N-glycolylneuraminic acid as a carbohydrate cancer biomarker

Improved breast cancer diagnosis using a CA15-3 capture antibody-lectin sandwich assay

PURPOSE

This study aims to test the hypothesis that an enzyme-linked antibody-lectin sandwich assay for a glycovariant of CA15-3 can deliver better diagnostic performance, defined by classification accuracy, sensitivity and specificity, for breast cancer compared to an existing FDA-approved CA15-3 test.

METHODS

A genetically engineered lectin (SubB2M) that specifically binds N-glycolylneuraminic acid (Neu5Gc) was used as a detection reagent in a CA15-3 capture antibody-lectin sandwich (neuCA15-3) assay. In a case: control cohort equivalence study the classification accuracy for the neuCA15-3 assay was determined and compared to an FDA-approved CA15-3 IVD test (Elecsys CA15-3 II, Roche Diagnostics).

RESULTS

Classification accuracy and AUC for neuCA15-3 were 81% and 0.886 ± 0.015 (standard error, n = 567) and for Elecsys CA15-3 II, 55% and 0.642 ± 0.023 (n = 558), respectively. At a threshold cut-off serum concentration of 23.6 units/ml, overall breast cancer classification accuracy of the neuCA15-3 was 81% (compared to 55% for the comparator assay, p < 0.001). At 95% specificity, the sensitivity of the neuCA15-3 assay was 69.5%, significantly greater than the comparator assay (11.9%, p < 0.001). neuCA15-3 concentrations did not vary significantly with breast cancer receptor subtype or comorbidities tested.

CONCLUSIONS

The diagnostic performance of neuCA15-3 was substantially improved by specifically targeting both a CA15-3 protein epitope and a pan-cancer glycan (Neu5Gc) epitope (the specific binding target of SubB2M). The reporter signal generated depends on the colocalization of the cancer antigen protein epitope and the aberrant sialylation of the protein, thus increasing the assay specificity. The presence of multiple Neu5Gc lectin-binding sites per glycoprotein molecule increases signal generation and assay sensitivity. The inclusion of additional cancer biomarkers in a multivariate index assay format may further increase diagnostic performance for breast cancer.

Variability of Sialic Acids in Beef Breeds and Nutritional Implications in Red Meat

This study examines the variability of sialic acids, specifically N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), in beef from seven cattle breeds (Holstein Friesian, Red Pied, Maremmana, Chianina, Charolais, Limousin, and Piemontese). Neu5Gc, a non-human sialic acid linked to inflammation and disease risk, showed significant breed differences (p < 0.001), with the highest concentration in Holstein Friesian (61.02 µg/g) and the lowest in Piemontese (20.87 µg/g). Neu5Ac, known for its neuroprotective properties, was most abundant in Piemontese (112.99 µg/g, p = 0.032) and lowest in Limousin (81.25 µg/g). The Neu5Ac/Neu5Gc ratio, critical for dietary health, exceeded the threshold of 5:1 only in Piemontese (5.49), identifying it as a breed with a higher ratio. This study highlights the influence of breed, with limited effects of muscle type and aging, on sialic acid content. Significant correlations were observed between Neu5Gc and fatty acid classes (p < 0.05) and between Neu5Ac and polar amino acid groups (p < 0.01). The findings support selective breeding to optimize beef's nutritional profile, enhancing its health benefits for consumers.

Multi-omics analysis reveals the interplay between intratumoral bacteria and glioma

Emerging evidence highlights the potential impact of intratumoral microbiota on cancer. However, the microbial composition and function in glioma remains elusive. Consequently, our study aimed to investigate the microbial community composition in glioma tissues and elucidate its role in glioma development. We parallelly performed microbial profiling, transcriptome sequencing, and metabolomics detection on tumor and adjacent normal brain tissues obtained from 50 glioma patients. We employed immunohistochemistry, multicolor immunofluorescence, and fluorescence in situ hybridization (FISH) staining to observe the presence and location of bacteria. Furthermore, an animal model was employed to validate the impact of key bacteria on glioma development. Six genera were found to be significantly enriched in glioma tissues compared to adjacent normal brain tissues, including Fusobacterium, Longibaculum, Intestinimonas, Pasteurella, Limosilactobacillus, and Arthrobacter. Both bacterial RNA and lipopolysaccharides (LPS) were observed in glioma tissues. Integrated microbiomics, transcriptomics, and metabolomics revealed that genes associated with intratumoral microbes were enriched in multiple synapse-associated pathways and that metabolites associated with intratumoral microbes were (R)-N-methylsalsolinol, N-acetylaspartylglutamic acid, and N-acetyl-l-aspartic acid. Further mediation analysis suggested that the intratumoral microbiome may affect the expression of neuron-related genes through bacteria-associated metabolites. In addition, both in vivo and in vitro models of glioma show that Fusobacterium nucleatum promotes glioma proliferation and upregulates CCL2, CXCL1, and CXCL2 levels. Our findings shed light on the intricate interplay between intratumoral bacteria and glioma.

IMPORTANCE

Our study adopted a multi-omics approach to unravel the impact of intratumoral microbes on neuron-related gene expression through bacteria-associated metabolites. Importantly, we found bacterial RNA and LPS signals within glioma tissues, which were traditionally considered sterile. We identified key microbiota within glioma tissues, including Fusobacterium nucleatum (Fn). Through in vivo and in vitro experiments, we identified the crucial role of Fn in promoting glioma progression, suggesting that Fn could be a potential diagnostic and therapeutic target for glioma patients. These findings offer valuable insights into the intricate interplay between intratumoral bacteria and glioma, offering novel inspiration to the realm of glioma biology.

Don't Be Surprised When These Surprise You: Some Infrequently Studied Sphingoid Bases, Metabolites, and Factors That Should Be Kept in Mind During Sphingolipidomic Studies

Sphingolipidomic mass spectrometry has provided valuable information-and surprises-about sphingolipid structures, metabolism, and functions in normal biological processes and disease. Nonetheless, many noteworthy compounds are not routinely determined, such as the following: most of the sphingoid bases that mammals biosynthesize de novo other than sphingosine (and sometimes sphinganine) or acquire from exogenous sources; infrequently considered metabolites of sphingoid bases, such as N-(methyl)n-derivatives; "ceramides" other than the most common N-acylsphingosines; and complex sphingolipids other than sphingomyelins and simple glycosphingolipids, including glucosyl- and galactosylceramides, which are usually reported as "monohexosylceramides". These and other subspecies are discussed, as well as some of the circumstances when they are likely to be seen (or present and missed) due to experimental conditions that can influence sphingolipid metabolism, uptake from the diet or from the microbiome, or as artifacts produced during extraction and analysis. If these compounds and factors are kept in mind during the design and interpretation of lipidomic studies, investigators are likely to be surprised by how often they appear and thereby advance knowledge about them.

Arsenite increases sialic acid levels on the cellular surface through the inhibition of sialidase activity

Chronic exposure to arsenic has been shown to induce carcinogenesis in multiple organs, but the mechanisms underlying the multi-organ carcinogenicity of arsenic remain unknown. We here examined whether arsenic affects the amount of sialic acid on the cellular surface of immortalized HaCaT cells rather than cancerous cells to clarify the process of arsenic-induced carcinogenesis, since sialic acid is known to assist cancer cells in suppressing attacks by natural killer (NK) cells. Our results indicated that exposure to arsenite (As(III)) increases the amounts of sialic acid on the cell surface of HaCaT cells. To elucidate the mechanisms underlying the increase in the levels of sialic acid on the cell surface by As(III) exposure, we measured the activities of sialyltransferase and sialidase in HaCaT cells exposed to As(III). The results showed there was no significant change in the silalyltransferase activity, and the sialidase activity was significantly inhibited by As(III) exposure. When we examined the mRNA levels of NEU1-4, the four types of sialidases identified in mammals after exposure to As(III), no significant change was observed. Furthermore, sialidase activity was significantly reduced in NEU1 siRNA-transfected HaCaT cells, which showed the highest mRNA levels among NEU1-4 in HaCaT cells. These results suggest that inhibition of NEU1-derived sialidase activity by exposure to As(III) resulted in an increase in the amounts of sialic acid on the cell surface.

When a negative (charge) is not a positive: sialylation and its role in cancer mechanics and progression

Sialic acids and sialoglycans are critical actors in cancer progression and metastasis. These terminal sugar residues on glycoproteins and glycolipids modulate key cellular processes such as immune evasion, cell adhesion, and migration. Aberrant sialylation is driven by overexpression of sialyltransferases, resulting in hypersialylation on cancer cell surfaces as well as enhancing tumor aggressiveness. Sialylated glycans alter the structure of the glycocalyx, a protective barrier that fosters cancer cell detachment, migration, and invasion. This bulky glycocalyx also increases membrane tension, promoting integrin clustering and downstream signaling pathways that drive cell proliferation and metastasis. They play a critical role in immune evasion by binding to Siglecs, inhibitory receptors on immune cells, which transmit signals that protect cancer cells from immune-mediated destruction. Targeting sialylation pathways presents a promising therapeutic opportunity to understand the complex roles of sialic acids and sialoglycans in cancer mechanics and progression, which is crucial for developing novel diagnostic and therapeutic strategies that can disrupt these processes and improve cancer treatment outcomes.

Screening and Characterization of Sialic Acid-Binding Variable Lymphocyte Receptors from Hagfish

Sialic acid is a diverse group of monosaccharides often found on the termini of N- and O-linked glycans as well as being components of glycoconjugates. Hypersialylation has been associated with the progression of chronic inflammation-mediated diseases such as cardiovascular disease and cancer. Given its role in infection and disease-related processes, sialic acid is a promising target for therapeutic approaches that utilize carbohydrate-binding molecules. In this study, we screened for sialic acid-recognizing variable lymphocyte receptors (VLRBs) or ccombodies from inshore hagfish (Eptatretus burgeri) using a synthetic Neu5Ac-glycoconjugate as an antigen in immunoassay. Resulting ccombodies, 2D8, 5G11, 4A1, and 5F8 were further characterized in terms of their binding activity and specificity. A competitive ELISA using free haptens showed strong inhibition using either N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc). The half-maximal inhibitory concentrations (IC50) for Neu5Ac ranged from 7.02 to 17.06 mM, with candidates 4A1 and 5G11 requiring the least and highest amounts, respectively. IC50 values for Neu5Gc ranged from 8.12 to 13.91 mM, for 4A1 and 5G11, respectively. Candidate ccombodies also detected naturally occurring sialic acid from known sialoglycoproteins using a dot blot assay. Neu5Gc-5G11 and Neu5Ac-2D8 yielded the strongest and weakest docking interactions with affinity values of -5.9 kcal/mol and -4.9 kcal/mol, respectively. Hydrogen bonding and hydrophobic interactions were predicted to be the predominant noncovalent forces observed between the ccombodies and sialic acid. This study demonstrates that glycan-binding VLRBs from hagfish hold promise in augmenting the glycobiologists' toolkit in investigating the roles of glycans in human and animal health and disease.

Glycosylation in cancer as a source of biomarkers

INTRODUCTION

Glycosylation, the process of glycan synthesis and attachment to target molecules, is a crucial and common post-translational modification (PTM) in mammalian cells. It affects the protein's hydrophilicity, charge, solubility, structure, localization, function, and protection from proteolysis. Aberrant glycosylation in proteins can reveal new detection and therapeutic Glyco-biomarkers, which help to improve accurate early diagnosis and personalized treatment. This review underscores the pivotal role of glycans and glycoproteins as a source of biomarkers in human diseases, particularly cancer.

AREAS COVERED

This review delves into the implications of glycosylation, shedding light on its intricate roles in cancer-related cellular processes influencing biomarkers. It is underpinned by a thorough examination of literature up to June 2024 in PubMed, Scopus, and Google Scholar; concentrating on the terms: (Glycosylation[Title/Abstract]) OR (Glycan[Title/Abstract]) OR (glycoproteomics[Title/Abstract]) OR (Proteoglycans[Title/Abstract]) OR (Glycomarkers[Title/Abstract]) AND (Cancer[Title/Abstract]) AND ((Diagno*[Title/Abstract]) OR (Progno*[Title/Abstract])).

EXPERT OPINION

Glyco-biomarkers enhance early cancer detection, allow early intervention, and improve patient prognoses. However, the abundance and complex dynamic glycan structure may make their scientific and clinical application difficult. This exploration of glycosylation signatures in cancer biomarkers can provide a detailed view of cancer etiology and instill hope in the potential of glycosylation to revolutionize cancer research.

Experimentally Determined Diagnostic Ions for Identification of Peptide Glycotopes

The analysis of the structures of glycans present on glycoproteins is an essential component for determining glycoprotein function; however, detailed glycan structural assignment on glycopeptides from proteomics mass spectrometric data remains challenging. Glycoproteomic analysis by mass spectrometry currently can provide significant, yet incomplete, information about the glycans present, including the glycan monosaccharide composition and in some circumstances the site(s) of glycosylation. Advancements in mass spectrometric resolution, using high-mass accuracy instrumentation and tailored MS/MS fragmentation parameters, coupled with a dedicated definition of diagnostic fragmentation ions have enabled the determination of some glycan structural features, or glycotopes, expressed on glycopeptides. Here we present a collation of diagnostic glycan fragments produced by traditional positive-ion-mode reversed-phase LC-ESI MS/MS proteomic workflows and describe the specific fragmentation energy settings required to identify specific glycotopes presented on N- or O-linked glycopeptides in a typical proteomics MS/MS experiment.

A systematic review reveals conflicting evidence for the prevalence of antibodies against the sialic acid 'xenoautoantigen' Neu5Gc in humans and the need for a standardised approach to quantification

Despite an array of hypothesised implications for health, disease, and therapeutic development, antibodies against the non-human sialic acid N-glycolylneuraminic acid (Neu5Gc) remain a subject of much debate. This systematic review of 114 publications aimed to generate a comprehensive overview of published studies in this field, addressing both the reported prevalence of anti-Neu5Gc antibodies in the human population and whether experimental variation accounts for the conflicting reports about the extent of this response. Absolute titres of anti-Neu5Gc antibodies, the reported prevalence of these antibodies, and the individual variation observed within experiments were analysed and grouped according to biological context ('inflammation', 'xenotransplantation', 'biotherapeutic use', 'cancer', and 'healthy populations'), detection method, target epitope selection, and choice of blocking agent. These analyses revealed that the experimental method had a notable impact on both the reported prevalence and absolute titres of anti-Neu5Gc antibodies in the general population, thereby limiting the ability to ascribe reported trends to genuine biological differences or the consequence of experimental design. Overall, this review highlights important knowledge gaps in the study of antibodies against this important xenoautoantigen and the need to establish a standardised method for their quantification if the extent of the importance of Neu5Gc in human health is to be fully understood.

Characterization of an Aptamer Targeting Neu5Gc, as an Endogenous Pathogenic Factor Derived from Red Meat

N-glycolylneuraminic acid (Neu5Gc), a sialic acid predominantly found in the non-neurohumoral fluids of hind-mouthed animals, is incapable of synthesizing Neu5Gc due to a deletion in the CMAH exon of the gene encoding human CMP-Neu5Gc hydroxylase. But consumption of animal-derived foods that contain Neu5Gc, such as red meat, can instigate an immune response in humans, as Neu5Gc is recognized as a foreign substance by the human immune system. This recognition leads to the production of anti-Neu5Gc antibodies, subsequently resulting in chronic inflammation. When Neu5Gc is consumed excessively or frequently, it may contribute to the development of heart disease and cancer. This makes Neu5Gc, an endogenous pathogenic factor derived from red meat, a new hot topic in red meat safety research. In this study, aptamers obtained by the magnetic bead SELEX technique were subjected to homology and secondary structure prediction analysis as well as affinity determination. The result indicated that the aptamer 2B.N2A9 exhibited a robust binding affinity, with an affinity constant (Ka) of 1.87 × 108 L/mol. This aptamer demonstrated optimal binding specificity within a pH range of 5.4 to 7.4. Molecular docking analysis further revealed that aptamer 2B.N2A9 formed stable binding interactions with the target Neu5Gc at specific sites, namely G-14, C-15, G-13, G-58, G-60, and C-59. An Enzyme-Linked Oligonucleotide Sorbent Assay (ELOSA) methodology was established to detect the endogenous pathogenic factor Neu5Gc present in red meat. This method demonstrated a limit of detection (LOD) of 0.71 ng/mL, along with an average recovery rate of 92.23%. The aptamer obtained in this study exhibited favorable binding properties to Neu5Gc. The assay was relatively convenient and demonstrated good sensitivity. Further investigation into the distribution of Neu5Gc in various red meats is of public health significance and scientific potential. A practical detection method should be provided to guide red meat diets and ensure the nutrition and safety of meat products.

The Regulatory Effect of Huangshui Polysaccharides on Intestinal Microbiota and Metabolites during In Vitro Fermentation

Huangshui polysaccharides (HSPs) have attracted extensive attention recently for their biological activity and physicochemical property. This research investigated the extraction, structural characterization, and prebiotic activity of three different HSPs (HSP40-0, HSP60-0, and HSP80-0) in vitro to reveal the scientific support for the high-value utilization of Huangshui. HSPs were heteropolysaccharide with diverse structures and surface morphologies. Comprehensive analysis was conducted through 16S rRNA gene sequencing and metabolite profiling techniques, and results showed that HSPs had different potentials to regulate the gut microbiota due to their different structures; for instance, both HSP40-0 and HSP80-0 could notably increase the relative abundance of Bacteroidota, whereas HSP60-0 could increase the relative abundance of Phascolarctobacterium. In addition, HSPs upregulated beneficial differential metabolites, especially short-chain fatty acids (SCFAs). Fermentation products containing these metabolites exhibited anti-inflammatory effects on LPS-treated Caco-2 cells. This study will provide reference for exploring the relationship between the natural polysaccharide structure and the prebiotic activity and widen the application of Huangshui.

N-glycolylneuraminic acid in red meat and processed meat is a health concern: A review on the formation, health risk, and reduction

One of the most consistent epidemiological associations between diet and human disease risk is the impact of consuming red meat and processed meat products. In recent years, the health concerns surrounding red meat and processed meat have gained worldwide attention. The fact that humans have lost the ability to synthesize N-glycolylneuraminic acid (Neu5Gc) makes red meat and processed meat products the most important source of exogenous Neu5Gc for humans. As our research of Neu5Gc has increased, it has been discovered that Neu5Gc in red meat and processed meat is a key factor in many major diseases. Given the objective evidence of the harmful risk caused by Neu5Gc in red meat and processed meat to human health, there is a need for heightened attention in the field of food. This updated review has several Neu5Gc aspects given including biosynthetic pathway of Neu5Gc and its accumulation in the human body, the distribution of Neu5Gc in food, the methods for detecting Neu5Gc, and most importantly, a systematic review of the existing methods for reducing the content of Neu5Gc in red meat and processed meat. It also provides some insights into the current status and future directions in this area.