Recent advances in the development of sialyltransferase inhibitors to control cancer metastasis: A comprehensive review

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.

ST3GAL4 promotes tumorigenesis in breast cancer by enhancing aerobic glycolysis

Sialyltransferases are enzymes that play a crucial role in regulating cancer progression by modifying glycoproteins through sialylation. In particular, the ST3 beta-galactoside alpha-2,3-sialyltransferase 4 (ST3GAL4) enzyme is known to be upregulated in breast cancer, but its specific biological functions have not been fully understood. This study aimed to investigate the impact and mechanisms of ST3GAL4 on aerobic glycolysis in breast cancer. We examined ST3GAL4 expression in tumor tissue samples and breast cancer cell lines and also manipulated ST3GAL4 expression in breast cancer cells using lentivirus transduction. The study evaluated cellular processes such as cell viability, cell cycle progression, and aerobic glycolysis by measuring parameters like extracellular acidification rate, glucose uptake, lactate production, and lactate dehydrogenase A (LDHA) expression. We found that ST3GAL4 expression was consistently increased in tumor tissues and breast cancer cell lines. High ST3GAL4 expression was associated with a poor prognosis for patients with breast cancer. Inhibiting ST3GAL4 expression decreased cell viability, disrupted cell cycle progression, and reduced aerobic glycolysis and LDHA expression. Furthermore, suppressing ST3GAL4 expression in animal models reduced tumor growth and cell proliferation. Conversely, overexpressing ST3GAL4 promoted cell viability and cell cycle progression, but these effects were reversed when an inhibitor of aerobic glycolysis was used. The study provided evidence in cells and animal models that ST3GAL4 promotes tumorigenesis in breast cancer by enhancing aerobic glycolysis. These findings suggest that targeting ST3GAL4 may be a potential strategy for the treatment of breast cancer.

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.

Sialic Acids Blockade-Based Chemo-Immunotherapy Featuring Cancer Cell Chemosensitivity and Antitumor Immune Response Synergies

Immune checkpoint blockade (ICB) has significantly improved the prognosis of patients with cancer, although the majority of such patients achieve low response rates; consequently, new therapeutic approaches are urgently needed. The upregulation of sialic acid-containing glycans is a common characteristic of cancer-related glycosylation, which drives disease progression and immune escape via numerous pathways. Herein, the development of self-assembled core-shell nanoscale coordination polymer nanoparticles loaded with a sialyltransferase inhibitor, referred to as NCP-STI which effectively stripped diverse sialoglycans from cancer cells, providing an antibody-independent pattern to disrupt the emerging Siglec-sialic acid glyco-immune checkpoint is reported. Furthermore, NCP-STI inhibits sialylation of the concentrated nucleoside transporter 1 (CNT1), promotes the intracellular accumulation of anticancer agent gemcitabine (Gem), and enhances Gem-induced immunogenic cell death (ICD). As a result, the combination of NCP-STI and Gem (NCP-STI/Gem) evokes a robust antitumor immune response and exhibits superior efficacy in restraining the growth of multiple murine tumors and pulmonary metastasis. Collectively, the findings demonstrate a novel form of small molecule-based chemo-immunotherapy approach which features sialic acids blockade that enables cooperative effects of cancer cell chemosensitivity and antitumor immune responses for cancer treatment.

Blockade of Sialylation with Decrease in Polysialic Acid Levels Counteracts Transforming Growth Factor β1-Induced Skin Fibroblast-to-Myofibroblast Transition

Aberrant sialylation with overexpression of the homopolymeric glycan polysialic acid (polySia) was recently reported in fibroblasts from fibrotic skin lesions. Yet, whether such a rise in polySia levels or sialylation in general may be functionally implicated in profibrotic activation of fibroblasts and their transition to myofibroblasts remains unknown. Therefore, we herein explored whether inhibition of sialylation could interfere with the process of skin fibroblast-to-myofibroblast transition induced by the master profibrotic mediator transforming growth factor β1 (TGFβ1). Adult human skin fibroblasts were pretreated with the competitive pan-sialyltransferase inhibitor 3-Fax-peracetyl-Neu5Ac (3-Fax) before stimulation with recombinant human TGFβ1, and then analyzed for polySia expression, cell viability, proliferation, migratory ability, and acquisition of myofibroblast-like morphofunctional features. Skin fibroblast stimulation with TGFβ1 resulted in overexpression of polySia, which was effectively blunted by 3-Fax pre-administration. Pretreatment with 3-Fax efficiently lessened TGFβ1-induced skin fibroblast proliferation, migration, changes in cell morphology, and phenotypic and functional differentiation into myofibroblasts, as testified by a significant reduction in FAP, ACTA2, COL1A1, COL1A2, and FN1 gene expression, and α-smooth muscle actin, N-cadherin, COL1A1, and FN-EDA protein levels, as well as a reduced contractile capability. Moreover, skin fibroblasts pre-administered with 3-Fax displayed a significant decrease in Smad3-dependent canonical TGFβ1 signaling. Collectively, our in vitro findings demonstrate for the first time that aberrant sialylation with increased polySia levels has a functional role in skin fibroblast-to-myofibroblast transition and suggest that competitive sialyltransferase inhibition might offer new therapeutic opportunities against skin fibrosis.

Metabolic Signaling in Cancer Metastasis

Metastases, which are the leading cause of death in patients with cancer, have metabolic vulnerabilities. Alterations in metabolism fuel the energy and biosynthetic needs of metastases but are also needed to activate cell state switches in cells leading to invasion, migration, colonization, and outgrowth in distant organs. Specifically, metabolites can activate protein kinases as well as receptors and they are crucial substrates for posttranslational modifications on histone and nonhistone proteins. Moreover, metabolic enzymes can have moonlighting functions by acting catalytically, mainly as protein kinases, or noncatalytically through protein-protein interactions. Here, we summarize the current knowledge on metabolic signaling in cancer metastasis.

SIGNIFICANCE

Effective drugs for the prevention and treatment of metastases will have an immediate impact on patient survival. To overcome the current lack of such drugs, a better understanding of the molecular processes that are an Achilles heel in metastasizing cancer cells is needed. One emerging opportunity is the metabolic changes cancer cells need to undergo to successfully metastasize and grow in distant organs. Mechanistically, these metabolic changes not only fulfill energy and biomass demands, which are often in common between cancer and normal but fast proliferating cells, but also metabolic signaling which enables the cell state changes that are particularly important for the metastasizing cancer cells.

Regulation of sialic acid metabolism in cancer

Sialic acid, the terminal structure of cell surface glycans, has essential functions in regulating immune response, cell-to-cell communication, and cell adhesion. More importantly, an increased level of sialic acid, termed hypersialylation, has emerged as a commonly observed phenotype in cancer. Therefore, targeting sialic acid ligands (sialoglycans) and their receptors (Siglecs) may provide a new therapeutic approach for cancer immunotherapy. We highlight the complexity of the sialic acid metabolism and its involvement in malignant transformation within individual cancer subtypes. In this review, we focus on the dysregulation of sialylation, the intricate nature of sialic acid synthesis, and clinical perspective. We aim to provide a brief insight into the mechanism of hypersialylation and how our understanding of these processes can be leveraged for the development of novel therapeutics.

Bioinformatic Analysis of Gene Expression Related to Sialic Acid Biosynthesis in Patients With Medulloblastoma

Background Sialic acid, a critical component for cell membrane integrity, undergoes complex biosynthesis involving enzymes like sialyltransferases (STs), impacting cancer progression. Aberrant sialylation by STs is implicated in cancer growth, invasion, and therapy resistance. Medulloblastoma (MB), a pediatric brain tumor with distinct subgroups and variable genetic alterations, poses uncertainty regarding the implications of sialylation. Methodology This study employs bioinformatic analyses on bulk and single-cell RNA-sequenced samples to explore atypical gene expressions linked to sialic acid metabolism in MB. A list of sialic biosynthesis-related genes was compiled using the STRING database. Data of MB samples from bulk and single-cell RNA sequencing were obtained from open-source repositories and were differentially analyzed, focusing on molecular subgroups (WNT, SHH, Group 3, and Group 4). The study employed survival analyses, specifically Cox regression, to analyze the overall survival (OS) data obtained through bulk RNA sequencing. Results Thirty-eight genes/proteins related to sialic acid metabolism were identified. Differential expression analysis between WNT and Group 3 and WNT and Group 4 revealed significant differences in seven and eleven genes, respectively, with consistent ST6GAL2 expression disparities (false discovery rate [FDR] P-value < 0.01, log2FC > 0.58). Elevated ST6GAL2 expression correlated with improved OS, with mortality risk reductions ranging from 26% to 48% (P-value < 0.006, Bonferroni-corrected threshold). Conclusions Elevated ST6GAL2 expression correlated with improved OS in diverse MB sample subsets, suggesting potential mechanisms in inhibiting tumor progression and enhancing immune response, requiring experimental validation.

Negative Charge-Carrying Glycans Attached to Exosomes as Novel Liquid Biopsy Marker

Prostate cancer (PCa) is the second most common cancer. In this paper, the isolation and properties of exosomes as potential novel liquid biopsy markers for early PCa liquid biopsy diagnosis are investigated using two prostate human cell lines, i.e., benign (control) cell line RWPE1 and carcinoma cell line 22Rv1. Exosomes produced by both cell lines are characterised by various methods including nanoparticle-tracking analysis, dynamic light scattering, scanning electron microscopy and atomic force microscopy. In addition, surface plasmon resonance (SPR) is used to study three different receptors on the exosomal surface (CD63, CD81 and prostate-specific membrane antigen-PMSA), implementing monoclonal antibodies and identifying the type of glycans present on the surface of exosomes using lectins (glycan-recognising proteins). Electrochemical analysis is used to understand the interfacial properties of exosomes. The results indicate that cancerous exosomes are smaller, are produced at higher concentrations, and exhibit more nega tive zeta potential than the control exosomes. The SPR experiments confirm that negatively charged α-2,3- and α-2,6-sialic acid-containing glycans are found in greater abundance on carcinoma exosomes, whereas bisecting and branched glycans are more abundant in the control exosomes. The SPR results also show that a sandwich antibody/exosomes/lectins configuration could be constructed for effective glycoprofiling of exosomes as a novel liquid biopsy marker.

Functions of Sialyltransferases in gynecological malignancies: A systematic review

INTRODUCTION

The biosynthesis of tumor-associated sialoglycans involves Sialyltransferases expressed in cancer cells differentially. The current review aspires to bridge the existing knowledge gaps by consolidating evidence regarding the role of Sialyltransferases in gynecological malignant tumors (ovarian, cervix, endometrial, and breast).

METHODS

In this systematic review, we searched databases, including PubMed, Embase, Web of Science, Scopus and Cochrane Library. Twenty-two high-quality articles were selected out of 559 researched studies using radiomics quality score (RQS) tools.

RESULTS

Our findings indicated that 7 articles were related to Sialyltransferases in ovarian cancer, in which 6 studies was examined only ST6Gal-I and one study examined the ST3Gal-I, ST3Gal-II, ST3Gal-III, ST3Gal-IV, ST3Gal-VI, and ST3Gal-6. In addition, 5 articles were related to Sialyltransferases in cervix cancer (ST6Gal-I), 3 articles to endometrial cancer (ST6Gal-I, ST3Gal-III, ST3Gal-IV, and ST3Gal-6), and 7 articles to breast cancer (ST6Gal-I gene in 5 studies, ST6GAL-II gene in one study, and ST8SIA1 and ST3GAL-V genes in one study).

CONCLUSION

ST6Gal-I gene expression occurs at a high speed in ovarian, cervix, endometrial, and breast cancers, leading to metastasis to distant cells, cell destruction, cell invasion, and reduced patient survival.