The sweet and sour of serological glycoprotein tumor biomarker quantification

A compact microfluidic laser-induced fluorescence immunoassay system using avalanche photodiode for rapid detection of alpha-fetoprotein

Alpha-fetoprotein (AFP), commonly employed for early diagnosis of liver cancer, serves as a biomarker for cancer screening and diagnosis. Combining the high sensitivity and specificity of fluorescence immunoassay (FIA), developing a low-cost and efficient immunoassay system for AFP detection holds significant importance in disease diagnosis. In this work, we developed a miniaturized oblique laser-induced fluorescence (LIF) immunoassay system, coupled with a microfluidic PMMA/paper hybrid chip, for rapid detection of AFP. The system employed an avalanche photodiode (APD) as the detector, and implemented multi-level filtering in the excitation light channel using the dichroic mirror and optical trap. At first, we employed the Savitzky-Golay filter and baseline off-set elimination methods to denoise and normalize the original data. Then the cutoff frequency of the low-pass filter and the reverse voltage of the APD were optimized to enhance the detection sensitivity of the system. Furthermore, the effect of laser power on the fluorescence excitation efficiency was investigated, and the sampling time during the scanning process was optimized. Finally, a four-parameter logistic (4PL) model was utilized to establish the concentration-response equation for AFP. The system was capable of detecting concentrations of AFP standard solution within the range of 1-500 ng/mL, with a detection limit of 0.8 ng/mL. The entire immunoassay process could be completed within 15 min. It has an excellent potential for applications in low-cost portable diagnostic instruments for the rapid detection of biomarkers.

LeGenD: determining N-glycoprofiles using an explainable AI-leveraged model with lectin profiling

Glycosylation affects many vital functions of organisms. Therefore, its surveillance is critical from basic science to biotechnology, including biopharmaceutical development and clinical diagnostics. However, conventional glycan structure analysis faces challenges with throughput and cost. Lectins offer an alternative approach for analyzing glycans, but they only provide glycan epitopes and not full glycan structure information. To overcome these limitations, we developed LeGenD, a lectin and AI-based approach to predict N-glycan structures and determine their relative abundance in purified proteins based on lectin-binding patterns. We trained the LeGenD model using 309 glycoprofiles from 10 recombinant proteins, produced in 30 glycoengineered CHO cell lines. Our approach accurately reconstructed experimentally-measured N-glycoprofiles of bovine Fetuin B and IgG from human sera. Explanatory AI analysis with SHapley Additive exPlanations (SHAP) helped identify the critical lectins for glycoprofile predictions. Our LeGenD approach thus presents an alternative approach for N-glycan analysis.

Development and validation of glycosyltransferase related-gene for the diagnosis and prognosis of head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a highly heterogeneous cancer characterized by difficulties in early diagnosis and outcome prediction. Aberrant glycosylated structures produced by the aberrant expression of glycosyltransferases are prevalent in HNSCC. In this study, we aim to construct glycosyltransferase-related gene signatures with diagnostic and prognostic value to better stratify patients with HNSCC and improve their diagnosis and prognosis.

METHODS

Bioinformatic tools were used to process data of patients with HNSCC from The Cancer Genome Atlas (TCGA) database. The prognostic model was formatted using univariate and multivariate Cox regression methods, while the diagnostic signature was constructed using support vector machine (SVM) and LASSO analysis. The results were verified using the Gene Expression Omnibus (GEO) cohort. The tumor microenvironment and benefits of immune checkpoint inhibitor (ICI) therapy in subgroups defined by glycosyltransferase-related genes were analyzed. Molecular biology experiments, including western blotting, cell counting kit (CCK)-8, colony formation, wound healing, and Transwell assays, were conducted to confirm the oncogenic function of beta-1,4-galactosyltransferase 3 (B4GALT3) in HNSCC.

RESULTS

We established a five-gene prognostic signature and a 15-gene diagnostic model. Based on the median risk score, patients with low risk had longer overall survival than those in the high-risk group, which was consistent with the results of the GEO cohort. The concrete results suggested that high-risk samples were related to a high tumor protein (TP)53 mutation rate, high infiltration of resting memory cluster of differentiation (CD)4 T cells, resting natural killer (NK) cells, and M0 macrophages, and benefited from ICI therapy. In contrast, the low-risk subgroup was associated with a low TP53 mutation rate; and high infiltration of naive B cells, plasma cells, CD8 T cells, and resting mast cells; and benefited less from ICI therapy. In addition, the diagnostic model had an area under curve (AUC) value of 0.997 and 0.978 in the training dataset and validation cohort, respectively, indicating the high diagnostic potential of the model. Ultimately, the depletion of B4GALT3 significantly hindered the proliferation, migration, and invasion of HNSCC cells.

CONCLUSIONS

We established two new biomarkers that could provide clinicians with diagnostic, prognostic, and treatment guidance for patients with HNSCC.

Evaluation of catalytic activity of human and animal origin viral neuraminidase: Current prospect

With the exception of plants, almost all living organisms synthesize neuraminidase/sialidase. It is a one among the crucial proteins that controls how virulent a microorganism is. An essential enzyme in orthomyxoviruses and paramyxoviruses that destroys receptors is neuraminidase. It plays a number of roles throughout the viral life cycle in addition to one that involves the release of progeny virus particles. This protein is an important target for therapeutic interventions and diagnostic assays. Neuraminidase inhibitors effectively prevent the spread of disease and viral infection. Sensitive, quick, and inexpensive high throughput assays are needed to screen for specific neuraminidase inhibitory chemicals. To characterize the neuraminidase catalytic activity, however, the traditional assays are still the most common in laboratories. This review gives a brief overview of these neuraminidase assays and recent, innovative developments, particularly those involving biosensors.

Comparative site-specific N-glycoproteome analysis reveals aberrant N-glycosylation and gives insights into mannose-6-phosphate pathway in cancer

N-glycosylation is implicated in cancers and aberrant N-glycosylation is recognized as a hallmark of cancer. Here, we mapped and compared the site-specific N-glycoproteomes of colon cancer HCT116 cells and isogenic non-tumorigenic DNMT1/3b double knockout (DKO1) cells using Fbs1-GYR N-glycopeptide enrichment technology and trapped ion mobility spectrometry. Many significant changes in site-specific N-glycosylation were revealed, providing a molecular basis for further elucidation of the role of N-glycosylation in protein function. HCT116 cells display hypersialylation especially in cell surface membrane proteins. Both HCT116 and DKO1 show an abundance of paucimannose and 80% of paucimannose-rich proteins are annotated to reside in exosomes. The most striking N-glycosylation alteration was the degree of mannose-6-phosphate (M6P) modification. N-glycoproteomic analyses revealed that HCT116 displays hyper-M6P modification, which was orthogonally validated by M6P immunodetection. Significant observed differences in N-glycosylation patterns of the major M6P receptor, CI-MPR in HCT116 and DKO1 may contribute to the hyper-M6P phenotype of HCT116 cells. This comparative site-specific N-glycoproteome analysis provides a pool of potential N-glycosylation-related cancer biomarkers, but also gives insights into the M6P pathway in cancer.

Preparation of IgG imprinted polymers by metal-free visible-light-induced ATRP and its application in biosensor

Immunoglobulin G (IgG) is related to the occurrence of many diseases, such as measles and inflammatory. In this paper, IgG imprinted polymers (IgGIPs) were fabricated on the surface of nano Au/nano Ni modified Au electrode (IgGIPs/AuNCs/NiNCs/Au) via metal-free visible-light-induced atom transfer radical polymerization (MVL ATRP). The IgGIPs were prepared by IgG conjugated with fluorescein isothiocyanate (FITC-IgG) as both a template and a photocatalyst. After the templates were removed, the photocatalysts (FITC) would not remain in the polymer and avoided all the effect of catalysts on the electrode. The fabricated electrodes were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Under the optimized conditions, IgGIPs/AuNCs/NiNCs/Au was prepared and used as an electrochemical biosensor. The biosensor could be successfully applied for the determination of IgG by differential pulse voltammetry (DPV) measurement. The results showed that the proposed biosensor displayed a broader linear range and a lower detection limit for IgG determination when it was compared to those similar IgG sensors. The linear range from 1.0 × 10^-6 mg L^-1 to 1.0 × 10¹ mg L^-1 was obtained with a low detection limit (LOD) of 2.0 × 10^-8 mg L^-1 (S/N = 3). Briefly, the biosensor in this study introduced an easy and non-toxic method for IgG determination and also provided a progressive approach for designing protein imprinted polymers.

Glycomic-Based Biomarkers for Ovarian Cancer: Advances and Challenges

Ovarian cancer remains one of the most common causes of death among gynecological malignancies afflicting women worldwide. Among the gynecological cancers, cervical and endometrial cancers confer the greatest burden to the developing and the developed world, respectively; however, the overall survival rates for patients with ovarian cancer are worse than the two aforementioned. The majority of patients with ovarian cancer are diagnosed at an advanced stage when cancer has metastasized to different body sites and the cure rates, including the five-year survival, are significantly diminished. The delay in diagnosis is due to the absence of or unspecific symptoms at the initial stages of cancer as well as a lack of effective screening and diagnostic biomarkers that can detect cancer at the early stages. This, therefore, provides an imperative to prospect for new biomarkers that will provide early diagnostic strategies allowing timely mitigative interventions. Glycosylation is a protein post-translational modification that is modified in cancer patients. In the current review, we document the state-of-the-art of blood-based glycomic biomarkers for early diagnosis of ovarian cancer and the technologies currently used in this endeavor.

Clinical Perspective on Proteomic and Glycomic Biomarkers for Diagnosis, Prognosis, and Prediction of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is known as a highly aggressive malignant disease. Prognosis for patients is notoriously poor, despite improvements in surgical techniques and new (neo)adjuvant chemotherapy regimens. Early detection of PDAC may increase the overall survival. It is furthermore foreseen that precision medicine will provide improved prognostic stratification and prediction of therapeutic response. In this review, omics-based discovery efforts are presented that aim for novel diagnostic and prognostic biomarkers of PDAC. For this purpose, we systematically evaluated the literature published between 1999 and 2020 with a focus on protein- and protein-glycosylation biomarkers in pancreatic cancer patients. Besides genomic and transcriptomic approaches, mass spectrometry (MS)-based proteomics and glycomics of blood- and tissue-derived samples from PDAC patients have yielded new candidates with biomarker potential. However, for reasons discussed in this review, the validation and clinical translation of these candidate markers has not been successful. Consequently, there has been a change of mindset from initial efforts to identify new unimarkers into the current hypothesis that a combination of biomarkers better suits a diagnostic or prognostic panel. With continuing development of current research methods and available techniques combined with careful study designs, new biomarkers could contribute to improved detection, prognosis, and prediction of pancreatic cancer.

Preparation and Nanoencapsulation of Lectin from Lepidium sativum on Chitosan-Tripolyphosphate Nanoparticle and Their Cytotoxicity against Hepatocellular Carcinoma Cells (HepG2)

Lectins are the oligomeric sugar-specific glycoprotein of nonimmune origin, are involved in the multiple biological recognition process, and have the capacity to perform a wide variety of physiological functions including antifungal, antiviral, antitumor, and cell agglutination. The main objective of the current study was to prepare lectin protein-loaded chitosan-TPP nanoparticles via ionic gelation methods with different CS/TPP ratios and to investigate anticancer potential against HepG2 cells. The best ratio showed the mean particle size (298.10 ± 1.9 nm, 21.05 ± 0.95 mv) with optimal encapsulation efficiencies of 52.435 ± 0.09%. The cytotoxicity was evaluated against HepG2 cells, and IC₅₀ values obtained were 265 μg/ml for lectin protein and 105 μg/ml for lectin-loaded chitosan-TPP nanoparticles, respectively. The mRNA expression of proliferation markers like GPC3 was significantly decreased in hepatocellular carcinoma cells (HepG2) during lectin protein-loaded chitosan-TPP nanoparticle treatment. Apoptotic genes that indicating a marked increase in expression are Caspase 3, p53, and Bax, while Bcl2 and AFP showed a downregulation of expression after treatment of HepG2 cells with lectin-loaded chitosan-TPP nanoparticles. The preliminary findings of our study highlighted that lectin protein-loaded chitosan-TPP nanoparticles could be a promising anticancer agent.

POFUT1 mRNA expression as an independent prognostic parameter in muscle-invasive bladder cancer

Muscle-invasive bladder cancer (MIBC) is characterized by high recurrence and rapid progression. Progression is linked to changes in glycan structures and altered levels of glycosyltransferases. The relationship of mRNA expression by glycosyltransferase genes B4GALT1, EXT1, MGAT5B, and POFUT1 to the probability of surviving MIBC after radical cystectomy has not yet been investigated.

mRNA expression was analyzed using qRT-PCR in formalin-fixed and paraffin-embedded tumor samples (n = 105; 74% male patients and 26% female patients; median age = 72 years), correlated with histopathological variables, and evaluated by means of multivariable Cox regression analysis regarding to overall survival (OS), cancer-specific survival (CSS), and disease-free survival (DFS).

Multivariable Cox regression analysis identified POFUT1 mRNA expression as superior prognostic marker, compared with currently used histological tumor stage methods, for CSS by MIBC patients following radical cystectomy. Thus, the patients with low POFUT1 mRNA were at a 4.9-fold greater risk for cancer-specific death according to the multivariable analysis (p = 0.0001). Low mRNA levels predicted poor survival according to the Kaplan-Meier analysis ((POFUT1:OS p = 0.0014; CSS p = 0.0007; DFS p = 0.0088); (EXT1:OS p = 0.0150; CSS p = 0.0130; DFS p = 0.0286); (B4GALT1:CSS p = 0.0134; DFS p = 0.0493)). A subgroup analysis of patients without lymph node metastasis (pN−; n = 73) indicated that low expression of POFUT1 predicted reduced OS (p = 0.0073), CSS (p = 0.0058,) and DSS (p = 0.0079).

Low levels of POFUT1 mRNA are an independent prognostic indicator for OS and CSS in MIBC patients following radical cystectomy. This finding demonstrates the importance of altered glycosylation for the progress of MIBC.

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Low POFUT1 mRNA expression is associated with a higher risk for overall and cancer-specific death in MIBC treated with RC.

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MIBC patients with pN0 histology and, decreased POFUT1 mRNA levels showed poor outcome for OS, CSS and, DFS.

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POFUT1 mRNA is an independent prognostic indicator for OS and CSS in multivariable analysis of MIBC patients following RC.

Antibody Panel Based N-Glycan Imaging for N-Glycoprotein Biomarker Discovery

Antibody panel based N-glycan imaging is a novel platform for N-glycan analysis of immunocaptured proteins. N-glycosylation is a post-translational modification of pathophysiological importance and is often studied in the context of disease biomarkers. Determination of protein-specific N-glycosylation changes in patient samples has traditionally been laborious or limited to study of a single protein per analysis. This novel technique allows for the multiplexed analysis of N-glycoproteins from biofluids. Briefly, this platform consists of antibodies spotted in an array panel to a microscope slide, specific capture of glycoproteins from a biological sample, and then enzymatic release of N-glycans for analysis by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). N-glycans are detected at each individual spot, allowing N-glycan information to easily be linked back to its protein carrier. Using this protocol, multiplexed analysis of N-glycosylation on serum glycoproteins can be performed. Human serum is discussed here, but this method has potential to be applied to other biofluids and to any glycoprotein that can be captured by a validated antibody. © 2019 by John Wiley & Sons, Inc. Basic Protocol: Antibody panel based N-glycan imaging by MALDI MS Support Protocol: Confirmation of antibody capture by IR-labeled proteins.

Protein Glycosylation Investigated by Mass Spectrometry: An Overview

The protein glycosylation is a post-translational modification of crucial importance for its involvement in molecular recognition, protein trafficking, regulation, and inflammation. Indeed, abnormalities in protein glycosylation are correlated with several disease states such as cancer, inflammatory diseases, and congenial disorders. The understanding of cellular mechanisms through the elucidation of glycan composition encourages researchers to find analytical solutions for their detection. Actually, the multiplicity and diversity of glycan structures bond to the proteins, the variations in polarity of the individual saccharide residues, and the poor ionization efficiencies make their detection much trickier than other kinds of biopolymers. An overview of the most prominent techniques based on mass spectrometry (MS) for protein glycosylation (glycoproteomics) studies is here presented. The tricks and pre-treatments of samples are discussed as a crucial step prodromal to the MS analysis to improve the glycan ionization efficiency. Therefore, the different instrumental MS mode is also explored for the qualitative and quantitative analysis of glycopeptides and the glycans structural composition, thus contributing to the elucidation of biological mechanisms.

Aptamers targeting protein-specific glycosylation in tumor biomarkers: general selection, characterization and structural modeling

Detecting specific protein glycoforms is attracting particular attention due to its potential to improve the performance of current cancer biomarkers. Although natural receptors such as lectins and antibodies have served as powerful tools for the detection of protein-bound glycans, the development of effective receptors able to integrate in the recognition both the glycan and peptide moieties is still challenging. Here we report a method for selecting aptamers toward the glycosylation site of a protein. It allows identification of an aptamer that binds with nM affinity to prostate-specific antigen, discriminating it from proteins with a similar glycosylation pattern. We also computationally predict the structure of the selected aptamer and characterize its complex with the glycoprotein by docking and molecular dynamics calculations, further supporting the binary recognition event. This study opens a new route for the identification of aptamers for the binary recognition of glycoproteins, useful for diagnostic and therapeutic applications.

Binary recognition of the glycoprotein prostate specific antigen by aptamers: a tool for detecting aberrant glycosylation associated with cancer.

Aberrant sialylation in ovarian cancers

Sialylation (the covalent addition of sialic acid to the terminal end of glycoproteins or glycans), tightly regulated cell- and microenvironment-specific process and orchestrated by sialyltransferases and sialidases (neuraminidases) family, is one of the posttranslational modifications, which plays an important biological role in the maintenance of normal physiology and involves many pathological dysfunctions. Glycans have roles in all the cancer hallmarks, referring to capabilities acquired during all steps of cancer development to initiate malignant transformation (a driver of a malignant genotype), enable cancer cells to survive, proliferate, and metastasize (a consequence of a malignant phenotype), which includes sustaining proliferative signaling, evading growth suppressor, resisting cell apoptosis, enabling replicative immortality, inducing angiogenesis, reprogramming of energy metabolism, evading tumor destruction, accumulating inflammatory microenvironment, and activating invasion and accelerating metastases. Regarding the important role of altered sialylation of cancers, further knowledge about the initiation and the consequences of altered sialylation pattern in tumor cells is needed, because all may offer a better chance for developing novel therapeutic strategy. In this review, we would like to update alteration of sialylation in ovarian cancers.

Lectin biosensors in cancer glycan biomarker detection

Cancer has high incidence and it will continue to increase over the next decades. Detection and quantification of cancer-associated biomarkers is frequently carried out for diagnosis, prognosis and treatment monitoring at various disease stages. It is well-known that glycosylation profiles change significantly during oncogenesis. Aberrant glycans produced during tumorigenesis are, therefore, valuable molecules for detection and characterization of cancer, and for therapeutic design and monitoring. Although glycoproteomics has benefited from the development of analytical tools such as high performance liquid chromatography, two-dimensional gel and capillary electrophoresis and mass spectrometry, these approaches are not well suited for rapid point-of-care (POC) testing easily performed by medical staff. Lectins are biomolecules found in nature with specific affinities toward particular glycan structures and bind them thus forming a relatively strong complex. Because of this characteristic, lectins have been used in analytical techniques for the selective capture or separation of certain glycans in complex samples, namely, in lectin affinity chromatography, or to characterize glycosylation profiles in diverse clinical situations, using lectin microarrays. Lectin-based biosensors have been developed for the detection of specific aberrant and cancer-associated glycostructures to aid diagnosis, prognosis and treatment assessment of these patients. The attractive features of biosensors, such as portability and simple use make them highly suitable for POC testing. Recent developments in lectin biosensors, as well as their potential and pitfalls in cancer glycan biomarker detection, are presented in this chapter.

Glycosylation and its implications in breast cancer

Introduction: For decades, the role of glycans and glycoproteins in the progression of breast cancer and other cancers have been evaluated. Through extensive studies focused on elucidating the biological functions of glycosylation, researchers have been able to implicate alterations in these functions to tumor formation and metastasis. Areas covered: In this review, we summarize how changes in glycosylation are associated with tumorigenesis, with emphasis on breast cancers. An overview of the changes in N-linked and O-linked glycans associated with breast cancer tumors and biofluids are described. Recent advances in glycomics are emphasized in the context of continuing to decipher the glycosylation changes associated with breast cancer progression. Expert opinion: While changes in glycosylation have been studied in breast cancer for many years, the clinical relevance of these studies has been limited. This reflects the inherent biological and clinical heterogeneity of breast cancers. Glycomics analysis lags behind the advances in genomics and proteomics, but new approaches are emerging. A summary of known glycosylation changes associated with breast cancer is necessary to implement new findings in the context of clinical outcomes and therapeutic strategies. A better understanding of the dynamics of tumor and immune glycosylation is critical to improving emerging immunotherapeutic treatments.

A Novel Mass Spectrometry Platform for Multiplexed N-Glycoprotein Biomarker Discovery from Patient Biofluids by Antibody Panel Based N-Glycan Imaging

A new platform for N-glycoprotein analysis from serum that combines matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) workflows with antibody slide arrays is described. Antibody panel based (APB) N-glycan imaging allows for the specific capture of N-glycoproteins by antibodies on glass slides and N-glycan analysis in a protein-specific and multiplexed manner. Development of this technique has focused on characterizing two abundant and well-studied human serum glycoproteins, alpha-1-antitrypsin and immunoglobulin G. Using purified standard solutions and 1 μL samples of human serum, both glycoproteins can be immunocaptured and followed by enzymatic release of N-glycans. N-Glycans are detected with a MALDI FT-ICR mass spectrometer in a concentration-dependent manner while maintaining specificity of capture. Importantly, the N-glycans detected via slide-based antibody capture were identical to that of direct analysis of the spotted standards. As a proof of concept, this workflow was applied to patient serum samples from individuals with liver cirrhosis to accurately detect a characteristic increase in an IgG N-glycan. This novel approach to protein-specific N-glycan analysis from an antibody panel can be further expanded to include any glycoprotein for which a validated antibody exists. Additionally, this platform can be adapted for analysis of any biofluid or biological sample that can be analyzed by antibody arrays.

Glycosylation markers in cancer

Alteration of glycosylation, a hallmark of cancer, results in the production of tumor-associated glycans or glycoproteins. These molecules are subsequently secreted or membrane-shed into the blood stream and thus serve as tumor-associated markers. Increased glycosylation in cancer is triggered by overexpression of glycoproteins that carry certain specific glycans, increase or decrease of nucleotide sugar donors and altered expression of glycosyltransferase and glycosidase enzymes. In this chapter, the biochemistry and function of glycoprotein, glycan and enzyme markers are reviewed. These glycosylation markers, applicable for detection and monitoring of cancer, include CA19-9, CA125, CEA, PSA and AFP. Because of their specific affinity to distinct sugar moieties, lectins are useful for developing assays to detect these tumor associated glycans and glycoproteins in clinical samples. As such, various enzyme-linked lectin assays (ELLA) have been developed for diagnosis, monitoring and prognosis. Because glycosylation changes occur early in cancer, the detection of tumor associated glycosylation markers using lectin based assays is an effective strategy to improve diagnosis and treatment resulting better outcomes clinically.

Unravelling the lipocalin 2 interaction with aptamers: May rolling circle amplification improve their functional affinity?

Cancer diagnosis based on serum biomarkers requires receptors of extreme sensitivity and selectivity. Tunability of aptamer selection makes them ideal for that challenge. However, aptamer characterization is a time-consuming task, not always thoroughly addressed, leading to suboptimal aptamer performance. In this work, we report on the affinity characterization and potential usage of two aptamers against a candidate cancer biomarker, the neutrophil gelatinase-associated lipocalin (NGAL). Electrochemical sandwich assays on Au electrodes and SPR experiments showed a restricted capture ability of one of the aptamers (LCN2-4) and a small detectability of the other (LCN2-2). Interestingly, a truncated version of the signaling aptamer LCN2-2 selectively binds to NGAL covalently linked to magnetic beads due to high local protein concentration. The functional affinity of this aptamer is enhanced by three-orders of magnitude using rolling circle amplification (RCA), completed in only 15 min, followed by hybridization with short complementary fluorescein-tag probes, enzyme labeling and chronoamperometric measurement. Microscale thermophoresis experiments show a poor affinity for the protein in solution, which urges the importance of a full and in-depth characterization of aptamers to be used as diagnostic reagents.

Clinical significance of fucosylated GP73 in the differential diagnosis of hepatocellular carcinoma

OBJECTIVE:

To investigate the clinical value of fucosylated GP73 (Fuc-GP73) levels for differential diagnosis of hepatocellular carcinoma from other liver diseases.

METHODS:

Serum specimens were collected from 50 patients with hepatocellular carcinoma, 60 patients with other digestive system diseases (ODSD), and 40 normal controls. Lectin affinity chromatography column combining with the enzyme-linked immunosorbent assay (ELISA) using the ELISA index was utilized to measure the level of Fuc-GP73. By receiver operating characteristic (ROC) curve analysis its sensitivity and specificity were used to evaluate the diagnostic significance of Fuc-GP73 in hepatocellular carcinoma.

RESULTS:

The median serum Fuc-GP73 level of hepatocellular carcinoma (20.4 μg/L) was much higher than that of ODSD patients (1.8 μg/L) and the normal controls group (0.3 μg/L), significantly ( P <0.01). There was no significant correlation between serum Fuc-GP73 level and sex, age, and tumor size in the hepatocellular carcinoma group ( P > 0.05); however, it was related to tumor, node, metastasis stage and lymph node metastasis ( P <0.05). The area under the ROC curve (AUC) of Fuc-GP73 to detect hepatocellular carcinoma alone was 0.885; with the prespecified specificity of 95%, the sensitivity and the cutoff value were 82% and 3.1 μg/L. In addition, the combined test of Fuc-GP73 with other biomarkers can improve the clinical diagnostic efficiency; the AUC can reach to 0.983; and with the prespecified specificity of 95% its sensitivity increased to 94%.

CONCLUSION:

Fuc-GP73 can act as a superior glycobiomarker for the differential diagnosis of hepatocellular carcinoma; its combined detection with other biomarkers can improve diagnostic accuracy.

Lectin-based biosensors as analytical tools for clinical oncology

The review focus on the use of lectin-based biosensors in the oncology field, and ponders the potentialities of using these devices as analytical tools to monitor the levels of cancer glycobiomarkers in biological fluids, helping in the diagnosis, prognosis and treatment assessment. Several examples of lectin-based biosensors directed for cancer biomarkers are described and discussed, and their potential application in the clinic is considered, taking into account their analytical features, advantages and performance in sample analysis. Technical and practical aspects in the construction process, which are specific for lectin biosensors, are debated, as well as the requirements in sample collection and processing, and biosensor validation. Today's challenges for real implementation of these devices in the clinic are presented, along with the future trends in the field.

N-glycan microheterogeneity regulates interactions of plasma proteins

Glycosylation is one of the most common and complex posttranslation modifications that significantly influences protein structure and function. However, linking individual glycan structures to protein interactions remains challenging and typically requires multiple techniques. Here, we establish a mass-spectrometric approach to systematically dissect the microheterogeneity of two important serum proteins, α1-acid glycoprotein and haptoglobin, and relate glycan features to drug and protein-binding interaction kinetics. We found that the degree of N-glycan branching and extent of terminal fucosylation can attenuate or enhance these interactions, providing important insight into drug transport in plasma. Our study demonstrates an approach capable of investigating how protein glycosylation fine-tunes protein–drug interactions at the glycan-specific level and will prove universally useful for studying glycoprotein interactions.

Altered glycosylation patterns of plasma proteins are associated with autoimmune disorders and pathogenesis of various cancers. Elucidating glycoprotein microheterogeneity and relating subtle changes in the glycan structural repertoire to changes in protein–protein, or protein–small molecule interactions, remains a significant challenge in glycobiology. Here, we apply mass spectrometry-based approaches to elucidate the global and site-specific microheterogeneity of two plasma proteins: α1-acid glycoprotein (AGP) and haptoglobin (Hp). We then determine the dissociation constants of the anticoagulant warfarin to different AGP glycoforms and reveal how subtle N-glycan differences, namely, increased antennae branching and terminal fucosylation, reduce drug-binding affinity. Conversely, similar analysis of the haptoglobin–hemoglobin (Hp–Hb) complex reveals the contrary effects of fucosylation and N-glycan branching on Hp–Hb interactions. Taken together, our results not only elucidate how glycoprotein microheterogeneity regulates protein–drug/protein interactions but also inform the pharmacokinetics of plasma proteins, many of which are drug targets, and whose glycosylation status changes in various disease states.

Glycoprotein biomarkers for the detection of pancreatic ductal adenocarcinoma

Pancreatic cancer (PaC) shows a clear tendency to increase in the next years and therefore represents an important health and social challenge. Currently, there is an important need to find biomarkers for PaC early detection because the existing ones are not useful for that purpose. Recent studies have indicated that there is a large window of time for PaC early detection, which opens the possibility to find early biomarkers that could greatly improve the dismal prognosis of this tumor. The present manuscript reviews the state of the art of the existing PaC biomarkers. It focuses on the anomalous glycosylation process and its role in PaC. Glycan structures of glycoconjugates such as glycoproteins are modified in tumors and these modifications can be detected in biological fluids of the cancer patients. Several studies have found serum glycoproteins with altered glycan chains in PaC patients, but they have not shown enough specificity for PaC. To find more specific cancer glycoproteins we propose to analyze the glycan moieties of a battery of glycoproteins that have been reported to increase in PaC tissues and that can also be found in serum. The combination of these new candidate glycoproteins with their aberrant glycosylation together with the existing biomarkers could result in a panel, which would expect to give better results as a new tool for early diagnosis of PaC and to monitor the disease.

Use of CA15‑3 for screening breast cancer: An antibody‑lectin sandwich assay for detecting glycosylation of CA15‑3 in sera

Elevated serum CA15-3 assessed by enzyme-linked immunosorbent assay (ELISA) has been considered a diagnostic marker of breast cancer. However, accumulating data indicate that the current ELISA system for detecting CA15-3, which targets the peptide backbone of CA15-3, is not sufficiently sensitive to detect early or localized breast cancer. In the present study, we designed an antibody-lectin sandwich assay detecting glycosylation of CA15-3 in patients with breast cancer. Immobilized anti-CA15-3 monoclonal antibody captures CA15-3 in serum, and glycosylation of the CA15-3 is detected with Concanavalin A (ConA) lectin, which preferentially bind high-mannose N-glycans. ConA provided the best signal for detecting serum CA15-3 among 9 types of lectin, Since CA15-3 is a heavily glycosylated protein, detecting the glycosylation of CA15-3 should be a much more sensitive way to assess CA15-3 than the current ELISA method. Linear responses were obtained in the anti-CA15-3 antibody-ConA sandwich assay when sera were diluted up to 2000-fold. This dilution factor is comparable with that of the current ELISA system which allows 50- to 100-fold serum dilutions. The glycosylation level of CA15-3 was found to increase with increasing breast cancer stage in the sandwich assay. The assay system appeared to efficiently discriminate breast cancer stage I (sensitivity: 63%, specificity: 69%), IIA (sensitivity: 77%, specificity: 75%), IIB (sensitivity: 69%, specificity: 86%) and III (sensitivity: 80%, specificity: 65%) from benign breast disease. The antibody-lectin sandwich assay shows promise as a new prospect for the early detection of breast cancer.

Diagnostic utility of glycosyltransferase mRNA expression in gastric cancer

OBJECTIVE/BACKGROUND

Posttranslational modification of proteins, including glycosylation, is known to differ between normal and tumor cells. Altered glycosyltransferase levels have been observed in tumor tissues and their role in tumor metastasis and invasion has been implicated. In this study the role of altered glycosyltransferase messenger RNA (mRNA) levels in serum of gastric cancer patients as early markers of gastric cancer was evaluated.

METHODS

In this case control study the expression profile of ppGalNAc-T6, GlcNAcT-V, ST3Gal I, ST3 Gal IV, and ST6GalNAc-I in normal healthy control and gastric cancer patients was compared. Serum was isolated from blood samples of gastric cancer patients (n = 200) and controls (n = 200). Following RNA extraction, reverse transcription was carried out and transcript levels of glycosyltransferases were determined using real-time quantitative polymerase chain reaction and normalized against glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression. The amount of target gene, normalized to an endogenous reference gene relative to calibrator was calculated by using ΔΔCT method. Transcript levels in the serum samples of gastric cancer patients were compared with those of controls; also the same was correlated within sex and different stages of disease.

RESULTS

The mRNA expression of ppGalNAc-T6 and ST6GalNAc-I was significantly higher in serum samples of gastric cancer patients on comparison with controls (p = .008), however, there was no significant difference in mRNA expression of GlcNAcT-V, ST3Gal I, and ST3 Gal IV in serum samples of gastric cancer patients and controls (p = .097). In addition, no significant association of mRNA expression of these glycosyltransferases was found within sex and stages in this study.

CONCLUSION

This study revealed the potential of ppGalNAc-T6 and ST6GalNAc-I mRNA transcript levels in serum as markers of gastric cancer. Further studies on the wider range of glycosyltransferases in various cancers are needed to establish signature mRNA batteries as minimally invasive markers of gastric cancer.

Recent advances in mass spectrometry-based glycoproteomics

Protein glycosylation plays fundamental roles in many biological processes as one of the most common, and the most complex, posttranslational modification. Alterations in glycosylation profile are now known to be associated with many diseases. As a result, the discovery and detailed characterization of glycoprotein disease biomarkers is a primary interest of biomedical research. Advances in mass spectrometry (MS)-based glycoproteomics and glycomics are increasingly enabling qualitative and quantitative approaches for site-specific structural analysis of protein glycosylation. While the complexity presented by glycan heterogeneity and the wide dynamic range of clinically relevant samples like plasma, serum, cerebrospinal fluid, and tissue make comprehensive analyses of the glycoproteome a challenging task, the ongoing efforts into the development of glycoprotein enrichment, enzymatic digestion, and separation strategies combined with novel quantitative MS methodologies have greatly improved analytical sensitivity, specificity, and throughput. This review summarizes current MS-based glycoproteomics approaches and highlights recent advances in its application to cancer biomarker and neurodegenerative disease research.

Synthesis of magnetic molecularly imprinted nanoparticles with multiple recognition sites for the simultaneous and selective capture of two glycoproteins

Magnetic molecularly imprinted nanoparticles with multiple recognition sites were prepared, which exhibited excellent selectivity for two glycoproteins simultaneously.

Correlation of serum sialyl Tn antigen values determined by immunoassay and SRM based method

We previously identified four glycan tumor marker candidates using a HPLC-based method. One candidate was sialyl Tn (STN), NeuAcα2-6-GalNAc. In this study, glycans were prepared from sera by hydrazine treatment followed by fluorescent labeling with aminopyridine. Pyridylaminated-STN levels of 147 gastric cancer, 85 pancreatic cancer and 10 cholangiocarcinoma patients together with 102 normal controls were accurately quantified using HPLC separation followed by selected reaction monitoring (SRM) assay, which used a stable isotope, tetradeuterium-labeled pyridylamino glycan as an internal standard. Additionally, STN values were also quantified using conventional competitive inhibition radioimmunoassay (RIA). The two STN levels determined by RIA and SRM gave a similar distribution pattern in sera. STN levels were increased in sera from cancer patients compared to those from normal controls. Moreover, the STN levels in sera of cancer patients determined by the two different assay procedures showed a good correlation (i.e., correlation coefficient >0.9). Our results suggest it may be better to determine STN levels using SRM instead of RIA.

Lectins: an effective tool for screening of potential cancer biomarkers

In recent years, the use of lectins for screening of potential biomarkers has gained increased importance in cancer research, given the development in glycobiology that highlights altered structural changes of glycans in cancer associated processes. Lectins, having the properties of recognizing specific carbohydrate moieties of glycoconjugates, have become an effective tool for detection of new cancer biomarkers in complex bodily fluids and tissues. The specificity of lectins provides an added advantage of selecting peptides that are differently glycosylated and aberrantly expressed in cancer patients, many of which are not possibly detected using conventional methods because of their low abundance in bodily fluids. When coupled with mass spectrometry, research utilizing lectins, which are mainly from plants and fungi, has led to identification of numerous potential cancer biomarkers that may be used in the future. This article reviews lectin-based methods that are commonly adopted in cancer biomarker discovery research.

The potent anti-cancer activity of Dioclea lasiocarpa lectin

The lectin DLasiL was isolated from seeds of the Dioclea lasiocarpa collected from the northeast coast of Brazil and characterized for the first time by mass spectrometry, DNA sequencing, inductively coupled plasma-mass spectrometry, electron paramagnetic resonance, and fluorescence spectroscopy. The structure of DLasiL lectin obtained by homology modelling suggested strong conservation of the dinuclear Ca/Mn and sugar-binding sites, and dependence of the solvent accessibility of tryptophan-88 on the oligomerisation state of the protein. DLasiL showed highly potent (low nanomolar) antiproliferative activity against several human carcinoma cell lines including A2780 (ovarian), A549 (lung), MCF-7 (breast) and PC3 (prostate), and was as, or more, potent than the lectins ConBr (Canavalia brasiliensis), ConM (Canavalia maritima) and DSclerL (Dioclea sclerocarpa) against A2780 and PC3 cells. Interestingly, DLasiL lectin caused a G2/M arrest in A2780 cells after 24h exposure, activating caspase 9 and delaying the on-set of apoptosis. Confocal microscopy showed that fluorescently-labelled DLasiL localized around the nuclei of A2780 cells at lectin doses of 0.5-2× IC₅₀ and gave rise to enlarged nuclei and spreading of the cells at high doses. These data reveal the interesting antiproliferative activity of DLasiL lectin, and suggest that further investigations to explore the potential of DLasiL as a new anticancer agent are warranted.

Assessment of Hepatocellular Carcinoma Metastasis Glycobiomarkers Using Advanced Quantitative N-glycoproteome Analysis

Hepatocelluar carcinoma (HCC) is one of the most common malignant tumors with high incidence of metastasis. Glycosylation is involved in fundamental molecular and cell biology process occurring in cancer including metastasis formation. In this study, lectin microarray, lectin blotting, lectin affinity chromatography and tandem ¹⁸O stable isotope labeling coupled with liquid chromatography-mass spectrometer (LC-MS) analysis were applied to quantify the changes in N-glycosite occupancy for HCC metastasis serum. Firstly, lectin microarray was used to screen glycoforms and Phaseolus vulgaris Leucoagglutinin (PHA-L) reactive structure (β1,6-GlcNAc branched N-glycan) was found to be increased significantly in HCC patients with metastasis compared with those with non-metastasis. Then, PHA-L affinity glycoproteins were enriched followed by N-glycosite occupancy measurement with strategy of tandem ¹⁸O stable isotope labeling. 11 glycoproteins with significantly changed N-glycosite occupancy were identified, they were associated with cell migration, invasion and adhesion through p38 mitogen-activated protein kinase signaling pathway and nuclear factor kappa B signaling pathway. Quantification of N-glycosite occupancy for PHA-L reactive glycoproteins could help to discover important glycoproteins of potential clinically significance in terms of HCC etiology. Also, understanding of N-glycosite occupancy alterations will aid the characterization of molecular mechanism of HCC metastasis as well as establishment of novel glycobiomarkers.

Analysis of urinary PSA glycosylation is not indicative of high-risk prostate cancer

The levels of core fucosylation and α2,3-linked sialic acid in serum Prostate Specific Antigen (PSA), using the lectins Pholiota squarrosa lectin (PhoSL) and Sambucus nigra agglutinin (SNA), can discriminate between Benign Prostatic Hyperplasia (BPH) and indolent prostate cancer (PCa) from aggressive PCa. In the present work we evaluated whether these glycosylation determinants could also be altered in urinary PSA obtained after digital rectal examination (DRE) and could also be useful for diagnosis determinations. For this purpose, α2,6-sialic acid and α1,6-fucose levels of urinary PSA from 53 patients, 18 biopsy-negative and 35 PCa patients of different aggressiveness degree, were analyzed by sandwich ELLA (Enzyme Linked Lectin Assay) using PhoSL and SNA. Changes in the levels of specific glycosylation determinants, that in serum PSA samples were indicative of PCa aggressiveness, were not found in PSA from DRE urine samples. Although urine is a simpler matrix for analyzing PSA glycosylation compared to serum, an immunopurification step was necessary to specifically detect the glycans on the PSA molecule. Those specific glycosylation determinants on urinary PSA were however not useful to improve PCa diagnosis. This could be probably due to the low proportion of PSA from the tumor in urine samples, which precludes the identification of aberrantly glycosylated PSA.

Biomarkers for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. The HCC diagnosis is usually achieved by biomarkers, which can also help in prognosis prediction. Furthermore, it might represent certain therapeutic interventions through some combinations of biomarkers. Here, we review on our current understanding of HCC biomarkers.

Label-Free Proteome Analysis of Plasma from Patients with Breast Cancer: Stage-Specific Protein Expression

Breast cancer is one of the most commonly diagnosed types of cancer among women. Breast cancer mortality rates remain high probably because its diagnosis is hampered by inaccurate detection methods. Since changes in protein expression as well as modifications in protein glycosylation have been frequently reported in cancer development, the aim of this work was to study the differential expression as well as modifications of glycosylation of proteins from plasma of women with breast cancer at different stages of disease (n = 30) compared to healthy women (n = 10). A proteomics approach was used that depleted albumin and IgG from plasma followed by glycoprotein enrichment using immobilized Moraceae lectin (frutalin)-affinity chromatography and data-independent label-free mass spectrometric analysis. Data are available via ProteomeXchange with identifier PXD003106. As result, 57,016 peptides and 4,175 proteins among all samples were identified. From this, 40 proteins present in unbound (PI—proteins that did not interact with lectin) and bound (PII—proteins that interacted with lectin) fractions were differentially expressed. High levels of apolipoprotein A-II were detected here that were elevated significantly in the early and advanced stages of the disease. Apolipoprotein C-III was detected in both fractions, and its level was increased slightly in the PI fraction of patients with early-stage breast cancer and expressed at higher levels in the PII fraction of patients with early and intermediate stages. Clusterin was present at higher levels in both fractions of patients with early and intermediate stages of breast cancer. Our findings reveal a correlation between alterations in protein glycosylation, lipid metabolism, and the progression of breast cancer.

Reverse lectin ELISA for detecting fucosylated forms of α1-acid glycoprotein associated with hepatocellular carcinoma

Altered fucosylation of glycoproteins is associated with development of hepatocellular carcinoma (HCC). Lectins have been commonly used to assay changes in fucosylation of plasma glycoproteins. In the present study a recombinantly engineered form of the fucose binding lectin Aleuria aurantia (AAL) consisting of a single binding site for fucose (S2), was used to construct a reverse lectin ELISA method. Microtiter plates coated with the S2 lectin were used to capture glycoproteins from plasma samples followed by antibody detection of S2-bound fucosylated α1-acid glycoprotein (S2-bound AGP). The method was used to compare the level of S2-bound AGP in serum samples from a small cohort of patients with hepatitis, cirrhosis or HCC. Using the reverse S2 lectin ELISA it was shown that the levels of S2-bound AGP was significantly higher in HCC patients compared to non-cancer patients and that there was also a significant elevation of S2-bound AGP in HCC patients compared to cirrhosis patients. There was no correlation between the level of S2-bound AGP and total AGP concentration. The performance of S2-bound AGP in differentiating HCC from cirrhosis samples or hepatitis samples were compared to other markers. A combination of S2-bound AGP, α-fetoprotein and AGP concentration showed performances giving area under receiver operating curves of 0.87 and 0.95 respectively.

Improved surface imprinting based on a simplified mass-transfer process for the selective extraction of IgG

The adsorption and elution efficiencies of conventional MMIPs were almost doubled by preparing MMINs.

Aberrant Glycosylation in the Left Ventricle and Plasma of Rats with Cardiac Hypertrophy and Heart Failure

Targeted proteomics focusing on post-translational modifications, including glycosylation, is a useful strategy for discovering novel biomarkers. To apply this strategy effectively to cardiac hypertrophy and resultant heart failure, we aimed to characterize glycosylation profiles in the left ventricle and plasma of rats with cardiac hypertrophy. Dahl salt-sensitive hypertensive rats, a model of hypertension-induced cardiac hypertrophy, were fed a high-salt (8% NaCl) diet starting at 6 weeks. As a result, they exhibited cardiac hypertrophy at 12 weeks and partially impaired cardiac function at 16 weeks compared with control rats fed a low-salt (0.3% NaCl) diet. Gene expression analysis revealed significant changes in the expression of genes encoding glycosyltransferases and glycosidases. Glycoproteome profiling using lectin microarrays indicated upregulation of mucin-type O-glycosylation, especially disialyl-T, and downregulation of core fucosylation on N-glycans, detected by specific interactions with Amaranthus caudatus and Aspergillus oryzae lectins, respectively. Upregulation of plasma α-l-fucosidase activity was identified as a biomarker candidate for cardiac hypertrophy, which is expected to support the existing marker, atrial natriuretic peptide and its related peptides. Proteomic analysis identified cysteine and glycine-rich protein 3, a master regulator of cardiac muscle function, as an O-glycosylated protein with altered glycosylation in the rats with cardiac hypertrophy, suggesting that alternations in O-glycosylation affect its oligomerization and function. In conclusion, our data provide evidence of significant changes in glycosylation pattern, specifically mucin-type O-glycosylation and core defucosylation, in the pathogenesis of cardiac hypertrophy and heart failure, suggesting that they are potential biomarkers for these diseases.

Cadherin-5: a biomarker for metastatic breast cancer with optimum efficacy in oestrogen receptor-positive breast cancers with vascular invasion

BACKGROUND

A glycoproteomic study has previously shown cadherin-5 (CDH5) to be a serological marker of metastatic breast cancer when both protein levels and glycosylation status were assessed. In this study we aimed to further validate the utility of CDH5 as a biomarker for breast cancer progression.

METHODS

A nested case-control study of serum samples from breast cancer patients, of which n=52 had developed a distant metastatic recurrence within 5 years post-diagnosis and n=60 had remained recurrence-free. ELISAs were used to quantify patient serum CDH5 levels and assess glycosylation by Helix pomatia agglutinin (HPA) binding. Clinicopathological, treatment and lifestyle factors associated with metastasis and elevated biomarker levels were identified.

RESULTS

Elevated CDH5 levels (P=0.028) and ratios of CDH5:HPA binding (P=0.007) distinguished patients with metastatic disease from those that remained metastasis-free. Multivariate analysis showed that the association between CDH5:HPA ratio and the formation of distant metastases was driven by patients with oestrogen receptor (ER+) positive cancer with vascular invasion (VI+).

CONCLUSIONS

CDH5 levels and the CDH5 glycosylation represent biomarker tests that distinguish patients with metastatic breast cancer from those that remain metastasis-free. The test reached optimal sensitivity and specificity in ER-positive cancers with vascular invasion.

Identification of six cell surface proteins for specific liver targeting

PURPOSE

Cell surface proteins are the primary means for a cell to sense and interact with its environment and their dysregulation has been linked to numerous diseases. In particular, the identification of proteins specific to a single tissue type or to a given disease phenotype may enable the characterization of novel therapeutic targets. We tested here the feasibility of a cell surface proteomics approach to identify pertinent markers directly in a clinically relevant tissue.

EXPERIMENTAL DESIGN

We analyzed the cell surface proteome of freshly isolated primary heptatocytes using a glycocapture-specific approach combined with a robust bioinformatics filtering.

RESULTS

Using primary lung epithelial cell cultures as negative controls, we identified 32 hepatocyte-specific cell surface proteins candidates. We used mRNA expression to select six markers that may provide adequate specificity for targeting therapeutics to the liver.

CONCLUSIONS AND CLINICAL RELEVANCE

We demonstrate the feasibility and the importance of conducting such studies directly in a clinically relevant tissue. In particular, the cell surface proteome of freshly isolated hepatocytes differed substantially from cultured cell lines.

Fast solid-phase extraction of N-linked glycopeptides by amine-functionalized mesoporous silica nanoparticles

For the first time, mesoporous material has been introduced into N-glycoproteome extraction based on a reductive amination reaction, which greatly enhanced the enrichment efficiency and deglycosylation efficiency.

Glycan-Dependent Mutual and Reversible Sequestration of Two Thyroid Cancer Biomarkers

BACKGROUND

Thyroglobulin (Tg), the major thyroidal protein, plays important roles in thyroid hormone biosynthesis and in autoimmune thyroid diseases (AITD). Tg also serves as a pre- and postoperative biomarker of differentiated thyroid cancer (DTC). The endogenous β-galactoside binding lectin galectin-3 (Gal-3), secreted by transformed thyroid cells, has been shown to be another useful biomarker of DTC. Tg contains covalently linked complex-type glycans that can serve as binding epitopes of Gal-3. The objective of the study is to investigate the interaction between Tg and Gal-3 and discuss its potential consequences.

METHODS

Binding interaction between Tg and Gal-3 was first studied by hemagglutination inhibition assays. Subsequently, a detailed analysis of binding thermodynamics was carried out by isothermal titration calorimetry. Quantitative precipitation was performed to study the complex formation between Tg and Gal-3 and to determine the binding stoichiometry. The concentration-dependent rate and amount of complex formation between Tg and Gal-3 was examined spectrophotometrically. A similar approach was taken to study the effect of free Tg and Gal-3 on preformed Tg-Gal-3 complex.

RESULTS

Quantitative biochemical and biophysical data show that these two biomarkers produced by thyroid cancer cells interact with each other with submicromolar affinity and form an insoluble complex at their stoichiometric concentration. One Tg molecule could bind up to 14 molecules of Gal-3. Such complex formation mutually sequestered both Tg and Gal-3, decreasing the concentration of their freely available forms. Formation of the Tg-Gal-3 complex was reversible as the preformed complex was dissolved by free Tg as well as free Gal-3. While free Tg rapidly dissolved preformed Tg-Gal-3 complex in a concentration-dependent manner, Gal-3 was found to be much less efficient and slowly dissolved only a fraction of the preformed complex at a relatively higher Gal-3 concentration.

CONCLUSIONS

Complex formation between Tg and Gal-3 through high affinity binding and the sensitivity of the complex to free Tg and Gal-3 can potentially influence their biological functions. Interactions between Tg and Gal-3 might also interfere with their clinical detection, the same way Tg autoantibody (TgAb) is reported to interfere with Tg assays. The data support a model of Gal-3-mediated homeostatic process of Tg.

Serum Glycoprotein Biomarker Discovery and Qualification Pipeline Reveals Novel Diagnostic Biomarker Candidates for Esophageal Adenocarcinoma

We report an integrated pipeline for efficient serum glycoprotein biomarker candidate discovery and qualification that may be used to facilitate cancer diagnosis and management. The discovery phase used semi-automated lectin magnetic bead array (LeMBA)-coupled tandem mass spectrometry with a dedicated data-housing and analysis pipeline; GlycoSelector (http://glycoselector.di.uq.edu.au). The qualification phase used lectin magnetic bead array-multiple reaction monitoring-mass spectrometry incorporating an interactive web-interface, Shiny mixOmics (http://mixomics-projects.di.uq.edu.au/Shiny), for univariate and multivariate statistical analysis. Relative quantitation was performed by referencing to a spiked-in glycoprotein, chicken ovalbumin. We applied this workflow to identify diagnostic biomarkers for esophageal adenocarcinoma (EAC), a life threatening malignancy with poor prognosis in the advanced setting. EAC develops from metaplastic condition Barrett's esophagus (BE). Currently diagnosis and monitoring of at-risk patients is through endoscopy and biopsy, which is expensive and requires hospital admission. Hence there is a clinical need for a noninvasive diagnostic biomarker of EAC. In total 89 patient samples from healthy controls, and patients with BE or EAC were screened in discovery and qualification stages. Of the 246 glycoforms measured in the qualification stage, 40 glycoforms (as measured by lectin affinity) qualified as candidate serum markers. The top candidate for distinguishing healthy from BE patients' group was Narcissus pseudonarcissus lectin (NPL)-reactive Apolipoprotein B-100 (p value = 0.0231; AUROC = 0.71); BE versus EAC, Aleuria aurantia lectin (AAL)-reactive complement component C9 (p value = 0.0001; AUROC = 0.85); healthy versus EAC, Erythroagglutinin Phaseolus vulgaris (EPHA)-reactive gelsolin (p value = 0.0014; AUROC = 0.80). A panel of 8 glycoforms showed an improved AUROC of 0.94 to discriminate EAC from BE. Two biomarker candidates were independently verified by lectin magnetic bead array-immunoblotting, confirming the validity of the relative quantitation approach. Thus, we have identified candidate biomarkers, which, following large-scale clinical evaluation, can be developed into diagnostic blood tests. A key feature of the pipeline is the potential for rapid translation of the candidate biomarkers to lectin-immunoassays.

Mass-spectrometry-based molecular characterization of extracellular vesicles: lipidomics and proteomics

This review discusses extracellular vesicles (EVs), which are submicron-scale, anuclear, phospholipid bilayer membrane enclosed vesicles that contain lipids, metabolites, proteins, and RNA (micro and messenger). They are shed from many, if not all, cell types and are present in biological fluids and conditioned cell culture media. The term EV, as coined by the International Society of Extracellular Vesicles (ISEV), encompasses exosomes (30-100 nm in diameter), microparticles (100-1000 nm), apoptotic blebs, and other EV subsets. EVs have been implicated in cell-cell communication, coagulation, inflammation, immune response modulation, and disease progression. Multiple studies report that EV secretion from disease-affected cells contributes to disease progression, e.g., tumor niche formation and cancer metastasis. EVs are attractive sources of biomarkers due to their biological relevance and relatively noninvasive accessibility from a range of physiological fluids. This review is focused on the molecular profiling of the protein and lipid constituents of EVs, with emphasis on mass-spectrometry-based "omic" analytical techniques. The challenges in the purification and molecular characterization of EVs, including contamination of isolates and limitations in sample quantities, are discussed along with possible solutions. Finally, the review discusses the limited but growing investigation of post-translational modifications of EV proteins and potential strategies for future in-depth molecular characterization of EVs.