an important role of glycosylation on antibodies in the pathogenesis of thyroid diseases. Since IgG1 and IgG4 are the primary TgAb IgG subclasses, this study aimed to investigate the glycosylation of TgAb IgG1 and IgG4 subclasses in thyroid diseases.

METHODS

TgAb IgG was purified by affinity chromatography from the serum of patients with Hashimoto's thyroiditis (HT) (n = 16), Graves' disease (GD) (n = 8), papillary thyroid carcinoma (PTC) (n = 6), and PTC with histological lymphocytic thyroiditis (PTC-T) (n = 9) as well as healthy donors (n = 10). TgAb IgG1 and IgG4 concentrations were determined by enzyme-linked immunosorbent assay, and a lectin microassay was used to assess TgAb IgG1 and IgG4 glycosylation.

RESULTS

Significantly elevated mannose, sialic acid, and galactose levels on TgAb IgG1 were found in HT and PTC patients compared to GD patients and healthy controls (all p < 0.05). The mannose, sialic acid, and core fucose levels on TgAb IgG1 in PTC-T patients were higher than in healthy controls (all p < 0.05). Additionally, TgAb IgG1 from PTC-T patients exhibited lower sialylation than that from patients with PTC and higher fucosylation than that from patients with HT (both p < 0.05). However, TgAb IgG4 glycosylation did not differ among the five groups (p < 0.05).

CONCLUSION

Our study describes different distributions of TgAb IgG1 glycosylation in various thyroid diseases. The aberrantly increased glycosylation levels of TgAb IgG1 observed in HT, PTC, and PTC-T might be indicative of immune disorders and participate in the pathogenesis of these diseases.

Causal link between immunoglobulin G glycosylation and cancer: A potential glycobiomarker for early tumor detection

Changes in immunoglobulin G (IgG) glycan structures are currently believed to closely related to the emergence of cancer. In this review, we summarize the current body of evidence suggesting that differences in serum IgG glycosylation patterns correspond to changes in multiple types of cancer. Modifications include IgG terminal N-link galactosylation, IgG core fucosylation, IgG terminal sialylation, and IgG terminal bisecting N-acetylglucosamine. IgG N-glycomic alterations represent promising novel biomarkers for non-invasive-cancer diagnosis, prognosis, and progression monitoring; they are characterized by high sensitivity and specificity, compensating for previously identified glycobiomarkers.

The Repertoire of Glycan Alterations and Glycoproteins in Human Cancers

Cancer as the leading cause of death worldwide has many issues that still need to be addressed. Since the alterations on the glycan compositions or/and structures (i.e., glycosylation, sialylation, and fucosylation) are common features of tumorigenesis, glycomics becomes an emerging field examining the structure and function of glycans. In the past, cancer studies heavily relied on genomics and transcriptomics with relatively little exploration of the glycan alterations and glycoprotein biomarkers among individuals and populations. Since glycosylation of proteins increases their structural complexity by several orders of magnitude, glycome studies resulted in highly dynamic biomarkers that can be evaluated for cancer diagnosis, prognosis, and therapy. Glycome not only integrates our genetic background with past and present environmental factors but also offers a promise of more efficient patient stratification compared with genetic variations. Therefore, studying glycans holds great potential for better diagnostic markers as well as developing more efficient treatment strategies in human cancers. While recent developments in glycomics and associated technologies now offer new possibilities to achieve a high-throughput profiling of glycan diversity, we aim to give an overview of the current status of glycan research and the potential applications of the glycans in the scope of the personalized medicine strategies for cancer.

Immunoglobulin G Glycosylation in Diseases

Changes in immunoglobulin G (IgG) glycosylation pattern have been observed in a vast array of auto- and alloimmune, infectious, cardiometabolic, malignant, and other diseases. This chapter contains an updated catalog of over 140 studies within which IgG glycosylation analysis was performed in a disease setting. Since the composition of IgG glycans is known to modulate its effector functions, it is suggested that a changed IgG glycosylation pattern in patients might be involved in disease development and progression, representing a predisposition and/or a functional effector in disease pathology. In contrast to the glycopattern of bulk serum IgG, which likely relates to the systemic inflammatory background, the glycosylation profile of antigen-specific IgG probably plays a direct role in disease pathology in several infectious and allo- and autoimmune antibody-dependent diseases. Depending on the specifics of any given disease, IgG glycosylation read-out might therefore in the future be developed into a useful clinical biomarker or a supplementary to currently used biomarkers.

Immunoglobulin G Glycosylation Changes in Aging and Other Inflammatory Conditions

Among the multiple roles played by protein glycosylation, the fine regulation of biological interactions is one of the most important. The asparagine 297 (Asn₂₉₇) of IgG heavy chains is decorated by a diantennary glycan bearing a number of galactose and sialic acid residues on the branches ranging from 0 to 2. In addition, the structure can present core-linked fucose and/or a bisecting GlcNAc. In many inflammatory and autoimmune conditions, as well as in metabolic, cardiovascular, infectious, and neoplastic diseases, the IgG Asn₂₉₇-linked glycan becomes less sialylated and less galactosylated, leading to increased expression of glycans terminating with GlcNAc. These conditions alter also the presence of core-fucose and bisecting GlcNAc. Importantly, similar glycomic alterations are observed in aging. The common condition, shared by the above-mentioned pathological conditions and aging, is a low-grade, chronic, asymptomatic inflammatory state which, in the case of aging, is known as inflammaging. Glycomic alterations associated with inflammatory diseases often precede disease onset and follow remission. The aberrantly glycosylated IgG glycans associated with inflammation and aging can sustain inflammation through different mechanisms, fueling a vicious loop. These include complement activation, Fcγ receptor binding, binding to lectin receptors on antigen-presenting cells, and autoantibody reactivity. The complex molecular bases of the glycomic changes associated with inflammation and aging are still poorly understood.

Glycosylation and Aging

Human lifespan has increased significantly in the last 200 years, emphasizing our need to age healthily. Insights into molecular mechanisms of aging might allow us to slow down its rate or even revert it. Similar to aging, glycosylation is regulated by an intricate interplay of genetic and environmental factors. The dynamics of glycopattern variation during aging has been mostly explored for plasma/serum and immunoglobulin G (IgG) N-glycome, as we describe thoroughly in this chapter. In addition, we discuss the potential functional role of agalactosylated IgG glycans in aging, through modulation of inflammation level, as proposed by the concept of inflammaging. We also comment on the potential to use the plasma/serum and IgG N-glycome as a biomarker of healthy aging and on the interventions that modulate the IgG glycopattern. Finally, we discuss the current knowledge about animal models for human plasma/serum and IgG glycosylation and mention other, less explored, instances of glycopattern changes during organismal aging and cellular senescence.

A nomogram based on glycomic biomarkers in serum and clinicopathological characteristics for evaluating the risk of peritoneal metastasis in gastric cancer

Background

Peritoneal metastasis (PM) in gastric cancer (GC) remains an untreatable disease, and is difficult to diagnose preoperatively. Here, we aim to establish a novel prediction model.

Methods

The clinicopathologic characteristics of a cohort that included 86 non-metastatic GC patients and 43 PMGC patients from Zhongshan Hospital were retrospectively analysed to identify PM associated variables. Additionally, mass spectrometry and glycomic analysis were applied in the same cohort to find glycomic biomarkers in serum for the diagnosis of PM. A nomogram was established based on the associations between potential risk variables and PM.

Results

Overexpression of 4 N-glycans (H6N5L1E1: m/z 2620.93; H5N5F1E2: m/z 2650.98; H6N5E2, m/z 2666.96; H6N5L1E2, m/z 2940.08); weight loss ≥ 5 kg; tumour size ≥ 3 cm; signet ring cell or mucinous adenocarcinoma histology type; poor differentiation; diffuse or mixed Lauren classification; increased CA19-9, CA125, and CA724 levels; decreased lymphocyte count, haemoglobin, albumin, and pre-albumin levels were identified to be associated with PM. A nomogram that integrated with five independent risk factors (weight loss ≥ 5 kg, CA19-9 ≥ 37 U/mL, CA125 ≥ 35 U/mL, lymphocyte count < 2.0 * 10 ~ 9/L, and H5N5F1E2 expression ≥ 0.0017) achieved a good performance for diagnosis (AUC: 0.892, 95% CI 0.829–0.954). When 160 was set as the cut-off threshold value, the proposed nomogram represented a perfectly discriminating power for both sensitivity (0.97) and specificity (0.88).

Conclusions

The nomogram achieved an individualized assessment of the risk of PM in GC patients; thus, the nomogram could be used to assist clinical decision-making before surgery.

Sialylated Immunoglobulins for the Treatment of Immuno-Inflammatory Diseases

Immunoglobulins are the potent effector proteins of the humoral immune response. In the course of evolution, immunoglobulins have formed extremely diverse types of molecular structures with antigen-recognizing, antigen-binding, and effector functions embedded in a single molecule. Polysaccharide moiety of immunoglobulins plays the essential role in immunoglobulin functioning. There is growing evidence that the carbohydrate composition of immunoglobulin-linked glycans, and especially their terminal sialic acid residues, provide a key effect on the effector functions of immunoglobulins. Possibly, sialylation of Fc glycan is a common mechanism of IgG anti-inflammatory action in vivo. Thus, the post-translational modification (glycosylation) of immunoglobulins opens up significant possibilities in the diagnosis of both immunological and inflammatory disorders and in their therapies. This review is focused on the analysis of glycosylation of immunoglobulins, which can be a promising addition to improve existing strategies for the diagnosis and treatment of various immuno-inflammatory diseases.

Haptoglobin: From hemoglobin scavenging to human health

Haptoglobin (Hp) belongs to the family of acute-phase plasma proteins and represents the most important plasma detoxifier of hemoglobin (Hb). The basic Hp molecule is a tetrameric protein built by two α/β dimers. Each Hp α/β dimer is encoded by a single gene and is synthesized as a single polypeptide. Following post-translational protease-dependent cleavage of the Hp polypeptide, the α and β chains are linked by disulfide bridge(s) to generate the mature Hp protein. As human Hp gene is characterized by two common Hp1 and Hp2 alleles, three major genotypes can result (i.e., Hp1-1, Hp2-1, and Hp2-2). Hp regulates Hb clearance from circulation by the macrophage-specific receptor CD163, thus preventing Hb-mediated severe consequences for health. Indeed, the antioxidant and Hb binding properties of Hp as well as its ability to stimulate cells of the monocyte/macrophage lineage and to modulate the helper T-cell type 1 and type 2 balance significantly associate with a variety of pathogenic disorders (e.g., infectious diseases, diabetes, cardiovascular diseases, and cancer). Alternative functions of the variants Hp1 and Hp2 have been reported, particularly in the susceptibility and protection against infectious (e.g., pulmonary tuberculosis, HIV, and malaria) and non-infectious (e.g., diabetes, cardiovascular diseases and obesity) diseases. Both high and low levels of Hp are indicative of clinical conditions: Hp plasma levels increase during infections, inflammation, and various malignant diseases, and decrease during malnutrition, hemolysis, hepatic disease, allergic reactions, and seizure disorders. Of note, the Hp:Hb complexes display heme-based reactivity; in fact, they bind several ferrous and ferric ligands, including O₂, CO, and NO, and display (pseudo-)enzymatic properties (e.g., NO and peroxynitrite detoxification). Here, genetic, biochemical, biomedical, and biotechnological aspects of Hp are reviewed.

Multi-Domain Networks Association for Biological Data Using Block Signed Graph Clustering

Multi-domain biological network association and clustering have attracted a lot of attention in biological data integration and understanding, which can provide a more global and accurate understanding of biological phenomenon. In many problems, different domains may have different cluster structures. Due to rapid growth of data collection from different sources, some domains may be strongly or weakly associated with the other domains. A key challenge is how to determine the degree of association among different domains, and to achieve accurate clustering results by data integration. In this paper, we propose an unsupervised learning approach for multi-domain network association by using block signed graph clustering. In particular, with consistency weights calculation, the proposed algorithm automatically identify domains relevant to each other strongly (or weakly) by assigning them larger (or smaller) weights. This approach not only significantly improve clustering accuracy but also understand multi-domain networks association. In each iteration of the proposed algorithm, we update consistency weights based on cluster structure of each domain, and then make use of different sets of eigenvectors to obtain different cluster structures in each domain. Experimental results on both synthetic data sets and real data sets (including neuron activity data and gene expression data) empirically demonstrate the effectiveness of the proposed algorithm in clustering performance and in domain association capability.

Abnormal Galactosylated-Glycans recognized by Bandeiraea Simplicifolia Lectin I in saliva of patients with breast Cancer

Currently, the definitive diagnosis in breast cancer requires biopsy and histopathology, such the most effective markers are tissue-based. However, the advantages of saliva in collection and storage make it possible for assessing human pathology and contributing to the development of cancer-related biomarkers for clinical application. The present study validated alteration of salivary protein glycopatterns recognized by Bandeiraea simplicifolia lectin I (BS-I) in the saliva of patients with breast diseases using saliva microarrays, and the N/O-glycan profiles of their salivary glycoproteins isolated by the BS-I-magnetic particle conjugates from 259 female subjects (66 healthy volunteers (HV), 65 benign breast cyst or tumor patients (BB), 66 patients with breast cancer in stage I (BC-I) and 62 patients with breast cancer in stage II (BC-II)) were analyzed by MALDI-TOF/TOF-MS. The results showed that the expression level of galactosylated glycans recognized by BS-I was significantly increased in patients with breast cancer compared with HV (p < 0.05). Totally, there were 11/10, 10/19, 7/24 and 7/9 galactosylated N-/O-linked glycans were identified and annotated from the pooled salivary samples of HV, BB, BC-I and BC-II, respectively. One galactosylated N-glycan peak (m/z 2773.977), and 4 galactosylated O-glycan peaks (m/z 868.295, 882.243, 884.270 and 1030.348) were found only in BC-I. These findings could provide pivotal information on galactosylated N/O-linked glycans related to breast cancer, and promote the study of biomarkers for early-stage breast cancer based on precise alterations of galactosylated N/O-glycans in saliva.

Glycomic Signatures of Plasma IgG Improve Preoperative Prediction of the Invasiveness of Small Lung Nodules

Preoperative assessment of tumor invasiveness is essential to avoid overtreatment for patients with small-sized ground-glass nodules (GGNs) of 10 mm or less in diameter. However, it is difficult to determine the pathological state by computed tomography (CT) examination alone. Aberrant glycans has emerged as a tool to identify novel potential disease biomarkers. In this study, we used a lectin microarray-based strategy to investigate whether glycosylation changes in plasma immunoglobulin G (IgG) provide additional information about the invasiveness of small GGNs before surgery. Two independent cohorts (discovery set, n = 92; test set, n = 210) of GGN patients were used. Five of 45 lectins (Sambucus nigra agglutinin, SNA; Datura stramonium agglutinin, DSA; Galanthus nivalis agglutinin, GNA; Euonymus europaeus lectin, EEL; and Vicia villosa agglutinin, VVA) were identified as independent factors associated with pathological invasiveness of small GGNs (p < 0.01). Receiver-operating characteristic (ROC) curve analysis indicated the combination of these five lectins could significantly improve the accuracy of CT in diagnosing invasive GGNs, with an area under the curve (AUC) of 0.792 (p < 0.001), a sensitivity of 74.6%, and specificity of 74.4%, which was superior to current clinical biomarkers. These results suggest that the multilectin assay based on plasma IgG glycosylation may be a useful in vitro complementary test to enhance preoperative determination of the invasiveness of GGNs and guide surgeons to select proper clinical management to avoid overtreatment.

Disease-Specific IgG Fc Glycosylation Ratios as Personalized Biomarkers to Differentiate Non-Small Cell Lung Cancer from Benign Lung Diseases

PURPOSE

The authors aimed to separate Fc N-glycopeptides of disease-specific immunoglobulin G (DSIgG) as personalized biomarkers to distinguish non-small cell lung cancer (NSCLC) from benign lung diseases (BLDs).

EXPERIMENTAL DESIGN

DSIgG from 509 BLDs patients and 477 NSCLC patients was isolated using native polyacrylamide gel electrophoresis and then the Fc glycosylation was determined using mass spectrometry.

RESULTS

For the patients below 60 years of age, a combination of the glycopeptides ratios with one fucose residue difference of DSIgG1 and DSIgG2 can differentiate NSCLC from BLDs, with area under curve (AUC) values of >0.76, sensitivities of >87%, and specificities of >61%. For the patients above 60 years of age, a combination of the glycopeptides ratios with one monosaccharide residue of DSIgG2 can differentiate NSCLC from BLDs, with AUC values of >0.78, sensitivities of >91%, and specificities of >54%. For the same participants, the commonly used clinical biomarkers have AUC values of 0.5-0.621, sensitivities of 15.8-32.9%, and specificities of 75.7-90.5%.

CONCLUSIONS

These findings indicate that these DSIgG Fc glycoforms are potential personalized biomarkers to differentiate NSCLC from BLDs.

Early Stage Glycosylation Biomarkers in Alzheimer's Disease

Alzheimer's disease (AD) is of great cause for concern in our ageing population, which currently lacks diagnostic tools to permit accurate and timely diagnosis for affected individuals. The development of such tools could enable therapeutic interventions earlier in the disease course and thus potentially reducing the debilitating effects of AD. Glycosylation is a common, and important, post translational modification of proteins implicated in a host of disease states resulting in a complex array of glycans being incorporated into biomolecules. Recent investigations of glycan profiles, in a wide range of conditions, has been made possible due to technological advances in the field enabling accurate glycoanalyses. Amyloid beta (Aβ) peptides, tau protein, and other important proteins involved in AD pathogenesis, have altered glycosylation profiles. Crucially, these abnormalities present early in the disease state, are present in the peripheral blood, and help to distinguish AD from other dementias. This review describes the aberrant glycome in AD, focusing on proteins implicated in development and progression, and elucidates the potential of glycome aberrations as early stage biomarkers of AD.

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.

Immunoglobulins G from patients with ANCA-associated vasculitis are atypically glycosylated in both the Fc and Fab regions and the relation to disease activity

Background

Anti-neutrophil cytoplasmic autoantibodies (ANCA) directed against myeloperoxidase (MPO) and proteinase 3 (PR3) are pathogenic in ANCA-associated vasculitis (AAV). The respective role of IgG Fc and Fab glycosylation in mediating ANCA pathogenicity is incompletely understood. Herein we investigate in detail the changes in Fc and Fab glycosylation in MPO-ANCA and Pr3-ANCA and examine the association of glycosylation aberrancies with disease activity.

Methodology

Total IgG was isolated from serum or plasma of a cohort of 30 patients with AAV (14 MPO-ANCA; 16 PR3-ANCA), and 19 healthy control subjects. Anti-MPO specific IgG was affinity-purified from plasma of an additional cohort of 18 MPO-ANCA patients undergoing plasmapheresis. We used lectin binding assays, liquid chromatography, and mass spectrometry-based methods to analyze Fc and Fab glycosylation, the degree of sialylation of Fc and Fab fragments and to determine the exact localization of N-glycans on Fc and Fab fragments.

Principal findings

IgG₁ Fc glycosylation of total IgG was significantly reduced in patients with active AAV compared to controls. Clinical remission was associated with complete glycan normalization for PR3-ANCA patients but not for MPO-ANCA patients. Fc-glycosylation of anti-MPO specific IgG was similar to total IgG purified from plasma. A major fraction of anti-MPO specific IgG harbor extensive glycosylation within the variable domain on the Fab portion.

Conclusions/Significance

Significant differences exist between MPO and PR3-ANCA regarding the changes in amounts and types of glycans on Fc fragment and the association with disease activity. These differences may contribute to significant clinical difference in the disease course observed between the two diseases.

Identification of N- and O-linked glycans recognized by AAL in saliva of patients with atrophic gastritis and gastric cancer

BACKGROUND AND AIM

Gastric cancer (GC) is a common and fatal malignancy with a worldwide occurrence. There still lacks effective biomarkers for precisely evaluating GC. Saliva is a biological fluid with enormous diagnostic potentials which emerged many advantages. We aimed to discover the novel biomarkers for accurately distinguishing early GC based on saliva glycopatterns.

METHODS

We used Aleuria Aurantia Lectin (AAL)-magnetic particle conjugates to isolate fucosylated glycoproteins in the pooled saliva of healthy volunteers (HV, n= 51) and patients with atrophic gastritis (AG, n= 51) or GC (n= 51), following to release the N- and O-linked glycans from the isolated proteins with PNGase F and NaClO, and further identified the released glycans by MALDI-TOF/TOF-MS, respectively.

RESULTS

A total of 9/9, 8/11, and 9/9 fucosylated N-/O-linked glycans were annotated in the isolated salivary proteins from HV, AG, and GC, respectively. Among these, six fucosylated N-linked glycansand four O-linked glycans exhibited significantly increased expression levels in GC, while five fucosylated N-linked glycans and ten fucosylated O-linked glycans exhibited significantly decreased expression levels in GC. The proportion of fucosylated N-linked glycans was decreased in GC (41.66%) compared with AG (43.63%) and HV (52.57%), as well as the fucosylated O-linked glycans was apparently decreased in GC (19.58%) compared with AG (25.43%) and HV (55.54%).

CONCLUSIONS

This study could provide pivotal information to distinguish among HV, AG, and GC, and facilitate the discovery of biomarkers for GC diagnosis based on precise alterations of N- and O-linked glycans in saliva.

Modification of α2,6-sialylation mediates the invasiveness and tumorigenicity of non-small cell lung cancer cells in vitro and in vivo via Notch1/Hes1/MMPs pathway

The alterations of sialylation on cell surface N-glycans due to overexpression of different sialyltransferases play a vital role in tumorigenesis and tumor progression. The β-galactoside α2-6-sialyltransferase 1 (ST6Gal-I) has been reported to be highly expressed in several cancers, including breast cancer, hepatocellular cancer and colon carcinoma. However, the roles and underlying mechanisms of ST6Gal-I in non-small cell lung cancer (NSCLC) still need to be elucidated. In this study, we determined that mRNA levels of ST3GAL1, ST6GALNAC3 and ST8SIA6 were remarkably reduced in lung cancer tissues and cells, whereas ST6GAL1 level significantly increased. The mRNA, protein and glycan levels of ST6Gal-I were higher in lung cancer tissues and cells. Moreover, down-regulation of ST6Gal-I decreased protein levels of Jagged1, DLL-1, Notch1, Hes1, Hey1, matrix-metalloproteinases (MMPs) and VEGF, and suppressed proliferation, migration and invasion capabilities of A549 and H1299 cells in vitro. In vivo, ST6Gal-I silencing suppressed tumorigenicity of NSCLC cells in athymic nude mice via the Notch1/Hes1/MMPs pathway. In addition, overexpression of Notch1 rescued the reduced growth and metastasis of A549 and H1299 cells resulted by ST6Gal-I silencing. Modification of α2,6-sialylation positively associates with lung cancer progression, thereby indicating that ST6Gal-I may mediate the invasiveness and tumorigenicity of NSCLC cells via the Notch1/Hes1/MMPs pathway both in vitro and in vivo. Thus, our results provide a novel therapeutic approach for blocking metastasis in lung cancer patients.

The Interaction of the Gut Microbiota with the Mucus Barrier in Health and Disease in Human

Glycoproteins are major players in the mucus protective barrier in the gastrointestinal and other mucosal surfaces. In particular the mucus glycoproteins, or mucins, are responsible for the protective gel barrier. They are characterized by their high carbohydrate content, present in their variable number, tandem repeat domains. Throughout evolution the mucins have been maintained as integral components of the mucosal barrier, emphasizing their essential biological status. The glycosylation of the mucins is achieved through a series of biosynthetic pathways processes, which generate the wide range of glycans found in these molecules. Thus mucins are decorated with molecules having information in the form of a glycocode. The enteric microbiota interacts with the mucosal mucus barrier in a variety of ways in order to fulfill its many normal processes. How bacteria read the glycocode and link to normal and pathological processes is outlined in the review.

Plasma N-glycans in colorectal cancer risk

Aberrant glycosylation has been associated with a number of diseases including cancer. Our aim was to elucidate changes in whole plasma N-glycosylation between colorectal cancer (CRC) cases and controls in one of the largest cohorts of its kind. A set of 633 CRC patients and 478 age and gender matched controls was analysed. Additionally, patients were stratified into four CRC stages. Moreover, N-glycan analysis was carried out in plasma of 40 patients collected prior to the initial diagnosis of CRC. Statistically significant differences were observed in the plasma N-glycome at all stages of CRC, this included a highly significant decrease in relation to the core fucosylated bi-antennary glycans F(6)A2G2 and F(6)A2G2S(6)1 (P < 0.0009). Stage 1 showed a unique biomarker signature compared to stages 2, 3 and 4. There were indications that at risk groups could be identified from the glycome (retrospective AUC = 0.77 and prospective AUC = 0.65). N-glycome biomarkers related to the pathogenic progress of the disease would be a considerable asset in a clinical setting and it could enable novel therapeutics to be developed to target the disease in patients at risk of progression.

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.

Alteration of Serum IgG Galactosylation as a Potential Biomarker for Diagnosis of Neuroblastoma

Background: Neuroblastoma (NB) is the most frequent pediatric malignant neoplasm that originates from embryonic neural crest cells. Urinary catecholamines in 24-h urine are most commonly analyzed for the diagnosis of neuroblastoma at good sensitivity; however, it is challenging to collect 24-h urine samples in a pediatric population. Therefore, development of more rapid, non-invasive and cost-effective tools for the diagnosis of NB remains needed. Serum immunoglobulin G (IgG) galactosylation have been found highly associated with adult cancers in our previous study.

Methods: To explore the potential use of serum IgG galactosylation in aiding diagnosis of neuroblastoma, serum IgG galactosylation profiles of 26 neuroblastoma cases and 30 age-matched non-malignant controls were analyzed by MALDI MS. The alteration of IgG galactosylation in neuroblastoma patients was measured by a Gal-ratio formula: G0/(G1+G2×2), calculating the relative intensities of agalactosylated N-glycan (G0) vs mono-galactosyl N-glycan (G1) and digalactosyl N-glycan (G2).

Results: The results showed that IgG Gal-ratios were significantly higher in neuroblastoma cases compared with non-malignant controls (p=5.0×10^-4). And the Gal-ratio data generated sensitivity and specificity of 84.62% and 60.00%, combined with an AUC (area under the curve) of 0.80.

Conclusions: The analysis of serum IgG galactosylation distribution may play a suggestive role for neuroblastoma diagnosis, or serve as a potential biomarker for NB diagnosis.

Evidence of Altered Glycosylation of Serum Proteins Prior to Pancreatic Cancer Diagnosis

Biomarkers for the early detection of pancreatic cancer are urgently needed. The aim of this pilot study was to evaluate changes in serum N-glycoproteins and their glycosylation status prior to clinical presentation of pancreatic cancer that may be potential biomarkers. Prediagnosis serum samples pooled according to five time-to-diagnosis groups and a non-cancer control pool were digested with trypsin, labelled with mass tags, and subjected to titanium dioxide capture, deglycosylation, and 2D-LC-MS/MS profiling. Unbound peptides were profiled in parallel. Across the sample groups, 703 proteins were quantified and 426 putative sites of N-glycosylation were identified with evidence of several novel sites. Altered proteins with biomarker potential were predominantly abundant inflammatory response, coagulation, and immune-related proteins. Whilst glycopeptide profiles largely paralleled those of their parent proteins, there was evidence of altered N-glycosylation site occupancy or sialic acid content prior to diagnosis for some proteins, most notably of immunoglobulin gamma chains. α-1-Antitrypsin was tested as a biomarker, but found not to complement carbohydrate antigen 19-9 (CA19-9) in early detection of cancer. In conclusion, we provide preliminary evidence of altered glycosylation of several serum proteins prior to pancreatic cancer diagnosis, warranting further investigation of these proteins as early biomarkers. These changes may be largely driven by inflammatory processes that occur in response to tumour formation and progression.

Clusterin inhibition mediates sensitivity to chemotherapy and radiotherapy in human cancer

Since its discovery in 1983, the protein clusterin (CLU) has been isolated from almost all human tissues and fluids and linked to the development of different physiopathological processes, including carcinogenesis and tumor progression. During the last few years, several studies have shown the cytoprotective role of secretory CLU in tumor cells, inhibiting their apoptosis and enhancing their resistance to conventional treatments including hormone depletion, chemotherapy, and radiotherapy. In an effort to determine the therapeutic potential that the inhibition of this protein could have on the development of new strategies for cancer treatment, numerous studies have been carried out in this field, with results, in most cases, satisfactory but sometimes contradictory. In this document, we summarize for the first time the current knowledge of the effects that CLU inhibition has on sensitizing tumor cells to conventional cancer treatments and discuss its importance in the development of new strategies against cancer.

Discovery of gastric cancer specific biomarkers by the application of serum proteomics

Current diagnostic markers for gastric cancer are not sufficiently specific or sensitive for use in clinical practice. The aims of this study are to compare the proteomes of serum samples from patients with gastric cancers and normal controls, and to develop useful tumor markers of gastric cancer by quantitative proteomic analysis. We identified a total of 388 proteins with a ≤1% FDR and with at least two unique peptides from the sera of each group. Among them, 215, 251, and 260 proteins were identified in serum samples of patients in an advanced cancer group, early cancer group, and normal control group, respectively. We selected differentially expressed proteins in cancer patients compared with those of normal controls via semiquantitative analyses comparing the spectral counts of identified proteins. These differentially expressed proteins were successfully verified using an MS-based quantitative assay, multiple reactions monitoring analysis. Four proteins (vitronectin, clusterin isoform 1, thrombospondin 1, and tyrosine-protein kinase SRMS) were shown to have significant changes between the cancer groups and the normal control group. These four serum proteins were able to discriminate gastric cancer patients from normal controls with sufficient specificity and selectivity.

Alterations in expressed prostate secretion-urine PSA N-glycosylation discriminate prostate cancer from benign prostate hyperplasia

The prostate specific antigen (PSA) test is widely used for early diagnosis of prostate cancer (PCa). However, its limited sensitivity has led to over-diagnosis and over-treatment of PCa. Glycosylation alteration is a common phenomenon in cancer development. Different PSA glycan subforms have been proposed as diagnostic markers to better differentiate PCa from benign prostate hyperplasia (BPH). In this study, we purified PSA from expressed prostate secretions (EPS)-urine samples from 32 BPH and 30 PCa patients and provided detailed PSA glycan profiles in Chinese population. We found that most of the PSA glycans from EPS-urine were complex type biantennary glycans. We observed two major patterns in PSA glycan profiles. Overall there was no distinct separation of PSA glycan profiles between BPH and PCa patients. However, we detected a significant increase of glycan FA2 and FM5A2G2S1 in PCa when compared with BPH patients. Furthermore, we observed that the composition of FA2 glycan increased significantly in advanced PCa with Gleason score ≥8, which potentially could be translated to clinic as a marker for aggressive PCa.

Direct analysis of aberrant glycosylation on haptoglobin in patients with gastric cancer

Based on our previous studies, differential analysis of N-glycan expression bound on serum haptoglobin reveals the quantitative variation on gastric cancer patients. In this prospective case-control study, we explore the clinically relevant glycan markers for gastric cancer diagnosis. Serum samples were collected from patients with gastric cancer (n = 44) and healthy control (n = 44). N-glycans alteration was monitored by intact analysis of Hp using liquid chromatography–mass spectrometry followed by immunoaffinity purification with the serum samples. Intensity and frequency markers were defined depending on the mass spectrometry data analysis. Multiple markers were found with high diagnostic efficacy. As intensity markers (I-marker), six markers were discovered with the AUC > 0.8. The high efficiency markers exhibited AUC of 0.93 with a specificity of 86% when the sensitivity was set to 95%. We additionally established frequency marker (f-marker) panels based on the tendency of high N-glycan expression. The AUC to conclude patients and control group were 0.82 and 0.79, respectively. This study suggested that N-glycan variation of serum haptoglobin were associated with patients with gastric cancer and might be a promising marker for the cancer screening.

Glycomic profiling of targeted serum haptoglobin for gastric cancer using nano LC/MS and LC/MS/MS

Gastric cancer has one of the highest cancer mortality rates worldwide, largely because of difficulties in early-stage detection. Aberrant glycosylation in serum proteins is associated with many human diseases including inflammation and various types of cancer. Serum-based global glycan profiling using mass spectrometry has been explored and has already led to several potential glycan markers for several disease states. However, localization of the aberrant glycosylation is desirable in order to improve the specificity and sensitivity for clinical use. Here, we combined protein-specific immunoaffinity purification, glycan release, and MS analysis to examine haptoglobin glycosylation of gastric cancer patients for glyco-markers. Age- and sex-matched 60 serum samples (30 cancer patients and 30 healthy controls) were used to profile and quantify haptoglobin N-glycans. A T-test based statistical analysis was performed to identify potential glyco-markers for gastric cancer. Interestingly, abundances of several tri- and tetra-antennary fucosylated N-glycans were increased in gastric cancer patients. Additionally, structural analysis via LC/MS/MS indicated that the fucosylated complex type N-glycans were primarily decorated with antenna fucose, which can be categorized as sialyl-Le^a or sialyl-Le^x type structures. This platform demonstrates quantitative, structure-specific profiling of haptoglobin glycosylation for the purposes of biomarker discovery for gastric cancer.

Discovery of Non-invasive Glycan Biomarkers for Detection and Surveillance of Gastric Cancer

Purpose: Gastric cancer (GC), one of the world's top five most common cancers, is the third leading cause of cancer related death. It is urgent to identify non-invasive biomarkers for GC. The objective of our study was to find out non-invasive biomarkers for early detection and surveillance of GC based on glycomic analysis.

Method: Ethyl esterification derivatization combined with MALDI-TOF MS analysis was employed for the comprehensive serum glycomic analysis in order to investigate glycan markers that would indicate the onset and progression of gastric cancer. Upon the discovery of the candidate biomarkers, those with great potential were further validated in an independent test set. Peaks were acquired by the software of MALDI-MS sample acquisition and processing and analyzed by the software of Progenesis MALDI. 


Results: The differences in glycosylation were found between non-cancer controls and gastric cancer samples: hybrid and multi-branched type (tri-, tetra-antennnary glycans) N-glycans were increased in GC, yet monoantennary, galactose, bisecting type and core fucose N-glycans were decreased. In training set, core fucose (AUC=0.923, 95%CI: 0.8485 to 0.9967) played an excellent diagnostic performance for the early detection of gastric cancer. The diagnostic potential of core fucose was further validated in an independent cohort (AUC=0.854, 95%CI: 0.7592 to 0.9483). Besides, several individual glycan structures reached both statistical criteria (p-values less than 0.05 and AUC scores that were at least moderately accurate) when comparing different stages of GC samples.

Conclusion: We comprehensively evaluate the serum glycan changes in different stages of GC patients including peritoneal metastasis for the first time. We determined several N-glycan biomarkers, some of these have potential in distinguishing the early stage GC from healthy controls, and the others can help to monitor the progression of GC. The findings also enhance understanding of gastric cancer.