Aberrant N-glycosylation in cancer: MGAT5 and β1,6-GlcNAc branched N-glycans as critical regulators of tumor development and progression

Glycoproteomics of Gastrointestinal Cancers and Its Use in Clinical Diagnostics

Cancer is a leading cause of death worldwide, resulting in substantial economic costs. Because cancer is a complex, heterogeneous group of diseases affecting a variety of cells, its detection may sometimes be difficult. Herein we review a large group of the gastrointestinal cancers (oral, esophageal, stomach, pancreatic, liver, and bowel cancers) and the possibility of using glycans conjugated to protein backbones for less-invasive diagnoses than the commonly used endoscopic approaches. The reality of bacterial N-glycosylation and the effect of epithelial mucosa on gut microbiota are discussed. Current advantages, barriers, and advantages in the prospective use of selected glycomic approaches in clinical practice are also detailed.

Aberrant protein glycosylation in the colon adenoma-cancer sequence: Colorectal cancer mechanisms and clinical implications

Colorectal cancer (CRC) is a leading contributor to global cancer-related morbidity and mortality. Glycosylation is a common post-translational protein modification. Aberrant protein glycosylation is a hallmark of cancer, affecting biological processes and driving malignant CRC phenotypes. Specifically, abnormal N-glycosylation manifests as structural alterations in high mannose, sialylated, and fucosylated structures, collectively promoting cancer stemness and invasiveness. Concurrently, O-GlcNAcylation facilitates tumorigenesis through metabolic reprogramming and oncogene activation. Dysregulated mucin-type O-glycans (e.g., Core-1/Core-3 imbalance) and elevated SLex/SLea antigen expression are significantly correlated with tumor adhesion, metastatic dissemination, and adverse clinical outcomes. Furthermore, protein glycosylation contributes to chemoresistance through anti-apoptotic mechanisms, aberrant signaling activation, and pro-angiogenic pathways. This review systematically examines the dynamic evolution of protein glycosylation during CRC progression from normal mucosa to adenoma to adenocarcinoma. It also evaluates the CRC diagnostic and therapeutic implications of glycoproteins and glycans. This review can provide a molecular understanding for advancing CRC diagnostics and treatment.

Glycosylation editing: an innovative therapeutic opportunity in precision oncology

Cancer is still one of the most arduous challenges in the human society, even though humans have found many ways to try to conquer it. With our incremental understandings on the impact of sugar on human health, the clinical relevance of glycosylation has attracted our attention. The fact that altered glycosylation profiles reflect and define different health statuses provide novel opportunities for cancer diagnosis and therapeutics. By reviewing the mechanisms and critical enzymes involved in protein, lipid and glycosylation, as well as current use of glycosylation for cancer diagnosis and therapeutics, we identify the pivotal connection between glycosylation and cellular redox status and, correspondingly, propose the use of redox modulatory tools such as cold atmospheric plasma (CAP) in cancer control via glycosylation editing. This paper interrogates the clinical relevance of glycosylation on cancer and has the promise to provide new ideas for laboratory practice of cold atmospheric plasma (CAP) and precision oncology therapy.

Modulation of N-glycosylation in the PD-1: PD-L1 axis as a strategy to enhance cancer immunotherapies

The modulation of the N-glycosylation status in immune checkpoints, particularly the PD-1/PD-L1 axis, has emerged as a promising approach to enhance cancer immunotherapies. While immune checkpoint inhibitors (ICIs) targeting PD-1 and PD-L1 have achieved significant clinical success, recent studies highlight the critical role of N-glycosylation in regulating their expression, stability, and function. Alterations in N-glycosylation might affect the efficacy of ICIs by modulating the interactions between immune checkpoints and antibodies used in therapy. This review focuses on the glycosylation of PD-1 and its ligands PD-L1 and PD-L2, examining how N-glycans influence immune responses and contribute to immune evasion by tumors. It explores innovative strategies to modulate glycosylation in tumor and immune cells, including the use of N-glycosylation inhibitors and novel genetic manipulation techniques. Understanding the interplay between N-glycosylation and immune checkpoint functions is essential for optimizing immunotherapy outcomes and overcoming therapeutic resistance in cancer patients.

Exploring the relationship between MGAT2 and glioblastoma: A Mendelian Randomization and bioinformatics approach

BACKGROUND

Mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase 2 (MGAT2) and tumors' relevant research was in full swing recently. Therefore, we employed Mendelian Randomization (MR) alongside bioinformatics to thoroughly investigate the possible relationship between MGAT2 and glioblastoma (GBM).

METHODS

We utilized the summary statistics of genome-wide association studies (GWAS) for MGAT2 (N = 35,559 from deCODE) and glioblastoma (N = 379,155 from FinnGen). MR was used to assess the causal relationship between MGAT2 and GBM. Bioinformatics was used for a more in-depth exploration of the relationship between MGAT2 and GBM.

RESULTS

MR analysis demonstrated a causal relationship, showing that elevated levels of MGAT2 are associated with an increased risk of GBM (OR = 2.59, 95 % CI: 1.13-5.91, p = 0.023). Further investigation revealed significant differences in MGAT2 expression across normal tissue, tumor tissue, and gliomas of different types. Additionally, we found that MGAT2 may influence GBM through immune-related pathways, particularly through the role of macrophages. Proteins associated with MGAT2 were also identified in the PPI network.

CONCLUSION

This study first validated the causal relationship between MGAT2 and glioblastoma, and used bioinformatics to explore the relationship from multiple perspectives. Additionally, we proposed hypotheses for further research to investigate the potential mechanisms underlying this connection.

Integrated ceRNAs regulating relationship and bioinformatics analysis to study the molecular mechanisms of the inhibition of puerarin on bladder cancer cell

Based on previous experiments, we demonstrated puerarin inhibited the proliferation of BC T24 cells. To further explore the molecular mechanisms, whole transcriptome sequencing combined with bioinformatics analysis was performed. The results showed puerarin significantly inhibited T24 proliferation and pathway enrichment analysis of differentially expressed RNAs were mainly enriched in Cell cycle, PI3K/AKT, Ras family chromatin remodeling. lncRNAs and circRNAs may regulate miRNAs, thereby regulating the expression of ITGA1, PAK2 and UTRN. The predicted upstream transcription factor ERG and puerarin were well docked, which may be one of the underlying mechanisms by which puerarin inhibiting BC cells.

Synergy of genetics and lipid metabolism driving feed utilization efficiency in chickens

Residual feed intake (RFI) is a key indicator of feed efficiency, critical for enhancing the economic sustainability of poultry production. However, the genetic and metabolic regulatory mechanisms of RFI remain unclear. This study analyzed the genome, liver transcriptome, metabolome, and lipidome of hens with low and high feed efficiency (N = 60) from the previously established RFI divergent broiler lines (F15). Our results revealed pronounced genetic differentiation between low RFI (LRFI) and high RFI (HRFI) lines and identified genomic signatures of selection associated with feed efficiency. Transcriptomic analysis showed differential expression of genes involved in neural regulation and lipid metabolism. Notably, LRFI chickens exhibited reduced hepatic lipid accumulation, which was associated with decreased fatty acid metabolism and increased cholesterol metabolism (P < 0.05). The lipidomic analysis uncovered distinct profiles of glycerophospholipids (e.g., PE-P and PC-O) and sphingolipids (e.g., ceramides), which were more abundant in LRFI chickens (P < 0.05) and strongly correlated with key lipid metabolism processes (P < 0.05). Despite improved feed efficiency, LRFI chickens demonstrated signs of increased oxidative stress. Moreover, integrative analyses revealed that genes such as MGAT5, GABRA4, and LRRC4C, exhibiting strong selection signatures and higher expression in the LRFI line (P < 0.05), were identified as key regulators of lipid metabolism, potentially contributing to the observed differences in feed efficiency. This comprehensive study highlights the synergistic effect of genetics and lipid metabolism in driving feed utilization efficiency in chickens, establishing a scientific foundation for breeding strategies aimed at improving feed efficiency in poultry production.

Clinical impacts of Artocarpus lakoocha agglutinin-binding glycans for prognosis and treatment of cholangiocarcinoma

Artocarpus lakoocha agglutinin (ALA), which specifically targets the Gal/GalNAc components of complex glycans, was isolated from the seeds of Artocarpus lakoocha. This study is the first to explore the role of ALA in identifying aberrant glycans, designated ALA-binding glycans (ALAG), and its implications in cholangiocarcinoma (CCA). ALA-histochemistry was used to evaluate ALAG expression in liver fluke-induced CCA tissues from hamsters (n = 60). Elevated ALAG expression was observed in hyperplastic ducts and significantly increased in CCA tissues, while normal biliary epithelium and hepatocytes showed no expression. Similar results were found in patient CCA tissues (n = 68), where higher ALAG levels correlated with shorter survival rates, indicating the involvement of ALAG in CCA development and progression. Furthermore, ALA treatment inhibited cell viability in CCA cell lines, as demonstrated by MTT and colony formation assays, and Ki-67 expression. ALA treatment also decreased cell migration and invasion, as shown by Transwell assays. Gelatin zymography suggested that these effects might be associated with reduced MMP-9 activity. Overall, these findings may position ALAG as a potential marker for poor prognosis in CCA, while ALA may serve as a novel lectin for both detection and therapeutic applications in CCA.

Thyroid Carcinoma Glycoproteins Express Altered N-Glycans with 3-O-Sulfated Galactose Residues

Aberrant protein glycosylation is a hallmark alteration of cancer and is highly associated with cancer progression. Papillary thyroid cancer (PTC) is the most common type of thyroid cancer, but the N-glycosylation of its glycoproteins has not been well characterized. In this work, we analyzed multiple freshly prepared PTC specimens along with paired normal tissue obtained from thyroidectomies. Glycomic analyses focused on Asn-linked (N)-glycans and employed mass spectrometry (MS), along with Western blot approaches of total solubilized materials that were examined for binding by specific lectins and a monoclonal antibody (mAb) O6, specific for 3-O-sulfated galactose residues. We observed major differences in PTC versus paired normal specimens, as PTC specimens exhibited higher levels of N-glycan branching and bisection with N-acetylglucosamine residues, consistent with RNAseq data. We also found that 3-O-sulfated galactose was present in N-glycans of multiple glycoproteins from both PTC and control specimens, as recognized by the O6 mAb and as confirmed by MS analyses. These results provide new insights into the N-glycans present in glycoproteins of thyroid cancer and context for further studies of these altered glycans as biomarkers and targets for therapeutics.

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.

Regulation of human GnT-IV family activity by the lectin domain

N-Glycan branching critically regulates glycoprotein functions and is involved in various diseases. Among the glycosyltransferases involved in N-glycan branching is the human N-acetylglucosaminyltransferase-IV (GnT-IV) family, which has four members: GnT-IVa, GnT-IVb, GnT-IVc, and GnT-IVd. GnT-IVa and GnT-IVb have glycosyltransferase activity that generates the type-2 diabetes-related β1,4-GlcNAc branch on the α1,3-Man arm of N-glycans, whereas GnT-IVc and GnT-IVd do not. Recently, this enzyme family was found to have a unique lectin domain in the C-terminal region, which is essential for enzyme activity toward glycoprotein substrates but not toward free N-glycans. Furthermore, interaction between the lectin domain of GnT-IV and N-glycan attached to GnT-IV enables self-regulation of GnT-IV activity, indicating that the lectin domain plays a unique and pivotal role in the regulation of GnT-IV activity. In this review, we summarize the GnT-IV family's biological functions, selectivity for glycoprotein substrates, and regulation of enzymatic activity, with a focus on its unique C-terminal lectin domain.

The tissue glycome as regulator of immune activation and tolerance mediated by C-type lectins and Siglecs

The immune system is a complex network of highly specialized microenvironments, denominated niches, which arise from dynamic interactions between immune and parenchymal cells as well as acellular components such as structural elements and local molecular signals. A critical, yet underexplored, layer shaping these niches is the glycome, the complete repertoire of glycans and glycoconjugates produced by cells. The glycome is prevalent in the outer membrane of cells and their secreted components, and can be sensed by glycan binding receptors on immune cells. These receptors detect changes in glycosylation and consequently modulate immune cell activity, trafficking, and signalling, altering homeostasis. Tissues like the brain and the placenta are prone to accommodate tolerance, while the gut and the thymus are sensitive to inflammation. We provide here an overview of current literature that shows the impact of altered glycosylation of tissues on host immune cells and how interference in this process may lead to new diagnostics and immune therapeutics, aiming to restore the immune balance in autoimmunity and cancer.

A Bioorthogonal Precision Tool for Human N-Acetylglucosaminyltransferase V

Correct elaboration of N-linked glycans in the secretory pathway of human cells is essential in physiology. Early N-glycan biosynthesis follows an assembly line principle before undergoing crucial elaboration points that feature the sequential incorporation of the sugar N-acetylglucosamine (GlcNAc). The activity of GlcNAc transferase V (MGAT5) primes the biosynthesis of an N-glycan antenna that is heavily upregulated in cancer. Still, the functional relevance and substrate choice of MGAT5 are ill-defined. Here, we employ protein engineering to develop a bioorthogonal substrate analog for the activity of MGAT5. Chemoenzymatic synthesis is used to produce a collection of nucleotide-sugar analogs with bulky, bioorthogonal acylamide side chains. We find that WT-MGAT5 displays considerable activity toward such substrate analogues. Protein engineering yields an MGAT5 variant that loses activity against the native nucleotide sugar and increases activity toward a 4-azidobutyramide-containing substrate analogue. By such restriction of substrate specificity, we show that the orthogonal enzyme-substrate pair is suitable to bioorthogonally tag glycoproteins. Through X-ray crystallography and molecular dynamics simulations, we establish the structural basis of MGAT5 engineering, informing the design rules for bioorthogonal precision chemical tools.

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.

Glycosylation: mechanisms, biological functions and clinical implications

Protein post-translational modification (PTM) is a covalent process that occurs in proteins during or after translation through the addition or removal of one or more functional groups, and has a profound effect on protein function. Glycosylation is one of the most common PTMs, in which polysaccharides are transferred to specific amino acid residues in proteins by glycosyltransferases. A growing body of evidence suggests that glycosylation is essential for the unfolding of various functional activities in organisms, such as playing a key role in the regulation of protein function, cell adhesion and immune escape. Aberrant glycosylation is also closely associated with the development of various diseases. Abnormal glycosylation patterns are closely linked to the emergence of various health conditions, including cancer, inflammation, autoimmune disorders, and several other diseases. However, the underlying composition and structure of the glycosylated residues have not been determined. It is imperative to fully understand the internal structure and differential expression of glycosylation, and to incorporate advanced detection technologies to keep the knowledge advancing. Investigations on the clinical applications of glycosylation focused on sensitive and promising biomarkers, development of more effective small molecule targeted drugs and emerging vaccines. These studies provide a new area for novel therapeutic strategies based on glycosylation.

Sialic acid blockade inhibits the metastatic spread of prostate cancer to bone

BACKGROUND

Bone metastasis is a common consequence of advanced prostate cancer. Bisphosphonates can be used to manage symptoms, but there are currently no curative treatments available. Altered tumour cell glycosylation is a hallmark of cancer and is an important driver of a malignant phenotype. In prostate cancer, the sialyltransferase ST6GAL1 is upregulated, and studies show ST6GAL1-mediated aberrant sialylation of N-glycans promotes prostate tumour growth and disease progression.

METHODS

Here, we monitor ST6GAL1 in tumour and serum samples from men with aggressive prostate cancer and using in vitro and in vivo models we investigate the role of ST6GAL1 in prostate cancer bone metastasis.

FINDINGS

ST6GAL1 is upregulated in patients with prostate cancer with tumours that have spread to the bone and can promote prostate cancer bone metastasis in vivo. The mechanisms involved are multi-faceted and involve modification of the pre-metastatic niche towards bone resorption to promote the vicious cycle, promoting the development of M2 like macrophages, and the regulation of immunosuppressive sialoglycans. Furthermore, using syngeneic mouse models, we show that inhibiting sialylation can block the spread of prostate tumours to bone.

INTERPRETATION

Our study identifies an important role for ST6GAL1 and α2-6 sialylated N-glycans in prostate cancer bone metastasis, provides proof-of-concept data to show that inhibiting sialylation can suppress the spread of prostate tumours to bone, and highlights sialic acid blockade as an exciting new strategy to develop new therapies for patients with advanced prostate cancer.

FUNDING

Prostate Cancer Research and the Mark Foundation For Cancer Research, the Medical Research Council and Prostate Cancer UK.

Functional genomics identifies N-acetyllactosamine extension of complex N-glycans as a mechanism to evade lysis by natural killer cells

Natural killer (NK) cells are primary defenders against cancer precursors, but cancer cells can persist by evading immune surveillance. To investigate the genetic mechanisms underlying this evasion, we perform a genome-wide CRISPR screen using B lymphoblastoid cells. SPPL3, a peptidase that cleaves glycosyltransferases in the Golgi, emerges as a top hit facilitating evasion from NK cytotoxicity. SPPL3-deleted cells accumulate glycosyltransferases and complex N-glycans, disrupting not only binding of ligands to NK receptors but also binding of rituximab, a CD20 antibody approved for treating B cell cancers. Notably, inhibiting N-glycan maturation restores receptor binding and sensitivity to NK cells. A secondary CRISPR screen in SPPL3-deficient cells identifies B3GNT2, a transferase-mediating poly-LacNAc extension, as crucial for resistance. Mass spectrometry confirms enrichment of N-glycans bearing poly-LacNAc upon SPPL3 loss. Collectively, our study shows the essential role of SPPL3 and poly-LacNAc in cancer immune evasion, suggesting a promising target for cancer treatment.

Targeting branched N-glycans and fucosylation sensitizes ovarian tumors to immune checkpoint blockade

Aberrant glycosylation is a crucial strategy employed by cancer cells to evade cellular immunity. However, it's unclear whether homologous recombination (HR) status-dependent glycosylation can be therapeutically explored. Here, we show that the inhibition of branched N-glycans sensitizes HR-proficient, but not HR-deficient, epithelial ovarian cancers (EOCs) to immune checkpoint blockade (ICB). In contrast to fucosylation whose inhibition sensitizes EOCs to anti-PD-L1 immunotherapy regardless of HR-status, we observe an enrichment of branched N-glycans on HR-proficient compared to HR-deficient EOCs. Mechanistically, BRCA1/2 transcriptionally promotes the expression of MGAT5, the enzyme responsible for catalyzing branched N-glycans. The branched N-glycans on HR-proficient tumors augment their resistance to anti-PD-L1 by enhancing its binding with PD-1 on CD8+ T cells. In orthotopic, syngeneic EOC models in female mice, inhibiting branched N-glycans using 2-Deoxy-D-glucose sensitizes HR-proficient, but not HR-deficient EOCs, to anti-PD-L1. These findings indicate branched N-glycans as promising therapeutic targets whose inhibition sensitizes HR-proficient EOCs to ICB by overcoming immune evasion.

Navigating PRKCSH's impact on cancer: from N-linked glycosylation to death pathway and anti-tumor immunity

PRKCSH, also known as Glucosidase II beta subunit (GluIIβ), is a crucial component of the endoplasmic reticulum (ER) quality control system for N-linked glycosylation, essential for identifying and eliminating misfolded proteins. Glucosidase II consists of the catalytic alpha subunit (GluIIα) and the regulatory beta subunit (GluIIβ), ensuring proper protein folding and release from the ER. The induction of PRKCSH in cancer and its interaction with various cellular components suggest broader roles beyond its previously known functions. Mutations in the PRKCSH gene are linked to autosomal dominant polycystic liver disease (ADPLD). Alternative splicing generates distinct PRKCSH isoforms, which can influence processes like epithelial-mesenchymal transition (EMT) and the proliferation of lung cancer cells. PRKCSH's involvement in cancer is multifaceted, impacting cell growth, metastasis, and response to growth factors. Additionally, PRKCSH orchestrates cell death programs, affecting both autophagy and apoptosis. Its role in facilitating N-linked glycoprotein release from the ER is hypothesized to assist cancer cells in managing increased demand and ER stress. Moreover, PRKCSH modulates anti-tumor immunity, with its suppression augmenting NK cell and T cell activity, promising enhanced cancer therapy. PRKCSH's diverse functions, including regulation of IGF1R and IRE1α, implicate it as a therapeutic target and biomarker in cancer immunotherapy. However, targeting its glucosidase II activity alone may not fully counteract its effects, suggesting broader mechanisms in cancer development. Further investigations are needed to elucidate PRKCSH's precise role and validate its therapeutic potential in cancer treatment.

Association of Genetic Markers with the Risk of Early-Onset Breast Cancer in Kazakh Women

Breast cancer is a global health problem. It is an age-dependent disease, but cases of early-onset breast cancer (eBC) are gradually increasing. There are many unresolved questions regarding eBC risk factors, mechanisms of development and screening. Only 10% of eBC cases are due to mutations in the BRCA1/BRCA2 genes, and 90% have a more complex genetic background. This poses a significant challenge to timely cancer detection in young women and highlights the need for research and awareness. Therefore, identifying genetic risk factors for eBC is essential to solving these problems. This study represents an association analysis of 144 eBC cases and 163 control participants to identify genetic markers associated with eBC risks in Kazakh women. We performed a two-stage approach in association analysis to assess genetic predisposition to eBC. First-stage genome-wide association analysis revealed two risk intronic loci in the CHI3L2 gene (p = 5.2 × 10-6) and MGAT5 gene (p = 8.4 × 10-6). Second-stage exonic polymorphisms haplotype analysis showed significant risks for seven haplotypes (p < 9.4 × 10-4). These results point to the importance of studying medium- and low-penetrant genetic markers in their haplotype combinations for a detailed understanding of the role of detected genetic markers in eBC development and prediction.