Mucins: Structural diversity, biosynthesis, its role in pathogenesis and as possible therapeutic targets

Inhalable lipid-based nanocarriers covered by polydopamine for effective mucus penetration and pulmonary retention

To overcome the critical challenge in drug inhalation for pulmonary diseases, we innovatively proposed that polydopamine (PDA) as a surface modification material had great potential to improve the mucus permeation and pulmonary retention of inhalable lipid-based nanocarriers. We prepared PDA coated lipid nanoemulsions/solid lipid nanoparticles/liposomes and systematically evaluated their interactions with mucin and pulmonary retention after inhalation. PDA-coated lipid-based nanocarriers exhibited weaker interactions with mucins, higher mucus permeability and cellular uptake by the respiratory epithelium cells compared to PEGylated lipid-based nanocarriers. However, the pulmonary retention advantage of PDA coating was shown in lipid nanoemulsions (< 50 nm) and solid lipid nanoparticles (< 100 nm). Liposomes (∼ 150 nm) with PEGylation possessed higher pulmonary retention than that coated by PDA. It was suggested that PEGylated liposomes were liable to be phagocytosed by alveolar macrophages due to binding with specific antibodies. Overall, this work suggests that PDA as a surface modification material of inhalable lipid-based nanocarriers holds promise for effective mucus penetration and pulmonary retention.

Unveiling the role of poly(vinyl alcohol) in the production of mucus-penetrating PLGA nanoparticles

Mucosal drug delivery offers a promising non-invasive approach in pharmaceutical sciences but faces challenges from the protective mucus layer on mucosal surfaces, limiting drug absorption. Polymeric nanoparticles (NPs) have emerged as effective carriers, leveraging their small size to enhance mucus penetration and drug absorption. This study investigates polyvinyl alcohol (PVA)'s role in enhancing poly(lactic-co-glycolic acid) (PLGA) NPs for mucosal drug delivery. While PVA is commonly used as an emulsion stabilizer, its impact on NP mucoadhesiveness and mucodiffusivity is often overlooked. We characterized PLGA-based NPs with varying PVA types, employing particle tracking and molecular dynamics to demonstrate PVA's direct interaction with mucin MUC 5B. Our findings show reduced interaction with lower PVA hydrolysis, with particle tracking confirming PVA properties influence mucoadhesion. This study underscores PVA's critical role in optimizing NP efficacy for mucosal drug delivery, offering insights for developing more effective drug delivery systems.

In vitro pharmacokinetic/pharmacodynamic modeling of the effect of mucin on polymyxin B activity against Acinetobacter baumannii

The antibacterial efficacy of polymyxins in lungs may be impacted by mucin. The aim of this study was to characterize in vitro the effect of mucin on polymyxin B (PMB) activity against two multidrug-resistant Acinetobacter baumannii strains isolated from a patient before (AB121-D0) and after colistin treatment (AB122-D12), using a pharmacokinetic/pharmacodynamic (PK/PD) modeling approach. PMB binding to mucin was characterized by ultracentrifugation in cation-adjusted Mueller-Hinton broth (CAMHB) supplemented with 1% mucin. Time-kill (TK) experiments were performed in CAMHB, with 1% mucin or without as control, and with PMB total concentrations ranging from 0.25 to 512 mg/L based on the strain's minimum inhibitory concentration (MIC). For each strain, TK data were modeled based on unbound PMB concentrations. Bacterial resistance to PMB was investigated via MIC and whole genome sequencing from bacteria that regrew in the presence of antibiotics at the end of the TK experiments. PMB unbound fraction increased nonlinearly from 6% to 60% when total concentration increased from 0.5 to 512 mg/L. In addition to binding to PMB, mucin had an impact on PMB activity, which differed between the two strains. For AB121-D0, PMB activity increased in the presence of mucin resulting in a reduction of the bacterial regrowth, whereas for AB122-D12, a decrease in PMB activity was observed. Mutations in genes involved in PMB resistance appeared randomly and explained only partially the bacterial regrowth observed in TK with antibiotics. This study showed that PMB binding to mucin had a real and important impact but was not the only factor explaining the impaired PMB efficacy in the presence of mucin.

Harnessing Helix aspersa mucins as an innovative gelling agent for the synthesis of Punica granatum peel extract-loaded chitosan nanoparticles (CSNPs-M) with enhanced biological properties

Valorizing natural waste materials is crucial for sustainable biomedical innovation. This study explores a nanomedicine approach using waste from shrimp shells, pomegranate peels, and snail mucus to produce mucin-stabilized chitosan nanoparticles (CSNPs-M) as delivery systems for Punica granatum peel extract (PgPE). Chitosan was derived from shrimp shells, while mucins from Helix aspersa snail slime served as a bio-stabilizer and crosslinking agent, creating CSNPs-M through an eco-friendly synthesis. Characterization confirmed CSNPs-M are spherical (54-98 nm) with a zeta potential of -35.5 mV. The encapsulation efficiency is about 79 %, indicating effective loading of the Punica granatum peel extract within the CSNPs-M nanoparticles. Antioxidant capacity, tested by ABTS scavenging activity, showed that CSNPs-M achieved 89 % inhibition, close to free PgPE (93 %), indicating preserved extract activity. CSNPs-M also exhibited antimicrobial activity against several bacteria and fungi. The antiproliferative activity was evaluated by monitoring cell growth after 24, 48, and 72 h of incubation with CSNPs-M in human colon adenocarcinoma cells (Caco-2), showing that CSNPs-M at a 1: 50 dilution significantly reduced cell proliferation (p 〈0,0001) without any cytotoxic effects. This study addresses a critical need for eco-friendly nanocarriers with preserved bioactivity, presenting CSNPs-M as a promising platform for delivering therapeutic compounds in biomedical applications.

Synergistic effects of Candida albicans and Porphyromonas gingivalis biofilms on epithelial barrier function in a 3D aspiration pneumonia model

Introduction

Polymicrobial infections involving Candida albicans and Porphyromonas gingivalis represent a significant challenge in maintaining epithelial barrier integrity. This study explores their synergistic effects on epithelial cells using an air-liquid interface (ALI) model.

Methods

Mixed-species biofilms were developed and analyzed for their impact on epithelial permeability and tight junction proteins. The effects of biofilm supernatants on IL-8 secretion and oxidative stress markers were also evaluated. The role of P. gingivalis proteases was assessed using a gingipain-null mutant (ΔKΔRAB) compared to the wild-type strain (W83). Survival experiments were conducted using Galleria mellonella larvae to examine the pathogenicity of dual-species biofilms.

Results

Mixed-species biofilms significantly increased epithelial permeability and disrupted tight junction proteins, as evidenced by reduced levels of ZO-1 and E-cadherin. These changes were accompanied by oxidative stress, characterized by decreased HO-1 expression and enhanced Bax/Bcl-xL ratios, indicating increased pro-apoptotic activity. Supernatants from dual-species biofilms demonstrated a pronounced effect on epithelial cells, modulating IL-8 secretion and exacerbating oxidative damage. C. albicans was identified as the dominant driver of pro-inflammatory responses, while P. gingivalis contributed through immune modulation and enzymatic activity, primarily via gingipains. The ΔKΔRAB mutant biofilms caused less epithelial disruption and oxidative stress compared to the wild-type, highlighting the critical role of gingipains in pathogenesis.

Discussion

Survival experiments using Galleria mellonella larvae supported these findings, highlighting the reduced survival associated with dual-species biofilms and the potential for high-dose antimicrobial therapies to mitigate this effect. These results emphasize the cooperative mechanisms of C. albicans and P. gingivalis in compromising epithelial barriers and underline the importance of combination therapies targeting both fungal and bacterial components in polymicrobial infections.

Mucin1 N-domain variant contributes to dry eye syndrome in diabetes by increasing immature mucus secretory granules

BACKGROUND

Diabetes-associated dry eye syndrome (DMDES) affects 20-54 % of diabetes, leading to ocular irritation and blurry vision. Decreased conjunctival goblet cell mucus secretion is one of the major pathological processes of DMDES. This study aims to investigate the mechanism of mucus granule maturation and secretion disturbance in DMDES.

METHODS

Tear samples from diabetic patients with and without dry eye syndrome were analyzed by mass spectrometry to identify proteins associated with ocular mucous layer reduction. The N-terminal domain fragment of Mucin1 (MUC1-ND) was transfected into the mouse conjunctiva to investigate alterations in goblet cell mucus secretion. Protein localization and granule morphology were explored through transmission electron microscopy with colloidal gold labeling and immunohistochemistry. Immunofluorescence, co-immunoprecipitation, and integrative computational modeling of protein interactions were employed to explore protein-protein interactions.

RESULTS

Tear proteomic analysis revealed significantly elevated MUC1-ND levels in tears from DMDES patients, which correlated with reduced goblet cell mucus secretion and tear film instability. Upregulation of MUC1-ND in mice conjunctiva inhibited the maturation of secretory mucus granules, contributing to tear mucous layer reduction. Protein docking and co-immunoprecipitation analysis demonstrated that the binding of MUC1-ND and Syntaxin6 prevents granule fusion and maintains the immature state of secretory granules, which leads to reduced mucus secretion.

CONCLUSION

In DMDES, MUC1-ND binds with Syntaxin6 to disrupt the fusion and maturation of secretory mucus granules in conjunctival goblet cells, which provides a new insight into DMDES pathophysiology.

Deep Saliva Proteomics Elucidating the Pathogenesis of Early Childhood Caries and Identifying Biomarkers for Early Prediction

Early childhood caries (ECC) significantly impacts the physical and mental health of children. Saliva stands as a critical model for investigating the pathogenesis of caries disease since it reflects both host and microbial dynamics. However, the specific contributions of salivary host factors to ECC have not been fully understood. In this study, we monitored a prospective cohort of 3-4 year-old healthy children for 12 months, who either stayed caries-free or developed caries. Deep quantitative proteomics analysis of saliva was conducted at both recruitment and end point of the cohort to investigate the molecular mechanisms underlying ECC etiology and identify potential biomarkers for caries prediction. Proteomics analysis identified a total of 2873 proteins and revealed involvement of immune response, dental structure repair, and regeneration, as well as interactions with microorganisms during caries pathogenesis. Characteristic salivary proteins were identified in caries-susceptible children prior to caries development. An ECC prediction panel of proteins keratin 3 (KRT3) and mucin 21 (MUC21) was established and further validated through another independent cohort. This study illuminated the role of the complex salivary microenvironment in caries etiology and offered a prognostic tool for early ECC prediction, thus facilitating the precise prevention and control of ECC to ultimately reduce its incidence.

Mucin Colocalizes with Influenza Virus and Preserves Infectivity in Deposited Model Respiratory Droplets

The stability of influenza virus in respiratory particles varies with relative humidity (RH) and protein content. This study investigated the decay, or loss of infectivity, of influenza A virus (IAV) in 1-μL respiratory droplets deposited on a surface with varying concentrations of mucin, one of the most abundant proteins in respiratory mucus, and examined the localization of virions within droplets. IAV remained stable at 0.1% and 0.5% mucin in phosphate-buffered saline (PBS) over 4 h at 20%, 50%, and 80% RH, with a maximum decay of 1.2 log10/mL. In contrast, in pure PBS droplets, the virus decayed by at least 2.6 log10/mL after 4 h at 50% and 80% RH. Mucin's protective effect was independent of its concentration, except at 80% RH after 4 h. Confocal microscopy of the particles revealed that at 20% and 50% RH, mucin led to thicker coffee rings and dendritic patterns where virions colocalized with mucin. At 80% RH, no morphological difference was observed between PBS-only and mucin-containing droplets, but virions still colocalized with mucin in the center of droplets with 0.5% mucin. Analysis by digital droplet PCR showed that mucin helped maintain virus integrity. To our knowledge, this is the first study to localize influenza virus in model respiratory droplets. The results suggest that mucin's colocalization with virions in droplets may protect the virus from environmental stressors, enhancing its stability.

Bacillus coagulans alleviates intestinal barrier injury induced by Klebsiella pneumoniae in rabbits by regulating the TLR4/MyD88/NF-κB signalling pathway

Probiotics effectively alleviate host diarrhoea, but the specific mechanism is not clear. Therefore, we explored the protective mechanism of Bacillus coagulans (BC) on intestinal barrier injury induced by Klebsiella pneumoniae (K. pneumoniae) in rabbits by HE, immunofluorescence and 16S rRNA. The results showed that BC pretreatment alleviated the changes in average daily gain, average daily feed intake and FCR caused by K. pneumoniae in rabbits. Moreover, BC alleviated the inflammatory cell infiltration, intestinal villus reduction, crypt deepening and goblet cell reduction caused by K. pneumoniae in rabbits. Further research revealed that BC improved the intestinal barrier by improving the mechanical barrier, chemical barrier, immune barrier and microbial barrier. Specifically, BC improved the intestinal mechanical barrier by improving the intestinal structure, increasing the protein expression of PCNA, increasing the number of goblet cells, and altering the expression of occludin, claudin-1 and ZO-1. BC improved the intestinal chemical barrier by regulating the expression of MUC1 and MUC2 and inhibited the TLR4/MyD88/NF-κB signalling pathway by altering the expression levels of the inflammatory factors IL-1β, IL-6 and TNF-α, thus optimizing the intestinal immune barrier. In addition, adding BC to the diet improved the intestinal microbial barrier of rabbits by reducing the abundance of harmful bacteria and increasing the abundance of beneficial bacteria. In summary, BC protects against K. pneumoniae-induced intestinal barrier damage by improving intestinal morphology, mitigating the inflammatory response and regulating the microbial composition. Among the pretreatments, the pretreatment effect of 1 × 106 CFU/g was the best. This study provides a theoretical basis for the use of BC to prevent and treat diarrhoea caused by K. pneumoniae in rabbits.

Androgens suppress the sialyltransferases ST3GAL1 and ST3GAL4 and modulate mucin 10 glycosylation in the submandibular gland, related to sex differences in commensal microbiota composition in mice

Sex differences exist in the commensal microbiota that impact on multiple physiological processes in the host. Here, we examined the mechanism by which the sex differences are formed. In addition to the epithelial ductal cell, the acinar cell mass in the submandibular gland was associated with androgen-androgen receptor (AR) signaling. Sex differences in the formation of submandibular mucin 10 (MUC10) were identified using SDS-PAGE. Neuraminidase treatment, which hydrolyzes terminal sialic acid, influenced the mobility shift of MUC10. Androgen-AR signaling negatively regulated ST3 β-galactoside α-2,3-sialyltransferase 1 (St3gal1) and St3gal4 in the submandibular gland. There was a trend and significant sex differences in α-diversity (Shannon, P = .09) and β-diversity (unweighted UniFrac) in oral microbiota composition, respectively. Some female-preferring bacteria including Akkermansia muciniphila can assimilate mucin by degrading terminal sialic acids. Our results indicate that androgen-AR signaling suppresses ST3GAL1 and ST3GAL4, which can influence sex differences in commensal microbiota composition.

Enhanced intestinal epithelial co-culture model with orbital mechanical stimulation: a proof-of-concept application in food nanotoxicology

Introduction

Current in vitro intestinal models lack the mechanical forces present in the physiological environment, limiting their reliability for nanotoxicology studies. Here, we developed an enhanced Caco-2/HT29-MTX-E12 co-culture model incorporating orbital mechanical stimulation to better replicate intestinal conditions and investigate nanoparticle interactions.

Methods

We established co-cultures under static and dynamic conditions, evaluating their development through multiple approaches including barrier integrity measurements, gene expression analysis, and confocal microscopy. We introduced novel quantitative analysis of dome formation as a differentiation marker and demonstrated the model application by investigating cellular responses to titanium dioxide (TiO₂) nanoparticles in a digested food matrix.

Results

Dynamic conditions accelerated epithelial differentiation, achieving functional barrier properties by day 14 rather than day 21, with enhanced mucin production and more organized three-dimensional structure. Mechanical stimulation selectively promoted goblet cell differentiation without affecting general epithelial markers. The optimized model successfully detected concentration-dependent oxidative stress responses to TiO₂ exposure, revealing cellular dysfunction preceding membrane damage.

Discussion

This improved co-culture system provides a better physiological platform for nanotoxicology studies. By incorporating mechanical forces, each cell type exhibits more representative behavior, creating a more realistic experimental setup. The model bridges the gap between simple monocultures and complex 3D systems, offering a practical approach for investigating nanoparticle-epithelium interactions in a food-relevant context.

Salivary Transmembrane Mucins of the MUC1 Family (CA 15-3, CA 27.29, MCA) in Breast Cancer: The Effect of Human Epidermal Growth Factor Receptor 2 (HER2)

The MUC1 family of transmembrane glycoproteins (CA 15-3, CA 27.29, MCA) is aberrantly expressed among patients with breast cancer. Objectives: to measure the level of degradation products of MUC1, including CA 15-3, CA 27.29, and MCA, in the saliva of breast cancer patients and to describe the biochemical processes that influence their expression and the regulation of their biological functions. Methods: The case-control study included three groups (breast cancer, fibroadenomas, and healthy controls). All study participants provided saliva samples strictly before starting treatment. The levels of MUC1, including CA 15-3, CA 27.29, and MCA, free progesterone and estradiol, cytokines (MCP-1, VEGF, TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-18), and amino acids (Asp, Gln, Gly, His, Leu + Ile, Orn, Phe, Pro, Tyr) were determined. Results: It was shown that the levels of the MUC1 family in the saliva of patients with HER2-positive breast cancer were significantly lower compared to the control group. The level of pro-inflammatory cytokines and the level of free estradiol affected the expression of MUC1. We obtained a reliable relationship between the aggressive nature of tumor growth, an increased level of pro-inflammatory cytokines, a low level of free estradiol, and the suppressed expression of salivary MUC1. Conclusions: Among patients with aggressive breast cancer, a high level of pro-inflammatory cytokines, and a low level of free estradiol, there was an inhibition of the expression of pathologically unchanged glycoprotein MUC1 in saliva.

Genome-Wide and Exome-Wide Association Study Identifies Genetic Underpinning of Comorbidity between Myocardial Infarction and Severe Mental Disorders

BACKGROUND

Myocardial Infarction (MI) and severe mental disorders (SMDs) are two types of highly prevalent and complex disorders and seem to have a relatively high possibility of mortality. However, the contributions of common and rare genetic variants to their comorbidity arestill unclear.

METHODS

We conducted a combined genome-wide association study (GWAS) and exome-wide association study (EWAS) approach.

RESULTS

Using gene-based and gene-set association analyses based on the results of GWAS, we found the common genetic underpinnings of nine genes (GIGYF2, KCNJ13, PCCB, STAG1, HLA-C, HLA-B, FURIN, FES, and SMG6) and nine pathways significantly shared between MI and SMDs. Through Mendelian randomization analysis, we found that twenty-seven genes were potential causal genes for SMDs and MI. Based on the exome sequencing data of MI and SMDs patients from the UK Biobank, we found that MUC2 was exome-wide significant in the two diseases. The gene-set analyses of the exome-wide association study indicated that pathways related to insulin processing androgen catabolic process and angiotensin receptor binding may be involved in the comorbidity between SMDs and MI. We also found that six candidate genes were reported to interact with known therapeutic drugs based on the drug-gene interaction information in DGIdb.

CONCLUSIONS

Altogether, this study revealed the overlap of common and rare genetic underpinning between SMDs and MI and may provide useful insights for their mechanism study and therapeutic investigations.

Deciphering cellular and molecular mechanism of MUC13 mucin involved in cancer cell plasticity and drug resistance

There has been a surge of interest in recent years in understanding the intricate mechanisms underlying cancer progression and treatment resistance. One molecule that has recently emerged in these mechanisms is MUC13 mucin, a transmembrane glycoprotein. Researchers have begun to unravel the molecular complexity of MUC13 and its impact on cancer biology. Studies have shown that MUC13 overexpression can disrupt normal cellular polarity, leading to the acquisition of malignant traits. Furthermore, MUC13 has been associated with increased cancer plasticity, allowing cells to undergo epithelial-mesenchymal transition (EMT) and metastasize. Notably, MUC13 has also been implicated in the development of chemoresistance, rendering cancer cells less responsive to traditional treatment options. Understanding the precise role of MUC13 in cellular plasticity, and chemoresistance could pave the way for the development of targeted therapies to combat cancer progression and enhance treatment efficacy.

Altered glycosylation in secreting cells of the gastric glands of aquaporin-4-deficient mice

Aquaporins (AQPs) are important for water transport in the gastrointestinal tract. Changes in their expression and/or localization could cause in disorders and be used as therapeutic targets. Aquaporin-4 (AQP4) is expressed predominantly on the basolateral membrane of the parietal cells in the corpus of the murine gastric glands. Although the secretion of gastric juice is not affected in AQP4-deficient knockout, we evaluated by light microscopy whether the lack of AQP4 affects the glycopatterns of secreting gastric cells. Wild type (WT) and AQP4-deficient knockout mice (KO) were fed a standard diet ad libitum before sacrifice. Segments of stomach corpus were collected, fixed in buffered formalin, and embedded in paraffin wax. Sections, 5-μm thick, were analyzed by histochemical methods (Periodic acid-Schiff, Alcian Blue pH 2.5), and binding of lectins specific to GalNAc (SBA, DBA), Gal (PNA) GlcNAc (WGA, GSAII) mannose and/or glucose (ConA), and fucose (UEA-I, AAA, LTA). Immunohistochemical methods such as anti-Muc6 for neck cells and anti- β- H+/K+-ATPase for parietal cells were also performed. Compared to WT mice, in the mucous cells of KO lower amounts of glycans with galactosyl/galactosaminylated, glycosyl/glycosaminylated, and fucosylated residues were observed; lower fucosylation resulted also in the parietal cells. The observed differences of KO in respect to WT could lead to severer pathological conditions. RESEARCH HIGHLIGHTS: Glycopatterns in gastric glands were compared between wild type (WT) and AQP4-deficient knockout (KO) mice by histochemical and lectin-binding methods. In the mucous cells of KO lower amounts of glycans with galactosyl/galactosaminylated, glycosyl/glycosaminylated and fucosylated residues were observed. In the parietal cells lower fucosylation also resulted. AQP4-deficiency affects glycosylation and could result in altered functionality and pathological conditions.

Interaction and competition for intestinal absorption by zinc, iron, copper, and manganese at the intestinal mucus layer

Trace elements such as zinc, manganese, copper, or iron are essential for a wide range of physiological functions. It is therefore crucial to ensure an adequate supply of these elements to the body. Many previous investigations have dealt with the role of transport proteins, in particular their selectivity for, and competition between, different ions. Another so far less well investigated major factor influencing the absorption of trace elements seems to be the intestinal mucus layer. This gel-like substance covers the entire gastrointestinal tract and its physiochemical properties can be mainly assigned to the glycoproteins it contains, so-called mucins. Interaction with mucins has already been demonstrated for some metals. However, knowledge about the impact on the respective bioavailability and competition between those metals is still sketchy. This review therefore aims to summarize the findings and knowledge gaps about potential effects regarding the interaction between gastrointestinal mucins and the trace elements iron, zinc, manganese, and copper. Mucins play an indispensable role in the absorption of these trace elements in the neutral to slightly alkaline environment of the intestine, by keeping them in a soluble form that can be absorbed by enterocytes. Furthermore, the studies so far indicate that the competition between these trace elements for uptake already starts at the intestinal mucus layer, yet further research is required to completely understand this interaction.

The MUC2 Gene Product: Polymerisation and Post-Secretory Organisation-Current Models

MUC2 mucin, the primary gel-forming component of intestinal mucus, is well researched and a model of polymerisation and post-secretory organisation has been published previously. Recently, several significant developments have been made which either introduce new ideas or challenge previous theories. New ideas include an overhaul of the MUC2 C-terminal globular structure which is proposed to harbour several previously unobserved domains, and include a site for an extra intermolecular disulphide bridge dimer between the cysteine 4379 of adjacent MUC2 C-termini. MUC2 polymers are also now thought to be secreted attached to the epithelial surface of goblet cells in the small intestine and removed following secretion via a metalloprotease meprin β-mediated cleavage of the von Willebrand D2 domain of the N-terminus. It remains unclear whether MUC2 forms intermolecular dimers, trimers, or both, at the N-termini during polymerisation, with several articles supporting either trimer or dimer formation. The presence of a firm inner mucus layer in the small intestine is similarly unclear. Considering this recent research, this review proposes an update to the previous model of MUC2 polymerisation and secretion, considers conflicting theories and data, and highlights the importance of this research to the understanding of MUC2 mucus layers in health and disease.

MUC21: a new target for tumor treatment

MUC21, also known as Epiglycanin, is a high-molecular-weight glycoprotein with transmembrane mucin properties. It consists of a tandem repeat domain, a stem domain, a transmembrane domain and a cytoplasmic tail. MUC21 is expressed is observed in normal tissues in organs like the thymus, testes, lungs, and large intestine. Research has shown that MUC21 is expressed in esophageal squamous cell carcinoma, lung adenocarcinoma, glioblastoma, thyroid cancer, melanoma, and various other malignant tumors in distinctive manner. Additionally, tumor invasion, metastasis, and poor prognosis are linked to it. Some researchers believe that MUC21 has the potential to become a new target in cancer treatment. This review aims to deliver a comprehensive overview of the glycosylation, function, and research progress of MUC21 in multiple types of cancer and infectious diseases.

Role of Secretory Mucins in the Occurrence and Development of Cholelithiasis

Cholelithiasis is a common biliary tract disease. However, the exact mechanism underlying gallstone formation remains unclear. Mucin plays a vital role in the nuclear formation and growth of cholesterol and pigment stones. Excessive mucin secretion can result in cholestasis and decreased gallbladder activity, further facilitating stone formation and growth. Moreover, gallstones may result in inflammation and the secretion of inflammatory factors, which can further increase mucin expression and secretion to promote the growth of gallstones. This review systematically summarises and analyses the role of mucins in gallstone occurrence and development and its related mechanisms to explore new ideas for interventions in stone formation or recurrence.

Ectoine Enhances Mucin Production Via Restoring IL-13/IFN-γ Balance in a Murine Dry Eye Model

Purpose

This study aimed to explore protective effects and potential mechanism of ectoine, a natural osmoprotectant, on ocular surface mucin production in dry eye disease.

Methods

A dry eye model was established in C57BL/6 mice exposed to desiccating stress (DS) with untreated (UT) mice as controls. DS mice were topically treated with 2.0% ectoine or PBS vehicle. Corneal epithelial defects were assessed by Oregon Green Dextran (OGD) fluorescent staining. Conjunctival goblet cells, ocular mucins, and T help (Th) cytokines were evaluated by immunofluorescent staining or ELISA, and RT-qPCR.

Results

Compared with UT mice, corneal epithelial defects were detected as strong punctate OGD fluorescent staining in DS mice with vehicle, whereas ectoine treatment largely reduced OGD staining to near-normal levels. Conjunctival goblet cell density and cell size decreased markedly in DS mice, but was significantly recovered by ectoine treatment. The protein production and mRNA expression of two gel-forming secreted MUC5AC and MUC2, and 4 transmembrane mucins, MUC1, MUC4, MUC16, and MUC15, largely decreased in DS mice, but was restored by ectoine. Furthermore, Th2 cytokine IL-13 was inhibited, whereas Th1 cytokine IFN-γ was stimulated at protein and mRNA levels in conjunctiva and draining cervical lymph nodes (CLNs) of DS mice, leading to decreased IL-13/IFN-γ ratio. Interestingly, 2.0% ectoine reversed their alternations and restored IL-13/IFN-γ balance.

Conclusions

Our findings demonstrate that topical ectoine significantly reduces corneal damage, and enhances goblet cell density and mucin production through restoring imbalanced IL-13/IFN-γ signaling in murine dry eye model. This suggests therapeutic potential of natural osmoprotectant ectoine for dry eye disease.

The effects of fine particulate matter (SRM 2786) on three different 3D lung models exposed at the air-liquid interface - A comparative study

3D cell culture models exposed at the air-liquid interface (ALI) represent a potential alternative to animal experiments for hazard and risk assessment of inhaled compounds. This study compares cocultures composed of either Calu-3, A549 or HBEC3-KT lung epithelial cells, cultured together with THP-1-derived macrophages and EA.hy926 endothelial cells, in terms of barrier capacity and responses to a standard reference sample of fine particulate matter (SRM 2786). High-content imaging analysis revealed a similar cellular composition between the different cell models. The 3D cell cultures with Calu-3 cells showed the greatest barrier capacity, as measured by transepithelial electrical resistance and permeability to Na-fluorescein. Mucus production was detected in 3D cell cultures based on Calu-3 and A549 cells. Exposure to SRM 2786 at ALI increased cytokine release and expression of genes associated with inflammation and xenobiotic metabolism. Moreover, the presence of THP-1-derived macrophages was central to the cytokine responses in all cell models. While the different 3D cell culture models produced qualitatively similar responses, more pronounced pro-inflammatory responses were observed in the basolateral compartment of the A549 and HBEC3-KT models compared to the Calu-3 model, likely due to their reduced barrier capacity and lower retention of secreted mediators in the apical compartment.

MUC1 promotes cervical squamous cell carcinoma through ERK phosphorylation-mediated regulation of ITGA2/ITGA3

In contrast to the decreasing trends in developed countries, the incidence and mortality rates of cervical squamous cell carcinoma in China have increased significantly. The screening and identification of reliable biomarkers and candidate drug targets for cervical squamous cell carcinoma are urgently needed to improve the survival rate and quality of life of patients. In this study, we demonstrated that the expression of MUC1 was greater in neoplastic tissues than in non-neoplastic tissues of the cervix, and cervical squamous cell carcinoma patients with high MUC1 expression had significantly worse overall survival than did those with low MUC1 expression, indicating its potential for early diagnosis of cervical squamous cell carcinoma. Next, we explored the regulatory mechanism of MUC1 in cervical squamous cell carcinoma. MUC1 could upregulate ITGA2 and ITGA3 expression via ERK phosphorylation, promoting the proliferation and metastasis of cervical cancer cells. Further knockdown of ITGA2 and ITGA3 significantly inhibited the tumorigenesis of cervical cancer cells. Moreover, we designed a combination drug regimen comprising MUC1-siRNA and a novel ERK inhibitor in vivo and found that the combination of these drugs achieved better results in animals with xenografts than did MUC1 alone. Overall, we discovered a novel regulatory pathway, MUC1/ERK/ITGA2/3, in cervical squamous cell carcinoma that may serve as a potential biomarker and therapeutic target in the future.

Proteomic Analysis of Salivary Secretions from the Tea Green Leafhopper, Empoasca flavescens Fabrecius

Saliva plays a crucial role in shaping the compatibility of piercing-sucking insects with their host plants. Understanding the complex composition of leafhopper saliva is important for developing effective and eco-friendly control strategies for the tea green leafhopper, Empoasca flavescens Fabrecius, a major piercing-sucking pest in Chinese tea plantations. This study explored the saliva proteins of tea green leafhopper adults using a custom collection device, consisting of two layers of Parafilm stretched over a sucrose diet. A total of 152 proteins were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) following the filter-aided sample preparation (FASP). These proteins were categorized into six groups based on their functions, including enzymes, transport proteins, regulatory proteins, cell structure proteins, other proteins, and unknown proteins. Bioinformatics analyses predicted 16 secreted proteins, which were successfully cloned and transcriptionally analyzed across various tissues and developmental stages. Genes encoding putative salivary secretory proteins, including Efmucin1, EfOBP1, EfOBP2, EfOBP3, Efmucin2, low-density lipoprotein receptor-related protein (EfLRP), EFVg1, and EFVg2, exhibited high expressions in salivary gland (SG) tissues and feeding-associated expressions at different developmental stages. These findings shed light on the potential elicitors or effectors mediating the leafhopper feeding and defense responses in tea plants, providing insights into the coevolution of tea plants and leafhoppers. The study's conclusions open avenues for the development of innovative leafhopper control technologies that reduce the reliance on pesticides in the tea industry.

Establishment of a cholangiocarcinoma risk evaluation model based on mucin expression levels

BACKGROUND

Cholangiocarcinoma (CCA) is a highly malignant cancer, characterized by frequent mucin overexpression. MUC1 has been identified as a critical oncogene in the progression of CCA. However, the comprehensive understanding of how the mucin family influences CCA progression and prognosis is still incomplete.

AIM

To investigate the functions of mucins on the progression of CCA and to establish a risk evaluation formula for stratifying CCA patients.

METHODS

Single-cell RNA sequencing data from 14 CCA samples were employed for elucidating the roles of mucins, complemented by bioinformatic analyses. Subsequent validations were conducted through spatial transcriptomics and immunohistochemistry. The construction of a risk evaluation model utilized the least absolute shrinkage and selection operator regression algorithm, which was further confirmed by independent cohorts and diverse data types.

RESULTS

CCA tumor cells with elevated levels of MUC1 and MUC4 showed activated nucleotide metabolic pathways and increased invasiveness. MUC5AC-high cells were found to promote CCA progression through WNT signaling. MUC5B-high cells exhibited robust cellular oxidation activities, leading to resistance against antitumoral treatments. MUC13-high cells were observed to secret chemokines, recruiting and transforming macrophages into the M2-polarized state, thereby suppressing antitumor immunity. MUC16-high cells were found to promote tumor progression through interleukin-1/nuclear factor kappa-light-chain-enhancer of activated B cells signaling upon interaction with neutrophils. Utilizing the expression levels of these mucins, a risk factor evaluation formula for CCA was developed and validated across multiple cohorts. CCA samples with higher risk factors exhibited stronger metastatic potential, chemotherapy resistance, and poorer prognosis.

CONCLUSION

Our study elucidates the functional mechanisms through which mucins contribute to CCA development, and provides tools for risk stratification in CCA.

Progress in Biological Research and Treatment of Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a rare disease characterized by extensive peritoneal implantation and mass secretion of mucus after primary mucinous tumors of the appendix or other organ ruptures. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is currently the preferred treatment, with excellent efficacy and safety, and is associated with breakthrough progress in long-term disease control and prolonged survival. However, the high recurrence rate of PMP is the key challenge in its treatment, which limits the clinical application of multiple rounds of CRS-HIPEC and does not benefit from conventional systemic chemotherapy. Therefore, the development of alternative therapies for patients with refractory or relapsing PMP is critical. The literature related to PMP research progress and treatment was searched in the Web of Science, PubMed, and Google Scholar databases, and a literature review was conducted. The overview of the biological research, treatment status, potential therapeutic strategies, current research limitations, and future directions associated with PMP are presented, focuses on CRS-HIPEC therapy and alternative or combination therapy strategies, and emphasizes the clinical transformation prospects of potential therapeutic strategies such as mucolytic agents and targeted therapy. It provides a theoretical reference for the treatment of PMP and the main directions for future research.

Preventative Effects of Milk Fat Globule Membrane Ingredients on DSS-Induced Mucosal Injury in Intestinal Epithelial Cells

The goblet cells of the gastrointestinal tract (GIT) produce glycoproteins called mucins that form a protective barrier from digestive contents and external stimuli. Recent evidence suggests that the milk fat globule membrane (MFGM) and its milk phospholipid component (MPL) can benefit the GIT through improving barrier function. Our objective was to compare the effects of two digested MFGM ingredients with or without dextran sodium sulfate (DSS)-induced barrier stress on mucin proteins. Co-cultured Caco-2/HT29-MTX intestinal cells were treated with in vitro digests of 2%, 5%, and 10% (w/v) MFGM or MPL alone for 6 h or followed by challenge with 2.5% DSS (6 h). Transepithelial electrical resistance and fluorescein isothiocyanate (FITC)-dextran (FD4) permeability measurements were used to measure changes in barrier integrity. Mucin characterization was performed using a combination of slot blotting techniques for secreted (MUC5AC, MUC2) and transmembrane (MUC3A, MUC1) mucins, scanning electron microscopy (SEM), and periodic acid Schiff (PAS)/Alcian blue staining. Digested MFGM and MPL prevented a DSS-induced reduction in secreted mucins, which corresponded to the prevention of DSS-induced increases in FD4 permeability. SEM and PAS/Alcian blue staining showed similar visual trends for secreted mucin production. A predictive bioinformatic approach was also used to identify potential KEGG pathways involved in MFGM-mediated mucosal maintenance under colitis conditions. This preliminary in silico evidence, combined with our in vitro findings, suggests the role of MFGM in inducing repair and maintenance of the mucosal barrier.

Bifidobacterium mediate gut microbiota-remedied intestinal barrier damage caused by cyproconazole in zebrafish (Danio rerio)

The widespread use of cyproconazole (CPZ) enhances food security but may pose potential risks to non-target organisms. Therefore, we applied Multi-omics techniques to reveal the response of the intestinal barrier to CPZ exposure and explore whether the Bifidobacterium intervention experiment can repair the damage. First, we found that exposure to CPZ at environmentally relevant concentrations led to intestinal injury phenotype, significantly down-regulated intestinal protein gene expression, and up-regulated pro-inflammatory gene expression, further causing intestinal dysbacteriosis and metabolic disorders. In particular, by combining analysis of gut microbiota and metabolites, we noticed acetate, a key metabolite, which decreased sharply after exposure to high concentration of CPZ. Expectedly, after supplementing with Bifidobacterium (a core bacterium that produces acetate), we noticed that the acetate content was quickly restored. Further, we also verified that the increase in acetate content after Bifidobacterium supplementation at least partially promoted IL-22 secretion, which in turn stimulated the secretion of β-defensins (zfbd-1, zfbd-2, zfbd-3), thereby repairing the intestinal damage. In conclusion, our work confirms the potential of Bifidobacterium to improve intestinal damage and metabolic dysbiosis caused by CPZ exposure. It provides directional recommendations for the application of probiotics to repair the toxicological risk of pesticide exposure.

The potential role of ocular and otolaryngological mucus proteins in myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating illness associated with a constellation of other symptoms. While the most common symptom is unrelenting fatigue, many individuals also report suffering from rhinitis, dry eyes and a sore throat. Mucin proteins are responsible for contributing to the formation of mucosal membranes throughout the body. These mucosal pathways contribute to the body's defense mechanisms involving pathogenic onset. When compromised by pathogens the epithelium releases numerous cytokines and enters a prolonged state of inflammation to eradicate any particular infection. Based on genetic analysis, and computational theory and modeling we hypothesize that mucin protein dysfunction may contribute to ME/CFS symptoms due to the inability to form adequate mucosal layers throughout the body, especially in the ocular and otolaryngological pathways leading to low grade chronic inflammation and the exacerbation of symptoms.

Role of Alpha-Fetoprotein in the Pathogenesis of Cancer

Alpha-fetoprotein (AFP) belongs to the albuminoid protein family and is considered as the fetal analog of serum albumin. This plasma protein is initially synthesized in the fetal liver and yolk sac and shows a maximum peak near the end of the first trimester. Later, concentrations begin to decline prenatally and drop precipitously after birth. This protein has three key ligand-binding pockets for interactions with various biomolecules. It contains multiple phosphorylation and acetylation sites for the regulation of physiological and pathophysiological states. High serum AFP titer is an established biomarker for yolk sac, embryonal and hepatocellular carcinoma. The present review critically analyzes the chemical nature, receptors, clinical implications, and therapeutic aspects of AFP, underpinning the development of different types of cancer.

Gastric Mucosal Protective Effects of Cinnamomum cassia in a Rat Model of Ethanol-Induced Gastric Injury

Cinnamomum cassia (cassia) is a tropical aromatic evergreen tree of the Lauraceae family well known for its fragrance and spicy flavor and widely used in Asian traditional medicine. It has recently garnered attention for its diverse potential health benefits, including anti-inflammatory, anti-cancer, and anti-diabetic properties. However, the gastroprotective effect of C. cassia, particularly against ethanol-induced gastric damage, remains unclear. We investigated the potential gastroprotective property of C. cassia and the underlying mechanisms of action in a rat model of ethanol-induced gastric injury. To assess its effectiveness, rats were fed C. cassia for a 14-day period prior to inducing gastric damage by oral administration of ethanol. Our results indicated that pre-treatment with C. cassia mitigated ethanol-induced gastric mucosal lesions and bleeding. Reduced gastric acid secretion and expression of acid secretion-linked receptors were also observed. Additionally, pretreatment with C. cassia led to decreased levels of inflammatory factors, including TNF-α, p-p65, and IκBα. Notably, C. cassia upregulated the expressions of HO1 and HSP90, with particular emphasis on the enhanced expression of PAS and MUC, the crucial gastric mucosa defense molecules. These findings suggest that C. cassia has protective effects on the gastric mucosa and can effectively reduce oxidative stress and inflammation.

Advances in the Evaluation of Gastrointestinal Absorption Considering the Mucus Layer

Because of the increasing sophistication of formulation technology and the increasing polymerization of compounds directed toward undruggable drug targets, the influence of the mucus layer on gastrointestinal drug absorption has received renewed attention. Therefore, understanding the complex structure of the mucus layer containing highly glycosylated glycoprotein mucins, lipids bound to the mucins, and water held by glycans interacting with each other is critical. Recent advances in cell culture and engineering techniques have led to the development of evaluation systems that closely mimic the ecological environment and have been applied to the evaluation of gastrointestinal drug absorption while considering the mucus layer. This review provides a better understanding of the mucus layer components and the gastrointestinal tract's biological defense barrier, selects an assessment system for drug absorption in the mucus layer based on evaluation objectives, and discusses the overview and features of each assessment system.

Role of Anthocyanins in the Interaction between Salivary Mucins and Wine Astringent Compounds

Wine astringency is a very complex sensation whose complete mechanism has not been entirely described. Not only salivary proline-rich proteins (PRPs) are involved in its development; salivary mucins can also play an important role. On the other hand, it has been described that anthocyanins can interact with PRPs, but there is no information about their potential role on the interactions with mucins. In this work, the molecular interactions between salivary mucins (M) and different wine phenolic compounds, such as catechin (C), epicatechin (E) and quercetin 3-β-glucopyranoside (QG), as well as the effect of the anthocyanin malvidin 3-O-glucoside (Mv) on the interactions with mucins, were assessed by isothermal titration calorimetry (ITC). Results showed that the interaction between anthocyanin and mucins is stronger than that of both flavanols analyzed, since the affinity constant values were 10 times higher for anthocyanin than for catechin, the only flavanol showing interaction in binary assay. Moreover, at the concentration at which polyphenols are usually found in wine, flavonols seem not to be involved in the interactions with mucins. These results showed, for the first time, the importance of wine anthocyanins in the mechanisms of astringency involving high-molecular-weight salivary proteins like mucins.

Analysis of MUC6 polymorphisms on the clinicopathologic characteristics of Asian patients with oral squamous cell carcinoma

Head and neck squamous cell carcinomas (HNSCCs) are generally associated with tobacco consumption, alcohol abuse or both. Mucins (MUCs) are high-molecular-weight glycoproteins produced by many epithelial tissues. Many studies have indicated that MUCs play an important role in cancer metastasis. MUC6 expression has been observed in gastric and oncocytic phenotypes and plays an important role during cancer progression. We found that levels of MUC6 are lower in Asian HNCC patients and affect the disease-free survival of HNCC patients. Next, we investigated the combined effect of MUC6 polymorphisms and exposure to environmental carcinogens on the susceptibility to and clinicopathological characteristics of HNCC. Three single-nucleotide polymorphisms (SNPs) of MUC6 (rs7481521, rs6597947 and rs61869016) were analysed using real-time PCR. After adjusting for other co-variants, we found that carrying a CC genotype at MUC6 rs6597947 led to a lower risk of developing oral squamous cell carcinoma (OSCC) than wild-type carriers among non-betel-quid chewers. Moreover, male oral cancer patients who carried the AA + CC genotype at MUC6 rs6597947 had a lower risk of lymph node metastasis than other genotypes, suggesting a significant functional compromise and decompensated disease. Therefore, our findings suggest that genetic variations in MUC6 may correlate to OSCC and indicate the progression in OSCC patients.

Deep Learning-based structure modelling illuminates structure and function in uncharted regions of β-solenoid fold space

Repeat proteins are common in all domains of life and exhibit a wide range of functions. One class of repeat protein contains solenoid folds where the repeating unit consists of β-strands separated by tight turns. β-solenoids have distinguishing structural features such as handedness, twist, oligomerisation state, coil shape and size which give rise to their diversity. Characterised β-solenoid repeat proteins are known to form regions in bacterial and viral virulence factors, antifreeze proteins and functional amyloids. For many of these proteins, the experimental structure has not been solved, as they are difficult to crystallise or model. Here we use various deep learning-based structure-modelling methods to discover novel predicted β-solenoids, perform structural database searches to mine further structural neighbours and relate their predicted structure to possible functions. We find both eukaryotic and prokaryotic adhesins, confirming a known functional linkage between adhesin function and the β-solenoid fold. We further identify exceptionally long, flat β-solenoid folds as possible structures of mucin tandem repeat regions and unprecedentedly small β-solenoid structures. Additionally, we characterise a novel β-solenoid coil shape, the FapC Greek key β-solenoid as well as plausible complexes between it and other proteins involved in Pseudomonas functional amyloid fibres.

Milk fat globule membrane: composition, production and its potential as encapsulant for bioactives and probiotics

Milk fat globule membrane (MFGM) is a complex trilayer structure present in mammalian milk and is mainly composed of phospholipids and proteins (>90%). Many studies revealed MFGM has positive effects on the immune system, brain development, and cognitive function of infants. Probiotics are live microorganisms that have been found to improve mental health and insulin sensitivity, regulate immunity, and prevent allergies. Probiotics are unstable and prone to degradation by environmental, processing, and storage conditions. In this review, the processes used for encapsulation of probiotics particularly the potential of MFGM and its constituents as encapsulating materials for probiotics are described. This study analyzes the importance of MFGM in encapsulating bioactive substances and emphasizes the interaction with probiotics and the gut as well as its resistance to adverse environmental factors in the digestive system when used as a probiotic embedding material. MFGM can enhance the gastric acid resistance and bile resistance of probiotics, mainly manifested in the survival rate of probiotics. Due to the role of digestion, MFGM-coated probiotics can be released in the intestine, and due to the biocompatibility of the membrane, it can promote the binding of probiotics to intestinal epithelial cells, and promote the colonization of some probiotics in the intestine.

Plasma Bile Acid Profiling and Modulation of Secreted Mucin 5AC in Cholangiocarcinoma

Studies investigating the potential role of circulating bile acids (BAs) as diagnostic biomarkers for cholangiocarcinoma (CCA) are sparse and existing data do not adjust for confounding variables. Furthermore, the mechanism by which BAs affect the expression of the oncogenic mucin 5AC (MUC5AC) has never been investigated. We performed a case-control study to characterise the profile of circulating BAs in patients with CCA (n = 68) and benign biliary disease (BBD, n = 48) with a validated liquid chromatography-tandem mass spectrometry technique. Odd ratios (OR) for CCA associations were calculated with multivariable logistic regression models based on a directed acyclic graph structure learning algorithm. The most promising BAs were then tested in an in vitro study to investigate their interplay in modulating MUC5AC expression. The total concentration of BAs was markedly higher in patients with CCA compared with BBD controls and accompanied by a shift in BAs profile toward a higher proportion of primary conjugated BAs (OR = 1.50, CI: 1.14 to 1.96, p = 0.003), especially taurochenodeoxycholic acid (TCDCA, OR = 42.29, CI: 3.54 to 504.63, p = 0.003) after multiple adjustments. Western blot analysis of secreted MUC5AC in human primary cholangiocytes treated with primary conjugated BAs or with TCDCA alone allowed us to identify a novel 230 kDa isoform, possibly representing a post-translationally modified MUC5AC specie.

Impact of Early Weaning on Development of the Swine Gut Microbiome

Considering that pigs are naturally weaned between 12 and 18 weeks of age, the common practice in the modern swine industry of weaning as early as between two and four weeks of age increases challenges during this transition period. Indeed, young pigs with an immature gut are suddenly separated from the sow, switched from milk to a diet consisting of only solid ingredients, and subjected to a new social hierarchy from mixing multiple litters. From the perspective of host gut development, weaning under these conditions causes a regression in histological structure as well as in digestive and barrier functions. While the gut is the main center of immunity in mature animals, the underdeveloped gut of early weaned pigs has yet to contribute to this function until seven weeks of age. The gut microbiota or microbiome, an essential contributor to the health and nutrition of their animal host, undergoes dramatic alterations during this transition, and this descriptive review aims to present a microbial ecology-based perspective on these events. Indeed, as gut microbial communities are dependent on cross-feeding relationships, the change in substrate availability triggers a cascade of succession events until a stable composition is reached. During this process, the gut microbiota is unstable and prone to dysbiosis, which can devolve into a diseased state. One potential strategy to accelerate maturation of the gut microbiome would be to identify microbial species that are critical to mature swine gut microbiomes, and develop strategies to facilitate their establishment in early post-weaning microbial communities.

Mucins as contrast agent targets for fluorescence-guided surgery of pancreatic cancer

Pancreatic cancer is difficult to resect due to its unique challenges, often leading to incomplete tumor resections. Fluorescence-guided surgery (FGS), also known as intraoperative molecular imaging and optical surgical navigation, is an intraoperative tool that can aid surgeons in complete tumor resection through an increased ability to detect the tumor. To target the tumor, FGS contrast agents rely on biomarkers aberrantly expressed in malignant tissue compared to normal tissue. These biomarkers allow clinicians to identify the tumor and its stage before surgical resection and provide a contrast agent target for intraoperative imaging. Mucins, a family of glycoproteins, are upregulated in malignant tissue compared to normal tissue. Therefore, these proteins may serve as biomarkers for surgical resection. Intraoperative imaging of mucin expression in pancreatic cancer can potentially increase the number of complete resections. While some mucins have been studied for FGS, the potential ability to function as a biomarker target extends to the entire mucin family. Therefore, mucins are attractive proteins to investigate more broadly as FGS biomarkers. This review summarizes the biomarker traits of mucins and their potential use in FGS for pancreatic cancer.

Alleviative effects of natural plant polysaccharides against DSS-induced ulcerative colitis via inhibiting inflammation and modulating gut microbiota

Ulcerative colitis (UC) treatment usually involves either drug therapy or surgery. Natural food polysaccharides have showed great potential for preventing UC. In this study, the therapeutic effects of Cyclocarya paliurus (Batal.) Iljinskaja polysaccharide (CP) and Chinese yam polysaccharide (CYP) on dextran sodium sulfate (DSS)-induced mice UC model and their underlying mechanisms were explored. The results suggested that CP and CYP could improve colitis symptoms in DSS-induced mice, enhance the production of IL-10, inhibit cytokines (IL-1β, TNF-α) and reduce MPO activity. Furthermore, they maintained the integrity of intestine by improving the expression of mucin MUC-2, ZO-1 and occludin, which in turn reduced the contents of lipopolysaccharide binding protein (LBP) and endotoxin (ET) in serum and oxidative stress in liver. Finally, they modulated the composition and metabolism of gut microbiota. Notably, Alistipes and Bacteroides were the specific genera in CP and CYP groups, respectively. These findings indicated that polysaccharides might alleviate the development of colitis and inform other relevant studies.

Altered Glycosylation in Progression and Management of Bladder Cancer

Bladder cancer (BC) is the 10th most common malignancy worldwide, with an estimated 573,000 new cases and 213,000 deaths in 2020. Available therapeutic approaches are still unable to reduce the incidence of BC metastasis and the high mortality rates of BC patients. Therefore, there is a need to deepen our understanding of the molecular mechanisms underlying BC progression to develop new diagnostic and therapeutic tools. One such mechanism is protein glycosylation. Numerous studies reported changes in glycan biosynthesis during neoplastic transformation, resulting in the appearance of the so-called tumor-associated carbohydrate antigens (TACAs) on the cell surface. TACAs affect a wide range of key biological processes, including tumor cell survival and proliferation, invasion and metastasis, induction of chronic inflammation, angiogenesis, immune evasion, and insensitivity to apoptosis. The purpose of this review is to summarize the current information on how altered glycosylation of bladder cancer cells promotes disease progression and to present the potential use of glycans for diagnostic and therapeutic purposes.

Aberrant protein glycosylation: Implications on diagnosis and Immunotherapy

Glycosylation-mediated post-translational modification is critical for regulating many fundamental processes like cell division, differentiation, immune response, and cell-to-cell interaction. Alterations in the N-linked or O-linked glycosylation pattern of regulatory proteins like transcription factors or cellular receptors lead to many diseases, including cancer. These alterations give rise to micro- and macro-heterogeneity in tumor cells. Here, we review the role of O- and N-linked glycosylation and its regulatory function in autoimmunity and aberrant glycosylation in cancer. The change in cellular glycome could result from a change in the expression of glycosidases or glycosyltransferases like N-acetyl-glucosaminyl transferase V, FUT8, ST6Gal-I, DPAGT1, etc., impact the glycosylation of target proteins leading to transformation. Moreover, the mutations in glycogenes affect glycosylation patterns on immune cells leading to other related manifestations like pro- or anti-inflammatory effects. In recent years, understanding the glycome to cancer indicates that it can be utilized for both diagnosis/prognosis as well as immunotherapy. Studies involving mass spectrometry of proteome, site- and structure-specific glycoproteomics, or transcriptomics/genomics of patient samples and cancer models revealed the importance of glycosylation homeostasis in cancer biology. The development of emerging technologies, such as the lectin microarray, has facilitated research on the structure and function of glycans and glycosylation. Newly developed devices allow for high-throughput, high-speed, and precise research on aberrant glycosylation. This paper also discusses emerging technologies and clinical applications of glycosylation.

Mucin 4 (MUC4) Protein is Expressed in B-Acute Lymphoblastic Leukemia (B-ALL) and is restricted to BCR::ABL1 Positive and BCR::ABL-like Subtypes

Mucin 4 (MUC4) is a transmembrane mucin that, like most mucins, is not expressed in normal hematopoietic cells but little is known about its expression in malignant hematopoiesis. B-Acute Lymphoblastic Leukemia (B-ALL) consists of genetically distinct disease subtypes with similarities and differences in gene expression most frequently studied at the mRNA level, which is less amenable to widespread routine clinical use. Here, we demonstrate using immunohistochemistry (IHC) that MUC4 protein is expressed in less than 10% of B-ALL with expression restricted to BCR::ABL1+ and BCR::ABL1-like (CRLF2 rearranged) subtypes of B-ALL (4/13, 31%). None (0/36, 0%) of the remaining B-ALL subtypes expressed MUC4. We compare clinical and pathologic features of MUC4+ and MUC4- BCR::ABL1+/like cases and most significantly report a possible shorter time to relapse for MUC4+ BCR::ABL1 B-ALL that would need to be validated in larger studies. In conclusion, MUC4 is a specific, albeit insensitive, marker for these high-risk subtypes of B-ALL. We propose that MUC4 IHC may be employed diagnostically to rapidly identify these B-ALL subtypes particularly in resource limited settings or when an aspirate sample is not available for ancillary genetic studies.

Mucin 13 (MUC13) as a candidate biomarker for ovarian cancer detection: potential to complement CA125 in detecting non-serous subtypes

OBJECTIVES

Ovarian cancer is the most lethal gynecological malignancy in developed countries. One of the key associations with the high mortality rate is diagnosis at late stages. This clinical limitation is primarily due to a lack of distinct symptoms and detection at the early stages. The ovarian cancer biomarker, CA125, is mainly effective for identifying serous ovarian carcinomas, leaving a gap in non-serous ovarian cancer detection. Mucin 13 (MUC13) is a transmembrane, glycosylated protein with aberrant expression in malignancies, including ovarian cancer. We explored the potential of MUC13 to complement CA125 as an ovarian cancer biomarker, by evaluating its ability to discriminate serous and non-serous subtypes of ovarian cancer at FIGO stages I-IV from benign conditions.

METHODS

We used our newly developed, high sensitivity ELISA to measure MUC13 protein in a large, well-defined cohort of 389 serum samples from patients with ovarian cancer and benign conditions.

RESULTS

MUC13 and CA125 serum levels were elevated in malignant compared to benign cases (p<0.0001). Receiver-operating characteristic (ROC) curve analysis showed similar area under the curve (AUC) of 0.74 (MUC13) and 0.76 (CA125). MUC13 concentrations were significantly higher in mucinous adenocarcinomas compared to benign controls (p=0.0005), with AUC of 0.80. MUC13 and CA125 showed significant elevation in early-stage cases (stage I-II) in relation to benign controls (p=0.0012 and p=0.014, respectively).

CONCLUSIONS

We report the novel role of MUC13 as a serum ovarian cancer biomarker, where it could complement CA125 for detecting some subtypes of non-serous ovarian carcinoma and early-stage disease.

Aberrant MUC Immunohistochemical Expressions in Inflammatory Bowel Diseases

Ulcerative colitis (UC) and Crohn disease (CD) are cryptogenic inflammatory bowel diseases that are suggestive of aberrant mucin (MUC) expression; however, their relationship remains unclear. Here, we examined aberrant MUC expression in intestinal samples from UC and CD patients in comparison to samples from patients with ischemic colitis and control groups. To study the expression of MUC1 , MUC5AC , and MUC6 in different patient groups, we reviewed the slides stained with hematoxylin and eosin and performed immunohistochemistry. The results revealed that MUC1 was expressed more in the UC group and MUC6 in the CD group. No significant changes were observed in MUC expression in the ischemic colitis group. Overall, we demonstrated changes in MUC expression in UC and CD, which can help in the diagnosis and early clinical management of UC and CD.

Pathological Implications of Mucin Signaling in Metastasis

The dynamic mucosal layer provides a selective protective barrier for the epithelial cells lining the body cavities. Diverse human malignancies exploit their intrinsic role to protect and repair epithelia for promoting growth and survival. Aberrant expression of mucin has been known to be associated with poor prognosis of many cancers. However, the emergence of new paradigms in the study of metastasis recognizes the involvement of MUC1, MUC4, MUC5AC, MUC5B, and MUC16 during metastasis initiation and progression. Hence mucins can be used as an attractive target in future diagnostic and therapeutic strategies. In this review, we discuss in detail about mucin family and its domains and the role of different mucins in regulating cancer progression and metastasis. In addition, we briefly discuss insights into mucins as a therapeutic agent.

The diagnostic and prognostic potential of the EGFR/MUC4/MMP9 axis in glioma patients

Glioblastoma is the most aggressive form of brain cancer, presenting poor prognosis despite current advances in treatment. There is therefore an urgent need for novel biomarkers and therapeutic targets. Interactions between mucin 4 (MUC4) and the epidermal growth factor receptor (EGFR) are involved in carcinogenesis, and may lead to matrix metalloproteinase-9 (MMP9) overexpression, exacerbating cancer cell invasiveness. In this study, the role of MUC4, MMP9, and EGFR in the progression and clinical outcome of glioma patients was investigated. Immunohistochemistry (IHC) and immunofluorescence (IF) in fixed tissue samples of glioma patients were used to evaluate the expression and localization of EGFR, MMP9, and MUC4. Kaplan-Meier survival analysis was also performed to test the prognostic utility of the proteins for glioma patients. The protein levels were assessed with enzyme-linked immunosorbent assay (ELISA) in serum of glioma patients, to further investigate their potential as non-invasive serum biomarkers. We demonstrated that MUC4 and MMP9 are both significantly upregulated during glioma progression. Moreover, MUC4 is co-expressed with MMP9 and EGFR in the proliferative microvasculature of glioblastoma, suggesting a potential role for MUC4 in microvascular proliferation and angiogenesis. The combined high expression of MUC4/MMP9, and MUC4/MMP9/EGFR was associated with poor overall survival (OS). Finally, MMP9 mean protein level was significantly higher in the serum of glioblastoma compared with grade III glioma patients, whereas MUC4 mean protein level was minimally elevated in higher glioma grades (III and IV) compared with control. Our results suggest that MUC4, along with MMP9, might account for glioblastoma progression, representing potential therapeutic targets, and suggesting the 'MUC4/MMP9/EGFR axis' may play a vital role in glioblastoma diagnostics.

Expression of MUC16/CA125 Is Associated with Impaired Survival in Patients with Surgically Resected Cholangiocarcinoma

MUC16/CA125 is associated with cancer proliferation in several tumor entities. The data on MUC16 expression in cholangiocarcinoma (CCA) tissue are very limited. The aim of this study was to assess the MUC16 status and its impact on survival in CCA patients. All the patients with surgically resected CCA that were diagnosed between August 2005 and December 2021 at the University Hospital Frankfurt were retrospectively analyzed. A 7-Mucin biomarker panel was assessed by immunohistochemistry. For overall survival (OS), Kaplan−Meier curves and Cox-regression analyses were performed. Randomly selected intrahepatic cholangiocarcinoma (iCCA) were further processed for differential expression profiling. A total of 168 patients with CCA were classified as MUC16 (−) (66%, n = 111) and MUC16 (+) (34%, n = 57). Subgroup analyses revealed a median OS of 56.1 months (95% CI = 42.4−69.9 months) and 27.4 months (95% CI = 15.8−39.1 months) for MUC16 (−) and MUC16 (+), respectively (p < 0.001). In multivariate analysis, MUC16 (+) (HR = 1.6, 95% CI = 1−2.6, p = 0.032) was an independent risk factor for poor prognosis. Prominently deregulated pathways have been identified following MUC16 expression, overrepresented in cell cycle and immune system exhaustion processes. These findings suggest including MUC16 in clinical routine diagnostics as well as studying its molecular pathways to identify further mechanistic key players.

Analysis of MUC6 Genetic Variants on the Clinicopathologic Characteristics of Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the leading malignancy associated with cancer-related deaths worldwide. Many studies have indicated that mucin (MUC) expression plays an important role in cancer metastasis and recurrence. MUC6 expression is observed in gastric and oncocytic phenotypes and may play an important role during cancer progression. We found the level of MUC6 is lower in HCC patients but did not affect the survival of HCC patients. Therefore, in this study, we investigated the combined effect of MUC6 polymorphisms and exposure to environmental carcinogens on the susceptibility to and clinicopathological characteristics of HCC. Three single-nucleotide polymorphisms (SNPs) of MUC6 (rs61869016, rs6597947, and rs7481521) from 1197 healthy controls and 423 HCC patients were analyzed using real-time PCR. After adjusting for other co-variants, we found that carrying a CC genotype at MUC6 rs61869016 had a lower risk of developing HCC than wildtype carriers. Moreover, patients with a smoking habit who carried the C allele of rs61869016 and T allele of rs7481521 had a higher (B or C) Child-Pugh score than other genotypes, suggesting significant functional compromise and decompensated disease. Therefore, our findings suggest that genetic variations in MUC6 may corelate to HCC and indicate progression in HCC patients.

Advances in the management of peritoneal malignancies

Peritoneal surface malignancies (PSMs) are usually associated with a poor prognosis. Nonetheless, in line with advances in the management of most abdominopelvic metastatic diseases, considerable progress has been made over the past decade. An improved understanding of disease biology has led to the more accurate prediction of neoplasia aggressiveness and the treatment response and has been reflected in the proposal of new classification systems. Achieving complete cytoreductive surgery remains the cornerstone of curative-intent treatment of PSMs. Alongside centralization in expert centres, enabling the delivery of multimodal and multidisciplinary strategies, preoperative management is a crucial step in order to select patients who are most likely to benefit from surgery. Depending on the specific PSM, the role of intraperitoneal chemotherapy and of perioperative systemic chemotherapy, in particular, in the neoadjuvant setting, is established in certain scenarios but questioned in several others, although more prospective data are required. In this Review, we describe advances in all aspects of the management of PSMs including disease biology, assessment and improvement of disease resectability, perioperative management, systemic therapy and pre-emptive management, and we speculate on future research directions.

INHBB is a novel prognostic biomarker and correlated with immune infiltrates in gastric cancer

Inhibin subunit beta B (INHBB) is a potential prognostic biomarker for a variety of cancers. However, its role in gastric cancer (GC) remains elusive. The differential expression data of INHBB in tumor and normal tissues were extracted from several databases and genetic alterations of INHBB were assessed by cBioPortal. Kaplan-Meier analysis was used to evaluate the survival rate of patients with GC with INHBB and association with clinical features in GC. Cox regression analysis was used to explore the prognostic value of clinical indicators and INHBB in GC, and a nomogram prognostic model was established. In addition, the predictive validity of the nomogram model was assessed by time-depended receiver operating characteristic (ROC) and calibration curves. Functional enrichment analyses were conducted to functionally annotate INHBB. Notably, we found that the quantitative assessment of immune cell subpopulation infiltration correlated with INHBB expression. INHBB expression is upregulated in GC and is correlated with several clinical features including prognostic indicators and a histological type. Genetic alterations were observed in INHBB, its DNA methylation level was negatively correlated with INHBB expression. High INHBB expression is associated with a poor prognosis and is an independent risk factor for prognosis in GC, along with age and residual tumor. The nomogram model showed a good prediction ability and was validated by time-depended ROC and calibration curves. Functional enrichment analysis indicated that INHBB-associated genes were enriched in tumor microenvironment Gene Ontology (GO) terms and were correlated with tumor-associated pathways. INHBB has a regulatory function in immune cell infiltration, especially macrophage infiltration in GC. Specifically, patients with GC with high INHBB expression and high macrophage infiltration have a worse prognosis. INHBB expression was negatively correlated with the expression of chemokines/chemokine receptors and plays a regulatory role in immunoinhibitor/immunostimulator-involved pathways. INHBB is a potential prognostic biomarker for GC and may drive the abnormal activity of critical cancer-associated pathways, potentially contributing to immune cell infiltration to promote GC development.