Detection of glyco-mucin profiles improves specificity of MUC16 and MUC1 biomarkers in ovarian serous tumours

MUC16/CA125 in cancer: new advances

MUC16/CA125 is a common diagnostic marker for many types of cancer. However, due to the widespread expression of MUC16 in cancer, its specificity and sensitivity as a target are poor, which severely limits its clinical application. In recent years, various studies have shown that the clinical application potential of MUC16/CA125 has been greatly improved. The update of detection technology improves the accuracy and range of detection, and improves the early diagnosis rate of cancer. Targeting MUC16/CA125 is an important strategy for tumor therapy. Targeting residual amino acids, n-glycoylation structures or other targets on the surface of MUC16 cells can greatly improve the accuracy of detection and therapy. The new drug delivery method broke through the original technical shackles, targeted MUC16 positive cells more specifically and improved the drug efficacy. In this paper, the technological advances in detecting and identifying MUC16 targets and the great progress in cancer screening and treatment based on MUC16 as a target are described in detail, revealing the great potential of MUC16 as a target in cancer screening and treatment, and illustrating the potential clinical application value of MUC16.

Spectrally separated dual-label upconversion luminescence lateral flow assay for cancer-specific STn-glycosylation in CA125 and CA15-3

Multiplexed lateral flow assays (LFAs) offer efficient on-site testing by simultaneously detecting multiple biomarkers from a single sample, reducing costs. In cancer diagnostics, where biomarkers can lack specificity, multiparameter detection provides more information at the point-of-care. Our research focuses on epithelial ovarian cancer (EOC), where STn-glycosylated forms of CA125 and CA15-3 antigens can better discriminate cancer from benign conditions. We have developed a dual-label LFA that detects both CA125-STn and CA15-3-STn within a single anti-STn antibody test line. This utilizes spectral separation of green (540 nm) and blue (450 nm) emitting erbium (NaYF4:Yb3+, Er3+)- and thulium (NaYF4: Yb3+, Tm3+)-doped upconverting nanoparticle (UCNP) reporters conjugated with antibodies against the protein epitopes in CA125 or CA15-3. This technology allows the simultaneous detection of different antigen variants from a single test line. The developed proof-of-concept dual-label LFA was able to distinguish between the ascites fluid samples from diagnosed ovarian cancer patients (n = 10) and liver cirrhosis ascites fluid samples (n = 3) used as a negative control. The analytical sensitivity of CA125-STn for the dual-label LFA was 1.8 U/ml in buffer and 3.6 U/ml in ascites fluid matrix. Here we demonstrate a novel approach of spectrally separated measurement of STn-glycosylated forms of two different cancer-associated protein biomarkers by using UCNP reporter technology.

Targeted and Self-Adjuvated Nanoglycovaccine Candidate for Cancer Immunotherapy

Advanced-stage solid primary tumors and metastases often express mucin 16 (MUC16), carrying immature glycans such as the Tn antigen, resulting in specific glycoproteoforms not found in healthy human tissues. This presents a valuable approach for designing targeted therapeutics, including cancer glycovaccines, which could potentially promote antigen recognition and foster the immune response to control disease spread and prevent relapse. In this study, we describe an adjuvant-free poly(lactic-co-glycolic acid) (PLGA)-based nanoglycoantigen delivery approach that outperforms conventional methods by eliminating the need for protein carriers while exhibiting targeted and adjuvant properties. To achieve this, we synthesized a library of MUC16-Tn glycoepitopes through single-pot enzymatic glycosylation, which were then stably engrafted onto the surface of PLGA nanoparticles, generating multivalent constructs that better represent cancer molecular heterogeneity. These glycoconstructs demonstrated affinity for Macrophage Galactose-type Lectin (MGL) receptor, known to be highly expressed by immature antigen-presenting cells, enabling precise targeting of immune cells. Moreover, the glycopeptide-grafted nanovaccine candidate displayed minimal cytotoxicity and induced the activation of dendritic cells in vitro, even in the absence of an adjuvant. In vivo, the formulated nanovaccine candidate was also nontoxic and elicited the production of IgG specifically targeting MUC16 and MUC16-Tn glycoproteoforms in cancer cells and tumors, offering potential for precise cancer targeting, including targeted immunotherapies.

Advancements in protein glycosylation biomarkers for ovarian cancer through mass spectrometry-based approaches

INTRODUCTION

Ovarian cancer, characterized by metastasis and reduced 5-year survival rates, stands as a substantial factor in the mortality of gynecological malignancies worldwide. The challenge of delayed diagnosis originates from vague early symptoms and the absence of efficient screening and diagnostic biomarkers for early cancer detection. Recent studies have explored the intricate interplay between ovarian cancer and protein glycosylation, unveiling the potential significance of glycosylation-oriented biomarkers.

AREAS COVERED

This review examines the progress in glycosylation biomarker research, with particular emphasis on advances driven by mass spectrometry-based technologies. We document milestones achieved, discuss encountered limitations, and also highlight potential areas for future research and development of protein glycosylation biomarkers for ovarian cancer.

EXPERT OPINION

The association of glycosylation in ovarian cancer is well known, but current research lacks desired sensitivity and specificity for early detection. Notably, investigations into protein-specific and site-specific glycoproteomics have the potential to significantly enhance our understanding of ovarian cancer and facilitate the identification of glycosylation-based biomarkers. Furthermore, the integration of advanced mass spectrometry techniques with AI-driven analysis and glycome databases holds the promise for revolutionizing biomarker discovery for ovarian cancer, ultimately transforming diagnosis and improving patient outcomes.

Capitalizing glycomic changes for improved biomarker-based cancer diagnostics

Cancer serum biomarkers are valuable or even indispensable for cancer diagnostics and/or monitoring and, currently, many cancer serum markers are routinely used in the clinic. Most of those markers are glycoproteins, carrying cancer-specific glycan structures that can provide extra-information for cancer monitoring. Nonetheless, in the majority of cases, this differential feature is not exploited and the corresponding analytical assays detect only the protein amount, disregarding the analysis of the aberrant glycoform. Two exceptions to this trend are the biomarkers α-fetoprotein (AFP) and cancer antigen 19-9 (CA19-9), which are clinically monitored for their cancer-related glycan changes, and only the AFP assay includes quantification of both the protein amount and the altered glycoform. This narrative review demonstrates, through several examples, the advantages of the combined quantification of protein cancer biomarkers and the respective glycoform analysis, which enable to yield the maximum information and overcome the weaknesses of each individual analysis. This strategy allows to achieve higher sensitivity and specificity in the detection of cancer, enhancing the diagnostic power of biomarker-based cancer detection tests.

Aberrant glycosylation of α3 integrins as diagnostic markers in epithelial ovarian cancer

BACKGROUND

Glycans are strongly involved in stability and function of integrins (ITG) and tetraspanin protein CD63 and their respective interaction partners as they are dysregulated in the tumorigenic processes. Glycosylation changes is a universal phenomenon of cancer cells. In this study, glycosylation changes in epithelial ovarian cancer (EOC) are explored using tetraspanin and integrin molecules.

METHODS

ITG and CD63 were immobilized from 10 EOC and 5 benign ovarian cyst fluid on microtiter wells and traced with 3 glycan binding proteins (STn, WGA, UEA) conjugated on europium nanoparticles. Total protein measurements (ITG & CD63 immunoassays) were also performed. The most promising glycovariant candidates identified were then clinically evaluated on the whole cohort of 77 ovarian cyst fluids. Additional testing was performed in ascites fluid samples of liver cirrhosis (n=2) and EOC (n=4).

RESULTS

Sialylated Tn antibody based glycovariants of ITGα3 (ITGα3^STn) and CD63 (CD63^STn) performed better than corresponding protein epitope-based immunoassays, ITGα3^IA and CD63^IA respectively. Combined ITGα3 based assays (ITGα3^IA + ITGα3^STn) detected 49 out of 55 malignant & borderline cases without detecting any of the 22 benign and healthy cysts.

CONCLUSION

Our findings indicate the potential diagnostic application of ITGα3^STn along with total ITGα3^IA, which could help reduce the unnecessary surgeries. The results encourage studying further the potential use of these novel assays to detect EOC at earlier clinical stages.

Diagnostic potential of nanoparticle aided assays for MUC16 and MUC1 glycovariants in ovarian cancer

Our study reports the discovery and evaluation of nanoparticle aided sensitive assays for glycovariants of MUC16 and MUC1 in a unique collection of paired ovarian cyst fluids and serum samples obtained at or prior to surgery for ovarian carcinoma suspicion. Selected glycovariants and the immunoassays for CA125, CA15‐3 and HE4 were compared and validated in 347 cyst fluid and serum samples. Whereas CA125 and CA15‐3 performed poorly in cyst fluid to separate carcinoma and controls, four glycovariants including MUC16^MGL, MUC16^STn, MUC1^STn and MUC1^Tn provided highly improved separations. In serum, the two STn glycovariants outperformed conventional CA125, CA15‐3 and HE4 assays in all subcategories analyzed with main benefits obtained at high specificities and at postmenopausal and early‐stage disease. Serum MUC16^STn performed best at high specificity (90%‐99%), but sensitivity was also improved by the other glycovariants and CA15‐3. The highly improved specificity, excellent analytical sensitivity and robustness of the nanoparticle assisted glycovariant assays carry great promise for improved identification and early detection of ovarian carcinoma in routine differential diagnostics.

Sulfation of O-glycans on Mucin-type Proteins From Serous Ovarian Epithelial Tumors

Despite sulfated O-linked glycans being abundant on ovarian cancer (OC) glycoproteins, their regulation during cancer development and involvement in cancer pathogenesis remain unexplored. We characterized O-glycans carrying sulfation on galactose residues and compared their expression with defined sulfotransferases regulated during OC development. Desialylated sulfated oligosaccharides were released from acidic glycoproteins in the cyst fluid from one patient with a benign serous cyst and one patient with serous OC. Oligosaccharides characterized by LC-MSⁿ were identified as core 1 and core 2 O-glycans up to the size of decamers and with 1 to 4 sulfates linked to GlcNAc residues and to C-3 and/or C-6 of Gal. To study the specificity of the potential ovarian sulfotransferases involved, Gal3ST2 (Gal-3S)-, Gal3ST4 (Gal-3S)-, and CHST1 (Gal-6S)-encoding expression plasmids were transfected individually into CHO cells also expressing the P-selectin glycoprotein ligand-1/mouse immunoglobulin G2b (PSGL-1/mIg G2b) fusion protein and the human core 2 transferase (GCNT1). Characterization of the PSGL-1/mIg G2b O-glycans showed that Gal3ST2 preferentially sulfated Gal on the C-6 branch of core 2 structures and Gal3ST4 preferred Gal on the C-3 branch independently if core-1 or -2. CHST1 sulfated Gal residues on both the C-3 (core 1/2) and C-6 branches of core 2 structures. Using serous ovarian tissue micro array, Gal3ST2 was found to be decreased in tissue classified as malignant compared with tissues classified as benign or borderline, with the lowest expression in poorly differentiated malignant tissue. Neither Gal3ST4 nor CHST1 was differentially expressed in benign, borderline, or malignant tissue, and there was no correlation between expression level and differentiation stage. The data displays a complex sulfation pattern of O-glycans on OC glycoproteins and that aggressiveness of the cancer is associated with a decreased expression of the Gal3ST2 transferase.

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Ovarian cancer tissue contains highly sulfated O-glycoproteins.

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Sulfation occurs on GlcNAc (6-position) and Gal (3- and 6-position).

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Sulfation of Gal can be mimicked recombinantly with selected sulfotransferase.

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The Gal3ST2 sulfotransferase level is lower in malignant cancer compared with benign.

Mapping of truncated O-glycans in cancers of epithelial and non-epithelial origin

BACKGROUND

Novel immunotherapies targeting cancer-associated truncated O-glycans Tn (GalNAcα-Ser/Thr) and STn (Neu5Acα2-6GalNacα-Ser/Thr) are promising strategies for cancer treatment. However, no comprehensive, antibody-based mapping of truncated O-glycans in tumours exist to guide drug development.

METHODS

We used monoclonal antibodies to map the expression of truncated O-glycans in >700 tissue cores representing healthy and tumour tissues originating from breast, colon, lung, pancreas, skin, CNS and mesenchymal tissue. Patient-derived xenografts were used to evaluate Tn expression upon tumour engraftment.

RESULTS

The Tn-antigen was highly expressed in breast (57%, n = 64), colorectal (51%, n = 140) and pancreatic (53%, n = 108) tumours, while STn was mainly observed in colorectal (80%, n = 140) and pancreatic (56%, n = 108) tumours. We observed no truncated O-glycans in mesenchymal tumours (n = 32) and low expression of Tn (5%, n = 87) and STn (1%, n = 75) in CNS tumours. No Tn-antigen was found in normal tissue (n = 124) while STn was occasionally observed in healthy gastrointestinal tissue. Surface expression of Tn-antigen was identified across several cancers. Tn and STn expression decreased with tumour grade, but not with cancer stage. Numerous xenografts maintained Tn expression.

CONCLUSIONS

Surface expression of truncated O-glycans is limited to cancers of epithelial origin, making Tn and STn attractive immunological targets in the treatment of human carcinomas.

Analysis of blood group antigens on MUC5AC in mucinous ovarian cancer tissues using in situ proximity ligation assay

MUC5AC has been indicated to be a marker for mucinous ovarian cancer (OC). We investigated the use of in situ proximity ligation assay (PLA) for blood group ABH expressing MUC5AC to differentiate between serous and mucinous OC, to validate preceding observations that also MUC5AC ABH expression is increased in mucinous OC. We developed PLA for anti-A, B, and H/anti-MUC5AC and a PLA using a combined lectin Ulex europaeus agglutinin I (UEA I)/anti-MUC5AC assay. The PLAs were verified with mass spectrometry, where mucinous OC secretor positive patients’ cysts fluids containing ABH O-linked oligosaccharides also showed positive OC tissue PLA staining. A nonsecretor mucinous OC cyst fluid was negative for ABH and displayed negative PLA staining of the matched tissue. Using the UEA I/MUC5AC PLA, we screened a tissue micro array of 410 ovarian tissue samples from patients with various stages of mucinous or serous OC, 32 samples with metastasis to the ovaries and 34 controls. The PLA allowed differentiating mucinous tumors with a sensitivity of 84% and a specificity of 97% both against serous cancer but also compared to tissues from controls. This sensitivity is close to the expected incidence of secretor individuals in a population. The recorded sensitivity was also found to be higher compared to mucinous type cancer with metastasis to the ovaries, where only 32% were positive. We conclude that UEA 1/MUC5AC PLA allows glycospecific differentiation between serous and mucinous OC in patients with positive secretor status and will not identify secretor negative individuals with mucinous OC.

Glycan-specific antibodies as potential cancer biomarkers: a focus on microarray applications

Glycosylation is one of the most common posttranslational modifications of proteins and lipids. In the case of tumors, cell transformation accompanied by aberrant glycosylation results in the expression of tumor-associated glycans that promote tumor invasion. As part of the innate immunity, anti-glycan antibodies recognize tumor-associated glycans, and these antibodies can be present in the bloodstream in the early stages of cancer. Recently, anti-glycan antibody profiles have been of interest in various cancer studies. Novel advantages in the field of analytical techniques have simplified the analysis of anti-glycan antibodies and made it easier to have more comprehensive knowledge about their functions. One of the robust approaches for studying anti-glycan antibodies engages in microarray technology. The analysis of glycan microarrays can provide more expanded information to simultaneously specify or suggest the role of antibodies to a wide variety of glycans in the progression of different diseases, therefore making it possible to identify new biomarkers for diagnosing cancer and/or the state of the disease. Thus, in this review, we discuss antibodies to various glycans, their application for diagnosing cancer and one of the most promising tools for the investigation of these molecules, microarrays.

Global functions of O-glycosylation: promises and challenges in O-glycobiology

Mucin type O-glycosylation is one of the most diverse types of glycosylation, playing essential roles in tissue development and homeostasis. In complex organisms, O-GalNAc glycans comprise a substantial proportion of the glycocalyx, with defined functions in hemostatic, gastrointestinal, and respiratory systems. Furthermore, O-GalNAc glycans are important players in host-microbe interactions, and changes in O-glycan composition are associated with certain diseases and metabolic conditions, which in some instances can be used for diagnosis or therapeutic intervention. Breakthroughs in O-glycobiology have gone hand in hand with the development of new technologies, such as advancements in mass spectrometry, as well as facilitation of genetic engineering in mammalian cell lines. High-throughput O-glycoproteomics have enabled us to draw a comprehensive map of O-glycosylation, and mining this information has supported the definition and confirmation of functions related to site-specific O-glycans. This includes protection from proteolytic cleavage, as well as modulation of binding affinity or receptor function. Yet, there is still much to discover, and among the important next challenges will be to define the context-dependent functions of O-glycans in different stages of cellular differentiation, cellular metabolism, host-microbiome interactions, and in disease. In this review, we present the achievements and the promises in O-GalNAc glycobiology driven by technological advances in analytical methods, genetic engineering, and systems biology.

Display of the human mucinome with defined O-glycans by gene engineered cells

Mucins are a large family of heavily O-glycosylated proteins that cover all mucosal surfaces and constitute the major macromolecules in most body fluids. Mucins are primarily defined by their variable tandem repeat (TR) domains that are densely decorated with different O-glycan structures in distinct patterns, and these arguably convey much of the informational content of mucins. Here, we develop a cell-based platform for the display and production of human TR O-glycodomains (~200 amino acids) with tunable structures and patterns of O-glycans using membrane-bound and secreted reporters expressed in glycoengineered HEK293 cells. Availability of defined mucin TR O-glycodomains advances experimental studies into the versatile role of mucins at the interface with pathogenic microorganisms and the microbiome, and sparks new strategies for molecular dissection of specific roles of adhesins, glycoside hydrolases, glycopeptidases, viruses and other interactions with mucin TRs as highlighted by examples.

The evolving role of MUC16 (CA125) in the transformation of ovarian cells and the progression of neoplasia

MUC16 (the cancer antigen CA125) is the most commonly used serum biomarker in epithelial ovarian cancer, with increasing levels reflecting disease progression. It is a transmembrane glycoprotein with multiple isoforms, undergoing significant changes through the metastatic process. Aberrant glycosylation and cleavage with overexpression of a small membrane-bound fragment consist MUC16-related mechanisms that enhance malignant potential. Even MUC16 knockdown can induce an aggressive phenotype but can also increase susceptibility to chemotherapy. Variable MUC16 functions help ovarian cancer cells avoid immune cytotoxicity, survive inside ascites and form metastases. This review provides a comprehensive insight into MUC16 transformations and interactions, with description of activated oncogenic signalling pathways, and adds new elements on the role of its differential glycosylation. By following the journey of the molecule from pre-malignant states to advanced stages of disease it demonstrates its behaviour, in relation to the phenotypic shifts and progression of ovarian cancer. Additionally, it presents proposed differences of MUC16 structure in normal/benign conditions and epithelial ovarian malignancy.

In Situ Rolling Circle Amplification Förster Resonance Energy Transfer (RCA-FRET) for Washing-Free Real-Time Single-Protein Imaging

Fluorescence signal enhancement via isothermal nucleic acid amplification is an important approach for sensitive imaging of intra- or extracellular nucleic acid or protein biomarkers. Rolling circle amplification (RCA) is frequently applied for fluorescence in situ imaging but faces limitations concerning multiplexing, dynamic range, and the required multiple washing steps before imaging. Here, we show that Förster resonance energy transfer (FRET) between fluorescent dyes and between lanthanide (Ln) complexes and dyes that hybridize to β-actin-specific RCA products in HaCaT cells can afford washing-free imaging of single β-actin proteins. Proximity-dependent FRET could be monitored directly after or during (real-time monitoring) dye or Ln DNA probe incubation and could efficiently distinguish between photoluminescence from β-actin-specific RCA and DNA probes freely diffusing in solution or nonspecifically attached to cells. Moreover, time-gated FRET imaging with the Ln-dye FRET pairs efficiently suppressed sample autofluorescence and improved the signal-to-background ratio. Our results present an important proof of concept of RCA-FRET imaging with a strong potential to advance in situ RCA toward easier sample preparation, higher-order multiplexing, autofluorescence-free detection, and increased dynamic range by real-time monitoring of in situ RCA.

Mucin-Type O-GalNAc Glycosylation in Health and Disease

Mucin-type GalNAc O-glycosylation is one of the most abundant and unique post-translational modifications. The combination of proteome-wide mapping of GalNAc O-glycosylation sites and genetic studies with knockout animals and genome-wide analyses in humans have been instrumental in our understanding of GalNAc O-glycosylation. Combined, such studies have revealed well-defined functions of O-glycans at single sites in proteins, including the regulation of pro-protein processing and proteolytic cleavage, as well as modulation of receptor functions and ligand binding. In addition to isolated O-glycans, multiple clustered O-glycans have an important function in mammalian biology by providing structural support and stability of mucins essential for protecting our inner epithelial surfaces, especially in the airways and gastrointestinal tract. Here the many O-glycans also provide binding sites for both endogenous and pathogen-derived carbohydrate-binding proteins regulating critical developmental programs and helping maintain epithelial homeostasis with commensal organisms. Finally, O-glycan changes have been identified in several diseases, most notably in cancer and inflammation, where the disease-specific changes can be used for glycan-targeted therapies. This chapter will review the biosynthesis, the biology, and the translational perspectives of GalNAc O-glycans.

Comparative ligand structural analytics illustrated on variably glycosylated MUC1 antigen-antibody binding

When faced with the investigation of the preferential binding of a series of ligands against a known target, the solution is not always evident from single structure analysis. An ensemble of structures generated from computer simulations is valuable; however, visual analysis of the extensive structural data can be overwhelming. Rapid analysis of trajectory data, with tools available in the Galaxy platform, can be used to understand key features and compare differences that inform the preferential ligand structure that favors binding. We illustrate this informatics approach by investigating the in-silico binding of a peptide and glycopeptide epitope of the glycoprotein Mucin 1 (MUC1) binding with the antibody AR20.5. To study the binding, we performed molecular dynamics simulations using OpenMM and then used the Galaxy platform for data analysis. The same analysis tools are applied to each of the simulation trajectories and this process was streamlined by using Galaxy workflows. The conformations of the antigens were analyzed using root-mean-square deviation, end-to-end distance, Ramachandran plots, and hydrogen bonding analysis. Additionally, RMSF and clustering analysis were carried out. These analyses were used to rapidly assess key features of the system, interrogate the dynamic structure of the ligand, and determine the role of glycosylation on the conformational equilibrium. The glycopeptide conformations in solution change relative to the peptide; thus a partially pre-structuring is seen prior to binding. Although the bound conformation of peptide and glycopeptide is similar, the glycopeptide fluctuates less and resides in specific conformers for more extended periods. This structural analysis which gives a high-level view of the features in the system under observation, could be readily applied to other binding problems as part of a general strategy in drug design or mechanistic analysis.

Investigating Patterns of Immune Interaction in Ovarian Cancer: Probing the O-glycoproteome by the Macrophage Galactose-Like C-type Lectin (MGL)

Glycosylation, the posttranslational linking of sugar molecules to proteins, is notoriously altered during tumor transformation. More specifically in carcinomas, GalNAc-type O-glycosylation, is characterized by biosynthetically immature truncated glycans present on the cancer cell surface, which profoundly impact anti-tumor immune recognition. The tumor-associated glycan pattern may thus be regarded as a biomarker of immune modulation. In epithelial ovarian cancer (EOC) there is a particular lack of specific biomarkers and molecular targets to aid early diagnosis and develop novel therapeutic interventions. The aim of this study was to investigate the ovarian cancer O-glycoproteome and identify tumor-associated glycoproteins relevant in tumor-dendritic cell (DC) interactions, mediated by macrophage galactose-like C type lectin (MGL), which recognizes the tumor-associated Tn O-glycan. Lectin weak affinity chromatography (LWAC) was employed to probe the O-glycopeptidome by MGL and Vicia villosa agglutinin (VVA) lectin using glycoengineered ovarian cancer cell lines and ovarian cancer tissues as input material. Biochemical and bioinformatics analysis gave information on the glycan arrangement recognized by MGL in tumor cells. The potential MGL binders identified were located, as expected, at the cell membrane, but also within the intracellular compartment and the matrisome, suggesting that MGL in vivo may play a complex role in sensing microenvironmental cues. The tumor glycoproteins binders for MGL may become relevant to characterize the interaction between the immune system and tumor progression and contribute to the design of glycan targeting-based strategies for EOC immunotherapeutic interventions.

Epithelial Ovarian Cancer and the Immune System: Biology, Interactions, Challenges and Potential Advances for Immunotherapy

Recent advances in the understanding of immune function and the interactions with tumour cells have led to the development of various cancer immunotherapies and strategies for specific cancer types. However, despite some stunning successes with some malignancies such as melanomas and lung cancer, most patients receive little or no benefit from immunotherapy, which has been attributed to the tumour microenvironment and immune evasion. Although the US Food and Drug Administration have approved immunotherapies for some cancers, to date, only the anti-angiogenic antibody bevacizumab is approved for the treatment of epithelial ovarian cancer. Immunotherapeutic strategies for ovarian cancer are still under development and being tested in numerous clinical trials. A detailed understanding of the interactions between cancer and the immune system is vital for optimisation of immunotherapies either alone or when combined with chemotherapy and other therapies. This article, in two main parts, provides an overview of: (1) components of the normal immune system and current knowledge regarding tumour immunology, biology and their interactions; (2) strategies, and targets, together with challenges and potential innovative approaches for cancer immunotherapy, with attention given to epithelial ovarian cancer.

Electrochemical mixed aptamer-antibody sandwich assay for mucin protein 16 detection through hybridization chain reaction amplification

A mixed aptamer-antibody sandwich assay for the determination of mucin protein 16 (MUC16) was developed based on hybridization chain reaction (HCR) with methylene blue (MB) as an electrochemical indicator. First, MUC16 antibody was adsorbed onto the surface of the Au nanoparticle (AuNP)-modified indium tin oxide (ITO) electrode to effectively capture the target MUC16. After MUC16 was captured by the MUC16 aptamer, an antibody/MUC16/aptamer sandwich structure formed for the highly selective detection of MUC16. The 3' end of the aptamer was then subjected to HCR with the assistance of auxiliary probes to obtain DNA concatemers. Numerous MB molecules bonded with G bases in the DNA concatemers by immersing the modified ITO electrode into a stirred solution containing MB with KCl. Stepwise changes in the microscopic features of the electrode surface were studied by scanning electron microscopy (SEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical behavior of the different modified electrodes. The oxidation current of MB was detected by differential pulse voltammetry (DPV). Under the optimum conditions, the proposed mixed aptamer-antibody sandwich assay showed wide dynamic range from 0.39 to 200 unit mL^-1 with a low detection limit of 0.02 unit mL^-1 (S/N ratio = 3). The proposed method showed good accuracy, selectivity, and acceptable reproducibility. Graphical abstract An electrochemical mixed aptamer-antibody sandwich assay based on the aptamer-induced HCR amplification strategy was fabricated for the highly sensitive detection of MUC16. The mixed aptamer-antibody sandwich assay showed acceptable performance of detection range, detection limit, reproducibility, and selectivity.

Galectins and Ovarian Cancer

Ovarian cancer is known for its aggressive pathological features, including the capacity to undergo epithelial to mesenchymal transition, promoting angiogenesis, metastatic potential, chemoresistance, inhibiting apoptosis, immunosuppression and promoting stem-like features. Galectins, a family of glycan-binding proteins defined by a conserved carbohydrate recognition domain, can modulate many of these processes, enabling them to contribute to the pathology of ovarian cancer. Our goal herein was to review specific galectin members identified in the context of ovarian cancer, with emphasis on their association with clinical and pathological features, implied functions, diagnostic or prognostic potential and strategies being developed to disrupt their negative actions.

Intramolecular trigger remodeling-induced HCR for amplified detection of protein-specific glycosylation

Dynamic changes of protein-glycosylation on cell surface act as an important indicator that reflects cellular physiological states and disease developments. The enhanced visualization of protein-specific glycosylation is of great value to interpret its functions and mechanisms. Hence, we present an intramolecular trigger remodeling-induced hybridization chain reaction (HCR) for imaging protein-specific glycosylation. This strategy relies on designing two DNA probes, protein and glycan probes, labeled respectively on protein by aptamer recognition and glycan through metabolic oligosaccharide engineering (MOE). Upon the same glycoprotein was labeled, the complementary domain of two probes induces hybridization and thus to remodel an intact trigger, followed by initiating HCR assembly. Applying this strategy, we successfully achieved imaging of specific protein-glycosylation on CEM cell surface and monitored dynamic changes of the glycosylation after treating with drugs. It provides a powerful tool with high flexibility, specificity and sensitivity in the research field of protein-specific glycosylation on living cells.

Plant lectins and their usage in preparing targeted nanovaccines for cancer immunotherapy

Plant lectins, a natural source of glycans with a therapeutic potential may lead to the discovery of new targeted therapies. Glycans extracted from plant lectins are known to act as ligands for C-type lectin receptors (CLRs) that are primarily present on immune cells. Plant-derived glycosylated lectins offer diversity in their N-linked oligosaccharide structures that can serve as a unique source of homogenous and heterogenous glycans. Among the plant lectins-derived glycan motifs, Man₉GlcNAc₂Asn exhibits high-affinity interactions with CLRs that may resemble glycan motifs of pathogens. Thus, such glycan domains when presented along with antigens complexed with a nanocarrier of choice may bewilder the immune cells and direct antigen cross-presentation - a cytotoxic T lymphocyte immune response mediated by CD8⁺ T cells. Glycan structure analysis has attracted considerable interest as glycans are looked upon as better therapeutic alternatives than monoclonal antibodies due to their cost-effectiveness, reduced toxicity and side effects, and high specificity. Furthermore, this approach will be useful to understand whether the multivalent glycan presentation on the surface of nanocarriers can overcome the low-affinity lectin-ligand interaction and thereby modulation of CLR-dependent immune response. Besides this, understanding how the heterogeneity of glycan structure impacts the antigen cross-presentation is pivotal to develop alternative targeted therapies. In the present review, we discuss the findings on structural analysis of glycans from natural lectins performed using GlycanBuilder2 - a software tool based on a thorough literature review of natural lectins. Additionally, we discuss how multiple parameters like the orientation of glycan ligands, ligand density, simultaneous targeting of multiple CLRs and design of antigen delivery nanocarriers may influence the CLR targeting efficacy. Integrating this information will eventually set the ground for new generation immunotherapeutic vaccine design for the treatment of various human malignancies.

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.

Morniga-G, a T/Tn-Specific Lectin, Induces Leukemic Cell Death via Caspase and DR5 Receptor-Dependent Pathways

Morniga-G, the Gal-specific black mulberry (Morus nigra) lectin, displays high affinity for T (CD176) and Tn (CD175) antigens, frequently expressed at the cancer cell surface. The effects of Morniga-G were investigated on a Tn-positive leukemic Jurkat cell line. The lectin, used in a concentration range between 5⁻20 μg/mL, induced cell death in leukemic Jurkat cells. Microscopic and cytofluorometric analyses indicated that Jurkat cell death was essentially apoptotic, associated with an increase in the ceramide content and a depolarization of the mitochondrial transmembrane potential. This lectin-mediated cell death was inhibited by the pan caspase-inhibitor zVAD. In addition, cleavage of caspases 8, 9, and 3 was observed in Morniga-G-treated Jurkat cells whereas Jurkat cell lines that are deficient in caspase 8⁻10, caspase 9, or FADD, survived to the lectin-mediated toxicity. Furthermore, in the presence of TRAIL- or DR5-blocking mononoclonal antibodies, Jurkat cells became resistant to Morniga-G, suggesting that the lectin triggers cell death via the TRAIL/DR5 pathway. In silico computer simulations suggest that Morniga-G might facilitate both the DR5 dimerization and the building of TRAIL/DR5 complexes. Finally, upon treatment of Jurkat cells with benzyl-GalNAc, an O-glycosylation inhibitor, a decrease in Tn antigen expression associating with a reduced Morniga-G toxicity, was observed. Taken together, these results suggest that Morniga-G induces the cell death of Tn-positive leukemic cells via concomitant O-glycosylation-, caspase-, and TRAIL/DR5-dependent pathways.

MUC16 as a novel target for cancer therapy

INTRODUCTION

MUC16 is overexpressed in multiple cancers and plays an important role in tumorigenicity and acquired resistance to therapy. Area covered: In this review, we describe the role of MUC16 under normal physiological conditions and during tumorigenesis. First, we provide a summary of research on MUC16 from its discovery as CA125 to present anti-MUC16 therapy trials that are currently in the initial phases of clinical testing. Finally, we discuss the reasons for the limited effectiveness of these therapies and discuss the direction and focus of future research. Expert opinion: Apart from its protective role in normal physiology, MUC16 contributes to disease progression and metastasis in several malignancies. Due to its aberrant overexpression, it is a promising target for diagnosis and therapy. Cleavage and shedding of its extracellular domain is the major barrier for efficient targeting of MUC16-expressing cancers. Concerted efforts should be undertaken to target the noncleaved cell surface retained portion of MUC16. Such efforts should be accompanied by basic research to understand MUC16 cleavage and decipher the functioning of MUC16 cytoplasmic tail. While previous efforts to activate anti-MUC16 immune response using anti-CA125 idiotype antibodies have met with limited success, ideification of neo-antigenic epitopes in MUC16 that correlate with improved survival have raised raised hopes for developing MUC16-targeted immunotherapy.

Mucins and Truncated O-Glycans Unveil Phenotypic Discrepancies between Serous Ovarian Cancer Cell Lines and Primary Tumours

Optimal research results rely on the selection of cellular models capable of recapitulating the characteristics of primary tumours from which they originate. The expression of mucins (MUC16 and MUC1) and truncated O-glycans (Tn, STn and T) represents a characteristic footprint of serous ovarian carcinomas (SOCs). Therefore, selecting ovarian cancer (OVCA) cell lines that reflect this phenotype is crucial to explore the putative biological role of these biomarkers in the SOC setting. Here, we investigated a panel of OVCA cell lines commonly used as SOC models, and tested whether, when cultured in 2D and 3D conditions, these recapitulate the mucin and O-glycan expression profiles of SOCs. We further explored the role of truncating the O-glycosylation capacity in OVCAR3 cells through knockout of the COSMC chaperone, using in vitro and in vivo assays. We found that the majority of OVCA cell lines of serous origin do not share the mucin and truncated O-glycan footprint of SOCs, although 3D cultures showed a higher resemblance. We also found that genetic truncation of the O-glycosylation capacity of OVCAR3 cells did not enhance oncogenic features either in vitro or in vivo. This study underscores the importance of well-characterized cellular models to study specific features of ovarian cancer.

Treatment of ovarian cancer by targeting the tumor stem cell-associated carbohydrate antigen, Sialyl-Thomsen-nouveau

Recurrent ovarian cancer (OvCa) is thought to result in part from the inability to eliminate rare quiescent cancer stem cells (CSCs) that survive cytotoxic chemotherapy and drive tumor resurgence. The Sialyl-Thomsen-nouveau antigen (STn) is a carbohydrate moiety present on protein markers of CSCs in pancreatic, colon, and gastric malignancies. We have demonstrated that human OvCa cell lines contain varying levels of cells that independently express either STn or the ovarian CSC marker CD133. Here we determine co-expression of STn and CD133 in a subset of human OvCa cell lines. Analyses of colony and sphere forming capacity and of response to standard-of-care cytotoxic therapy suggest a subset of OvCa STn+ cells display some CSC features. The effect of the anti-STn antibody-drug conjugates (ADCs) S3F-CL-MMAE and 2G12-2B2-CL-MMAE on OvCa cell viability in vitro and in vivo was also assessed. Treatment with S3F-CL-MMAE reduced the viability of two of three OvCa cell lines in vitro and exposure to either S3F-CL-MMAE or 2G12-2B2-CL-MMAE reduced OVCAR3-derived xenograft volume in vivo, depleting STn+ tumor cells. In summary, STn+ cells demonstrate some stem-like properties and specific therapeutic targeting of STn in ovarian tumors may be an effective clinical strategy to eliminate both STn+ CSC and STn+ non-CSC populations.

Prognostic significance of ST6GalNAc-1 expression in patients with non-metastatic clear cell renal cell carcinoma

BACKGROUND

Sialyltransferase ST6GalNAc-1 is highly expressed in tumor cells and associated with tumor aggressiveness and poor prognosis. In the present study, we aimed to investigate the clinical and prognostic significance of sialyltransferase ST6GalNAc-1 in patients with non-metastatic ccRCC.

RESULTS

High expression of ST6GalNAc-1 in tumor tissue was an independent prognostic factor for overall survival (p<0.001) and recurrence free survival (p<0.001) in multivariate analysis. The nomograms could give better prediction for overall survival and recurrence free survival in ccRCC patients.

METHODS

264 patients diagnosed with non-metastatic clear cell renal cell carcinoma were enrolled in the present study. Immunohistochemical staining was performed on tissue microarrays to evaluate the intratumoral ST6GalNAc-1 expression. Kaplan-Meier method and Cox proportional hazard model were applied to assess the prognostic value of ST6GalNAc-1. Nomograms were generated to refine individual risk stratification in ccRCC patients.

CONCLUSION

ST6GalNAc-1 was an independent adverse prognostic factor for both overall survival and recurrence free survival in patients with non-metastatic ccRCC.

Peritoneal dissemination of ovarian cancer: role of MUC16-mesothelin interaction and implications for treatment

INTRODUCTION

Peritoneal dissemination is a particular form of malignant progression in ovarian cancer, preceding hematogenic or lymphatic dissemination. Thus, prevention of peritoneal implantation of cancer cells is envisioned to inhibit neoplastic dissemination and therefore prolong disease remission and patient's survival. Areas covered: An extended review on the role of MUC16 (CA125) and mesothelin (MSLN), expressed in a high percentage of ovarian carcinomas, indicate that this duet is relevant for the contact between cancer cells and mesothelial cells in homotypic (cancer cell-cancer cell) and heterotypic (cancer cell-mesothelial cell) interactions. This review discusses the reasons underlying the clinical failure of immunotherapeutic strategies targeting MUC16. Clinical data on MSLN targeting agents such as antibody-based immunotoxins or antibody drug conjugates are also reviewed. The promising anti-tumor effect of CAR-T cells directed to MUC16 or MSLN is emphasized. New emerging strategies specifically disrupting the MUC16-MSLN interaction are at the forefront of this review, including TRAIL ligands bound to MSLN targeting MUC16 expressing cells and single chain monoclonal antibodies and immunoadhesins recognizing MSLN-MUC16 binding domains. Expert commentary: Based on existing evidences the authors advocate that agents targeting MUC16-MSLN may add to the therapeutic armamentarium directed to abrogate peritoneal homing of ovarian cancer.

Characterization of H type 1 and type 1 N-acetyllactosamine glycan epitopes on ovarian cancer specifically recognized by the anti-glycan monoclonal antibody mAb-A4

Cancer-specific glycans of ovarian cancer are promising epitopes for targeting with monoclonal antibodies (mAb). Despite their potential, structural characterization of these glycan epitopes remains a significant challenge in mAb preclinical development. Our group generated the monoclonal antibody mAb-A4 against human embryonic stem cells (hESC), which also bound specifically to N-glycans present on 11 of 19 ovarian cancer (OC) and 8 of 14 breast cancer cell lines tested. Normal cell lines and tissue were unstained by mAb-A4. To characterize the N-linked glycan epitopes on OC cell lines targeted by mAb-A4, we used glycosidases, glycan microarray, siRNA, and advanced high sensitivity matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The mAb-A4 epitopes were found to be Fucα1-2Galβ1-3GlcNAcβ (H type 1) and Galβ1-3GlcNAcβ (type 1 LacNAc). These structures were found to be present on multiple proteins from hESC and OC. Importantly, endo-β-galactosidase coupled with MALDI-MS allowed these two epitopes, for the first time, to be directly identified on the polylactosamines of N-glycans of SKOV3, IGROV1, OV90, and OVCA433. Furthermore, siRNA knockdown of B3GALT5 expression in SKOV3 demonstrated that mAb-A4 binding was dependent on B3GALT5, providing orthogonal evidence of the epitopes' structures. The recognition of oncofetal H type 1 and type 1 LacNAc on OC by mAb-A4 is a novel and promising way to target OC and supports the theory that cancer can acquire stem-like phenotypes. We propose that the orthogonal framework used in this work could be the basis for advancing anti-glycan mAb characterization.

Altered (neo-) lacto series glycolipid biosynthesis impairs α2-6 sialylation on N-glycoproteins in ovarian cancer cells

The (neo-) lacto series glycosphingolipids (nsGSLs) comprise of glycan epitopes that are present as blood group antigens, act as primary receptors for human pathogens and are also increasingly associated with malignant diseases. Beta-1, 3-N-acetyl-glucosaminyl-transferase 5 (B3GNT5) is suggested as the key glycosyltransferase for the biosynthesis of nsGSLs. In this study, we investigated the impact of CRISPR-Cas9 -mediated gene disruption of B3GNT5 (∆B3GNT5) on the expression of glycosphingolipids and N-glycoproteins by utilizing immunostaining and glycomics-based PGC-UHPLC-ESI-QTOF-MS/MS profiling. ∆B3GNT5 cells lost nsGSL expression coinciding with reduction of α2-6 sialylation on N-glycoproteins. In contrast, disruption of B4GALNT1, a glycosyltransferase for ganglio series GSLs did not affect α2-6 sialylation on N-glycoproteins. We further profiled all known α2-6 sialyltransferase-encoding genes and showed that the loss of α2-6 sialylation is due to silencing of ST6GAL1 expression in ∆B3GNT5 cells. These results demonstrate that nsGSLs are part of a complex network affecting N-glycosylation in ovarian cancer cells.

Glycoconjugates from extracellular vesicles: Structures, functions and emerging potential as cancer biomarkers

Extracellular vesicles (EVs) are released by virtually all cells, carry cellular molecules to the extracellular environment, and may interact with other cells. They are found in body fluids, therefore, constituting useful target sources for the identification of disease biomarkers, for example, in cancer. EVs originate from the plasma membrane or from multivesicular endosomes. They have the same topology as the plasma membrane and are rich in glycoconjugates, displaying specific glycosignatures. Surface glycoconjugates play important roles in EVs biogenesis and in their interaction with other cells. Changes in glycosylation constitute a hallmark of different types of cancer, therefore, the study of glycoconjugates and glycosignatures of EVs appear as promising candidates to identify novel cancer biomarkers and to increase the specificity and sensitivity of the existing clinical biomarkers, many of which are glycosylated.

A standardized method for lectin microarray-based tissue glycome mapping

The significance of glycomic profiling has been highlighted by recent findings that structural changes of glycans are observed in many diseases, including cancer. Therefore, glycomic profiling of the whole body (glycome mapping) under different physiopathological states may contribute to the discovery of reliable biomarkers with disease-specific alterations. To achieve this, standardization of high-throughput and in-depth analysis of tissue glycome mapping is needed. However, this is a great challenge due to the lack of analytical methodology for glycans on small amounts of endogenous glycoproteins. Here, we established a standardized method of lectin-assisted tissue glycome mapping. Formalin-fixed, paraffin-embedded tissue sections were prepared from brain, liver, kidney, spleen, and testis of two C57BL/6J mice. In total, 190 size-adjusted fragments with different morphology were serially collected from each tissue by laser microdissection and subjected to lectin microarray analysis. The results and subsequent histochemical analysis with selected lectins were highly consistent with previous reports of mass spectrometry-based N- and/or O-glycome analyses and histochemistry. This is the first report to look at both N- and O-glycome profiles of various regions within tissue sections of five different organs. This simple and reproducible mapping approach is also applicable to various disease model mice to facilitate disease-related biomarker discovery.

Targeted O-glycoproteomics explored increased sialylation and identified MUC16 as a poor prognosis biomarker in advanced-stage bladder tumours

Bladder carcinogenesis and tumour progression is accompanied by profound alterations in protein glycosylation on the cell surface, which may be explored for improving disease management. In a search for prognosis biomarkers and novel therapeutic targets we have screened, using immunohistochemistry, a series of bladder tumours with differing clinicopathology for short-chain O-glycans commonly found in glycoproteins of human solid tumours. These included the Tn and T antigens and their sialylated counterparts sialyl-Tn(STn) and sialyl-T(ST), which are generally associated with poor prognosis. We have also explored the nature of T antigen sialylation, namely the sialyl-3-T(S3T) and sialyl-6-T(S6T) sialoforms, based on combinations of enzymatic treatments. We observed a predominance of sialoglycans over neutral glycoforms (Tn and T antigens) in bladder tumours. In particular, the STn antigen was associated with high-grade disease and muscle invasion, in accordance with our previous observations. The S3T and S6T antigens were detected for the first time in bladder tumours, but not in healthy urothelia, highlighting their cancer-specific nature. These glycans were also overexpressed in advanced lesions, especially in cases showing muscle invasion. Glycoproteomic analyses of advanced bladder tumours based on enzymatic treatments, Vicia villosa lectin-affinity chromatography enrichment and nanoLC-ESI-MS/MS analysis resulted in the identification of several key cancer-associated glycoproteins (MUC16, CD44, integrins) carrying altered glycosylation. Of particular interest were MUC16 STn⁺ -glycoforms, characteristic of ovarian cancers, which were found in a subset of advanced-stage bladder tumours facing the worst prognosis. In summary, significant alterations in the O-glycome and O-glycoproteome of bladder tumours hold promise for the development of novel noninvasive diagnostic tools and targeted therapeutics. Furthermore, abnormal MUC16 glycoforms hold potential as surrogate biomarkers of poor prognosis and unique molecular signatures for designing highly specific targeted therapeutics.

Applying DNA rolling circle amplification in fluorescence imaging of cell surface glycans labeled by a metabolic method

Glycans on the cell surfaces are essential for cellular communication. Metabolically labeling glycans can introduce unnatural sugars into cellular glycans, which can facilitate further labeling. We report herein imaging cell surface glycosylation by using click chemistry and DNA rolling circle amplification (RCA) to improve detection sensitivity. Through the RCA amplification, the image resolution of a cell was significantly improved and much fewer unnatural sugars were used than required previously. The advantage of this method is that it avoids introducing too much unnatural sugar, which can interfere with normal, physiological cell function. Simultaneously, the enhanced fluorescence intensity conveniently facilitates the detection of cells' own biosynthetic glycans by simply using a microplate reader. The results indicate that the metabolically labelling ability is different for different carbohydrates and different cells. Next, the RCA technique was adopted in a fluorescence resonance energy transfer (FRET)-based methodology that facilitated the glycan imaging of specific proteins on the cell surface. This method is broadly applicable to imaging the glycosylation of cellular proteins. Our results highlight the applications of RCA in metabolic glycan labeling, which can be used to monitor the glycosylation status on cells, and study the means by which glycosylation regulates cell function.

Silencing of ST6GalNAc I suppresses the proliferation, migration and invasion of hepatocarcinoma cells through PI3K/AKT/NF-κB pathway

ST6GalNAc I is the major Sialyl-Tn antigen (STn) synthase that is highly correlated with tumor invasion and metastasis. However, the roles and molecular mechanisms by which ST6GalNAc I mediates the malignant phenotypes of hepatocarcinoma cells still remain poorly unknown. In this study, we investigated the expression of STn and ST6GalNAc I in mouse hepatocarcinoma cell lines Hca-F, Hca-P, and Hepa1-6, which have different metastatic potential, as compared with normal mouse liver cell line IAR-20. The results showed that the expression of ST6GalNAc I and STn in Hca-F and Hca-P cells was much higher than that in Hepa1-6 and IAR20 cells. Knockdown of ST6GalNAc I by shRNA in Hca-F cells significantly decreased the expression of STn and inhibited the growth of tumor cells in vitro and in vivo. This reduction of ST6GalNAc I expression also led to the decreased migration and invasion of Hca-F cells. Furthermore, we found that ST6GalNAc I knockdown inhibited the expression levels of PI3k, p-Akt473, p-Akt308, NF-κB, and their downstream molecules. Together, our results suggest a role of ST6GalNAc I in promoting the growth and invasion of hepatocarcinoma cells through regulating PI3K/AKT signaling, and ST6GalNAc I might be a promising marker for the prognosis and therapy of hepatocarcinoma.

Mucins MUC16 and MUC1 are major carriers of SLe(a) and SLe(x) in borderline and malignant serous ovarian tumors

Mucins are heavily glycosylated proteins overexpressed and associated with truncated or sialylated glycans upon malignant transformation. We previously identified a panel of four glyco-mucin profiles (MUC16/Tn, MUC16/STn, MUC1/Tn, and MUC1/STn) with 100 % specificity and 100 % positive predictive value for detection of borderline/malignant serous tumors of the ovary, using proximity ligation assay (PLA). In the present work, using the same method, we studied other mucin glycosylation profiles that might add relevant information for diagnostic purposes. We used PLA probes to MUC16, MUC1, sialyl Lewis(a) (SLe(a)), and sialyl Lewis(x) (SLe(x)) to study a series of 39 ovarian serous tumors (14 adenocarcinomas, 10 borderline ovarian tumors (BOTs), and 15 cystadenomas). Our results demonstrated that, in adenocarcinomas and BOTs, the major carriers of SLe(a) and SLe(x) are MUC16 and/or MUC1 (100 and 92 % for SLe(a) and 64 and 70 % for SLe(x), respectively). In cystadenomas, SLe(a) and SLe(x) are mainly carried by unidentified proteins (85 and 78 %, respectively). Our study identified, for the first time, the major protein carriers of SLe(a) and SLe(x) in ovarian adenocarcinomas and BOTs, MUC1 and MUC16, and also that distinct unidentified carriers are involved in cystadenomas. These results emphasize the relevance of multiple biomarker recognition provided by multiplex assays, such as PLA, to enhance sensitivity and specificity of serum and tissue assays.

Short O-GalNAc glycans: regulation and role in tumor development and clinical perspectives

BACKGROUND

While the underlying causes of cancer are genetic modifications, changes in cellular states mediate cancer development. Tumor cells display markedly changed glycosylation states, of which the O-GalNAc glycans called the Tn and TF antigens are particularly common. How these antigens get over-expressed is not clear. The expression levels of glycosylation enzymes fail to explain it.

SCOPE OF REVIEW

We describe the regulation of O-GalNAc glycosylation initiation and extension with emphasis on the initiating enzymes ppGalNAcTs (GALNTs), and introduce the GALA pathway--a change in GALNTs compartmentation within the secretory pathway that regulates Tn levels. We discuss the roles of O-GalNAc glycans and GALNTs in tumorigenic processes and finally consider diagnostic and therapeutic perspectives.

MAJOR CONCLUSIONS

Contrary to a common hypothesis, short O-glycans in tumors are not the result of an incomplete glycosylation process but rather reveal the activation of regulatory pathways. Surprisingly, high Tn levels reveal a major shift in the O-glycoproteome rather than a shortening of O-glycans. These changes are driven by membrane trafficking events.

GENERAL SIGNIFICANCE

Many attempts to use O-glycans for biomarker, antibody and therapeutic vaccine development have been made, but suffer limitations including poor sensitivity and/or specificity that may in part derive from lack of a mechanistic understanding. Deciphering how short O-GalNAc glycans are regulated would open new perspectives to exploit this biology for therapeutic usage. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

The clinical utility of CA125/MUC16 in pancreatic cancer: A consensus of diagnostic, prognostic and predictive updates by the Chinese Study Group for Pancreatic Cancer (CSPAC)

The prognosis for pancreatic cancer (PC) is poor; however, the timely and accurate treatment of this disease will significantly improve prognosis. Serum biomarkers involve non-invasive tests that facilitate the early detection of tumors, predict outcomes and assess responses to therapy, so that the patient can be continuously monitored and receive the most appropriate therapy. Studies have reported that cancer antigen (CA)125 [also known as mucin 16 (MUC16)] has functional significance in the tumorigenic, metastatic and drug resistant properties of PC. Our aim was to use this biomarker in the diagnosis, detection of metastasis, prognosis and in the monitoring of the treatment effects of PC. Members of the Chinese Study Group for Pancreatic Cancer (CSPAC) reviewed the literature on CA125/MUC16 and developed an objective consensus on the clinical utility of CA125/MUC16 for PC. They confirmed the role of CA125/MUC16 in tumorigenesis and the progression of PC, and recommended monitoring CA125/MUC16 levels in all aspects of the diagnosis and treatment of PC, particularly those that involve the monitoring of treatments. In addition, they suggested that the combination of other biomarkers and imaging techniques, together with CA125/MUC16, would improve the accuracy of the clinical decision-making process, thereby facilitating the optimization of treatment strategies. Periodic clinical updates of the use of CA125/MUC16 have been established, which are important for further analyses and comparisons of clinical results from affiliates and countries, particularly as regards the in-depth biological function and clinical translational research of this biomarker.

Glycosylation-Based Serum Biomarkers for Cancer Diagnostics and Prognostics

Cancer is the second most common cause of death in developed countries with approximately 14 million newly diagnosed individuals and over 6 million cancer-related deaths in 2012. Many cancers are discovered at a more advanced stage but better survival rates are correlated with earlier detection. Current clinically approved cancer biomarkers are most effective when applied to patients with widespread cancer. Single biomarkers with satisfactory sensitivity and specificity have not been identified for the most common cancers and some biomarkers are ineffective for the detection of early stage cancers. Thus, novel biomarkers with better diagnostic and prognostic performance are required. Aberrant protein glycosylation is well known hallmark of cancer and represents a promising source of potential biomarkers. Glycoproteins enter circulation from tissues or blood cells through active secretion or leakage and patient serum is an attractive option as a source for biomarkers from a clinical and diagnostic perspective. A plethora of technical approaches have been developed to address the challenges of glycosylation structure detection and determination. This review summarises currently utilised glycoprotein biomarkers and novel glycosylation-based biomarkers from the serum glycoproteome under investigation as cancer diagnostics and for monitoring and prognostics and includes details of recent high throughput and other emerging glycoanalytical techniques.

Glycosylation in cancer: mechanisms and clinical implications

Despite recent progress in understanding the cancer genome, there is still a relative delay in understanding the full aspects of the glycome and glycoproteome of cancer. Glycobiology has been instrumental in relevant discoveries in various biological and medical fields, and has contributed to the deciphering of several human diseases. Glycans are involved in fundamental molecular and cell biology processes occurring in cancer, such as cell signalling and communication, tumour cell dissociation and invasion, cell-matrix interactions, tumour angiogenesis, immune modulation and metastasis formation. The roles of glycans in cancer have been highlighted by the fact that alterations in glycosylation regulate the development and progression of cancer, serving as important biomarkers and providing a set of specific targets for therapeutic intervention. This Review discusses the role of glycans in fundamental mechanisms controlling cancer development and progression, and their applications in oncology.

Detection of glyco-mucin profiles improves specificity of MUC16 and MUC1 biomarkers in ovarian serous tumours

The CA125 assay detects circulating MUC16 and is one of the most widely used cancer biomarkers for the follow-up of ovarian cancer. We previously demonstrated that detection of aberrant cancer-associated glycoforms of MUC16 as well as MUC1 in circulation could improve the yield of these serum assays. Our aim was to refine ovarian cancer biomarkers by detection of aberrant glycoforms (Tn, STn, and T) of MUC16 and MUC1 in ovarian cancer tissue using Proximity Ligation Assays (PLA). We studied two series of serous ovarian tumours, a pilot series of 66 ovarian tumours (27 cystadenomas, 16 borderline tumours and 23 adenocarcinomas) from Centro Hospitalar S. João, Porto and a validation series of 89 ovarian tumours (17 cystadenomas, 25 borderline tumours and 47 adenocarcinomas) from the Portuguese Institute of Oncology Francisco Gentil, Lisbon. PLA reactions for MUC16/Tn, MUC16/STn, MUC1/Tn and MUC1/STn were negative in benign lesions but often positive in borderline and malignant lesions, in both series. An even better yield was obtained based on positivity for any of the four glyco-mucin profiles, further increasing sensitivity to 72% and 83% in the two series, respectively, with 100% specificity. The strategy is designated glyco-mucin profiling and provides strong support for development of PLA-based serum assays for early diagnosis.