A lectin-based approach to detecting carcinogenesis in breast tissue

Beyond glyco-proteomics-Understanding the role of genetics in cancer biomarkers

The development of robust cancer biomarkers is the most effective way to improve overall survival, as early detection and treatment leads to significantly better clinical outcomes. Many of the cancer biomarkers that have been identified and are clinically utilized are glycoproteins, oftentimes a specific glycoform. Aberrant glycosylation is a common theme in cancer, with dysregulated glycosylation driving tumor initiation and metastasis, and abnormal glycosylation can be detection both on the tissue surface and in serum. However, most cancer types are heterogeneous in regard to tumor genomics, and this heterogeneity extends to cancer glycomics. This limits the sensitivity of standalone glycan-based biomarkers, which has slowed their implementation clinically. However, if targeted biomarker development can take into account genomic tumor information, the development of complementary biomarkers that target unique cancer subgroups can be accomplished. This idea suggests the need for algorithm-based cancer biomarkers, which can utilize multiple biomarkers along with relevant demographic information. This concept has already been established in the detection of hepatocellular carcinoma with the GALAD score, and an algorithm-based approach would likely be effective in improving biomarker sensitivity for additional cancer types. In order to increase cancer diagnostic biomarker sensitivity, there must be more targeted biomarker development that considers tumor genomic, proteomic, metabolomic, and clinical data while identifying tumor biomarkers.

Glycopattern Alteration of Glycoproteins in Gastrointestinal Cancer Cell Lines and Their Cell-Derived Exosomes

Gastrointestinal (GI) cancers constitute the largest portion of all human cancers, and the most prevalent GI cancers in China are colorectal cancer (CRC), gastric cancer (GC), and hepatocellular carcinoma (HCC). Exosomes are nanosized vesicles containing proteins, lipids, glycans, and nucleic acid, which play important roles in the tumor microenvironment and progression. Aberrant glycosylation is closely associated with GI cancers; however, little is known about the glycopattern of the exosomes from GI cancer cells. In this study, glycopatterns of HCC, CRC, and GC cell lines and their exosomes were detected using lectin microarrays. For all exosomes, (GlcNAcβ1-4)_n and Galβ1-4GlcNAc (DSA) were the most abundant glycans, but αGalNAc and αGal (GSL-II and SBA) were the least. Different cancers had various characteristic glycans in either cells or exosomes. Glycans altered in cell-derived exosomes were not always consistent with the host cells in the same cancer. However, Fucα1-6GlcNAc (core fucose) and Fucα1-3(Galβ1-4)GlcNAc (AAL) were altered consistently in cells and exosomes although they were decreased in HCC and CRC but increased in GC. The study drew the full-scale glycan fingerprint of cells and exosomes related to GI cancer, which may provide useful information for finding specific biomarkers and exploring the underlying mechanism of glycosylation in exosomes.

Systematic Optimisation of Microtiter Plate Lectin Assay to Improve Sialic Acid Linkage Detection

AIMS

We aimed to develop a high-throughput lectin assay with minimized background signals to investigate the interactions of lectins and sialic acid glycans, focusing on prostate-specific antigen (PSA).

BACKGROUND

High background signals resulting from nonspecific binding are a significant concern for microtiter plate-based enzyme-linked lectin sorbent assays (ELLSAs), as they can mask specific binding signals and cause false-positive results.

METHODS

In this study, we constructed an ELLSA based on different washing step parameters, including the number of washing cycles, NaCl and Tween-20 concentrations, and the type of blocking agent and evaluated the effects on both specific and nonspecific binding signals. Furthermore, we performed a PSA binding assay using the optimized ELLSA.

RESULTS

The optimal washing parameters based on the highest specific binding signal proposed four cycles of washing steps using a washing buffer containing a high salt concentration (0.5 M NaCl) and mild detergent (0.05% Tween-20). The utilization of the optimized washing parameters in this assay was shown to be sufficient to obtain the optimal binding signals without the use of any blocking agent. Binding assays performed using the optimized ELLSA revealed that the glycan of the PSA sample used in this study mainly consists of terminal α2,6-linked sialic acid, as strongly recognized by Sambucus nigra agglutinin (SNA) with a KD value of 12.38 nM.

CONCLUSION

The ELLSA reported in this study provides a simple yet sensitive assay for sialic acid linkage recognition.

Exploratory Analysis of CA125-MGL and -STn Glycoforms in the Differential Diagnostics of Pelvic Masses

BACKGROUND

The cancer antigen 125 (CA125) immunoassay (IA) does not distinguish epithelial ovarian cancer (EOC) from benign disease with the sensitivity needed in clinical practice. In recent studies, glycoforms of CA125 have shown potential as biomarkers in EOC. Here, we assessed the diagnostic abilities of two recently developed CA125 glycoform assays for patients with a pelvic mass. Detailed analysis was further conducted for postmenopausal patients with marginally elevated conventionally measured CA125 levels, as this subgroup presents a diagnostic challenge in the clinical setting.

METHODS

Our study population contained 549 patients diagnosed with EOC, benign ovarian tumors, and endometriosis. Of these, 288 patients were postmenopausal, and 98 of them presented with marginally elevated serum levels of conventionally measured CA125 at diagnosis. Preoperative serum levels of conventionally measured CA125 and its glycoforms (CA125-MGL and CA125-STn) were determined.

RESULTS

The CA125-STn assay identified EOC significantly better than the conventional CA125-IA in postmenopausal patients (85% vs. 74% sensitivity at a fixed specificity of 90%, P = 0.0009). Further, both glycoform assays had superior AUCs compared to the conventional CA125-IA in postmenopausal patients with marginally elevated CA125. Importantly, the glycoform assays reduced the false positive rate of the conventional CA125-IA.

CONCLUSIONS

The results indicate that the CA125 glycoform assays markedly improve the performance of the conventional CA125-IA in the differential diagnosis of pelvic masses. This result is especially valuable when CA125 is marginally elevated.

α1,6-Fucosyltransferase contributes to cell migration and proliferation as well as to cancer stemness features in pancreatic carcinoma

BACKGROUND

Pancreatic carcinoma is one of the deadliest malignant diseases, in which the increased expression of α1,6-fucosyltransferase (FUT8), a sole enzyme responsible for catalyzing core fucosylation, has been reported. However, its pathological roles and regulatory mechanisms remain largely unknown. Here, we use two pancreatic adenocarcinoma cell lines, MIA PaCa-2 and PANC-1 cells, as cell models, to explore the relationship of FUT8 with the malignant transformation of PDAC.

METHODS

FUT8 knockout (FUT8-KO) cells were established by the CRISPR/Cas9 system. Cell migration was analyzed by transwell and wound-healing assays. Cell proliferation was examined by MTT and colony-formation assays. Cancer stemness markers and spheroid formations were used to analyzed cancer stemness features.

RESULTS

Deficiency of FUT8 inhibited cell migration and proliferation in both MIA PaCa-2 and PANC-1 cells compared with wild-type cells. Moreover, the expression levels of cancer stemness markers such as EpCAM, CXCR4, c-Met, and CD133 were decreased in the FUT8-KO cells compared with wild-type cells. Also, the spheroid formations in the KO cells were loose and unstable, which could be reversed by restoration with FUT8 gene in the KO cells. Additionally, FUT8-KO increased the chemosensitivity to gemcitabine, which is the first-line therapy for advanced pancreatic cancer.

CONCLUSIONS

FUT8-KO reduced the cell proliferation and migration. Our results are the first to suggest that the expression of FUT8 is involved in regulating the stemness features of pancreatic cancer cells.

GENERAL SIGNIFICANCE

FUT8 could provide novel insights for the treatment of pancreatic carcinoma.

Use of Lectin-based Affinity Techniques in Breast Cancer Glycoproteomics: A Review

Changes in glycoprotein content, altered glycosylations, and aberrant glycan structures are increasingly recognized as cancer hallmarks. Because breast cancer is one of the most common causes of cancer deaths in the world, it is highly urgent to find other reliable biomarkers for its initial diagnosis and to learn as much as possible about this disease. In this Review, the applications of lectins to a screening of potential breast cancer biomarkers published during recent years are overviewed. These data provide a deeper insight into the use of modern strategies, technologies, and scientific knowledge in glycoproteomic breast cancer research. Particular attention is concentrated on the use of lectin-based affinity techniques, applied independently or most frequently in combination with mass spectrometry, as an effective tool for the targeting, separation, and reliable identification of glycoprotein molecules. Individual procedures and lectins used in published glycoproteomic studies of breast-cancer-related glycoproteins are discussed. The summarized approaches have the potential for use in diagnostic and predictive applications. Finally, the use of lectins is briefly discussed from the view of their future applications in the analysis of glycoproteins in cancer.

Altered glycosylation associated with dedifferentiation of hepatocellular carcinoma: a lectin microarray-based study

Background

Altered glycosylation associated with hepatocellular carcinoma (HCC) is well documented. However, few reports have investigated the association between dedifferentiation and glycosylation. Therefore, the aim of this study was to analyze glycosylation associated with dedifferentiation of HCC within the same nodule and to investigate glycosyltransferase related to the glycosylation.

Methods

We analyzed resected HCC specimens (n = 50) using lectin microarray to comprehensively and sensitively analyze glycan profiles, and identify changes to glycosylation between well- and moderately-differentiated components within the same nodule. Moreover, we performed immunohistochemical staining of mannosyl(α-1,3-)-glycoprotein β-1,2-N-acetylglucosaminyltransferase (MGAT1), which is an essential glycosyltransferase that converts high-mannose glycans to complex- or hybrid-type N-glycans.

Results

Four lectins from Narcissus pseudonarcissus agglutinin (NPA), Concanavalin A, Galanthus nivalis agglutinin, and Calystegia sepium agglutinin were significantly elevated in moderately-differentiated components of HCC compared with well-differentiated components, and all lectins showed binding specificity to high-mannose glycans. Therefore, these structures were represented to a greater extent in moderately-differentiated components than in well-differentiated ones. Immunohistochemical staining revealed significantly increased NPA expression and decreased MGAT1 expression in moderately-differentiated components. Low MGAT1 expression in moderately-differentiated components of tumors was associated with intrahepatic metastasis and had tendency for poor prognosis.

Conclusion

Dedifferentiation of well-differentiated HCC is associated with an increase in high-mannose glycans. MGAT1 may play a role in the dedifferentiation of HCC.

The Diverse Contributions of Fucose Linkages in Cancer

Fucosylation is a post-translational modification of glycans, proteins, and lipids that is responsible for many biological processes. Fucose conjugation via α(1,2), α(1,3), α(1,4), α(1,6), and O'- linkages to glycans, and variations in fucosylation linkages, has important implications for cancer biology. This review focuses on the roles that fucosylation plays in cancer, specifically through modulation of cell surface proteins and signaling pathways. How L-fucose and serum fucosylation patterns might be used for future clinical diagnostic, prognostic, and therapeutic approaches will be discussed.

Diagnostic Potential of Transferrin Glycoforms-A Lectin-Based Protein Microarray Approach

PURPOSE

Disease or a specific condition may cause alteration of human transferrin (hTf) glycosylation pattern. A specific analytical platform, lectin-based protein microarray, is designed and optimized for the investigation of hTf glycans, attached to the protein core in their native form.

EXPERIMENTAL DESIGN

hTf molecules isolated from healthy persons of different age, diabetes mellitus type 2 (T2DM) or colorectal carcinoma (CRC) patients are used for method validation. Reliability of the results is ensured by three criteria for the evaluation of hTf-lectin interactions: i) signal-to-noise ratio above 3, ii) signal intensity above 250 arbitrary units, and iii) hTf concentration ensuring high sensitivity of the assay.

RESULTS

Six lectins, out of fourteen tested, satisfy the criteria. hTf is spotted at concentration of 50 µg mL^-L . When physiological samples (isolated hTf) are analyzed, the highest potential to differentiate between population groups expresses Aleuria aurantia (AAL), Triticum vulgaris (WGA) and Phaseolus vulgaris (PHA-E) lectins. The initial amount of hTf which can be analyzed is very low (75 pg).

CONCLUSION AND CLINICAL RELEVANCE

Results confirm that a very sensitive, high-throughput lectin-based protein microarray platform can be formulated to detect changes in hTf glycan structures which can be considered as biomarkers of ageing or a disease.

The effect of pyometra on glycosylation of proteins in the uterine tissues from female dogs

The main aim of this study was to investigate the effect of pyometra on glycosylation of proteins in the uterine tissues from female dogs, using western blotting with selected lectins (Sambucus nigra agglutinin - SNA and Maackia amurensis agglutinin - MAL II). In addition protein pattern of examined tissues was also evaluated. The study was performed on 10 female dogs undergoing ovariohysterectomy because of pyometra and 10 clinically healthy female dogs, undergoing elective spaying (ovariohysterectomy). Uterine tissue samples of 1 cm² were taken from the middle region of each uterine horn in both group of animals immediately after ovariohysterectomy. Tissue samples were homogenized and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting with SNA and MAL II. SDS-PAGE analysis showed differences between pyometra samples and controls in the amount of obtained protein fractions and the protein content in the individual fractions. Five protein (with a molecular weight of 193.78 kDa, 103.18 kDa, 77.67 kDa, 70.39 kDa, and 53.00 kDa) were found only in the pyometra samples. The remaining fractions differed in intensity of staining, which indicated differ abundance of a given protein. The results of western blotting with SNA and MAL II demonstrated that the pattern obtained from densitometric analysis differs between adequate healthy and pyometra samples with regard to the amount of protein fraction obtained as well as the intensity of staining of particular fraction. The pyometra tissues contained seven SNA-binding proteins (with a molecular weight 189.94 kDa, 165.51 kDa, 100.94 kDa, 59.42 KDa, 41.32 kDa, 35.16 kDa, and 32.6 kDa) that were not in the healthy tissues. Of the nine remaining fractions, six showed significantly higher (P < 0.05) intensity of staining in the healthy uterine tissues. In turn, the MAL II-binding protein with a molecular weight 75.85 kDa, 51.12 kDa, and 49.98 kDa were found only in the pyometra samples. Of the 28 remaining fractions, ten demonstrated significantly higher (P < 0.05), and five fractions had significantly lower (P < 0.05) intensity of staining in the pyometra tissues. The results obtained indicate that proteins in uterine tissues from female dogs with pyometra are differently glycosylated compared to normal uterine tissues. These findings provide the basis for further studies of the possible role of glycosylation in the pathogenesis of canine pyometra.

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.

Using "spectral families" to assess the reproducibility of glycopeptide enrichment: human serum O-glycosylation revisited

Growing evidence on the diverse biological roles of extracellular glycosylation as well as the need for quality control of protein pharmaceuticals make glycopeptide analysis both exciting and important again after a long hiatus. High-throughput O-glycosylation studies have to tackle the complexity of glycosylation as well as technical difficulties and, up to now, have yielded only limited results mostly from single enrichment experiments. In this study, we address the technical reproducibility of the characterization of the most prevalent O-glycosylation (mucin-type core 1 structures) in human serum, using a two-step lectin affinity-based workflow. Our results are based on automated glycopeptide identifications from higher-energy C-trap dissociation and electron transfer dissociation MS/MS data. Assignments meeting strict acceptance criteria served as the foundation for generating "spectral families" incorporating low-scoring MS/MS identifications, supported by accurate mass measurements and expected chromatographic retention times. We show that this approach helped to evaluate the reproducibility of the glycopeptide enrichment more reliably and also contributed to the expansion of the glycoform repertoire of already identified glycosylated sequences. The roadblocks hindering more in-depth investigations and quantitative analyses will also be discussed.