Insights into the role of sialylation in cancer progression and metastasis

Overexpression of ST8Sia1 inhibits tumor progression by TGF-β1 signaling in rectal adenocarcinoma and promotes the tumoricidal effects of CD8+ T cells by granzyme B and perforin

BACKGROUND

Rectal adenocarcinoma (READ) involves the dysregulated expression of alpha 2,8-Sialyltransferase1 (ST8Sia1) although its role during READ's progression is unclear.

METHODS

The mRNA level of ST8Sia1 was analyzed based on The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Tumor Immune Estimation Resource (TIMER) 2.0. Furthermore, the prognostic and significance of ST8Sia1 in READ was assessed through Kaplan-Meier curve, univariate, multivariate Cox regression, and receiver operating characteristic (ROC) methods. The role of ST8Sia1 in the READ immune microenvironment was explored using ESTIMATE analysis and TIMER databases. Furthermore, the expression of ST8Sia1 in tissues was analyzed using real-time quantitative polymerase chain reaction (RT-qPCR), western blotting (WB), and immunohistochemistry (IHC). Perforin and Granzyme B secretion by CD8+ T cells, as well as tumor cell apoptosis, were detected after co-culturing CD8+ T cells with READ tumor cells and ST8Sia1-overexpression (ST8Sia1-OE) tumor cells. Furthermore, we examined the interaction between ST8Sia1 and TGF-β1 in READ cells.

RESULTS

ST8Sia1 exhibited excellent diagnostic capability for READ, with positive correlations to immune response and negative correlations to tumor purity. Increased levels of perforin and Granzyme B from CD8+ T cells were observed in vitro, enhancing tumor cell apoptosis. ST8Sia1 interacts with TGF-β1, mediating its inhibitory effects on READ development.

CONCLUSIONS

ST8Sia1 is a potential diagnostic biomarker and therapeutic target for READ, enhancing CD8+ T cell function and possibly improving patient outcomes through cellular immunotherapy.

ST6GAL1-Mediated Sialylation of PECAM-1 Promotes a Transcellular Diapedesis-Like Process That Directs Lung Tropism of Metastatic Breast Cancer

Metastasis is the leading cause of mortality in breast cancer, with lung metastasis being particularly detrimental. Identification of the processes determining metastatic organotropism could enable the development of approaches to prevent and treat breast cancer metastasis. In this study, we found that lung-tropic and non-lung-tropic breast cancer cells differ in their response to sialic acids, affecting the sialylation of surface proteins. Lung-tropic cells showed higher levels of ST6GAL1, whereas non-lung-tropic cells had more ST3GAL1. ST6GAL1-mediated α-2,6-sialylation, unlike ST3GAL1-mediated α-2,3-sialylation, increased lung metastasis by promoting cancer cell migration through pulmonary endothelial layers and reducing junction protein levels. α-2,6-Sialylated platelet/endothelial cell adhesion molecule 1 (PECAM-1) on breast cancer cells facilitated extravasation through the pulmonary endothelium, a critical step in lung metastasis. Knockdown of ST6GAL1 or PECAM-1 significantly reduced lung metastasis. The human pulmonary endothelium displayed high PECAM-1 levels. Through transhomophilic interaction with pulmonary PECAM-1, α-2,6-sialylated PECAM-1 on ST6GAL1-positive cancer cells increased pulmonary extravasation in a diapedesis-like, cell-autonomous manner. Additionally, lung-tropic cells and their exosomes increased the permeability of pulmonary endothelial cells, promoting metastasis in a non-cell-autonomous manner. Analysis of human breast cancer samples showed a correlation between elevated ST6GAL1/PECAM-1 expression and lung metastasis. These results suggest that targeting ST6GAL1-mediated α-2,6-sialylation could be a potential therapeutic strategy to prevent lung metastasis in patients with breast cancer. Significance: ST6GAL1-mediated α-2,6-sialylation of PECAM-1 dictates lung-tropic metastasis of breast cancer, revealing that the pattern of sialylation of breast cancer cells is a determinant of metastatic organ tropism and a potential therapeutic target.

Insights into stability, dimerisation, and ligand binding properties of Siglec-7: Isotope labelling in HEK293 cells for protein characterisation by NMR spectroscopy

Siglec-7, an immune checkpoint receptor, has emerged as a promising target for cancer immunotherapy due to its involvement in the regulation of immune and inflammatory responses. However, while its participation in immunoediting and immune evasion is well established, understanding its biological context, relevant ligands, and associated signalling pathways remains limited. Understanding these aspects is crucial for the development of effective immunotherapies targeting Siglec-7. In this study, three expression constructs of Siglec-7 were designed, expressed, and characterised, including an analysis of the oligomeric state of its extracellular domain. The N-terminal V-set Ig carbohydrate recognition domain was also produced in an isotopically double-labelled (13C,15N) mammalian cell growth medium. Two stable constructs suitable for biophysical and structural studies were identified. These findings reveal the noncovalent dimerisation of Siglec-7, offering new insights into its possible ligand interactions, signal transduction mechanisms, or receptor/ligand clustering. The dimerisation of Siglec-7 may be essential to achieve multivalent, high-avidity interactions with glycoconjugates, which may result in enhanced or alternative signalling processes within the NK cell immune synapse. In addition, a detailed protocol for generating double-labelled Siglec-7 in HEK293 cells, which may apply to other proteins under similar conditions, was described. These findings contribute to a better understanding of the biophysical and structural properties of Siglec-7 and are key to the design of more precise and effective cancer immunotherapies targeting Siglec-7.

Optimizing ST6GAL1 inhibition and selectivity using lithocholic acid-amino acid conjugates for antimetastatic and antiangiogenic agent development

A series of LCA-aromatic amino acid conjugates were synthesized and tested for their inhibitory effects on N-glycan specific ST6GAL1 and O-glycan specific ST3GAL1. The LCA-amino acid conjugates with phenyl and indole moieties showed enhanced inhibitory activity and selectivity towards the N-glycan-specific ST6GAL1, with the indole-containing compound 4e exhibiting the highest activity (IC50 = 20.0 ± 0.5 μM). In addition, compound 4e exhibited the highest antimetastatic potential, effectively inhibiting MDA-MB-231 cell migration at non-cytotoxic concentrations. Compound 4e also suppressed tumor growth and metastasis in vivo, attributing to its potential to disrupt integrins sialylation. The conjugate has also demonstrated excellent antiangiogenetic properties in vitro and ex vivo, owing to its ability to downregulate the VEGF/VEGFR2/Akt pathway. Taken together, these findings prove the practicality of employing LCA as a scaffold and aromatic amino acid conjugation in the discovery of novel, potent, and selective ST inhibitors necessary to address abnormal cell surface α-2,6-N-sialylation.

Surface-enhanced Raman spectroscopy as effective tool for detection of sialic acid as cancer biomarker

Sialic acid, a negatively charged nine-carbon monosaccharide, is mainly located at the terminal end of glycan chains on glycoproteins and glycolipids of cell surface and most secreted proteins. Elevated levels of sialylated glycans have been known as a hallmark in numerous cancers. As a result, sialic acid acts as a useful and accessible cancer biomarker for early cancer detection and monitoring the disease development during cancer treatment which is crucial in elevating the survival rate. The detection of sialic acid has been done by many tools including surface-enhanced Raman spectroscopy (SERS) which gained incredible attention due to its high selectivity and sensitivity. However, currently, comprehensive reviews of sialic acid detection and imaging as a cancer biomarker using SERS are still lacking. Here, we present the significant breakthroughs in SERS-based detection of sialic acid levels on cells, tissues, and body fluids due to the presence of cancer, different cancer metastasis stages, and in response to the external stimuli. This review covers the SERS substrate and novel SERS strategies, using lectin, boronic acid, metabolic glycan labelling and label-free methods, for sialic acid detection as cancer biomarker. The remaining challenges to detect sialic acid and prospect of future development of SERS for other carbohydrate-based cancer biomarker, for instance fucose, are also discussed.

Contribution of tumor microenvironment (TME) to tumor apoptosis, angiogenesis, metastasis, and drug resistance

The tumor microenvironment (TME) contains tumor cells, surrounding cells, and secreted factors. It provides a favorable environment for the maintenance of cancer stem cells (CSCs), the spread of cancer cells to metastatic sites, angiogenesis, and apoptosis, as well as the growth, proliferation, invasion, and drug resistance of cancer cells. Cancer cells rely on the activation of oncogenes, inactivation of tumor suppressors, and the support of a normal stroma for their growth, proliferation, and survival, all of which are provided by the TME. The TME is characterized by the presence of various cells, including cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), CD8 + cytotoxic T cells (CTLs), regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), mesenchymal stem cells (MSCs), endothelial cells, adipocytes, and neuroendocrine (NE) cells. The high expression of inflammatory cytokines, angiogenic factors, and anti-apoptotic factors, as well as drug resistance mechanisms in the TME, contributes to the poor therapeutic efficacy of anticancer drugs and tumor progression. Hence, this review describes the mechanisms through which the TME is involved in apoptosis, angiogenesis, metastasis, and drug resistance in tumor cells.

GOLPH3-mTOR Crosstalk and Glycosylation: A Molecular Driver of Cancer Progression

Originally identified in proteomic-based studies of the Golgi, Golgi phosphoprotein 3 (GOLPH3) is a highly conserved protein from yeast to humans. GOLPH3 localizes to the Golgi through the interaction with phosphatidylinositol-4-phosphate and is required for Golgi architecture and vesicular trafficking. Many studies revealed that the overexpression of GOLPH3 is associated with tumor metastasis and a poor prognosis in several cancer types, including breast cancer, glioblastoma multiforme, and colon cancer. The purpose of this review article is to provide the current progress of our understanding of GOLPH3 molecular and cellular functions, which may potentially reveal therapeutic avenues to inhibit its activity. Specifically, recent papers have demonstrated that GOLPH3 protein functions as a cargo adaptor for COP I-coated intra Golgi vesicles and impinges on Golgi glycosylation pathways. In turn, GOLPH3-dependent defects have been associated with malignant phenotypes in cancer cells. Additionally, the oncogenic activity of GOLPH3 has been linked with enhanced signaling downstream of mechanistic target of rapamycin (mTOR) in several cancer types. Consistent with these data, GOLPH3 controls organ growth in Drosophila by associating with mTOR signaling proteins. Finally, compelling evidence demonstrates that GOLPH3 is essential for cytokinesis, a process required for the maintenance of genomic stability.

Multi-omic landscape of human gliomas from diagnosis to treatment and recurrence

Gliomas are among the most lethal cancers, with limited treatment options. To uncover hallmarks of therapeutic escape and tumor microenvironment (TME) evolution, we applied spatial proteomics, transcriptomics, and glycomics to 670 lesions from 310 adult and pediatric patients. Single-cell analysis shows high B7H3+ tumor cell prevalence in glioblastoma (GBM) and pleomorphic xanthoastrocytoma (PXA), while most gliomas, including pediatric cases, express targetable tumor antigens in less than 50% of tumor cells, potentially explaining trial failures. Longitudinal samples of isocitrate dehydrogenase (IDH)-mutant gliomas reveal recurrence driven by tumor-immune spatial reorganization, shifting from T-cell and vasculature-associated myeloid cell-enriched niches to microglia and CD206+ macrophage-dominated tumors. Multi-omic integration identified N-glycosylation as the best classifier of grade, while the immune transcriptome best predicted GBM survival. Provided as a community resource, this study opens new avenues for glioma targeting, classification, outcome prediction, and a baseline of TME composition across all stages.

Serum N-Glycomics with Nano-LC-QToF LC-MS/MS Reveals N-Glycan Biomarkers for Glioblastoma, Meningioma, and High-Grade Meningioma

Alteration of glycosylation in cancer cells leads to the expression of tumor-associated glycans, which can be used as biomarkers for diagnosis and prognostic prediction of diseases. In this study, we used nano-LC-QToF to identify serum N-glycan biomarkers for the detection of brain tumors. We observed an increase in sialylated N-glycans and a decrease in fucosylated N-glycans in the serum of patients with glioblastoma (GBM) and meningioma (MG) compared to healthy individuals. In GBM, a combination of increased serum sialylated N-glycan (6_4_0_2 compound) and decreased fucosylated N-glycan (4_4_1_0 compound) was identified as the most appropriate panel, with an area under the curve (AUC) of 0.8660, 78.95% sensitivity, 84.21% specificity, and 82.89% accuracy. For MG, a combination of decreased 6_6_2_0 and 5_5_2_0 compounds and increased 4_4_1_1 compound achieved an AUC of 0.9260, 82.35% sensitivity, 78.57% specificity, and 80.26% accuracy for diagnosis of MG. Additionally, an increase in 5_5_1_0 and 4_3_0_0 compounds combined with a decrease in 7_7_4_3 was associated with high-grade MG (WHO grades II-III). In conclusion, we identified serum N-glycan profiles associated with brain tumors, highlighting their potential as biomarkers for the diagnosis and prognosis of these diseases.

Insights on the Role of Sialic Acids in Acute Lymphoblastic Leukemia in Children

Sialic acids serve as crucial terminal sugars on glycoproteins or glycolipids present on cell surfaces. These sugars are involved in diverse physiological and pathological processes through their interactions with carbohydrate-binding proteins, facilitating cell-cell communication and influencing the outcomes of bacterial and viral infections. The role of hypersialylation in tumor growth and metastasis has been widely studied. Recent research has highlighted the significance of aberrant sialylation in enabling tumor cells to escape immune surveillance and sustain their malignant behavior. Acute lymphoblastic leukemia (ALL) is a heterogenous hematological malignancy that primarily affects children and is the second leading cause of mortality among individuals aged 1 to 14. ALL is characterized by the uncontrolled proliferation of immature lymphoid cells in the bone marrow, peripheral blood, and various organs. Sialic acid-binding immunoglobulin-like lectins (Siglecs) are cell surface proteins that can bind to sialic acids. Activation of Siglecs triggers downstream reactions, including induction of cell apoptosis. Siglec-7 and Siglec-9 have been reported to promote cancer progression by driving macrophage polarization, and their expressions on natural killer cells can inhibit tumor cell death. This comprehensive review aims to explore the sialylation mechanisms and their effects on ALL in children. Understanding the complex interplay between sialylation and ALL holds great potential for developing novel diagnostic tools and therapeutic interventions in managing this pediatric malignancy.

The physiological characteristics and applications of sialic acid

Sialic acid (SA) is widely present at the end of the sugar chain of glycoproteins and glycolipids on the surface of animal and microbial cells and is involved in many physiological activities between microbial and host cells. Notably, these functions are attributed to the diversity of these SA types, their different transformation pathways, and their metabolic actions within the host, which are considered potential targets for affecting various diseases. However, developing disease mitigation strategies is often limited by an unclear understanding of the mechanisms of interaction of the causative agents with their hosts. This review mainly focuses on three types of SA: Neu5Ac, Neu5Gc, and KDN. The sources, main types, and distribution of these SAs are discussed in detail, emphasizing the metabolic processes of different SAs and their interaction mechanisms with the host. This review will help lay a foundation for developing functional foods and SA-targeted intervention strategies.

Sialic acid metabolism-based classification reveals novel metabolic subtypes with distinct characteristics of tumor microenvironment and clinical outcomes in gastric cancer

BACKGROUND

High heterogeneity in gastric cancer (GC) remains a challenge for standard treatments and prognosis prediction. Dysregulation of sialic acid metabolism (SiaM) is recognized as a key metabolic hallmark of tumor immune evasion and metastasis. Herein, we aimed to develop a SiaM-based metabolic classification in GC.

METHODS

SiaM-related genes were obtained from the MsigDB database. Bulk and single-cell transcriptional data of 956 GC patients were acquired from the GEO, TCGA, and MEDLINE databases. Proteomic profiles of 20 GC samples were derived from our institution. The consensus clustering algorithm was applied to identify SiaM-based clusters. The SiaM-based model was established via LASSO regression and evaluated via Kaplan‒Meier curve and ROC curve analyses. In vitro and in vivo experiments were conducted to explore the function of ST3GAL1 in GC.

RESULTS

Three SiaM clusters presented distinct patterns of clinicopathological features, transcriptomic alterations, and tumor immune microenvironment landscapes in GC. Compared with clusters A and B, cluster C presented elevated SiaM activity, higher metastatic potential, more abundant immunosuppressive features, and a worse prognosis. Based on the differentially expressed genes between these clusters, a risk model for six genes (ARHGAP6, ST3GAL1, ADAM28, C7, PLCL1, and TTC28) was then constructed. The model exhibited robust performance in predicting peritoneal metastasis and prognosis in four independent cohorts. As a hub gene in the model, ST3GAL1 promoted GC cell migration and invasion in vitro and in vivo.

CONCLUSIONS

Our study proposed a novel SiaM-based classification that identified three metabolic subtypes with distinct characteristics of tumor microenvironment and clinical outcomes in GC.

Metabolic Probing of Sialylated Glycoconjugates with Fluorine-Selenol Displacement Reaction (FSeDR)

Dysregulated sialic acid biosynthesis is characteristic of the onset and progression of human diseases including hormone-sensitive prostate cancer and breast cancer. The sialylated glycoconjugates involved in this process are therefore important targets for identification and functional studies. To date, one of the most common strategies is metabolic glycoengineering, which utilizes N-acetylmannosamine (ManNAc) analogues such as N-azidoacetylmannosamine (ManNAz) to hijack sialic acid biosynthesis and label the sialylated glycoconjugates with "click chemistry (CuAAC)" tags. Yet, current chemical modifications including those CuAAC-based alkyne/azide tags are still big in size, and the resulting steric hindrance perturbs the mannosamine and sialic acid derivatives' recognition and metabolism by enzymes involved in biosynthetic pathways. As a result, the peracetylated ManNAz has compromised incorporation to sialic acid substrates and manifests cellular growth inhibition and cytotoxicity. Herein, we show that the α-fluorinated peracetylated analogue ManN(F-Ac) displayed a satisfying safety profile in mammalian cell lines at concentrations as high as 500 μM. More importantly, aliphatic selenol-containing probes can efficiently displace α-fluorine in fluoroacetamide-containing substrates including ManN(F-Ac) at a neutral pH range (∼7.2). The combined use of peracetylated ManN(F-Ac) and the dethiobiotin-selenol probe as the fluorine-selenol displacement reaction (FSeDR) toolkit allowed for successful metabolic labeling of sialoglycoproteins in multiple prostate and cancer cell lines, including PC-3 and MDA-MB-231. More sialoglycoproteins in these cell lines were demonstrated to be labeled by FSeDR compared with the traditional CuAAC approach. Lastly, with FSeDR-mediated metabolic labeling, we were able to probe the cellular expression level and spatial distribution of sialylated glycoconjugates during the progression of these hormone-sensitive cancer cells. Taken together, the promising results suggest the potential of the FSeDR strategy to efficiently and systematically identify and study sialic acid substrates and potentially empower metabolic engineering on a diverse set of glycosylated proteins that are vital for human diseases.

A Rapid and Sensitive MicroPlate Assay (MPSA) Using an Alkyne-Modified CMP-Sialic Acid Donor to Evaluate Human Sialyltransferase Specificity

Human sialyltransferases primarily utilize CMP-Sias, especially transferring Neu5Ac from CMP-Neu5Ac to various acceptors. Advances in chemical biology have led to the synthesis of novel CMP-Sia donors suitable for bioorthogonal reactions in cell-based assays. However, the compatibility of these donors with all human enzymes remains uncertain. We synthesized a non-natural CMP-Sia donor with an alkyne modification on the N-acyl group of Neu5Ac, which was effectively used by human ST6Gal I and ST3Gal I. A sensitive MicroPlate Sialyltransferase Assay (MPSA) was developed and expanded to a panel of 13 human STs acting on glycoproteins. All assayed enzymes tolerated CMP-SiaNAl, allowing for the determination of kinetic parameters and turnover numbers. This study enhances the biochemical characterization of human sialyltransferases and opens new avenues for developing sialyltransferase inhibitors.

Multi-center study on the application potential of Siaα-2,6Gal in early and differential diagnosis of lung cancer

OBJECTIVE

This study aimed to investigate the application potential of the abnormal glycan structure Siaα-2,6Gal in the early and differential diagnosis of lung cancer.

METHODS

Clinical data and serum samples from 730 patients and 120 healthy individuals participating in clinical trials on Siaα-2,6Gal were collected at three medical centers between January 2022 and June 2023. The levels of Siaα-2,6Gal, carcinoembryonic antigen (CEA), cytokeratin 19 fragment antigen (CYFRA21-1), squamous cell carcinoma antigen (SCC), neuron-specific enolase (NSE), and pro-gastrin-releasing peptide (ProGRP) in serum were measured. The application potentials of these markers in the early and differential diagnosis, classification, and staging of lung cancer were explored.

RESULTS

(1) Serum Siaα-2,6Gal levels in the lung cancer group were 2,606 (1,970-3,458) U/mL, significantly higher than those in the benign lung disease, miscellaneous malignant tumor, miscellaneous benign disease, and healthy individual groups at 1,359 (950-1,528), 1,252 (903-1,532), 1,196 (850-1,490), and 1,210 (1,100-1,287) U/mL (P < 0.0001). (2) Serum Siaα-2,6Gal levels in the early-stage lung cancer (stages 0-II) group were 2,576 (1,929-3,338) U/mL, significantly higher than those in the benign pulmonary nodule group at 1,419 (1,105-1,820) U/mL (P < 0.0001). (3) Receiver operating characteristic curves showed that Siaα-2,6Gal had a high diagnostic efficiency for lung cancer (area under the curve (AUC) = 0.9217), significantly superior to CEA, CYFRA21-1, SCC, NSE, and ProGRP (AUCs of 0.6618, 0.6605, 0.5783, 0.5985, and 0.6381).

CONCLUSION

Siaα-2,6Gal is a promising biomarker for lung cancer diagnosis and may offer superior differential diagnosis of early-stage lung cancer from benign pulmonary nodules compared to traditional tumor markers.

Genetic Risk Profiling Reveals Altered Glycosyltransferase Expression as a Predictor for Patient Outcome in Neuroblastoma

Background/Objectives: Neuroblastoma is a highly aggressive pediatric cancer that arises from immature nerve cells and exhibits a broad spectrum of clinical presentations. While low- and intermediate-risk neuroblastomas often have favorable outcomes, high-risk neuroblastomas are associated with poor prognosis and significant treatment challenges. The complex genetic networks driving these high-risk cases remain poorly understood. This study aims to investigate differences in gene expression patterns that may contribute to disease outcomes. Methods: We employed an in silico approach to analyze a cohort of 493 neuroblastoma tumor samples that underwent mRNA sequencing (GSE49711). This dataset was reanalyzed in depth with a non-hypothesis-driven approach to identify the expression patterns and regulatory mechanisms associated with a poor prognosis. Results: By exploring global gene expression and the integration of clinical parameters, we stratified the samples into two groups with highly distinct gene expression profiles. MYCN amplification emerged as a major driver not only of poor prognosis but also of specific gene regulatory patterns. Notably, tumors with MYCN amplification exhibited the strong regulation of immune response genes and less immune infiltration, suggesting potential immune evasion. However, while we observed only minor changes in immune checkpoint expression, there was a strong modulation of glycosyltransferase genes in MYCN-amplified tumors. Using this information, we were able to construct a risk profile based on 12 glycosylation-related genes, which correlates with the survival outcomes of neuroblastoma patients. Conclusions: This study highlights the role of MYCN amplification in driving a poor prognosis in neuroblastoma through the regulation of immune response and glycosylation-related genes. Based on this finding, we developed a genetic risk profile that correlates with survival outcomes in neuroblastoma patients.

Sialic acid detection and theranostic activity of phenylboronic acid-based fluorescent probe in human colorectal adenocarcinoma HT-29 cells

A new probe, 4-(((3',6'-bis(diethylamino)-3-oxospiro[isoindoline-1,9'-xanthen]-2-yl)imino)methyl)phenyl)boronic acid (R4B) was prepared by facile condensation of 4-formylphenylboronic acid and rhodamine B hydrazide. R4B was characterized by spectroscopic methods and single crystal X-ray diffraction. The sensor R4B solution turned pink and emitted orange fluorescence only in the presence of sialic acid but remained colorless and non-fluorescent otherwise. The sugar recognition performance was investigated via UV-vis and fluorescence spectroscopic studies. Our results revealed that R4B has good affinity and selectivity for sialic acid over common monosaccharides, with a detection limit as low as 10-7 M. Furthermore, R4B selectively inhibited growth of human colorectal adenocarcinoma HT-29 (IC50 <20 µM) without significant cytotoxicity to normal human colon fibroblasts CCD-18Co. Treatment with R4B suppressed HT-29 colony formation via mitochondrial apoptosis in a time-dependent manner. Cellular imaging studies also revealed the ability of R4B as a fluorescence dye to detect intracellular sialic acid and showed mitochondria-tracking ability in HT-29 cells. In summary, R4B is a potential theranostic for the detection of intracellular sialic acid during the early incubation period, followed by induction of cancer apoptotic cell death at a later treatment point.

Sialidase NEU3 silencing inhibits angiogenesis of EA.hy926 cells by regulating Wnt/β-catenin signaling pathway

Angiogenesis significantly drives tumor progression, and the functions of vascular endothelial cells are influenced by various factors. Tumor cells are characterized by abnormal sialylation, and their dynamic balance depends on sialyltransferases and sialidases. NEU3 is a plasma membrane-associated sialidase, vital for the regulation of cell surface sialylation. Our study revealed that, NEU3 is the most abundantly expressed among the four sialidase subtypes in EA.hy926 cells. Silencing NEU3 expression resulted in cell apoptosis and reduced proliferation, highlighting its crucial function in the regulation of cell activity. Subsequent experiments using transwell and tube formation assays demonstrated that the inhibition of NEU3 expression suppressed cell migration and angiogenesis. RNA sequencing analysis further elucidated that altering NEU3 expression in EA.hy926 cells impacts the Wnt/β-Catenin signaling pathway and c-Myc levels, thereby modulating cellular survival and migration capacity and exerting a regulatory effect on angiogenesis. These findings suggest that targeting NEU3 in the vascular endothelium may represent a promising strategy for anti-angiogenic therapy in tumors.

Structure-Function Relationships of the CMP-Sialic Acid Transporter through Analysis of a Pathogenic Variant in an Alternatively Spliced Functional Isoform

The human CMP-sialic acid transporter (hCST) is a mammalian highly conserved type III antiporter that translocates CMP-sialic acid into the Golgi lumen, supporting sialylation. Although different works have focused on elucidating structure-function relationships in the hCST, this is the first study to address them in an alternatively spliced isoform. We have previously reported the expression of a functional human del177 isoform that has skipping of exon 6, resulting in a loss of 59 amino acids, without change in the open reading frame and conserving its C-terminal region. To elucidate structure-function relationships, we interrogated this isoform with a known pathogenic variant c.303C>T (p.Q101H) for the wt isoform, showing that its pathogenicity is significatively reduced in the mutated del177 isoform (del177Q101H). This is further explained by using a homology model based on previously reported mouse and maize crystal structures.

Salivary adenoid cystic carcinoma-derived α2,6-sialylated extracellular vesicles increase vascular permeability by triggering ER-stress in endothelial cells and promote lung metastasis

Salivary adenoid cystic carcinoma (SACC) tends to metastasize to the lungs in the early stages of the disease. Factors secreted by the primary tumor can induce the formation of a supportive microenvironment in distant organs prior to metastasis, a process known as pre-metastatic niche (PMN) formation. Extracellular vesicles (EVs) participate in PMN formation. In this study, α2,6-sialylation of EVs derived from SACC cells with high metastatic potential increased vascular permeability, thereby facilitating tumor metastasis to the lungs. Mechanistic studies indicated that EV α2,6-sialylation triggers protein kinase R-like endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor 2α (eIF2α)-dependent activation of endoplasmic reticulum (ER) stress in the endothelium, leading to the disruption of vascular endothelial cadherin membrane expression. Sialidase or an ER stress inhibitor rescued vascular permeability induced by SACC EVs, which decreased the number of SACC cells extravasating into the lungs both in vitro and in vivo. This study identified a critical role of α2,6-sialylation of SACC EVs in lung metastasis. The findings indicate that EV α2,6-sialylation-induced ER stress in endothelial cells might be a therapeutic target for preventing SACC lung metastasis.

Directed Mutagenesis for Arginine Substitution of a Phaseolus acutifolius Recombinant Lectin Disrupts Its Cytotoxic Activity

Recently, we reported that a recombinant Tepary bean (Phaseolus acutifolius) lectin (rTBL-1) induces apoptosis in colon cancer cell lines and that cytotoxicity was related to differential recognition of β1-6 branched N-glycans. Sequencing analysis and resolution of the rTBL-1 3D structure suggest that glycan specificity could be strongly influenced by two arginine residues, R103 and R130, located in the carbohydrate binding pocket. The aim of this work was to determine the contribution of these residues towards cytotoxic activity. Two rTBL-1 mutants were produced in Pichia pastoris, biochemically characterized, and cytotoxic effects were evaluated on human colorectal cancer cells (HT-29). Substitution of either of the arginine residues with glutamines resulted in significant reductions in cytotoxic activity, with losses of 1.5 and 3 times for R103 and R130, respectively. Docking analysis showed that the mutations decreased lectin affinity binding to some Epidermal Growth Factor Receptor (EGFR)-related N-glycans. Together, these findings confirm that both of the selected arginine residues (R103 and R130) play a key role in the recognition of tumor cell glycoconjugates by rTBL-1.

Spatial omics-based machine learning algorithms for the early detection of hepatocellular carcinoma

BACKGROUND

Worldwide, hepatocellular carcinoma (HCC) is the second most lethal cancer, although early-stage HCC is amenable to curative treatment and can facilitate long-term survival. Early detection has proved difficult, as proteomics, transcriptomics, and genomics have been unable to discover suitable biomarkers.

METHODS

To find new biomarkers of HCC, we utilized a spatial omics N-glycan imaging method to identify altered glycosylation in cancer tissue (n = 53) and in paired serum of individuals with HCC (n = 23). Glycoproteomics identified the glycoproteins carrying these N-glycan structures, and we utilized an antibody array-based glycan imaging method to examine all the N-glycans associated with the identified glycoproteins. N-glycans from the examined glycoproteins were used to create machine learning algorithms, which were tested in a case-control sample set of 100 patients with cirrhosis and HCC and 101 matched patients with cirrhosis alone.

RESULTS

Spatial glycan imaging identifies thirteen branched, fucosylated, and high mannose glycans as altered in HCC tissue and in matched patient serum. Glycoproteomics identifies over 50 proteins containing these changes, of which sixteen glycoproteins were selected for further testing in an independent patient set. Algorithms using a combination of glycan and glycoproteins accurately differentiate early-stage and all HCC from cirrhosis with AUROC values of 0.88-0.97.

CONCLUSIONS

In conclusion, we present the development and application of a new biomarker platform, which can identify effective biomarkers for the early detection of HCC. This platform may also apply to other diseases, in which changes in N-linked glycosylation are known to occur.

Germline copy number variants and endometrial cancer risk

Known risk loci for endometrial cancer explain approximately one third of familial endometrial cancer. However, the association of germline copy number variants (CNVs) with endometrial cancer risk remains relatively unknown. We conducted a genome-wide analysis of rare CNVs overlapping gene regions in 4115 endometrial cancer cases and 17,818 controls to identify functionally relevant variants associated with disease. We identified a 1.22-fold greater number of CNVs in DNA samples from cases compared to DNA samples from controls (p = 4.4 × 10-63). Under three models of putative CNV impact (deletion, duplication, and loss of function), genome-wide association studies identified 141 candidate gene loci associated (p < 0.01) with endometrial cancer risk. Pathway analysis of the candidate loci revealed an enrichment of genes involved in the 16p11.2 proximal deletion syndrome, driven by a large recurrent deletion (chr16:29,595,483-30,159,693) identified in 0.15% of endometrial cancer cases and 0.02% of control participants. Together, these data provide evidence that rare copy number variants have a role in endometrial cancer susceptibility and that the proximal 16p11.2 BP4-BP5 region contains 25 candidate risk gene(s) that warrant further analysis to better understand their role in human disease.

Identification of serum N-glycans signatures in three major gastrointestinal cancers by high-throughput N-glycome profiling

BACKGROUND

Alternative N-glycosylation of serum proteins has been observed in colorectal cancer (CRC), esophageal squamous cell carcinoma (ESCC) and gastric cancer (GC), while comparative study among those three cancers has not been reported before. We aimed to identify serum N-glycans signatures and introduce a discriminative model across the gastrointestinal cancers.

METHODS

The study population was initially screened according to the exclusion criteria process. Serum N-glycans profiling was characterized by a high-throughput assay based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Diagnostic model was built by random forest, and unsupervised machine learning was performed to illustrate the differentiation between the three major gastrointestinal (GI) cancers.

RESULTS

We have found that three major gastrointestinal cancers strongly associated with significantly decreased mannosylation and mono-galactosylation, as well as increased sialylation of serum glycoproteins. A highly accurate discriminative power (> 0.90) for those gastrointestinal cancers was obtained with serum N-glycome based predictive model. Additionally, serum N-glycome profile exhibited distinct distributions across GI cancers, and several altered N-glycans were hyper-regulated in each specific disease.

CONCLUSIONS

Serum N-glycome profile was differentially expressed in three major gastrointestinal cancers, providing a new clinical tool for cancer diagnosis and throwing a light upon the disease-specific molecular signatures.

Sialylation inhibition improves macrophage mediated tumor cell phagocytosis of breast cancer cells triggered by therapeutic antibodies of different isotypes

Tumor cell phagocytosis by macrophages is considered a relevant mechanism of action for many therapeutic IgG antibodies. However, tumor cells employ several mechanisms to evade immune recognition, including hypersialylation. Here, we describe how reduction of sialic acid exposure on tumor cells promotes antibody-dependent tumor cell phagocytosis (ADCP) by macrophages. Incubation with the sialyltransferase inhibitor (STi) P-3Fax-Neu5Ac reduced sialylation on two breast cancer cell lines, rendering these cells more susceptible to macrophage mediated phagocytosis by EGFR or HER2 antibodies. This was observed with not only IgG1 and IgG2 antibodies but also IgA2 variants. These results show that inhibiting sialic acid exposure triggers enhanced tumor cell phagocytosis by macrophages irrespective of the antibody isotype and the tumor target antigen. Investigating the underlying mechanisms of enhanced ADCP, we observed reduced binding of soluble sialic acid-binding immunoglobulin-like lectins (Siglec)-7 and Siglec-9 to tumor cells after sialylation inhibition. However, Fc silent blocking antibodies against Siglec-7 or Siglec-9, or their combination, only marginally improved ADCP. Our results further promote the concept of cancer hypersialylation as immune escape mechanism, which could serve as target to improve tumor immunotherapy with monoclonal antibodies.

Sugar Highs: Recent Notable Breakthroughs in Glycobiology

Glycosylation is biochemically complex and functionally critical to a wide range of processes and disease states, making it a vibrant area of contemporary research. Here, we highlight a selection of notable recent advances in the glycobiology of SARS-CoV-2 infection and immunity, cancer biology and immunotherapy, and newly discovered glycosylated RNAs. Together, these studies illustrate the significance of glycosylation in normal biology and the great promise of manipulating glycosylation for therapeutic benefit in disease.

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.

Sialic Acid-Targeted Ru(II)/Ir(III)/Re(I) Complexes for Ferroptosis Induction in Triple-Negative Breast Cancer

Ferroptosis has been recognized as an iron-based nonapoptotic-regulated cell death process. In the quest of resisting the unyielding vehemence of triple-negative breast cancer (TNBC), herein we have showcased the ferroptosis-inducing heteroleptic [LIrcRu], [LIrcIrh], and [LIrcRe] complexes, enabling them to selectively target "sialic acid", an overexpressed cancer cell-surface marker. The open-circuit potential (OCP) measurements in live cancer cells revealed the specific interaction between TNBC and the complexes, whereas control experiments with normal cells did not exhibit such interactions. GSH depletion, GPx4 inhibition, NADH/NADPH oxidation, lipid peroxidation, COX-2 activation, and Nrf2 inactivation were meticulously investigated upon treatment with these complexes to establish a strong basis for ferroptosis. Among all complexes, the complex [LIrcIrh] (IC50 = 25 ± 2.17 μM) has been well-documented as a potent ferroptosis inducer, which unveils the sturdy interaction with sialic acid possessing the highest binding constant (Kb = 0.71 × 105 M-1, ΔG = -279345.8026 kcal/mol) along with the highest serum albumin binding affinity (KHSA = 0.67 × 106 M-1) and significant DNA intercalation (Kb = 0.56 × 105 M-1, Kapp = 1.06 × 106 M-1, and C50 of intercalation is 76.56 μM), displaying the decreased current intensity in differential pulse voltammetry (DPV). Moreover, the complex [LIrcIrh] exhibited mitochondrial dysfunction and membrane damage (diminished MMP, ΔΨm) through the production of copious reactive oxygen species (ROS) in MDA-MB-231 cells upon considerable accumulation in mitochondria (Pearson's coefficient = 0.842). The analysis of the field emission scanning electron microscopy (FE-SEM) image has marked the vivid membrane damage induced by the complex [LIrcIrh], exhibiting ablaze evidence for the destruction of TNBC cells through ferroptosis.

N-Acetylated Monosaccharides and Derived Glycan Structures Occurring in N- and O-Glycans During Prostate Cancer Development

Post-translational modifications of proteins play an important role in their stability, solubility and in vivo function. Also, for several reasons, such as the Golgi fragmentation during cancerogenesis, glycosylation as the most common modification is especially promising in offering high cancer specificity which, in combination with tissue-specific biomarkers available in the case of prostate diseases (PSA, PSMA, PAP), may lead to the development of novel oncodiagnostic approaches. In this review, we present the importance of subterminal glycan structures based on the N-acetylated monosaccharides GlcNAc and GalNAc in N- and also O-glycans, structures of which they are a component (LacNAc, LacdiNAc, branched structures). We also discuss the importance and clinical performance of these structures in cases of prostate cancer diagnostics using lectin-based affinity methods, which could be implemented in clinical laboratory practice in the future.

Harnessing Gene Editing Technology for Tumor Microenvironment Modulation: An Emerging Anticancer Strategy

Cancer is a multifaceted disease influenced by both intrinsic cellular traits and extrinsic factors, with the tumor microenvironment (TME) being crucial for cancer progression. To satisfy their high proliferation and aggressiveness, cancer cells always plunder large amounts of nutrients and release various signals to their surroundings, forming a dynamic TME with special metabolic, immune, microbial and physical characteristics. Due to the neglect of interactions between tumor cells and the TME, traditional cancer therapies often struggle with challenges such as drug resistance, low efficacy, and recurrence. Importantly, the development of gene editing technologies, particularly the CRISPR-Cas system, offers promising new strategies for cancer treatment. Combined with nanomaterial strategies, CRISPR-Cas technology exhibits precision, affordability, and user-friendliness with reduced side effects, which holds great promise for profoundly altering the TME at the genetic level, potentially leading to lasting anticancer outcomes. This review will delve into how CRISPR-Cas can be leveraged to manipulate the TME, examining its potential as a transformative anticancer therapy.

Mechanistic and Therapeutic Implications of Protein and Lipid Sialylation in Human Diseases

Glycan structures of glycoproteins and glycolipids on the surface glycocalyx and luminal sugar layers of intracellular membrane compartments in human cells constitute a key interface between intracellular biological processes and external environments. Sialic acids, a class of alpha-keto acid sugars with a nine-carbon backbone, are frequently found as the terminal residues of these glycoconjugates, forming the critical components of these sugar layers. Changes in the status and content of cellular sialic acids are closely linked to many human diseases such as cancer, cardiovascular, neurological, inflammatory, infectious, and lysosomal storage diseases. The molecular machineries responsible for the biosynthesis of the sialylated glycans, along with their biological interacting partners, are important therapeutic strategies and targets for drug development. The purpose of this article is to comprehensively review the recent literature and provide new scientific insights into the mechanisms and therapeutic implications of sialylation in glycoproteins and glycolipids across various human diseases. Recent advances in the clinical developments of sialic acid-related therapies are also summarized and discussed.

Phenylboronic acid-functionalized biomaterials for improved cancer immunotherapy via sialic acid targeting

Phenylboronic acid (PBA) is recognized as one of the most promising cancer cell binding modules attributed to its potential to form reversible and dynamic boronic ester covalent bonds. Exploring the advanced chemical versatility of PBA is crucial for developing new anticancer therapeutics. The presence of a specific Lewis acidic boron atom-based functional group and a Π-ring-connected ring has garnered increasing interest in the field of cancer immunotherapy. PBA-derivatized functional biomaterials can form reversible bonds with diols containing cell surface markers and proteins. This review primarily focuses on the following topics: (1) the importance and versatility of PBA, (2) different PBA derivatives with pKa values, (3) specific key features of PBA-mediated biomaterials, and (4) cell surface activity for cancer immunotherapy applications. Specific key features of PBA-mediated materials, including sensing, bioadhesion, and gelation, along with important synthesis strategies, are highlighted. The utilization of PBA-mediated biomaterials for cancer immunotherapy, especially the role of PBA-based nanoparticles and PBA-mediated cell-based therapeutics, is also discussed. Finally, a perspective on future research based on PBA-biomaterials for immunotherapy applications is presented.

The pro-inflammatory cytokines IL-1β and IL-6 promote upregulation of the ST6GAL1 sialyltransferase in pancreatic cancer cells

The ST6GAL1 sialyltransferase is overexpressed in multiple cancers, including pancreatic ductal adenocarcinoma (PDAC). ST6GAL1 adds an α2-6-linked sialic acid to N-glycosylated membrane receptors, which consequently modulates receptor structure and function. While many studies have investigated the effects of ST6GAL1 on cell phenotype, there is a dearth of knowledge regarding mechanisms that regulate ST6GAL1 expression. In the current study, we evaluated the regulation of ST6GAL1 by two pro-inflammatory cytokines, IL-1β and IL-6, which are abundant within the PDAC tumor microenvironment. Cytokine activity was monitored using the Suit-2 PDAC cell line and two Suit-2-derived metastatic subclones, S2-013 and S2-LM7AA. For all three cell models, treatment with IL-1β or IL-6 increased the expression of ST6GAL1 protein and mRNA. Specifically, IL-1β and IL-6 induced expression of the ST6GAL1 YZ mRNA isoform, which is driven by the P3 promoter. The ST6GAL1 H and X isoforms were not detected. Promoter reporter assays confirmed that IL-1β and IL-6 activated transcription from the P3 promoter. We then examined downstream signaling mechanisms. IL-1β is known to signal through the NFκB transcription factor, whereas IL-6 signals through the STAT3 transcription factor. CUT&RUN experiments revealed that IL-1β promoted the binding of NFκB to the ST6GAL1 P3 promoter, and IL-6 induced the binding of STAT3 to the P3 promoter. Finally, we determined that inhibitors of NFκB and STAT3 blocked the upregulation of ST6GAL1 stimulated by IL-1β and IL-6, respectively. Together, these results highlight a novel molecular pathway by which cytokines within the tumor microenvironment stimulate the upregulation of ST6GAL1 in PDAC cells.

Biological function of sialic acid and sialylation in human health and disease

Sialic acids are predominantly found at the terminal ends of glycoproteins and glycolipids and play key roles in cellular communication and function. The process of sialylation, a form of post-translational modification, involves the covalent attachment of sialic acid to the terminal residues of oligosaccharides and glycoproteins. This modification not only provides a layer of electrostatic repulsion to cells but also serves as a receptor for various biological signaling pathways. Sialylation is involved in several pathophysiological processes. Given its multifaceted involvement in cellular functions, sialylation presents a promising avenue for therapeutic intervention. Current studies are exploring agents that target sialic acid residues on sialoglycans or the sialylation process. These efforts are particularly focused on the fields of cancer therapy, stroke treatment, antiviral strategies, and therapies for central nervous system disorders. In this review, we aimed to summarize the biological functions of sialic acid and the process of sialylation, explore their roles in various pathophysiological contexts, and discuss their potential applications in the development of novel therapeutics.

Exploring Lectin Bioactivity and Total Phenolic Compounds in Kiwifruit (Actinidia deliciosa var. Hayward)

BACKGROUND

The consumption of kiwifruit (Actinidia deliciosa var. Hayward) is recognized for its health benefits due to its high vitamin C content and bioactive secondary metabolites, such as phenolic compounds with antioxidant properties. These compounds may help prevent chronic noncommunicable diseases, currently the leading cause of death. Additionally, plants and fruits contain proteins like lectins, which contribute to plant defense and may also have health-promoting effects, including antitumor and hypoglycemic activities.

OBJECTIVES

The objective of this work was to evaluate and identify the phenolic compounds in this variety of kiwifruit, as well as to investigate the lectin activity and the potential dietary benefits of this combination.

METHODS

This study quantified and identified total phenolic compounds and flavonoids in a kiwifruit extract using HPLC-DAD-MS/MS, and assessed their antioxidant activity through the DPPH method.

RESULTS

Novel lectin activity was also investigated, with polypeptide characterization and glycoprotein profiling performed. The affinity of lectins for glycans was evaluated using a hemagglutination inhibition assay. Results indicated that kiwifruit lectins bind to glycoreceptors on tumor cell membranes, with a specific affinity for sialic acid, an important glycan in tumor-associated glycomic aberrations.

CONCLUSIONS

These findings suggest that the bioactive components of kiwifruit may offer multiple health benefits through a synergistic effect.

Effect of Different Glucose Levels and Glycation on Meningioma Cell Migration and Invasion

Meningiomas are predominantly benign tumors, but there are also malignant forms that are associated with a poor prognosis. Like almost all tumors, meningiomas metabolize glucose as part of aerobic glycolysis (Warburg effect) for energy supply, so there are attempts to influence the prognosis of tumor diseases using a glucose-reduced diet. This altered metabolism leads to so called hallmarks of cancer, such as glycation and glycosylation. In this study, we investigated the influence of low (3 mM), normal (5.5 mM) and high glucose (15 mM) on a malignant meningioma cell line (IOMM-Lee, WHO grade 3). In addition, the influence of methylglyoxal, a by-product of glycolysis and a precursor for glycation, was investigated. Impedance-based methods (ECIS and RTCA) were used to study migration and invasion, and immunoblotting was used to analyze the expression of proteins relevant to these processes, such as focal adhesion kinase (FAK), merlin or integrin ß1. We were able to show that low glucose reduced the invasive potential of the cells, which was associated with a reduced amount of sialic acid. Under high glucose, barrier function was impaired and adhesion decreased, which correlated with a decreased expression of FAK.

Beyond the lungs: Exploring diverse applications of bromhexine and ambroxol

The respiratory tract is commonly affected in multisystem disorders. Although many drugs have been developed to target various components of these diseases, there is still a need for effective treatments that can address both respiratory and non-respiratory symptoms. Bromhexine and ambroxol are mucolytic agents with a good safety profile that are widely used to treat respiratory conditions. These compounds seem to present several unresolved questions when carrying out their therapeutic effects, suggesting that they may not merely improve mucociliary clearance. These assumptions have provided the basis for researchers to investigate the specific characteristics of bromhexine and ambroxol. This has led to the emergence of several repositionings for this compound. Accordingly, these compounds have also shown potential benefits in the treatment of various extrapulmonary disorders, including neurological disorders, and inflammatory bowel disease. We gathered findings from relevant studies published in English between 1970 and December 2023 by searching databases including PubMed, Google Scholar, Scopus, Embase, and the Cochrane Library. Our findings revealed that most of the research on extrapulmonary uses has been conducted at the preclinical level. Accordingly, more clinical studies are needed to determine the effectiveness of bromhexine and ambroxol in these conditions. This article provides an overview of the potential extrapulmonary applications of bromhexine and ambroxol and discusses the potential advantages of using these drugs in multisystem disorders.

Bio-Pathological Functions of Posttranslational Modifications of Histological Biomarkers in Breast Cancer

Proteins are the most common types of biomarkers used in breast cancer (BC) theranostics and management. By definition, a biomarker must be a relevant, objective, stable, and quantifiable biomolecule or other parameter, but proteins are known to exhibit the most variate and profound structural and functional variation. Thus, the proteome is highly dynamic and permanently reshaped and readapted, according to changing microenvironments, to maintain the local cell and tissue homeostasis. It is known that protein posttranslational modifications (PTMs) can affect all aspects of protein function. In this review, we focused our analysis on the different types of PTMs of histological biomarkers in BC. Thus, we analyzed the most common PTMs, including phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, palmitoylation, myristoylation, and glycosylation/sialylation/fucosylation of transcription factors, proliferation marker Ki-67, plasma membrane proteins, and histone modifications. Most of these PTMs occur in the presence of cellular stress. We emphasized that these PTMs interfere with these biomarkers maintenance, turnover and lifespan, nuclear or subcellular localization, structure and function, stabilization or inactivation, initiation or silencing of genomic and non-genomic pathways, including transcriptional activities or signaling pathways, mitosis, proteostasis, cell-cell and cell-extracellular matrix (ECM) interactions, membrane trafficking, and PPIs. Moreover, PTMs of these biomarkers orchestrate all hallmark pathways that are dysregulated in BC, playing both pro- and/or antitumoral and context-specific roles in DNA damage, repair and genomic stability, inactivation/activation of tumor-suppressor genes and oncogenes, phenotypic plasticity, epigenetic regulation of gene expression and non-mutational reprogramming, proliferative signaling, endocytosis, cell death, dysregulated TME, invasion and metastasis, including epithelial-mesenchymal/mesenchymal-epithelial transition (EMT/MET), and resistance to therapy or reversal of multidrug therapy resistance. PTMs occur in the nucleus but also at the plasma membrane and cytoplasmic level and induce biomarker translocation with opposite effects. Analysis of protein PTMs allows for the discovery and validation of new biomarkers in BC, mainly for early diagnosis, like extracellular vesicle glycosylation, which may be considered as a potential source of circulating cancer biomarkers.

Single-cell profiling of surface glycosphingolipids opens a new dimension for deconvolution of breast cancer intratumoral heterogeneity and phenotypic plasticity

Glycosylated sphingolipids (GSLs) are a diverse group of cellular lipids typically reported as being rare in normal mammary tissue. In breast cancer (BCa), GSLs have emerged as noteworthy markers associated with breast cancer stem cells, mediators of phenotypic plasticity, and contributors to cancer cell chemoresistance. GSLs are potential surface markers that can uniquely characterize the heterogeneity of the tumor microenvironment, including cancer cell subpopulations and epithelial-mesenchymal plasticity (EMP). In this study, mass spectrometry analyses of the total sphingolipidome in breast epithelial cells and their mesenchymal counterparts revealed increased levels of Gb3 in epithelial cells and significantly elevated GD2 levels in the mesenchymal phenotype. To elucidate if GSL-related epitopes on BCa cell surfaces reflect EMP and cancer status, we developed and rigorously validated a 12-color spectral flow cytometry panel. This panel enables the simultaneous detection of native GSL epitopes (Gb3, SSEA1, SSEA3, SSEA4, and GD2), epithelial-mesenchymal transition markers (EpCAM, TROP2, and CD9), and lineage markers (CD45, CD31, and CD90) at the single-cell level. Next, the established panel was used for the analysis of BCa primary tumors and revealed surface heterogeneity in SSEA1, SSEA3, SSEA4, GD2, and Gb3, indicative of native epitope presence also on non-tumor cells. These findings further highlighted the phenotype-dependent alterations in GSL surface profiles, with differences between epithelial and stromal cells in the tumor. This study provides novel insights into BCa heterogeneity, shedding light on the potential of native GSL-related epitopes as markers for EMP and cancer status in fresh clinical samples. The developed single-cell approach offers promising avenues for further exploration.

TTYH3 promotes the malignant progression of oral squamous cell carcinoma SCC-9 cells by regulating tumor-associated macrophage polarization

OBJECTIVE

This study was designed to investigate the biological role and the reaction mechanism of Tweety family member 3 (TTYH3) in oral squamous cell carcinoma (OSCC).

DESIGN

The mRNA and protein expressions of TTYH3 were assessed with RT-qPCR and western blot. After silencing TTYH3 expression, the proliferation of OSCC cells were detected using cell counting kit-8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) staining and colony formation assay. Cell migration and invasion were detected using wound healing and transwell. Gelatin zymography protease assay was used to detect matrix metalloproteinase-2 (MMP2) and matrix metalloproteinase-2 (MMP9) activity and western blot was used to detect the expressions of proteins associated with proliferation and epithelial-mesenchymal transition (EMT). The mRNA expression of TTYH3 in THP-1-derived macrophage was detected using real-time reverse transcriptase-polymerase chain reaction (RT-qPCR). The number of CD86-positive cells and CD206-positive cells was detected using immunofluorescence assay. RT-qPCR was used to detect the expressions of M2 markers arginase 1 (ARG1), chitinase-like 3 (YM1) and mannose receptor C-type 1 (MRC1).

RESULTS

In this study, it was found that TTYH3 expression was upregulated in OSCC cell lines and TTYH3 knockdown could inhibit the proliferation, migration, invasion and EMT process in OSCC via suppressing M2 polarization of tumor-associated macrophages.

CONCLUSIONS

Collectively, TTYH3 facilitated the progression of OSCC through the regulation of tumor-associated macrophages polarization.

B4GALT5 a sialylation-related genes associated with patient prognosis and immune microenvironment in ovarian cancer and pan-cancer

BACKGROUND

Ovarian cancer (OC) is the predominant primary tumor in the human reproductive system. Abnormal sialylation has a significant impact on tumor development, metastasis, immune evasion, angiogenesis, and treatment resistance. B4GALT5, a gene associated with sialylation, plays a crucial role in ovarian cancer, and may potentially affect clinicopathological characteristics and prognosis.

METHODS

We conducted a comprehensive search across TIMER, GEPIA2, GeneMANIA, and Metascape to obtain transcription profiling data of ovarian cancer from The Cancer Genome Atlas (TCGA). The expression of B4GALT5 was test by immunohistochemistry. To investigate the impact of B4GALT5 on growth and programmed cell death in OC cells, we performed transwell assays and western blots.

RESULTS

The presence of B4GALT5 was strongly associated with an unfavorable outcome in OC. B4GALT5 significantly promoted the proliferation of OC cells. Upon analyzing gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), it was discovered that B4GALT5 played a crucial role in the extracellular matrix, particularly in collagen-containing structures, and exhibited correlations with ECM-receptor interactions, transcriptional dysregulation in cancer, as well as the interleukin-1 receptor signaling pathway. Furthermore, there is a clear link between B4GALT5 and the tumor immune microenvironment in OC. Moreover, B4GALT5 exhibits favorable expression levels across various types of cancers, including CHOL, KIRC, STAD and UCES.

CONCLUSION

In conclusion, it is widely believed that B4GALT5 plays a pivotal role in the growth and progression of OC, with its heightened expression serving as an indicator of unfavorable outcomes. Moreover, B4GALT5 actively participates in shaping the cancer immune microenvironment within OC. This investigation has the potential to contribute significantly to a deeper understanding of the substantial involvement of B4GALT5 in human malignancies, particularly OCs.

α2,6 sialylation distinguishes a novel active state in CD4+ and CD8+ cells during acute Toxoplasma gondii infection

Toxoplasmosis is a worldwide parasitosis that is usually asymptomatic; cell-mediated immunity, particularly T cells, is a crucial mediator of the immune response against this parasite. Membrane protein expression has been studied for a long time in T lymphocytes, providing vital information to determine functional checkpoints. However, less is known about the role of post-translational modifications in T cell function. Glycosylation plays essential roles during maturation and function; particularly, sialic acid modulation is determinant for accurate T cell regulation of processes like adhesion, cell-cell communication, and apoptosis induction. Despite its importance, the role of T cell sialylation during infection remains unclear. Herein, we aimed to evaluate whether different membrane sialylation motifs are modified in T cells during acute Toxoplasma gondii infection using different lectins. To this end, BALB/c Foxp3EGFP mice were infected with T. gondii, and on days 3, 7, and 10 post-infection, splenocytes were obtained to analyze conventional (Foxp3-) CD4+ and CD8+ populations by flow cytometry. Among the different lectins used for analysis, only Sambucus nigra lectin, which detects sialic acid α2,6 linkages, revealed two distinctive populations (SNBright and SN-/Dim) after infection. Further characterization of CD4+ and CD8+ SN-/Dim lymphocytes showed that these are highly activated cells, with a TEf/EM or TCM phenotype that produce high IFN-γ levels, a previously undescribed cell state. This work demonstrates that glycan membrane analysis in T cells reveals previously overlooked functional states by evaluating only protein expression.

Sialylation Inhibition Can Partially Revert Acquired Resistance to Enzalutamide in Prostate Cancer Cells

Prostate cancer is a lethal solid malignancy and a leading cause of cancer-related deaths in males worldwide. Treatments, including radical prostatectomy, radiotherapy, and hormone therapy, are available and have improved patient survival; however, recurrence remains a huge clinical challenge. Enzalutamide is a second-generation androgen receptor antagonist that is used to treat castrate-resistant prostate cancer. Among patients who initially respond to enzalutamide, virtually all acquire secondary resistance, and an improved understanding of the mechanisms involved is urgently needed. Aberrant glycosylation, and, in particular, alterations to sialylated glycans, have been reported as mediators of therapy resistance in cancer, but a link between tumour-associated glycans and resistance to therapy in prostate cancer has not yet been investigated. Here, using cell line models, we show that prostate cancer cells with acquired resistance to enzalutamide therapy have an upregulation of the sialyltransferase ST6 beta-galactoside alpha-2,6-sialyltransferase 1 (ST6GAL1) and increased levels of α2,6-sialylated N-glycans. Furthermore, using the sialyltransferase inhibitor P-SiaFNEtoc, we discover that acquired resistance to enzalutamide can be partially reversed by combining enzalutamide therapy with sialic acid blockade. Our findings identify a potential role for ST6GAL1-mediated aberrant sialylation in acquired resistance to enzalutamide therapy for prostate cancer and suggest that sialic acid blockade in combination with enzalutamide may represent a novel therapeutic approach in patients with advanced disease. Our study also highlights the potential to bridge the fields of cancer biology and glycobiology to develop novel combination therapies for prostate cancer.

Synthesis of α-Hydroxy-1,2,3-Triazole-linked Sialyltransferase Inhibitors and Evaluation of Selectivity Towards ST3GAL1, ST6GAL1 and ST8SIA2

Tumour-derived sialoglycans, bearing the charged nonulosonic sugar sialic acid at their termini, play a critical role in tumour cell adhesion and invasion, as well as evading cell death and immune surveillance. Sialyltransferases (ST), the enzymes responsible for the biosynthesis of sialylated glycans, are highly upregulated in cancer, with tumour hypersialylation strongly correlated with tumour growth, metastasis and drug resistance. As a result, desialylation of the tumour cell surface using either targeted delivery of a pan-ST inhibitor (or sialidase) or systemic delivery of a non-toxic selective ST inhibitors are being pursued as potential new anti-metastatic strategies against multiple cancers including pancreatic, ovarian, breast, melanoma and lung cancer. Herein, we have employed molecular modelling to give insights into the selectivity observed in a series of selective ST inhibitors that incorporate a uridyl ring in place of the cytidine of the natural donor (CMP-Neu5Ac) and replace the charged phosphodiester linker of classical ST inhibitors with a neutral α-hydroxy-1,2,3-triazole linker. The inhibitory activities of the nascent compounds were determined against recombinant human ST enzymes (ST3GAL1, ST6GAL1, ST8SIA2) showing promising activity and selectivity towards specific ST sub-types. Our ST inhibitors are non-toxic and show improved synthetic accessibility and drug-likeness compared to earlier nucleoside-based ST inhibitors.

Probing High-Order Transient Oligomers Using Ion Mobility Mass Spectrometry Coupled with Infrared Action Spectroscopy

Understanding and controlling peptide aggregation are critical due to its neurotoxic implications. However, structural information about the key intermediates, the oligomers, is obscured by a cascade of coinciding events occurring at various time and energy scales, which results in complex and heterogeneous mixtures of oligomers. To address this challenge, we have developed the Photo-Synapt, a novel, multidimensional spectrometer that integrates ion mobility mass spectrometry with infrared (IR) action spectroscopy within a single experiment. By combining three different orthogonal analytical dimensions, we can select and isolate individual oligomers by mass, charge, size, and shape and provide a unique molecular fingerprint for each oligomer. The broad application of this technology is demonstrated by its application to oligosaccharide analysis from glycoproteins, which are challenging to analyze due to the minute differences between isomers. By integration of IR action spectroscopy with ion mobility mass spectrometry, this approach adds an analytical dimension that effectively addresses this limitation, offering a unique molecular fingerprint for each isomer.

Designing SERS nanotags for profiling overexpressed surface markers on single cancer cells: A review

This review focuses on the chemical design and the use of Surface-Enhanced Raman Scattering (SERS)-active nanotags for measuring surface markers that can be overexpressed at the surface of single cancer cells. Indeed, providing analytical tools with true single-cell measurements capabilities is capital, especially since cancer research is increasingly leaning toward single-cell analysis, either to guide treatment decisions or to understand complex tumor behaviour including the single-cell heterogeneity and the appearance of treatment resistance. Over the past two decades, SERS nanotags have triggered significant interest in the scientific community owing their advantages over fluorescent tags, mainly because SERS nanotags resist photobleaching and exhibit sharper signal bands, which reduces possible spectral overlap and enables the discrimination between the SERS signals and the autofluorescence background from the sample itself. The extensive efforts invested in harnessing SERS nanotags for biomedical purposes, particularly in cancer research, highlight their potential as the next generation of optical labels for single-cell studies. The review unfolds in two main parts. The first part focuses on the structure of SERS nanotags, detailing their chemical composition and the role of each building block of the tags. The second part explores applications in measuring overexpressed surface markers on single-cells. The latter encompasses studies using single nanotags, multiplexed measurements, quantitative information extraction, monitoring treatment responses, and integrating phenotype measurements with SERS nanotags on single cells isolated from complex biological matrices. This comprehensive review anticipates SERS nanotags to persist as a pivotal technology in advancing single-cell analytical methods, particularly in the context of cancer research and personalized medicine.

Exploring the role of the immune microenvironment in hepatocellular carcinoma: Implications for immunotherapy and drug resistance

Hepatocellular carcinoma (HCC), the most common type of liver tumor, is a leading cause of cancer-related deaths, and the incidence of liver cancer is still increasing worldwide. Curative hepatectomy or liver transplantation is only indicated for a small population of patients with early-stage HCC. However, most patients with HCC are not candidates for radical resection due to disease progression, leading to the choice of the conventional tyrosine kinase inhibitor drug sorafenib as first-line treatment. In the past few years, immunotherapy, mainly immune checkpoint inhibitors (ICIs), has revolutionized the clinical strategy for HCC. Combination therapy with ICIs has proven more effective than sorafenib, and clinical trials have been conducted to apply these therapies to patients. Despite significant progress in immunotherapy, the molecular mechanisms behind it remain unclear, and immune resistance is often challenging to overcome. Several studies have pointed out that the complex intercellular communication network in the immune microenvironment of HCC regulates tumor escape and drug resistance to immune response. This underscores the urgent need to analyze the immune microenvironment of HCC. This review describes the immunosuppressive cell populations in the immune microenvironment of HCC, as well as the related clinical trials, aiming to provide insights for the next generation of precision immunotherapy.

Sialylation-induced stabilization of dynamic glycoprotein conformations unveiled by time-aligned parallel unfolding and glycan release mass spectrometry

Sialylation, a critical post-translational modification, regulates glycoprotein structure and function by tuning their molecular heterogeneity. However, characterizing its subtle and dynamic conformational effects at the intact glycoprotein level remains challenging. We introduce a glycoform-resolved unfolding approach based on a high-throughput ion mobility-mass spectrometry (IM-MS) platform. This method integrates high-throughput unfolding with parallel fragmentation, enabling simultaneous analysis of sialylation patterns, stoichiometries, and their impact on conformational stability. Applying this approach to fetuin, we identified distinct sialylation patterns and their differential influence on protein conformation, namely sialylation-induced stabilization during early unfolding and increased flexibility in later unfolding stages. IM-MS-guided molecular dynamics simulations revealed that increased sialylation enhances the initial conformational stability, likely through enhanced electrostatic interactions and hydrogen bonding. These findings highlight the complex interplay between sialylation and protein dynamics and establish glycoform-resolved unfolding IM-MS as a powerful tool for characterizing glycoprotein conformational landscapes.

FUCA1: An Underexplored p53 Target Gene Linking Glycosylation and Cancer Progression

Cancer is a difficult-to-cure disease with high worldwide incidence and mortality, in large part due to drug resistance and disease relapse. Glycosylation, which is a common modification of cellular biomolecules, was discovered decades ago and has been of interest in cancer research due to its ability to influence cellular function and to promote carcinogenesis. A variety of glycosylation types and structures regulate the function of biomolecules and are potential targets for investigating and treating cancer. The link between glycosylation and carcinogenesis has been more recently revealed by the role of p53 in energy metabolism, including the p53 target gene alpha-L-fucosidase 1 (FUCA1), which plays an essential role in fucosylation. In this review, we summarize roles of glycan structures and glycosylation-related enzymes to cancer development. The interplay between glycosylation and tumor microenvironmental factors is also discussed, together with involvement of glycosylation in well-characterized cancer-promoting mechanisms, such as the epidermal growth factor receptor (EGFR), phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and p53-mediated pathways. Glycan structures also modulate cell-matrix interactions, cell-cell adhesion as well as cell migration and settlement, dysfunction of which can contribute to cancer. Thus, further investigation of the mechanistic relationships among glycosylation, related enzymes and cancer progression may provide insights into potential novel cancer treatments.

Insights into molecular and cellular functions of the Golgi calcium/manganese-proton antiporter TMEM165

The Golgi compartment performs a number of crucial roles in the cell. However, the exact molecular mechanisms underlying these actions are not fully defined. Pathogenic mutations in genes encoding Golgi proteins may serve as an important source for expanding our knowledge. For instance, mutations in the gene encoding Transmembrane protein 165 (TMEM165) were discovered as a cause of a new type of congenital disorder of glycosylation (CDG). Comprehensive studies of TMEM165 in different model systems, including mammals, yeast, and fish uncovered the new realm of Mn2+ homeostasis regulation. TMEM165 was shown to act as a Ca2+/Mn2+:H+ antiporter in the medial- and trans-Golgi network, pumping the metal ions into the Golgi lumen and protons outside. Disruption of TMEM165 antiporter activity results in defects in N- and O-glycosylation of proteins and glycosylation of lipids. Impaired glycosylation of TMEM165-CDG arises from a lack of Mn2+ within the Golgi. Nevertheless, Mn2+ insufficiency in the Golgi is compensated by the activity of the ATPase SERCA2. TMEM165 turnover has also been found to be regulated by Mn2+ cytosolic concentration. Besides causing CDG, recent investigations have demonstrated the functional involvement of TMEM165 in several other pathologies including cancer and mental health disorders. This systematic review summarizes the available information on TMEM165 molecular structure, cellular function, and its roles in health and disease.