Site-specific and linkage analyses of fucosylated N-glycans on haptoglobin in sera of patients with various types of cancer: possible implication for the differential diagnosis of cancer

Deciphering N-Glycosylation Dynamics of Serum Monoclonal Immunoglobulins in Multiple Myeloma via EThcD-sceHCD-MS/MS

Serum glycoprotein glycosylation changes can indicate disease onset and progression. However, the site-specific N-glycosylation of monoclonal immunoglobulins (M-proteins) in multiple myeloma (MM) and its clinical implications are unclear. In this study, we isolated pathogenic micromonoclonal IgA or IgG (approximately 2 μg) from IgA-MM patients (n = 22) and IgG-MM patients (n = 30), and normal polyclonal IgA and IgG from healthy controls (HCs) (n = 16). Using EThcD-sceHCD-MS/MS, the N-glycosylation dynamics of serum M-proteins in MM were determined. Compared with polyclonal IgA1 from HCs, monoclonal IgA1 from IgA-MM patients had higher fucosylation (58.1% vs 32.1%, p < 0.001), sialylation (68.0% vs 50.8%, p = 0.011), and mannosylation (1.5% vs 0.3%, p < 0.001). While, monoclonal IgG1 from IgG-MM patients had higher fucosylation (97.8% vs 95.3%, p < 0.001). In addition, specific N-glycan abundances correlated with MM clinical features: for IgA1, HexNAc5Hex5Fuc1NeuAc1 was associated with hypocomplementemia; for IgG1, HexNAc4Hex3Fuc1 was associated with the serum albumin level (r = -0.363, p = 0.049) and estimated glomerular filtration rate (r = -0.433, p = 0.017); and HexNAc4Hex5 was associated with therapeutic prognosis. In conclusion, monoclonal IgA1 and IgG1 in MM patients and their polyclonal isotypes in HCs have distinct N-glycosylation profiles, and specific N-glycans of M-proteins are associated with MM characteristics and therapeutic prognosis.

Fucosylated haptoglobin promotes inflammation via Mincle in sepsis: an observational study

Haptoglobin (Hp) scavenges cell-free hemoglobin and correlates with the prognosis of human sepsis, a life-threatening systemic inflammatory condition. Despite extensive research on Hp glycosylation as a glyco-biomarker for cancers, understanding glycosylated modifications of Hp in sepsis patients (SPs) remains limited. Our study reveals elevated levels of terminal fucosylation at Asn207 and Asn211 of Hp in SP plasma, along with heightened inflammatory responses, compared to healthy controls (trial registration NCT05911711). Fucosylated (Fu)-Hp purified from SPs upregulates inflammatory cytokines and chemokines, along with NLRP3 inflammasome activation. Single-cell RNA sequencing identifies a distinct macrophage-like cell population with increased expressions of inflammatory mediators and FUT4 in response to Fu-Hp. Additionally, Mincle, a C-type lectin receptor, interacts with Fu-Hp to amplify the inflammatory responses and signaling. Moreover, the Hp fucosylation (AAL) level significantly correlates with the levels of inflammatory cytokines in sepsis patients, suggesting that Fu-Hp is clinically relevant. Finally, Fu-Hp treatment significantly enhances the levels of inflammatory cytokines in the plasma and various tissues of mice. Together, our findings reveal a role of Fu-Hp, derived from sepsis patients, in driving inflammation, and suggest that targeting Fu-Hp could serve as a promising intervention for combating sepsis. Trial registration NCT05911711.

Targeting fucosyltransferase FUT8 as a prospective therapeutic approach for DLBCL

Diffuse large B-cell lymphoma (DLBCL) is characterized by its aggressive nature and resistance to standard chemotherapy, necessitating the development of new therapeutic approaches. The emergence of natural products and their derivatives has notably influenced cancer treatment, making morusinol, a medicine-derived monomer, a promising candidate. Here, we showed that morusinol exerted antitumor effects on DLBCL in vitro by inducing apoptosis and cell cycle arrest. Impressively, morusinol treatment exhibited potent tumor growth inhibition in vivo, proving both well-tolerated and safe in mouse models. Moreover, our investigation identified FUT8, a fucosyltransferase, as a potential target for morusinol. FUT8's role as an oncogene in DLBCL and its correlation with poor survival further underscored its significance. Furthermore, our screening efforts involving clinical and preclinical drugs unveiled a compelling synergistic effect between chidamide and morusinol. Additionally, morusinol's ability to hinder M2-like polarization of tumor-associated macrophages suggested its potential in immune response modulation within DLBCL. Collectively, morusinol showcased substantial promise as an anti-tumor agent for potential clinical application in DLBCL management, potentially augmenting established therapeutic strategies. Moreover, our findings offered promising prospects for natural products to effectively leverage its therapeutic advantages. Working model: The role of Morusinol in treating DLBCL.

Identification of serum N-glycans signatures in three major gastrointestinal cancers by high-throughput N-glycome profiling

BACKGROUND

Alternative N-glycosylation of serum proteins has been observed in colorectal cancer (CRC), esophageal squamous cell carcinoma (ESCC) and gastric cancer (GC), while comparative study among those three cancers has not been reported before. We aimed to identify serum N-glycans signatures and introduce a discriminative model across the gastrointestinal cancers.

METHODS

The study population was initially screened according to the exclusion criteria process. Serum N-glycans profiling was characterized by a high-throughput assay based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Diagnostic model was built by random forest, and unsupervised machine learning was performed to illustrate the differentiation between the three major gastrointestinal (GI) cancers.

RESULTS

We have found that three major gastrointestinal cancers strongly associated with significantly decreased mannosylation and mono-galactosylation, as well as increased sialylation of serum glycoproteins. A highly accurate discriminative power (> 0.90) for those gastrointestinal cancers was obtained with serum N-glycome based predictive model. Additionally, serum N-glycome profile exhibited distinct distributions across GI cancers, and several altered N-glycans were hyper-regulated in each specific disease.

CONCLUSIONS

Serum N-glycome profile was differentially expressed in three major gastrointestinal cancers, providing a new clinical tool for cancer diagnosis and throwing a light upon the disease-specific molecular signatures.

Self-regulation of MGAT4A and MGAT4B activity toward glycoproteins through interaction of lectin domain with their own N-glycans

N-Acetylglucosaminyltransferases-IVa (GnT-IVa or MGAT4A) and -IVb (MGAT4B) are glycosyltransferase isozymes synthesizing the β1,4-GlcNAc branch in N-glycans, a glycan structure involved in diabetes. These enzymes uniquely have a non-catalytic lectin domain, which selectively recognizes the GnT-IV product N-glycan branch, but the role of this lectin domain has remained unclear. Here, using UDP-Glo enzyme assays, we discovered that this domain is required for activity toward glycoprotein substrates but not toward free glycans. Furthermore, we found that the lectin domain itself is decorated with an N-glycan, which can serve as a self-ligand and interact with the ligand binding site of the lectin domain in a glycan structure-dependent manner. Enzyme assays using glycan-remodeled GnT-IVa demonstrated that the interaction of the self-ligand with the lectin domain suppresses GnT-IVa activity toward glycoprotein substrates. These findings unveiled a lectin-assisted self-regulatory mechanism of glycosyltransferases, which deepens our understanding of the complex pathway of N-glycan biosynthesis.

Comprehensive serum glycopeptide spectra analysis to identify early-stage epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is widely recognized as the most lethal gynecological malignancy; however, its early-stage detection remains a considerable clinical challenge. To address this, we have introduced a new method, named Comprehensive Serum Glycopeptide Spectral Analysis (CSGSA), which detects early-stage cancer by combining glycan alterations in serum glycoproteins with tumor markers. We detected 1712 glycopeptides using liquid chromatography-mass spectrometry from the sera obtained from 564 patients with EOC and 1149 controls across 13 institutions. Furthermore, we used a convolutional neural network to analyze the expression patterns of the glycopeptides and tumor markers. Using this approach, we successfully differentiated early-stage EOC (Stage I) from non-EOC, with an area under the curve (AUC) of 0.924 in receiver operating characteristic (ROC) analysis. This method markedly outperforms conventional tumor markers, including cancer antigen 125 (CA125, 0.842) and human epididymis protein 4 (HE4, 0.717). Notably, our method exhibited remarkable efficacy in differentiating early-stage ovarian clear cell carcinoma from endometrioma, achieving a ROC-AUC of 0.808, outperforming CA125 (0.538) and HE4 (0.557). Our study presents a promising breakthrough in the early detection of EOC through the innovative CSGSA method. The integration of glycan alterations with cancer-related tumor markers has demonstrated exceptional diagnostic potential.

The role of protein post-translational modifications in prostate cancer

Involving addition of chemical groups or protein units to specific residues of the target protein, post-translational modifications (PTMs) alter the charge, hydrophobicity, and conformation of a protein, which in turn influences protein function, protein-protein interaction, and protein aggregation. These alterations, which include phosphorylation, glycosylation, ubiquitination, methylation, acetylation, lipidation, and lactylation, are significant biological events in the development of cancer, and play vital roles in numerous biological processes. The processes behind essential functions, the screening of clinical illness signs, and the identification of therapeutic targets all depend heavily on further research into the PTMs. This review outlines the influence of several PTM types on prostate cancer (PCa) diagnosis, therapy, and prognosis in an effort to shed fresh light on the molecular causes and progression of the disease.

Core fucosylation within the Fc-FcγR degradation pathway promotes enhanced IgG levels via exogenous L-fucose

α1,6-Fucosyltransferase (Fut8) is the enzyme responsible for catalyzing core fucosylation. Exogenous L-fucose upregulates fucosylation levels through the GDP-fucose salvage pathway. This study investigated the relationship between core fucosylation and immunoglobulin G (IgG) amounts in serum utilizing WT (Fut8+/+), Fut8 heterozygous knockout (Fut8+/-), and Fut8 knockout (Fut8-/-) mice. The IgG levels in serum were lower in Fut8+/- and Fut8-/- mice compared with Fut8+/+ mice. Exogenous L-fucose increased IgG levels in Fut8+/- mice, while the ratios of core fucosylated IgG versus total IgG showed no significant difference among Fut8+/+, Fut8+/-, and Fut8+/- mice treated with L-fucose. These ratios were determined by Western blot, lectin blot, and mass spectrometry analysis. Real-time PCR results demonstrated that mRNA levels of IgG Fc and neonatal Fc receptor, responsible for protecting IgG turnover, were similar among Fut8+/+, Fut8+/-, and Fut8+/- mice treated with L-fucose. In contrast, the expression levels of Fc-gamma receptor Ⅳ (FcγRⅣ), mainly expressed on macrophages and neutrophils, were increased in Fut8+/- mice compared to Fut8+/+ mice. The effect was reversed by administrating L-fucose, suggesting that core fucosylation primarily regulates the IgG levels through the Fc-FcγRⅣ degradation pathway. Consistently, IgG internalization and transcytosis were suppressed in FcγRⅣ-knockout cells while enhanced in Fut8-knockout cells. Furthermore, we assessed the expression levels of specific antibodies against ovalbumin and found they were downregulated in Fut8+/- mice, with potential recovery observed with L-fucose administration. These findings confirm that core fucosylation plays a vital role in regulating IgG levels in serum, which may provide insights into a novel mechanism in adaptive immune regulation.

Structural insights into the role of N-terminal integrity in PhoSL for core-fucosylated N-glycan recognition

PhoSL (Pholiota squarrosa Lectin) has an exceptional binding affinity for biomolecules with core-fucosylated N-glycans. This modification involves the addition of fucose to the inner N-acetylglucosamine within the N-glycan structure and is known to influence many physiological processes. Nevertheless, the molecular interactions underlying high-affinity binding of native PhoSL to core-fucosylated N-glycans remain largely unknown. In this study, we devised a strategy to produce PhoSL with the essential structural characteristics of the native protein (n-PhoSL). To do so, a fusion protein was expressed in E. coli and purified. Then, enzymatic cleavage and incubation with glutathione were utilized to recapitulate the native primary structure and disulfide bonding pattern. Subsequently, we identified the residues crucial for n-PhoSL binding to core-fucosylated chitobiose (N2F) via NMR spectroscopy. Additionally, crystal structures were solved for both apo n-PhoSL and its N2F complex. These analyses suggested a pivotal role of the N-terminal amine in maintaining the integrity of the binding pocket and actively contributing to core-fucose recognition. In support of this idea, the inclusion of additional residues at the N-terminus considerably reduced binding affinity and PhoSL cytotoxicity toward breast cancer cells. Taken together, these findings can facilitate the utilization of PhoSL in basic research, diagnostics and therapeutic strategies.

Disease-Specific Haptoglobin N-Glycosylation in Inflammatory Disorders between Cancers and Benign Diseases of 3 Types of Female Internal Genital Organs

BACKGROUND

N-glycosylation of the haptoglobin is closely related to pathological states. This study aims to evaluate the association of glycosylation of disease-specific Hp (DSHp) β chain with different pathological states of the cervix, uterus, and ovary to explore differences in their inflammatory responses and to screen potential biomarkers to distinguish cancer from benign diseases.

METHODS

DSHp-β chains of 1956 patients with cancers and benign diseases located in the cervix, uterus, and ovary organs were separated from serum immunoinflammatory-related protein complexes (IIRPCs). The N-glycopeptides from DSHp-β chains were detected using mass spectrometry, followed by an analysis of machine learning algorithms.

RESULTS

55 N-glycopeptides at N207/N211, 19 at N241, and 21 at N184 glycosylation sites of DSHp for each sample were identified. Fucosylation and sialylation of DSHp in cervix, uterus, and ovary cancer were significantly increased compared to their corresponding benign diseases (p < 0.001). The cervix diagnostic model, a combination of G2N3F, G4NFS, G7N2F2S5, GS-N&GS-N, G2N2&G4N3FS, G7N2F2S5, G2S2&G-N, and GN2F&G2F at N207/N211 sites, G3NFS2 and G3NFS at N241site, G9N2S, G6N3F6, G4N3F5S, G4N3F4S2, and G6N3F4S at N184 site), has shown a good diagnostic capability to distinguish cancer from benign diseases, with the area under curve (AUC) of 0.912. The uterus diagnostic model including G4NFS, G2S2&G2S2, G3N2S2, GG5N2F5, G2&G3NFS, and G5N2F3S3 at N207/N211 sites, and G2NF3S2 at N184 site, with an AUC of 0.731. The ovary diagnostic model including G2N3F, GF2S-N &G2F3S2, G2S&G2, and G2S&G3NS at N207/N211 sites; G2S and G3NFS at N241 site, G6N3F4S at N184 site, with an AUC of 0.747.

CONCLUSIONS

These findings provide insights into differences in organ-specific inflammatory responses of DSHp for different pathological states among the organs of the cervix, uterus, and ovary.

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.

Mass Spectrometry-Based Glycoproteomic Workflows for Cancer Biomarker Discovery

Glycosylation has a clear role in cancer initiation and progression, with numerous studies identifying distinct glycan features or specific glycoproteoforms associated with cancer. Common findings include that aggressive cancers tend to have higher expression levels of enzymes that regulate glycosylation as well as glycoproteins with greater levels of complexity, increased branching, and enhanced chain length1. Research in cancer glycoproteomics over the last 50-plus years has mainly focused on technology development used to observe global changes in glycosylation. Efforts have also been made to connect glycans to their protein carriers as well as to delineate the role of these modifications in intracellular signaling and subsequent cell function. This review discusses currently available techniques utilizing mass spectrometry-based technologies used to study glycosylation and highlights areas for future advancement.

Construction of long non-coding RNA- and microRNA-mediated competing endogenous RNA networks in alcohol-related esophageal cancer

The current study aimed to explore the lncRNA–miRNA–mRNA networks associated with alcohol-related esophageal cancer (EC). RNA-sequencing and clinical data were downloaded from The Cancer Genome Atlas and the differentially expressed genes (DEGs), long non-coding RNAs (lncRNAs, DELs), and miRNAs (DEMs) in patients with alcohol-related and non-alcohol-related EC were identified. Prognostic RNAs were identified by performing Kaplan–Meier survival analyses. Weighted gene co-expression network analysis was employed to build the gene modules. The lncRNA–miRNA–mRNA competing endogenous RNA (ceRNA) networks were constructed based on our in silico analyses using data from miRcode, starBase, and miRTarBase databases. Functional enrichment analysis was performed for the genes in the identified ceRNA networks. A total of 906 DEGs, 40 DELs, and 52 DEMs were identified. There were eight lncRNAs and miRNAs each, including ST7-AS2 and miR-1269, which were significantly associated with the survival rate of patients with EC. Of the seven gene modules, the blue and turquoise modules were closely related to disease progression; the genes in this module were selected to construct the ceRNA networks. SNHG12–miR-1–ST6GAL1, SNHG3–miR-1–ST6GAL1, SPAG5-AS1–miR-133a–ST6GAL1, and SNHG12–hsa-miR-33a–ST6GA interactions, associated with the N-glycan biosynthesis pathway, may have key roles in alcohol-related EC. Thus, the identified biomarkers provide a novel insight into the molecular mechanism of alcohol-related EC.

Comparison of Fucose-Specific Lectins to Improve Quantitative AFP-L3 Assay for Diagnosing Hepatocellular Carcinoma Using Mass Spectrometry

Glycoproteins have many important biological functions. In particular, aberrant glycosylation has been observed in various cancers, such as liver cancer. A well-known glycoprotein biomarker is α-fetoprotein (AFP), a surveillance biomarker for hepatocellular carcinoma (HCC) that contains a glycosylation site at asparagine 251. The low diagnostic sensitivity of AFP led researchers to focus on AFP-L3, which has the same sequence as conventional AFP but contains a fucosylated glycan. AFP-L3 has high affinity for Lens culinaris agglutinin (LCA) lectin, prompting many groups to use it for detecting AFP-L3. However, a few studies have identified more effective lectins for fractionating AFP-L3. In this study, we compared the amounts of enriched AFP-L3 with five fucose-specific lectins─LCA, Lotus tetragonolobus lectin (LTL), Ulex europaeus agglutinin I (UEA I), Aleuria aurantia lectin (AAL), and Aspergillus oryzae lectin (AOL)─to identify better lectins and improve HCC diagnostic assays using mass spectrometry (MS). Our results indicate that LTL was the most effective lectin for capturing AFP-L3 species, yielding approximately 3-fold more AFP-L3 than LCA from the same pool of HCC serum samples. Thus, we recommend the use of LTL for AFP-L3 assays, given its potential to improve the diagnostic sensitivity in patients having limited results by conventional LCA assay. The MS data have been deposited to the PeptideAtlas (PASS01752).

Quantitative glycoproteomics analysis identifies novel FUT8 targets and signaling networks critical for breast cancer cell invasiveness

BACKGROUND

We recently showed that fucosyltransferase 8 (FUT8)-mediated core fucosylation of transforming growth factor-β receptor enhances its signaling and promotes breast cancer invasion and metastasis. However, the complete FUT8 target glycoproteins and their downstream signaling networks critical for breast cancer progression remain largely unknown.

METHOD

We performed quantitative glycoproteomics with two highly invasive breast cancer cell lines to unravel a comprehensive list of core-fucosylated glycoproteins by comparison to parental wild-type and FUT8-knockout counterpart cells. In addition, ingenuity pathway analysis (IPA) was performed to highlight the most enriched biological functions and signaling pathways mediated by FUT8 targets. Novel FUT8 target glycoproteins with biological interest were functionally studied and validated by using LCA (Lens culinaris agglutinin) blotting and LC-MS/MS (liquid chromatography-tandem mass spectrometry) analysis.

RESULTS

Loss-of-function studies demonstrated that FUT8 knockout suppressed the invasiveness of highly aggressive breast carcinoma cells. Quantitative glycoproteomics identified 140 common target glycoproteins. Ingenuity pathway analysis (IPA) of these target proteins gave a global and novel perspective on signaling networks essential for breast cancer cell migration and invasion. In addition, we showed that core fucosylation of integrin αvβ5 or IL6ST might be crucial for breast cancer cell adhesion to vitronectin or enhanced cellular signaling to interleukin 6 and oncostatin M, two cytokines implicated in the breast cancer epithelial-mesenchymal transition and metastasis.

CONCLUSIONS

Our report reveals a comprehensive list of core-fucosylated target proteins and provides novel insights into signaling networks crucial for breast cancer progression. These findings will assist in deciphering the complex molecular mechanisms and developing diagnostic or therapeutic approaches targeting these signaling pathways in breast cancer metastasis.

Simultaneous analysis of serum α2,3-linked sialylation and core-type fucosylation of prostate-specific antigen for the detection of high-grade prostate cancer

BACKGROUND

Altered prostate-specific antigen (PSA) glycosylation patterns can be useful biomarkers in detecting high-grade prostate cancer (HGPC). The microfluidic immunoassay system can analyse α2,3-linked sialylated PSA (α2,3-Sia-PSA) and α1,6-linked fucosylated PSA (α1,6-Fuc-PSA) using different lectins, Mackkia amurensis agglutinin and Pholiota squarrosa lectin, respectively. Here, we investigated the diagnostic value of simultaneous analysis of α2,3-Sia-PSA and α1,6-Fuc-PSA for the detection of HGPC.

METHODS

Men with serum PSA levels of 4-20 ng/mL who underwent prostate biopsy were included. The model to predict HGPC (Gleason grade ≥2) was constructed by multivariate logistic regression analysis, in combination with α2,3-Sia-PSA and α1,6-Fuc-PSA (SF index).

RESULTS

In the development cohort (n = 150), the SF index showed good discrimination for HGPC (area under the receiver-operating curve (AUC) 0.842; 95% confidence interval (CI) 0.782-0.903), compared to the single PSA test (AUC 0.632, 95% CI 0.543-0.721), α2,3-Sia-PSA (AUC 0.711, 95% CI 0.629-0.793) and α1,6-Fuc-PSA (AUC 0.738, 95% CI 0.657-0.819). Decision-curve analysis showed the superior benefit of the SF index. In the validation cohort (n = 57), the SF index showed good discrimination for HGPC (AUC 0.769, 95% CI 0.643-0.895).

CONCLUSIONS

The SF index could differentiate HGPC, providing useful information for decision making for prostate biopsy in men with abnormal PSA levels.

Fucosylation in Urological Cancers

Fucosylation is an oligosaccharide modification that plays an important role in immune response and malignancy, and specific fucosyltransferases (FUTs) catalyze the three types of fucosylations: core-type, Lewis type, and H type. FUTs regulate cancer proliferation, invasiveness, and resistance to chemotherapy by modifying the glycosylation of signaling receptors. Oligosaccharides on PD-1/PD-L1 proteins are specifically fucosylated, leading to functional modifications. Expression of FUTs is upregulated in renal cell carcinoma, bladder cancer, and prostate cancer. Aberrant fucosylation in prostate-specific antigen (PSA) could be used as a novel biomarker for prostate cancer. Furthermore, elucidation of the biological function of fucosylation could result in the development of novel therapeutic targets. Further studies are needed in the field of fucosylation glycobiology in urological malignancies.

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.

Structural analysis of the GPI glycan

Glycosylphosphatidylinositol (GPI) anchoring of proteins is an essential post-translational modification in all eukaryotes that occurs at the endoplasmic reticulum (ER) and serves to deliver GPI-anchored proteins (GPI-APs) to the cell surface where they play a wide variety of vital physiological roles. This paper describes a specialized method for purification and structural analysis of the GPI glycan of individual GPI-APs in yeast. The protocol involves the expression of a specific GPI-AP tagged with GFP, enzymatic release from the cellular membrane fraction, immunopurification, separation by electrophoresis and analysis of the peptides bearing GPI glycans by mass spectrometry after trypsin digestion. We used specifically this protocol to address the structural remodeling that undergoes the GPI glycan of a specific GPI-AP during its transport to the cell surface. This method can be also applied to investigate the GPI-AP biosynthetic pathway and to directly confirm predicted GPI-anchoring of individual proteins.

Quantification of Intact O-Glycopeptides on Haptoglobin in Sera of Patients With Hepatocellular Carcinoma and Liver Cirrhosis

Haptoglobin (Hp) is one of the acute-phase response proteins secreted by the liver, and its aberrant N-glycosylation was previously reported in hepatocellular carcinoma (HCC). Limited studies on Hp O-glycosylation have been previously reported. In this study, we aimed to discover and confirm its O-glycosylation in HCC based on lectin binding and mass spectrometry (MS) detection. First, serum Hp was purified from patients with liver cirrhosis (LC) and HCC, respectively. Then, five lectins with Gal or GalNAc monosaccharide specificity were chosen to perform lectin blot, and the results showed that Hp in HCC bound to these lectins in a much stronger manner than that in LC. Furthermore, label-free quantification based on MS was performed. A total of 26 intact O-glycopeptides were identified on Hp, and most of them were elevated in HCC as compared to LC. Among them, the intensity of HYEGS³¹⁶TVPEK (H1N1S1) on Hp was the highest in HCC patients. Increased HYEGS³¹⁶TVPEK (H1N1S1) in HCC was quantified and confirmed using the MS method based on ¹⁸O/¹⁶O C-terminal labeling and multiple reaction monitoring. This study provided a comprehensive understanding of the glycosylation of Hp in liver diseases.

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.

Serum core-type fucosylated prostate-specific antigen index for the detection of high-risk prostate cancer

It is known that core-type fucosylation is higher in prostate cancer cells than in other cancer cell types and is associated with high-risk prostate cancer. Here, we developed an automated microcapillary electrophoresis-based immunoassay system for measuring serum core-type fucosylated prostate-specific antigen (PSA) and evaluated whether the serum fucosylated PSA index (FPI) can detect high-risk prostate cancer. Core-type fucosylated-free PSA was measured by our automated microcapillary electrophoresis-based immunoassay system with Pholiota squarrosa lectin. The FPI was calculated from total PSA and the percentage of fucosylated-free PSA. The optimum model to predict Gleason grade (GG) ≥2 was constructed by multivariate logistic regression analysis. Discrimination was assessed by determining the area under the receiver operator characteristic curve (AUC). The study included 252 men who underwent prostate needle biopsy due to elevated serum PSA levels (4-20 ng/mL), including 138 with GG ≥2. A higher FPI was significantly associated with GG (P < .0001). Multivariate logistic regression analysis showed that age, prostate volume and FPI were significant predictors of GG ≥2. The AUC of FPI and the model were 0.729 (95% confidence interval [CI]: 0.668-0.790) and 0.837 (95% CI: 0.788-0.886), respectively, compared to 0.629 (95% CI: 0.561-0.698) for PSA. Decision curve analysis showed the superior benefit of FPI and the model when compared to PSA. In a cohort with serum PSA levels <20 ng/mL, FPI could differentiate high-risk prostate cancer from biopsy-negative or low-risk prostate cancer. Therefore, FPI could be a useful adjunct in prostate biopsy counseling for men with abnormal PSA levels.

Fucosyltransferase 8 regulation and breast cancer suppression by transcription factor activator protein 2γ

Alterations of glycosyltransferase expression are often associated with tumor occurrence and progression. Among the many glycosyltransferases, increased expression of fucosyltransferase 8 (FUT8) has been frequently observed to be involved in progression and metastasis of various types of cancer. The regulatory mechanisms of FUT8 expression remain unclear. FUT8 expression was shown, in this study, to be elevated in breast cancer. Systematic analysis revealed that transcription factor activator protein 2γ (AP-2γ) is the target gene of microRNA-10b (miR-10b), which we previously identified as a positive regulator of FUT8. Overexpression of AP-2γ inhibited FUT8 expression, with associated reduction of cell invasiveness and migration ability. AP-2γ was capable of binding to transcription factor STAT3, and phosphorylation of STAT3 induced transcription of the FUT8 gene. On the basis of our findings, we propose that binding of AP-2γ to STAT3 results in formation of the AP-2γ/STAT3 complex and consequent inhibition of STAT3 phosphorylation, thereby preventing entry of p-STAT3 into the nucleus to initiate FUT8 transcription. This study clarifies the molecular mechanisms whereby transcription factor AP-2γ regulates FUT8 expression in breast cancer.

Glycosylation Biomarkers Associated with Age-Related Diseases and Current Methods for Glycan Analysis

Ageing is a complex process which implies the accumulation of molecular, cellular and organ damage, leading to an increased vulnerability to disease. In Western societies, the increase in the elderly population, which is accompanied by ageing-associated pathologies such as cardiovascular and mental diseases, is becoming an increasing economic and social burden for governments. In order to prevent, treat and determine which subjects are more likely to develop these age-related diseases, predictive biomarkers are required. In this sense, some studies suggest that glycans have a potential role as disease biomarkers, as they modify the functions of proteins and take part in intra- and intercellular biological processes. As the glycome reflects the real-time status of these interactions, its characterisation can provide potential diagnostic and prognostic biomarkers for multifactorial diseases. This review gathers the alterations in protein glycosylation profiles that are associated with ageing and age-related diseases, such as cancer, type 2 diabetes mellitus, metabolic syndrome and several chronic inflammatory diseases. Furthermore, the review includes the available techniques for the determination and characterisation of glycans, such as liquid chromatography, electrophoresis, nuclear magnetic resonance and mass spectrometry.

Functional milk proteome analysis of genetically diverse goats from different agro climatic regions

Goat milk, a choice of substitution to mother's milk for its composition, fulfils nutritional requirement of infants, pregnant mothers and older people. The present study was carried out to unravel the milk proteome profiles from geographically and genetically diverse goat breeds by gel based 2DE and nLC-MS/MS. A total of 1307 functional proteins comprising casein and other low abundance proteins were identified. Gene annotations revealed that the majority of the proteins were involved in binding function, catalytic activity and structural molecules and localised in nucleus and membrane. The distinguished proteins were involved in 144 KEGG pathways in information processing, metabolism, cellular process, organismal systems and diseases. The large number of proteins and peptides including bioactive peptides were reported from goat milk from diverse agro-climatic regions of India indicating their significant potential for human health applications. SIGNIFICANCE: Goat milk in India is used in various Ayurvedic formulations to treat a number of ailments and allergies as well as for nutraceutical formulations. The study identifies milk protein variants both at protein and DNA level and subsequent identification of proteins by 2DE and nLC-MS/MS resulting in a proteome comprising of 1307 proteins. The specific proteins and peptides having significant role in immune regulation, disease pathways, cellular growth and metabolism have been identified. The results contribute to goat milk protein and peptide database which is very limited. We identified proteins for specific functional categories and associated them with different pathways for studying functional diversity of goat milk proteins. The proteins and peptides identified can be used for multiple human health application.

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.

The Core Fucose on an IgG Antibody is an Endogenous Ligand of Dectin-1

The core fucose, a major modification of N-glycans, is implicated in immune regulation, such as the attenuation of the antibody-dependent cell-mediated cytotoxicity of antibody drugs and the inhibition of anti-tumor responses via the promotion of PD-1 expression on T cells. Although the core fucose regulates many biological processes, no core fucose recognition molecule has been identified in mammals. Herein, we report that Dectin-1, a known anti-β-glucan lectin, recognizes the core fucose on IgG antibodies. A combination of biophysical experiments further suggested that Dectin-1 recognizes aromatic amino acids adjacent to the N-terminal asparagine at the glycosylation site as well as the core fucose. Thus, Dectin-1 appears to be the first lectin-like molecule involved in the heterovalent and specific recognition of characteristic N-glycans on antibodies.

Structural basis for the specific cleavage of core-fucosylated N-glycans by endo-β-N-acetylglucosaminidase from the fungus Cordyceps militaris

N-Linked glycans play important roles in various cellular and immunological events. Endo-β-N-acetylglucosaminidase (ENGase) can release or transglycosylate N-glycans and is a promising tool for the chemoenzymatic synthesis of glycoproteins with homogeneously modified glycans. The ability of ENGases to act on core-fucosylated glycans is a key factor determining their therapeutic utility because mammalian N-glycans are frequently α-1,6-fucosylated. Although the biochemistries and structures of various ENGases have been studied extensively, the structural basis for the recognition of the core fucose and the asparagine-linked GlcNAc is unclear. Herein, we determined the crystal structures of a core fucose-specific ENGase from the caterpillar fungus Cordyceps militaris (Endo-CoM), which belongs to glycoside hydrolase family 18. Structures complexed with fucose-containing ligands were determined at 1.75-2.35 Å resolutions. The fucose moiety linked to GlcNAc is extensively recognized by protein residues in a round-shaped pocket, whereas the asparagine moiety linked to the GlcNAc is exposed to the solvent. The N-glycan-binding cleft of Endo-CoM is Y-shaped, and several lysine and arginine residues are present at its terminal regions. These structural features were consistent with the activity of Endo-CoM on fucose-containing glycans on rituximab (IgG) and its preference for a sialobiantennary substrate. Comparisons with other ENGases provided structural insights into their core fucose tolerance and specificity. In particular, Endo-F3, a known core fucose-specific ENGase, has a similar fucose-binding pocket, but the surrounding residues are not shared with Endo-CoM. Our study provides a foothold for protein engineering to develop enzymatic tools for the preparation of more effective therapeutic antibodies.

Identification of protein changes in the blood plasma of lung cancer patients subjected to chemotherapy using a 2D-DIGE approach

A comparative analysis of blood samples (depleted of albumin and IgG) obtained from lung cancer patients before chemotherapy versus after a second cycle of chemotherapy was performed using two-dimensional difference gel electrophoresis (2D-DIGE). The control group consisted of eight patients with non-cancerous lung diseases, and the experimental group consisted of four adenocarcinoma (ADC) and four squamous cell carcinoma (SCC) patients. Analyses of gels revealed significant changes in proteins and/or their proteoforms between control patients and lung cancer patients, both before and after a second cycle of chemotherapy. Most of these proteins were related to inflammation, including acute phase proteins (APPs) such as forms of haptoglobin and transferrin, complement component C3, and clusterin. The variable expression of APPs can potentially be used for profiling lung cancer. The greatest changes observed after chemotherapy were in transferrin and serotransferrin, which likely reflect disturbances in iron turnover after chemotherapy-induced anaemia. Significant changes in plasma proteins between ADC and SCC patients were also revealed, suggesting use of plasma vitronectin as a potential marker of SCC.

Analysis of serum Haptoglobin using glycoproteomics and lectin immunoassay in liver diseases in Hepatitis B virus infection

BACKGROUND

Hepatocellular carcinoma (HCC) due to Hepatitis B viral (HBV) infection is a major cause in Asia-Pacific countries. Its early detection is of paramount importance using a marker having both sensitivity and specificity. The present study promises diagnostic and prognostic markers by the identification of site-specific glycoforms on Haptoglobin (Hp) using LC-MS/MS and lectin ELISA in liver diseased conditions in HBV infection.

METHODS

Three groups of patients: chronic, liver cirrhosis and HCC with HBV infection along with controls were enrolled. Hp was purified using affinity column chromatography and, peptide sequence, N-glycosylation site, glycan composition and glycoforms were identified using mass spectrometry. Quantitative lectin ELISA was used to measure levels of fucosylation on Hp in liver diseases due to HBV.

RESULTS

Hp levels were significantly lower in HCC when compared with Non-HCC cases (p < .05). Fucosylated glycoforms were significantly increased at site Asn184, Asn207 and Asn211 in liver diseased stages versus controls. A significant association was observed between the Fuc-Hp/Hp Elisa index and, advanced liver disease stages and controls using lectin Elisa (p < .001).

CONCLUSION

Quantitation of fucosylation levels on Hp protein using Lectin ELISA may be useful glycobiomarker either alone or in combination (AFP + DCP + FucHp; AUC = 0.94) in HBV HCC diagnosis in clinical practice.

Glycan-based biomarkers for diagnosis of cancers and other diseases: Past, present, and future

Glycans are essential biomolecules in regulating human physiology and pathology ranging from signal transduction to microbial infections. Developing complex human diseases, such as cancer, diabetes, and cardiovascular diseases, are a combination of genetic and environmental factors. Genetics dominates embryonic development and the passing of genes to the next generation whereas the information in glycans reflects the impact of internal and external environmental factors, such as diseases, lifestyle, and social factors, on a person's health and disease. The reason behind this is that glycans are not directly encoded in a genetic template. Instead, they are assembled dynamically by hundreds of enzymes organized in more than 10 complex biosynthetic pathways. Any environmental changes affecting enzymatic activities or the availability of high-energy monosaccharide donors in a specific location will disturb the final structure of glycans. The glycan structure-dependent biological activities subsequently enable or disable gene expressions, which partially explain that it is difficult to pinpoint specific genetic defects to aging-associated diseases. Glycan-based biomarkers are currently used for diagnosis of diabetes, cancers, and other complex diseases. We will recapitulate the discovery of glucose, glycated proteins, glycan-, and glycoprotein-based biomarkers followed by summarizing clinically used glycan/glycoprotein-based biomarkers. The potential serum/plasma-derived N- and O-linked glycans as biomarkers will also be discussed.

Comparative Proteomics of Whey and Milk Fat Globule Membrane Proteins of Guanzhong Goat and Holstein Cow Mature Milk

Guanzhong goat and Holstein cow milks are the major milk supply for the Chinese dairy industry. Whey proteins and milk fat globule membrane (MFGM) proteins of both milk were characterized and compared using proteomic techniques. A total of 283, 159, 593, and 349 proteins were identified, respectively, in whey and MFGM for the two species using Liquid Chromatography combined with Tandem Mass Spectrometry (LC-MS/MS). Functional categories analyses showed that both goat and cow MFGM proteins had three most abundant proteins of phosphoproteins, membrane-related and acetylation-related proteins. Gene ontology (GO) annotation revealed that whey proteins in goat and cow milk exhibited different biological processes and molecular functions while both enriched in extracellular exosome for cellular components. Both goat and cow MFGM proteins showed main biological process of oxidation-reduction, cellular component of extracellular exosome, and molecular function of poly(A) RNA binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that large number of both goat and cow whey proteins were involved in disease, metabolism, and immune pathways with different number and types. The most general pathways for goat and cow MFGM proteins were metabolism pathways and disease pathways, respectively. The results indicated that Guanzhong goat and Holstein cow milk were different in varieties of whey proteins and MFGM proteins and their functions and pathways. PRACTICAL APPLICATION: Guanzhong goat and Holstein cow milks are the major milk sources for the Chinese consumers. However, information about proteomics of whey and MFGM proteins of Guanzhong goat and Holstein cow milk is limited. Our study characterized and compared both whey and MFGM proteins using proteomic techniques. The results provide useful information for infant formula and milk protein products in the Chinese dairy industry.

Differential Quantitative Determination of Site-Specific Intact N-Glycopeptides in Serum Haptoglobin between Hepatocellular Carcinoma and Cirrhosis Using LC-EThcD-MS/MS

Intact N-glycopeptide analysis remains challenging due to the complexity of glycopeptide structures, low abundance of glycopeptides in protein digests, and difficulties in data interpretation/quantitation. Herein, we developed a workflow that involved advanced methodologies, the EThcD-MS/MS fragmentation method and data interpretation software, for differential analysis of the microheterogeneity of site-specific intact N-glycopeptides of serum haptoglobin between early hepatocellular carcinoma (HCC) and liver cirrhosis. Haptoglobin was immunopurified from 20 μL of serum in patients with early HCC, liver cirrhosis, and healthy controls, respectively, followed by trypsin/GluC digestion, glycopeptide enrichment, and LC-EThcD-MS/MS analysis. Identification and differential quantitation of site-specific N-glycopeptides were performed using a combination of Byonic and Byologic software. In total, 93, 87, and 68 site-specific N-glycopeptides were identified in early HCC, liver cirrhosis, and healthy controls, respectively, with high confidence. The increased variety of N-glycopeptides in liver diseases compared to healthy controls was due to increased branching with hyper-fucosylation and sialylation. Differential quantitation analysis showed that 5 site-specific N-glycopeptides on sites N184 and N241 were significantly elevated in early HCC compared to cirrhosis ( p < 0.05) and normal controls ( p ≤ 0.001). The result demonstrates that the workflow provides a strategy for detailed profiles of N-glycopeptides of patient samples as well as for relative quantitation to determine the level changes in site-specific N-glycopeptides between disease states.

Clinical application of quantitative glycomics

Aberrant glycosylation has been associated with many diseases. Decades of research activities have reported many reliable glycan biomarkers of different diseases which enable effective disease diagnostics and prognostics. However, none of the glycan markers have been approved for clinical diagnosis. Thus, a review of these studies is needed to guide the successful clinical translation. Area covered: In this review, we describe and discuss advances in analytical methods enabling clinical glycan biomarker discovery, focusing only on studies of released glycans. This review also summarizes the different glycobiomarkers identified for cancers, Alzheimer's disease, diabetes, hepatitis B and C, and other diseases. Expert commentary: Along with the development of techniques in quantitative glycomics, more glycans or glycan patterns have been reported as better potential biomarkers of different diseases and proved to have greater diagnostic/diagnostic sensitivity and specificity than existing markers. However, to successfully apply glycan markers in clinical diagnosis, more studies and verifications on large biological cohorts need to be performed. In addition, faster and more efficient glycomic strategies need to be developed to shorten the turnaround time. Thus, glycan biomarkers have an immense chance to be used in clinical prognosis and diagnosis of many diseases in the near future.

Glycomics of prostate cancer: updates

Introduction: Prostate cancer (PCa) is a life-threatening disease affecting millions of men. The current best PCa biomarker (level of prostate-specific antigen in serum) lacks specificity for PCa diagnostics and this is why novel PCa biomarkers in addition to the conventional ones based on biomolecules such as DNA, RNA and proteins need to be identified. Areas covered: This review details the potential of glycans-based biomarkers to become diagnostic, prognostic, predictive and therapeutic PCa biomarkers with a brief description of the innovative approaches applied to glycan analysis to date. Finally, the review covers the possibility to use exosomes as a rich source of glycans for future innovative and advanced diagnostics of PCa. The review covers updates in the field since 2016. Expert commentary: The summary provided in this review paper suggests that glycan-based biomarkers can offer high-assay accuracy not only for diagnostic purposes but also for monitoring/surveillance of the PCa disease.

Mass Spectrometry Approaches to Glycomic and Glycoproteomic Analyses

Glycomic and glycoproteomic analyses involve the characterization of oligosaccharides (glycans) conjugated to proteins. Glycans are produced through a complicated nontemplate driven process involving the competition of enzymes that extend the nascent chain. The large diversity of structures, the variations in polarity of the individual saccharide residues, and the poor ionization efficiencies of glycans all conspire to make the analysis arguably much more difficult than any other biopolymer. Furthermore, the large number of glycoforms associated with a specific protein site makes it more difficult to characterize than any post-translational modification. Nonetheless, there have been significant progress, and advanced separation and mass spectrometry methods have been at its center and the main reason for the progress. While glycomic and glycoproteomic analyses are still typically available only through highly specialized laboratories, new software and workflow is making it more accessible. This review focuses on the role of mass spectrometry and separation methods in advancing glycomic and glycoproteomic analyses. It describes the current state of the field and progress toward making it more available to the larger scientific community.

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.

Establishment of an antibody specific for cancer-associated haptoglobin: a possible implication of clinical investigation

We previously found that the serum level of fucosylated haptoglobin (Fuc-Hpt) was significantly increased in pancreatic cancer patients. To delineate the mechanism underlying this increase and develop a simple detection method, we set out to generate a monoclonal antibody (mAb) specific for Fuc-Hpt. After multiple screenings by enzyme-linked immunosorbent assay (ELISA), a 10-7G mAb was identified as being highly specific for Fuc-Hpt generated in a cell line as well as for Hpt derived from a pancreatic cancer patient. As a result from affinity chromatography with 10-7G mAb, followed by lectin blot and mass spectrometry analyses, it was found that 10-7G mAb predominantly recognized both Fuc-Hpt and prohaptoglobin (proHpt), which was also fucosylated. In immunohistochemical analyses, hepatocytes surrounding metastasized cancer cells were stained by the 10-7G mAb, but neither the original cancer cells themselves nor normal hepatocytes exhibited positive staining, suggesting that metastasized cancer cells promote Fuc-Hpt production in adjacent hepatocytes. Serum level of Fuc-Hpt determined with newly developed ELISA system using the 10-7G mAb, was increased in patients of pancreatic and colorectal cancer. Interestingly, dramatic increases in Fuc-Hpt levels were observed at the stage IV of colorectal cancer. These results indicate that the 10-7G mAb developed is a promising antibody which recognizes Fuc-Hpt and could be a useful diagnostic tool for detecting liver metastasis of cancer.

Profiling of different pancreatic cancer cells used as models for metastatic behaviour shows large variation in their N-glycosylation

To characterise pancreatic cancer cells from different sources which are used as model systems to study the metastatic behaviour in pancreatic ductal adenocarcinoma (PDAC), we compared the N-glycan imprint of four PDAC cells which were previously shown to differ in their galectin-4 expression and metastatic potential in vivo. Next to the sister cell lines Pa-Tu-8988S and Pa-Tu-8988T, which were isolated from the same liver metastasis of a PDAC, this included two primary PDAC cell cultures, PDAC1 and PDAC2. Additionally, we extended the N-glycan profiling to a normal, immortalized pancreatic duct cell line. Our results revealed major differences in the N-glycosylation of the different PDAC cells as well as compared to the control cell line, suggesting changes of the N-glycosylation in PDAC. The N-glycan profiles of the PDAC cells, however, differed vastly as well and demonstrate the diversity of PDAC model systems, which ultimately affects the interpretation of functional studies. The results from this study form the basis for further biological evaluation of the role of protein glycosylation in PDAC and highlight that conclusions from one cell line cannot be generalised, but should be regarded in the context of the corresponding phenotype.

FUT8 promotes breast cancer cell invasiveness by remodeling TGF-β receptor core fucosylation

BACKGROUND

Core fucosylation (addition of fucose in α-1,6-linkage to core N-acetylglucosamine of N-glycans) catalyzed by fucosyltransferase 8 (FUT8) is critical for signaling receptors involved in many physiological and pathological processes such as cell growth, adhesion, and tumor metastasis. Transforming growth factor-β (TGF-β)-induced epithelial-mesenchymal transition (EMT) regulates the invasion and metastasis of breast tumors. However, whether receptor core fucosylation affects TGF-β signaling during breast cancer progression remains largely unknown.

METHOD

In this study, gene expression profiling and western blot were used to validate the EMT-associated expression of FUT8. Lentivirus-mediated gain-of-function study, short hairpin RNA (shRNA) or CRISPR/Cas9-mediated loss-of-function studies and pharmacological inhibition of FUT8 were used to elucidate the molecular function of FUT8 during TGF-β-induced EMT in breast carcinoma cells. In addition, lectin blot, luciferase assay, and in vitro ligand binding assay were employed to demonstrate the involvement of FUT8 in the TGF-β1 signaling pathway. The role of FUT8 in breast cancer migration, invasion, and metastasis was confirmed using an in vitro transwell assay and mammary fat pad xenograft in vivo tumor model.

RESULTS

Gene expression profiling analysis revealed that FUT8 is upregulated in TGF-β-induced EMT; the process was associated with the migratory and invasive abilities of several breast carcinoma cell lines. Gain-of-function and loss-of-function studies demonstrated that FUT8 overexpression stimulated the EMT process, whereas FUT8 knockdown suppressed the invasiveness of highly aggressive breast carcinoma cells. Furthermore, TGF-β receptor complexes might be core fucosylated by FUT8 to facilitate TGF-β binding and enhance downstream signaling. Importantly, FUT8 inhibition suppressed the invasive ability of highly metastatic breast cancer cells and impaired their lung metastasis.

CONCLUSIONS

Our results reveal a positive feedback mechanism of FUT8-mediated receptor core fucosylation that promotes TGF-β signaling and EMT, thus stimulating breast cancer cell invasion and metastasis.

Profiling of core fucosylated N-glycans using a novel bacterial lectin that specifically recognizes α1,6 fucosylated chitobiose

A novel fucose-binding lectin (SL2-1) from the bacterium Streptomyces rapamycinicus was identified by analysis of metagenomic DNA sequences. SL2-1 belongs to a new group of bacterial fucose-specific lectins that have no similarity to known bacterial fucose-binding proteins, but are related to certain eukaryotic fucose-binding lectins. The 17 kDa protein was expressed recombinantly in E. coli and purified by affinity chromatography. Glycan microarray analysis with fluorescently labeled recombinant SL2-1 demonstrated its ability to bind to core α1-6 fucosylated N-glycans, but not to core α1-3 fucosylated N-glycans, or other α1-2, α1-3 and α1-4 fucosylated oligosaccharides. The minimal high affinity binding epitope of SL2-1 was α1-6 fucosylated di-n-acetylchitobiose. The recombinant lectin was efficient in detection of N-glycan core fucosylation using lectin blotting and lectin ELISA assays. Finally, a workflow using SL2-1 for selective and quantitative profiling of core fucosylated N-glycans using UPLC-HILIC-FLR analysis was established. The approach was validated for selective capture and analysis of core fucosylated N-glycans present in complex glycan mixtures derived from mammalian serum IgG.

Enzymes for N-Glycan Branching and Their Genetic and Nongenetic Regulation in Cancer

N-glycan, a fundamental and versatile protein modification in mammals, plays critical roles in various physiological and pathological events including cancer progression. The formation of N-glycan branches catalyzed by specific N-acetylglucosaminyltransferases [GnT-III, GnT-IVs, GnT-V, GnT-IX (Vb)] and a fucosyltransferase, Fut8, provides functionally diverse N-glycosylated proteins. Aberrations of these branches are often found in cancer cells and are profoundly involved in cancer growth, invasion and metastasis. In this review, we focus on the GlcNAc and fucose branches of N-glycans and describe how their expression is dysregulated in cancer by genetic and nongenetic mechanisms including epigenetics and nucleotide sugar metabolisms. We also survey the roles that these N-glycans play in cancer progression and therapeutics. Finally, we discuss possible applications of our knowledge on basic glycobiology to the development of medicine and biomarkers for cancer therapy.