O-linked mucin-type glycosylation regulates the transcriptional programme downstream of EGFR

ST3GAL1 promotes malignant phenotypes in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) has poor prognosis and elucidation of the molecular mechanisms underlying iCCA malignancy is of great significance. Glycosylation, an important post-translational modification, is closely associated with tumor progression. Altered glycosylation, including aberrant sialylation resulting from abnormal expression of sialyltransferases (STs) and neuraminidases (NEUs), is a significant feature of cancer cells. However, there is limited information on the roles of STs and NEUs in iCCA malignancy. Here, utilizing our proteogenomic resources from a cohort of 262 iCCA patients, we identified ST3GAL1 as a prognostically relevant molecule in iCCA. Moreover, overexpression of ST3GAL1 promoted proliferation, migration and invasion and inhibited apoptosis of iCCA cells in vitro. Through proteomic analyses, we identified the downstream pathway potentially regulated by ST3GAL1, which was the NF-κB signaling pathway and further demonstrated that this pathway was positively correlated with malignancy in iCCA cells. Notably, glycoproteomics showed that O-glycosylation was changed in iCCA cells with high ST3GAL1 expression. Importantly, the altered O-glycopeptides underscored the potential utility of O-glycosylation profiling as a discriminatory marker for iCCA cells with ST3GAL1 overexpression. Additionally, miR-320b was identified as a post-transcriptional regulator of ST3GAL1, capable of suppressing ST3GAL1 expression and then reducing the proliferation, migration and invasion abilities of iCCA cell lines. Taken together, these results suggest ST3GAL1 could serve as a promising therapeutic target for iCCA.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

C1GALT1 induces the carcinogenesis of thyroid cancer through regulation by miR-141-3p and GLUT1

Core 1 β 1,3-galactosyltransferase 1 (C1GALT1) acts as an important glycosyltransferase in the occurrence and development of tumor glycosylation. However, the regulatory mechanisms of C1GALT1 in thyroid cancer (TC) is still unclear. In this study, we discovered that the expression level of C1GALT1 was significantly increased in thyroid adenocarcinoma tissues and cell lines (p < 0.01). Meanwhile, gene silencing of C1GALT1 inhibited the proliferation (CCK-8 assay), migration (wound healing), and invasion (Transwell) of TC cells (p < 0.05). Further investigation indicated that miR-141-3p had a negative correlation with C1GALT1 and suppressed cancer carcinogenesis in TC cells. Moreover, we first found that glucose transporter 1 (GLUT1) was a downstream element of C1GALT1 and was positively correlated with C1GALT1 levels in TC. The GLUT1 could reverse the inhibitory effects of siRNA C1GALT1 on cell development (p < 0.05). These data suggest that the miR-141-3p/C1GALT1/GLUT1 axis plays an essential role during TC progression and may be a probable biomarker or therapeutic target for thyroid cancer patients.

Tumor-associated carbohydrate antigens of MUC1 - Implication in cancer development

Glycosylation of cancerous epithelial MUC1 protein is specifically altered in comparison to that which is presented by healthy cells. One of such changes is appearing tumor-associated carbohydrate antigens (TACAs) which are rare in normal tissues and are highly correlated with poor clinical outcomes and cancer progression. This review summarizes and describes the role of Tn, T antigens, their sialylated forms as well as fucosylated Lewis epitopes in different aspects of tumor development, progression, and metastasis. Finally, applications of MUC1 glycan epitopes as potential targets for therapeutic strategy of cancers are notified. One of the novelties of this review is presentation of TACAs as inherently connected with MUC1 mucin.

A high heterozygosity genome assembly of Aedes albopictus enables the discovery of the association of PGANT3 with blood-feeding behavior

The Asian tiger mosquito, Aedes albopictus, is a global invasive species, notorious for its role in transmitting dangerous human arboviruses such as dengue and Chikungunya. Although hematophagous behavior is repulsive, it is an effective strategy for mosquitoes like Aedes albopictus to transmit viruses, posing a significant risk to human health. However, the fragmented nature of the Ae. albopictus genome assembly has been a significant challenge, hindering in-depth biological and genetic studies of this mosquito. In this research, we have harnessed a variety of technologies and implemented a novel strategy to create a significantly improved genome assembly for Ae. albopictus, designated as AealbF3. This assembly boasts a completeness rate of up to 98.1%, and the duplication rate has been minimized to 1.2%. Furthermore, the fragmented contigs or scaffolds of AealbF3 have been organized into three distinct chromosomes, an arrangement corroborated through syntenic plot analysis, which compared the genetic structure of Ae. albopictus with that of Ae. aegypti. Additionally, the study has revealed a phylogenetic relationship suggesting that the PGANT3 gene is implicated in the hematophagous behavior of Ae. albopictus. This involvement was preliminarily substantiated through RNA interference (RNAi) techniques and behavioral experiment. In summary, the AealbF3 genome assembly will facilitate new biological insights and intervention strategies for combating this formidable vector of disease. The innovative assembly process employed in this study could also serve as a valuable template for the assembly of genomes in other insects characterized by high levels of heterozygosity.

Mutation of SOCS2 induces structural and functional changes in mammary development

Lactation is an essential process for mammals. In sheep, the R96C mutation in suppressor of cytokine signaling 2 (SOCS2) protein is associated with greater milk production and increased mastitis sensitivity. To shed light on the involvement of R96C mutation in mammary gland development and lactation, we developed a mouse model carrying this mutation (SOCS2KI/KI). Mammary glands from virgin adult SOCS2KI/KI mice presented a branching defect and less epithelial tissue, which were not compensated for in later stages of mammary development. Mammary epithelial cell (MEC) subpopulations were modified, with mutated mice having three times as many basal cells, accompanied by a decrease in luminal cells. The SOCS2KI/KI mammary gland remained functional; however, MECs contained more lipid droplets versus fat globules, and milk lipid composition was modified. Moreover, the gene expression dynamic from virgin to pregnancy state resulted in the identification of about 3000 differentially expressed genes specific to SOCS2KI/KI or control mice. Our results show that SOCS2 is important for mammary gland development and milk production. In the long term, this finding raises the possibility of ensuring adequate milk production without compromising animal health and welfare.

Cisplatin induces acute kidney injury by downregulating miR-30e-5p that targets Galnt3 to activate the AMPK signaling pathway

Cisplatin nephrotoxicity is an etiological factor for acute kidney injury (AKI). MicroRNA (miRNA) expression is dysregulated in cisplatin-induced AKI (cAKI) although the underlying mechanisms are unclear. A cAKI model was established by intraperitoneally injecting cisplatin, and key miRNAs were screened using high-throughput miRNA sequencing. The functions of key miRNAs were determined using the cell viability, live/dead, reactive oxygen species (ROS), and 5-ethynyl-2'-deoxyuridine (EdU) proliferation assays. Additionally, the macrophage membrane was wrapped around a metal-organic framework (MOF) loaded with miRNA agomir to develop a novel composite material, macrophage/MOF/miRNA agomir nanoparticles (MMA NPs). High-throughput miRNA sequencing revealed that miR-30e-5p is a key miRNA that is downregulated in cAKI. The results of in vitro experiments demonstrated that miR-30e-5p overexpression partially suppressed the cisplatin-induced or lipopolysaccharide (LPS)-induced downregulation of cell viability, proliferation, upregulation of ROS production, and cell death. Meanwhile, the results of in vivo and in vitro experiments demonstrated that MMA NPs alleviated cAKI by exerting anti-inflammatory effects. Mechanistically, cisplatin downregulates the expression of miR-30e-5p, and the downregulated miR-30e-5p can target Galnt3 to activate the adenosine 5'-monophosphate activated protein kinase (AMPK) signaling pathway, which promotes the progression of AKI. Our study found that miR-30e-5p is a key downregulated miRNA in cAKI. The downregulated miR-30e-5p promotes AKI progression by targeting Galnt3 to activate the AMPK signaling pathway. The newly developed MMA NPs were found to have protective effects on cAKI, suggesting a potential novel strategy for preventing cAKI.

Truncated O-glycosylation in metastatic triple-negative breast cancer reveals a gene expression signature associated with extracellular matrix and proteolysis

Breast cancer (BC) is the leading cause of death by cancer in women worldwide. Triple-negative (TN) BC constitutes aggressive and highly metastatic tumors associated with shorter overall survival of patients compared to other BC subtypes. The Tn antigen, a glycoconjugated structure resulting from an incomplete O-glycosylation process, is highly expressed in different adenocarcinomas, including BC. It also favors cancer growth, immunoregulation, and metastasis in TNBC. This work describes the differentially expressed genes (DEGs) associated with BC aggressiveness and metastasis in an incomplete O-glycosylated TNBC cell model. We studied the transcriptome of a TNBC model constituted by the metastatic murine 4T1 cell line that overexpresses the Tn antigen due to a mutation in one of the steps of the O-glycosylation pathway. We analyzed and compared the results with the parental wild-type cell line and with a Tn-negative cell clone that was poorly metastatic and less aggressive than the 4T1 parental cell line. To gain insight into the generated expression data, we performed a gene set analysis. Biological processes associated with cancer development and metastasis, immune evasion, and leukocyte recruitment were highly enriched among functional terms of DEGs. Furthermore, different highly O-glycosylated protein-coding genes, such as mmp9, ecm1 and ankyrin-2, were upregulated in 4T1/Tn+ tumor cells. The altered biological processes and DEGs that promote tumor growth, invasion and immunomodulation might explain the aggressive properties of 4T1/Tn+ tumor cells. These results support the hypothesis that incomplete O-glycosylation that leads to the expression of the Tn antigen, which might regulate activity or interaction of different molecules, promotes cancer development and immunoregulation.

Predicting drug response from single-cell expression profiles of tumours

BACKGROUND

Intra-tumour heterogeneity (ITH) presents a significant obstacle in formulating effective treatment strategies in clinical practice. Single-cell RNA sequencing (scRNA-seq) has evolved as a powerful instrument for probing ITH at the transcriptional level, offering an unparalleled opportunity for therapeutic intervention.

RESULTS

Drug response prediction at the single-cell level is an emerging field of research that aims to improve the efficacy and precision of cancer treatments. Here, we introduce DREEP (Drug Response Estimation from single-cell Expression Profiles), a computational method that leverages publicly available pharmacogenomic screens from GDSC2, CTRP2, and PRISM and functional enrichment analysis to predict single-cell drug sensitivity from transcriptomic data. We validated DREEP extensively in vitro using several independent single-cell datasets with over 200 cancer cell lines and showed its accuracy and robustness. Additionally, we also applied DREEP to molecularly barcoded breast cancer cells and identified drugs that can selectively target specific cell populations.

CONCLUSIONS

DREEP provides an in silico framework to prioritize drugs from single-cell transcriptional profiles of tumours and thus helps in designing personalized treatment strategies and accelerating drug repurposing studies. DREEP is available at https://github.com/gambalab/DREEP .

Polypeptide N-acetylgalactosaminyltransferase (GalNAc-T) isozyme surface charge governs charge substrate preferences to modulate mucin type O-glycosylation

A large family of polypeptide N-acetylgalactosaminyltransferases (GalNAc-Ts) initiate mucin type O-glycosylation transferring α-GalNAc from a UDP-GalNAc donor to the hydroxyl groups of Ser and Thr residues of peptides and proteins, thereby defining sites of O-glycosylation. Mutations and differential expression of several GalNAc-Ts are associated with many disease states including cancers. The mechanisms by which these isozymes choose their targets and their roles in disease are not fully understood. We previously showed that the GalNAc-Ts possess common and unique specificities for acceptor type, peptide sequence and prior neighboring, and/or remote substrate GalNAc glycosylation. In the present study, the role of flanking charged residues was investigated using a library of charged peptide substrates containing the central -YAVTPGP- acceptor sequence. Eleven human and one bird GalNAc-T were initially characterized revealing a range of preferences for net positive, net negative, or unique combinations of flanking N- and/or C-terminal charge, correlating to each isozyme's different electrostatic surface potential. It was further found that isoforms with high sequence identity (>70%) within a subfamily can possess vastly different charge specificities. Enzyme kinetics, activities obtained at elevated ionic strength, and molecular dynamics simulations confirm that the GalNAc-Ts differently recognize substrate charge outside the common +/-3 residue binding site. These electrostatic interactions impact how charged peptide substrates bind/orient on the transferase surface, thus modulating their activities. In summary, we show the GalNAc-Ts utilize more extended surfaces than initially thought for binding substrates based on electrostatic, and likely other hydrophobic/hydrophilic interactions, furthering our understanding of how these transferases select their target.

The sialyl-Tn antigen synthase genes regulates migration-proliferation dichotomy in prostate cancer cells under hypoxia

A low-oxygen (hypoxia) tumor microenvironment can facilitate chemotherapy and radiation therapy resistance in tumors and is associated with a poor prognosis. Hypoxia also affects PCa (prostate cancer) phenotype transformation and causes therapeutic resistance. Although O-glycans are known to be involved in the malignancy of various cancers under hypoxia, the expression and function of O-glycans in PCa are not well understood. In this study, the saccharide primer method was employed to analyze O-glycan expression in PCa cells. Results showed that the expression of sTn antigens was increased in PCa cells under hypoxia. Furthermore, it was found that ST6GalNAc1, the sTn antigen synthase gene, was involved in the migration-proliferation dichotomy and drug resistance in PCa cells under hypoxia. The results of this study will contribute to the development of novel diagnostic markers and drug targets for PCa under hypoxia.

GALNT3 protects against vascular calcification by reducing oxidative stress and apoptosis of smooth muscle cells

Vascular calcification (VC) is the pathological deposition of calcium and phosphate minerals in blood vessels, which is a common complication of atherosclerosis. Polypeptide N-acetylgalactosamine transferase 3 (GALNT3) initiates O-glycosylation of proteins through addition of GalNAc to specific serine or threonine residues. Our previous studies revealed the potent role of GALNT3 in atherosclerosis, whereas the precise mechanisms remain obscure. This study investigated the regulatory effect and mechanism of GALNT3 on VC. Firstly, GALNT3 was overexpressed and knocked down by adenovirus in high-phosphate induced calcified HASMCs and overexpressed by adeno-associated virus in vitamin D3-induced arterial calcification mice. We showed that the calcium deposition and mRNA expression of osteogenic markers MSX2, ALPL, and Runx2 were all significantly reduced with GALNT3 overexpression. Moreover, overexpression of GALNT3 significantly down-regulated the expression of the oxidative stress markers Nox2 and Nox4, up-regulated total antioxidant capacity, decreased the expression of pro-inflammatory factors IL-1β, TNF-α and IL-8, matrix metalloproteinases MMP2 and MMP9, as well as reduced the apoptosis of cells in phosphate induced HASMCs. Furthermore, Vicia Villosa Lectin (VVL) pull down and TNFR1 immunoprecipitation assays showed that GALNT3 overexpression increased O-GalNAcylation of TNFR1 and blocked the activation of NF-κB signaling pathway. In addition, GALNT3 attenuates vitamin D3-induced aortic calcification in mice by alleviating oxidative stress and apoptosis of smooth muscle cells. In conclusion, this study indicates that GALNT3 protects against VC by reducing oxidative stress, vascular inflammation, and apoptosis of smooth muscle cells through the TNFR1/NF-κB signaling pathway. Thus, GALNT3 may be a potential therapeutic target for VC.

Recent advances in the use of legume lectins for the diagnosis and treatment of breast cancer

Poor lifestyle choices and genetic predisposition are factors that increase the number of cancer cases, one example being breast cancer, the third most diagnosed type of malignancy. Currently, there is a demand for the development of new strategies to ensure early detection and treatment options that could contribute to the complete remission of breast tumors, which could lead to increased overall survival rates. In this context, the glycans observed at the surface of cancer cells are presented as efficient tumor cell markers. These carbohydrate structures can be recognized by lectins which can act as decoders of the glycocode. The application of plant lectins as tools for diagnosis/treatment of breast cancer encompasses the detection and sorting of glycans found in healthy and malignant cells. Here, we present an overview of the most recent studies in this field, demonstrating the potential of lectins as: mapping agents to detect differentially expressed glycans in breast cancer, as histochemistry/cytochemistry analysis agents, in lectin arrays, immobilized in chromatographic matrices, in drug delivery, and as biosensing agents. In addition, we describe lectins that present antiproliferative effects by themselves and/or in conjunction with other drugs in a synergistic effect.

A single-cell analysis of breast cancer cell lines to study tumour heterogeneity and drug response

Cancer cells within a tumour have heterogeneous phenotypes and exhibit dynamic plasticity. How to evaluate such heterogeneity and its impact on outcome and drug response is still unclear. Here, we transcriptionally profile 35,276 individual cells from 32 breast cancer cell lines to yield a single cell atlas. We find high degree of heterogeneity in the expression of biomarkers. We then train a deconvolution algorithm on the atlas to determine cell line composition from bulk gene expression profiles of tumour biopsies, thus enabling cell line-based patient stratification. Finally, we link results from large-scale in vitro drug screening in cell lines to the single cell data to computationally predict drug responses starting from single-cell profiles. We find that transcriptional heterogeneity enables cells with differential drug sensitivity to co-exist in the same population. Our work provides a framework to determine tumour heterogeneity in terms of cell line composition and drug response.

Altered glycosylation of several metastasis-associated glycoproteins with terminal GalNAc defines the highly invasive cancer cell phenotype

Several distinct metastasis-associated glycosylation changes have been shown to promote cancer cell invasion and metastasis, the main cause of death of cancer patients. However, it is unclear whether their presence reflects cell- or tissue-specific variations for metastasis, or species needed to drive different phases of the metastatic cascade. To address this issue from a different perspective, we investigated here whether different cancer cell lines share any glycotopes that are common and important for their invasive phenotype. By using lectin microarray glycan profiling and an established myoma tissue-based 3D invasion assay, we identified a single glycotope recognized by Helix Pomatia agglutinin (HPA), whose expression level in different cancer cells correlated significantly with their invasive potential. Lectin pull-down assay and LC-MS/MS analysis in highly- (A431 and SW-48) and poorly invasive (HepG2 and RCC4) cancer cells revealed ~85 glycoproteins of which several metastasis-promoting members of the integrin family of cell adhesion receptors, the epidermal growth factor receptor (EGFR) and the matrix metalloproteinase-14 (MMP-14) were among the abundant ones. Moreover, we showed that the level of the GalNAc glycotope in MMP-14, EGFR, αV-, β1- and β4 integrin in highly and poorly invasive cancer cells correlated positively with their invasive potential. Collectively, our findings suggest that altered glycosylation of several metastasis-associated glycoproteins with terminal GalNAc drives the highly invasive cancer cell phenotype.

Breast cancer glycan biomarkers: their link to tumour cell metabolism and their perspectives in clinical practice

INTRODUCTION

Breast cancer (BCa) is the most common cancer type diagnosed in women and 5^th most common cause of deaths among all cancer deaths despite the fact that screening program is at place. This is why novel diagnostics approaches are needed in order to decrease number of BCa cases and disease mortality.

AREAS COVERED

In this review paper, we aim to cover some basic aspects regarding cellular metabolism and signalling in BCa behind altered glycosylation. We also discuss novel exciting discoveries regarding glycan-based analysis, which can provide useful information for better understanding of the disease. The final part deals with clinical usefulness of glycan-based biomarkers and the clinical performance of such biomarkers is compared to already approved BCa biomarkers and diagnostic tools based on imaging.

EXPERT OPINION

Recent discoveries suggest that glycan-based biomarkers offer high accuracy for possible BCa diagnostics in blood, but also for better monitoring and management of BCa patients. The review article was written using Web of Science search engine to include articles published between 2019 and 2021.

Role of Glycosylation in Vascular Calcification

Glycosylation is an important step in post-translational protein modification. Altered glycosylation results in an abnormality that causes diseases such as malignancy and cardiovascular diseases. Recent emerging evidence highlights the importance of glycosylation in vascular calcification. Two major types of glycosylation, N-glycosylation and O-glycosylation, are involved in vascular calcification. Other glycosylation mechanisms, which polymerize the glycosaminoglycan (GAG) chain onto protein, resulting in proteoglycan (PG), also have an impact on vascular calcification. This paper discusses the role of glycosylation in vascular calcification.

The protective effect and mechanism of epidermal growth factor on necrotizing enterocolitis in a neonatal rat model

BACKGROUND

Necrotizing enterocolitis (NEC) is the most common acquired gastrointestinal emergency in premature infants. This study aimed to investigate the protective effect and mechanism of epidermal growth factor (EGF) on NEC in a neonatal rat model.

METHODS

We randomly divided 50 newborn SD rats into a control group, NEC group, NEC + 50 ng/mL EGF group, NEC + 500 ng/mL EGF group, and NEC + 1,000 ng/mL EGF group, with 10 cases in each group. The appearance of intestinal tissue, physiological status score, inflammatory factor level, HE staining, and pathological score were used to evaluate the protective effect. A one cm tissue sample from the proximal ileum of the ileocecal area of five rats from the NEC group and the group that showed a significant protective effect were extracted for transcriptome sequencing.

RESULTS

The levels of IL-1β and IL-6 in the intestinal mucosa in the NEC + 500 ng/mL EGF group were significantly lower than those in the NEC + 1,000 ng/mL EGF group (P<0.05). Transcriptome sequencing suggested that EGF effects the intestinal barrier, apoptosis, and inflammation of the NEC intestine.

CONCLUSIONS

We conclude that the oral administration of 500 ng/mL EGF effectively inhibits intestinal inflammation in NEC neonatal rat models, thereby affecting the barrier function of the intestinal tract.

Cracking the Breast Cancer Glyco-Code through Glycan-Lectin Interactions: Targeting Immunosuppressive Macrophages

The immune microenvironment of breast cancer (BC) is composed by high macrophage infiltrates, correlated with the most aggressive subtypes. Tumour-associated macrophages (TAM) within the BC microenvironment are key regulators of immune suppression and BC progression. Nevertheless, several key questions regarding TAM polarisation by BC are still not fully understood. Recently, the modulation of the immune microenvironment has been described via the recognition of abnormal glycosylation patterns at BC cell surface. These patterns rise as a resource to identify potential targets on TAM in the BC context, leading to the development of novel immunotherapies. Herein, we will summarize recent studies describing advances in identifying altered glycan structures in BC cells. We will focus on BC-specific glycosylation patterns known to modulate the phenotype and function of macrophages recruited to the tumour site, such as structures with sialylated or N-acetylgalactosamine epitopes. Moreover, the lectins present at the surface of macrophages reported to bind to such antigens, inducing tumour-prone TAM phenotypes, will also be highlighted. Finally, we will discuss and give our view on the potential and current challenges of targeting these glycan-lectin interactions to reshape the immunosuppressive landscape of BC.

Glycoproteogenomics: Setting the Course for Next-generation Cancer Neoantigen Discovery for Cancer Vaccines

Molecular-assisted precision oncology gained tremendous ground with high-throughput next-generation sequencing (NGS), supported by robust bioinformatics. The quest for genomics-based cancer medicine set the foundations for improved patient stratification, while unveiling a wide array of neoantigens for immunotherapy. Upfront pre-clinical and clinical studies have successfully used tumor-specific peptides in vaccines with minimal off-target effects. However, the low mutational burden presented by many lesions challenges the generalization of these solutions, requiring the diversification of neoantigen sources. Oncoproteogenomics utilizing customized databases for protein annotation by mass spectrometry (MS) is a powerful tool toward this end. Expanding the concept toward exploring proteoforms originated from post-translational modifications (PTMs) will be decisive to improve molecular subtyping and provide potentially targetable functional nodes with increased cancer specificity. Walking through the path of systems biology, we highlight that alterations in protein glycosylation at the cell surface not only have functional impact on cancer progression and dissemination but also originate unique molecular fingerprints for targeted therapeutics. Moreover, we discuss the outstanding challenges required to accommodate glycoproteomics in oncoproteogenomics platforms. We envisage that such rationale may flag a rather neglected research field, generating novel paradigms for precision oncology and immunotherapy.

Cancer-associated hypersialylated MUC1 drives the differentiation of human monocytes into macrophages with a pathogenic phenotype

The tumour microenvironment plays a crucial role in the growth and progression of cancer, and the presence of tumour-associated macrophages (TAMs) is associated with poor prognosis. Recent studies have demonstrated that TAMs display transcriptomic, phenotypic, functional and geographical diversity. Here we show that a sialylated tumour-associated glycoform of the mucin MUC1, MUC1-ST, through the engagement of Siglec-9 can specifically and independently induce the differentiation of monocytes into TAMs with a unique phenotype that to the best of our knowledge has not previously been described. These TAMs can recruit and prolong the lifespan of neutrophils, inhibit the function of T cells, degrade basement membrane allowing for invasion, are inefficient at phagocytosis, and can induce plasma clotting. This macrophage phenotype is enriched in the stroma at the edge of breast cancer nests and their presence is associated with poor prognosis in breast cancer patients.

Beatson et al. show that a sialylated tumour-associated glycoform of the mucin MUC1 induces the differentiation of monocytes into tumour-associated macrophages. These macrophages are found in breast cancer stroma and their presence is associated with poor prognosis.

Determination of the glycoprotein specificity of lectins on cell membranes through oxidative proteomics

The cell membrane is composed of a network of glycoconjugates including glycoproteins and glycolipids that presents a dense matrix of carbohydrates playing critical roles in many biological processes. Lectin-based technology has been widely used to characterize glycoconjugates in tissues and cell lines. However, their specificity toward their putative glycan ligand and sensitivity in situ have been technologically difficult to study. Additionally, because they recognize primarily glycans, the underlying glycoprotein targets are generally not known. In this study, we employed lectin proximity oxidative labeling (Lectin PROXL) to identify cell surface glycoproteins that contain glycans that are recognized by lectins. Commonly used lectins were modified with a probe to produce hydroxide radicals in the proximity of the labeled lectins. The underlying polypeptides of the glycoproteins recognized by the lectins are oxidized and identified by the standard proteomic workflow. As a result, approximately 70% of identified glycoproteins were oxidized in situ by all the lectin probes, while only 5% of the total proteins were oxidized. The correlation between the glycosites and oxidation sites demonstrated the effectiveness of the lectin probes. The specificity and sensitivity of each lectin were determined using site-specific glycan information obtained through glycomic and glycoproteomic analyses. Notably, the sialic acid-binding lectins and the fucose-binding lectins had higher specificity and sensitivity compared to other lectins, while those that were specific to high mannose glycans have poor sensitivity and specificity. This method offers an unprecedented view of the interactions of lectins with specific glycoproteins as well as protein networks that are mediated by specific glycan types on cell membranes.