Mucin-interacting proteins: from function to therapeutics

A 35-gene mutation profile predicts the therapeutic outcome of patients with esophageal squamous cell carcinoma receiving neo-adjuvant chemoradiation

Esophageal cancer is a common malignancy worldwide with a poor prognosis without radical resection. Neoadjuvant concurrent chemoradiotherapy (NACRT) followed by esophagectomy is widely used for treating locally advanced esophageal cancer in the thorax. The study aimed to assess mutation profiles and their correlation with therapeutic outcomes in patients diagnosed with locally advanced thoracic esophageal squamous cell carcinoma (ESCC). A retrospective analysis was conducted on 62 patients with ESCC who underwent NACRT. All patients received concurrent chemoradiotherapy (CCRT) utilizing intensity-modulated radiation therapy alongside concurrent chemotherapy with a cisplatin-based regimen. A 35-gene next-generation sequencing (NGS) panel detecting 402 genetic variants was used, which has been proven predictive in ESCC patients who received definitive chemoradiation. The 35-gene mutation profiles were analyzed in pre-treatment biopsies. The results reveled there were variants correlated with pathological complete remission or partial response, overall survival, and progression-free survival. A combination of p.Pro1319Ser and p.Arg2159Gly mutations in the MUC17 gene demonstrated an adverse impact on pathological response (OR [95% CI] = 7.00 (3.07-15.94), P < 0.001). Additionally, the variants located in the MUC17, MUC4, and MYH4 genes exhibited notably effects on tumor recurrence or mortality. Patients harboring either the MUC17 p.Thr2702Val or MUC4 p.Thr3355Ser mutation displayed a more than four-fold increased risk for disease recurrence or mortality. We concluded that specific mutations correlated to the pathological complete response in ESCC receiving neoadjuvant chemoradiation can be identified through the utilization of 35-gene expression profiles. Further investigation into the pathophysiological roles of MUC17 and MUC4 mutations in ESCC is warranted.

Targeting Siglec-Sialylated MUC1 Immune Axis in Cancer

Siglecs play a key role in mediating cell-cell interactions via the recognition of different sialylated glycoconjugates, including tumor-associated MUC1, which can lead to the activation or inhibition of the immune response. The activation occurs through the signaling of Siglecs with the cytoplasmic immunoreceptor tyrosine-based activation motif (ITAM)-containing proteins, while the inhibition signal is a result of the interaction of intracellular immunoreceptor tyrosine-based inhibition motif (ITIM)-bearing receptors. The interaction of tumor-associated MUC1 sialylated glycans with Siglecs via ITIM motifs decreases antitumor immunity. Consequently, these interactions are expected to play a key role in tumor evasion. Efforts to modulate the response of immune cells by blocking the immune-suppressive effects of inhibitory Siglecs, driving immune-activating Siglecs, and/or altering the synthesis and expression of the sialic acid glycocalyx are new therapeutic strategies deserving further investigation. We will highlight the role of Siglec's family receptors in immune evasion through interactions with glycan ligands in their natural context, presented on the protein such as MUC1, factors affecting their fine binding specificities, such as the role of multivalency either at the ligand or receptor side, their spatial organization, and finally the current and future therapeutic interventions targeting the Siglec-sialylated MUC1 immune axis in cancer.

Highly Sensitive Labeling, Clickable Functionalization, and Glycoengineering of the MUC1 Neighboring System

This study introduces a novel wash-type affinity-primed proximity labeling (WAPL) strategy for labeling and surface engineering of the MUC1 protein neighboring system. The strategy entails the utilization of peroxidase in conjunction with a MUC1-selective aptamer, facilitating targeted binding to MUC1 and inducing covalent labeling of the protein neighboring system. This study reveals a novel finding that the WAPL strategy demonstrates superior labeling efficiency in comparison to nonwash-type affinity-primed proximity labeling, marking the first instance of such observations. The WAPL strategy provides signal amplification by converting a single recognition event into multiple covalent labeling events, thereby improving the detection sensitivity for subtle changes in MUC1. The WAPL platform employs two levels of labeling upgrades, modifying the biotin handles of the conventional labeling substrate, biotin-phenol. The first level involves a range of clickable molecules, facilitating dibenzoazacyclooctynylation, alkynylation, and trans-cyclooctenylation of the protein neighboring system. The second level utilizes lactose as a post-translational modification model, enabling rapid and reliable glycoengineering of the MUC1 neighboring system while remaining compatible with cell-based assays. The implementation of the WAPL strategy in protein neighboring systems has resulted in the establishment of a versatile platform that can effectively facilitate diverse monitoring and regulation techniques. This platform offers valuable insights into the regulation of relevant signaling pathways and promotes the advancement of novel therapeutic approaches, thereby bringing substantial implications for human health.

Mucin Expression Profiles in Ulcerative Colitis: New Insights on the Histological Mucosal Healing

A structural weakness of the mucus barrier (MB) is thought to be a cause of ulcerative colitis (UC). This study aims to investigate the mucin (MUC) composition of MB in normal mucosa and UC. Ileocolonic biopsies were taken at disease onset and after treatment in 40 patients, including 20 with relapsing and 20 with remitting UC. Ileocolonic biopsies from 10 non-IBD patients were included as controls. Gut-specific MUC1, MUC2, MUC4, MUC5B, MUC12, MUC13, MUC15, and MUC17 were evaluated immunohistochemically. The promoters of mucin genes were also examined. Normal mucosa showed MUC2, MUC5B, and MUC13 in terminal ileum and colon, MUC17 in ileum, and MUC1, MUC4, MUC12, and MUC15 in colon. Membranous, cytoplasmic and vacuolar expressions were highlighted. Overall, the mucin expression was abnormal in UC. Derangements in MUC1, MUC4, and MUC5B were detected both at onset and after treatment. MUC2 and MUC13 were unaffected. Sequence analysis revealed glucocorticoid-responsive elements in the MUC1 promoter, retinoic-acid-responsive elements in the MUC4 promoter, and butyrate-responsive elements in the MUC5B promoter. In conclusion, MUCs exhibited distinct expression patterns in the gut. Their expression was disrupted in UC, regardless of the treatment protocols. Abnormal MUC1, MUC4, and MUC5B expression marked the barrier dysfunction in UC.

Elucidating the molecular role of MUC5B in progressive lung adenocarcinoma: Prospects for early diagnosis

Gel-forming mucin MUC5B is significantly deregulated in lung adenocarcinoma (LUAD), however, its role in tumor progression is not yet clearly understood. Here, we used an integrated computational-pipeline-initiated with gene expression analysis followed by network, functional-enrichment, O-linked glycosylation analyses, mutational profiling, and immune cell infiltration estimation to functionally characterize MUC5B gene in LUAD. Thereafter, clinical biomarker validation was supported by the overall survival (OA) and comparative expression profiling across clinical stages using computational algorithms. The gene expression profile of LUAD identified MUC5B to be significantly up-regulated (logFC: 2.36; p-value: 0.01). Network analysis on LUAD interactome screened MUC5B-related genes, having key enrichment in immune suppression and O-linked glycosylation with serine-threonine-rich tandem repeats being highly glycosylated. Furthermore, positive correlation of mutant MUC5B with immune cells in tumor microenvironment (TME) such as cancer-associated fibroblasts and myeloid-derived suppressor cells indicates TME-mediated tumor progression. The positive correlation with immune inhibitors suggested the enhanced tumor proliferation mediated by MUC5B. Structural stability due to genetic alterations identified overall rigid N-H-backbone dynamics (S2 : 0.756), indicating an overall stable mutant protein. Moreover, the low median OA (<50 months) with a hazard ratio of 1.4 and clinical profile of MUC5B gene showed high median expression corresponding to lymph node (N2) and tumor (T3) stages. Our study concludes by highlighting the functional role of O-glycosylated and mutant MUC5B in promoting LUAD by immune suppression. Further, clinical gene expression validation of MUC5B suggests its potential role as a diagnostic biomarker for LUAD metastasis.

SHEAR saliva collection device augments sample properties for improved analytical performance

Despite being a convenient clinical substrate for biomonitoring, saliva's widespread utilization has not yet been realized. The non-Newtonian, heterogenous, and highly viscous nature of saliva complicate the development of automated fluid handling processes that are vital for accurate diagnoses. Furthermore, conventional saliva processing methods are resource and/or time intensive precluding certain testing capabilities, with these challenges aggravated during a pandemic. The conventional approaches may also alter analyte structure, reducing application opportunities in point-of-care diagnostics. To overcome these challenges, we introduce the SHEAR saliva collection device that mechanically processes saliva, in a rapid and resource-efficient way. We demonstrate the device's impact on reducing saliva's viscosity, improving sample's uniformity, and increasing diagnostic performance of a COVID-19 rapid antigen test. Additionally, a formal user experience study revealed generally positive comments. SHEAR saliva collection device may support realization of the saliva's potential, particularly in large-scale and/or resource-limited settings for global and community diagnostics.

Cinnamaldehyde alleviates zearalenone-induced LS174T cell apoptosis, barrier dysfunction and mucin reduction through JNK/NF-κB signaling pathway

As a natural aldehyde organic compound, cinnamaldehyde (CA) is one of the main components of cinnamon essential oil with multiple bioactivities. In this study, we investigated the protective effects of CA on zearalenone (ZEA)-induced apoptosis, barrier dysfunction and mucin reduction, as well as underlying mechanisms in LS174T cells. In the present study, cells pre-treated with or without CA for 24 h were left untreated or subjected to ZEA for indicated time points Our results showed that 10 μM CA significantly prevented ZEA-induced cell viability decline, reversed ZEA-induced increase of the LDH level, cell cycle disruption and apoptosis in LS174T cells. Periodic acid-schiff (PAS) staining analysis showed that CA significantly alleviated the reduction of mucin secretion in LS174T cells caused by ZEA exposure. Western blot analysis showed that CA significantly reversed ZEA-induced reduction of the expression of mucin 2 (MUC2) and tight junction (TJ) proteins (claudin-1, claudin-3, ZO-1 and ZO-2) in LS174T cells. Notably, CA can significantly reduce the upregulation of the main effector of MAPK and NF-κB signaling pathways in LS174T cells. Further study showed that CA protects cells against ZEA-induced cellular damage through JNK/NF-κB signaling pathway in LS174T cells. Supplementation with CA might be an potential strategy to alleviate the damaging effect of ZEA on epithelial cells.

Decoding the expression pattern of MUC3A in gastric adenocarcinoma: unveiling the key to successful immunotherapy

AIMS

Despite the promise of immunotherapy for gastric adenocarcinoma, resistance is common, necessitating the validation of new targets. Based on our previous bioinformatics analysis, the MUC3A antigen emerged as a promising candidate for immunotherapy against gastric adenocarcinoma. However, a comprehensive understanding of its expression at protein level remains elusive, despite its crucial role in determining clinical response. We also sought to establish a connection between the expression pattern and relevant clinical variables of the disease, whenever feasible.

METHODS

Immunohistochemistry was used to determine the percentage of MUC3A-positive tumor cells in primary (PT) and metastatic tumor (MT) sites of 190 gastric adenocarcinoma patients. We also evaluated the association between MUC3A expression and variables such as Lauren classification, history of neoadjuvant chemotherapy and/or radiotherapy, and overall patient survival.

RESULTS

Median MUC3A expression was 50% in PT and 70% in MT sites, exhibiting a positive correlation. MT intestinal type showed significantly higher MUC3A expression compared to other types. Neoadjuvant therapy history did not affect MUC3A expression. Higher MUC3A expression correlated with improved survival.

CONCLUSIONS

Based on our previous bioinformatics data and the consistently high expression of MUC3A on gastric tumor cells, we propose advancing experimental aspects of anti-MUC3A immunotherapy for gastric adenocarcinoma.

Orchestration of MUC2 - The key regulatory target of gut barrier and homeostasis: A review

The gut mucosa of human is covered by mucus, functioning as a crucial defense line for the intestine against external stimuli and pathogens. Mucin2 (MUC2) is a subtype of secretory mucins generated by goblet cells and is the major macromolecular component of mucus. Currently, there is an increasing interest on the investigations of MUC2, noting that its function is far beyond a maintainer of the mucus barrier. Moreover, numerous gut diseases are associated with dysregulated MUC2 production. Appropriate production level of MUC2 and mucus contributes to gut barrier function and homeostasis. The production of MUC2 is regulated by a series of physiological processes, which are orchestrated by various bioactive molecules, signaling pathways and gut microbiota, etc., forming a complex regulatory network. Incorporating the latest findings, this review provided a comprehensive summary of MUC2, including its structure, significance and secretory process. Furthermore, we also summarized the molecular mechanisms of the regulation of MUC2 production aiming to provide developmental directions for future researches on MUC2, which can act as a potential prognostic indicator and targeted therapeutic manipulation for diseases. Collectively, we elucidated the micro-level mechanisms underlying MUC2-related phenotypes, hoping to offer some constructive guidance for intestinal and overall health of mankind.

Detection of IL-1β, VEGF and IL-4 with their novel genetic variations in breast cancer patients

Interleukin-1β (IL-1β), vascular endothelial growth factor (VEGF), and IL-4 serum levels and new genetic mutations in breast cancer (BC) patients were assessed in the current study. The serum levels of the examined cytokines in 40 BC patients and 40 control subjects were assessed using the ELISA technique. In order to identify genotype variants of the IL-1β, IL-4, and VEGF genes in 40 Formalin Fixed Paraffin Embedded (FFPE) samples with BC and 10 FFPE samples from healthy women's breast tissue, Sanger sequencing was used. According to this study, BC patients had significantly lower serum concentrations of IL-4 and significantly higher quantities of the tumor markers, CA15-3, IL-1β, and VEGF. In terms of genotype alterations, a total of 21 mutations in three trialed genes (eight in IL-1β, 10 in IL-4, and three in VEGF) were found in BC patients. The results of the current investigation suggested that angiogenesis and the development of BC may be significantly influenced by the genetic differences and higher levels of the examined cytokines.

Transcriptome-based insights into the regulatory role of immune-responsive circular RNAs in Litopanaeus vannamei upon WSSV infection

Circular RNAs (circRNAs) are non-coding RNAs (ncRNAs) originating from a post-transcriptional modification process called back-splicing. Despite circRNAs being traditionally considered by-products rather than independently functional, circRNAs play many vital roles, such as in host immunity during viral infection. However, in shrimp, these remain largely unexplored. Therefore, this study aims to identify circRNAs in Litopenaeus vannamei in the context of WSSV infection, one of the most eradicative pathogens threatening shrimp populations worldwide. We identified 290 differentially expressed circRNAs (DECs) in L. vannamei upon WSSV infection. Eight DECs were expressed from their parental genes, including alpha-1-inhibitor-3, calpain-B, integrin-V, hemicentin-2, hemocytin, mucin-17, proPO2, and rab11-FIP4. These were examined quantitatively by qRT-PCR, which revealed the relevant expression profiles to those obtained from circRNA-Seq. Furthermore, the structural and chemical validation of the DECs conformed to the characteristics of circRNAs. One of the functional properties of circRNAs as a miRNA sponge was examined via the interaction network between DECs and WSSV-responsive miRNAs, which highlighted the targets of miRNA sponges. Our discovery could provide insight into the participation of these ncRNAs in shrimp antiviral responses.

MUC13-miRNA-4647 axis in colorectal cancer: Prospects to identifications of risk factors and clinical outcomes

MUC13, a transmembrane mucin glycoprotein, is overexpressed in colorectal cancer (CRC), however, its regulation and functions are not fully understood. It has been shown that MUC13 protects colonic epithelial cells from apoptosis. Therefore, studying MUC13 and MUC13-regulated pathways may reveal promising therapeutic approaches for CRC treatment. Growing evidence suggests that microRNAs (miRs) are involved in the development and progression of CRC. In the present study, the MUC13-miR-4647 axis was addressed in association with survival of patients. miR-4647 is predicted in silico to bind to the MUC13 gene and was analyzed by RT-qPCR in 187 tumors and their adjacent non-malignant mucosa of patients with CRC. The impact of previously mentioned genes on survival and migration abilities of cancer cells was validated in vitro. Significantly upregulated MUC13 (P=0.02) in was observed tumor tissues compared with non-malignant adjacent mucosa, while miR-4647 (P=0.05) showed an opposite trend. Higher expression levels of MUC13 (log-rank P=0.05) were associated with worse patient's survival. The ectopic overexpression of studied miR resulted in decreased migratory abilities and worse survival of cells. Attenuated MUC13 expression levels confirmed the suppression of colony forming of CRC cells. In summary, the present data suggested the essential role of MUC13-miR-4647 in patients' survival, and this axis may serve as a novel therapeutic target. It is anticipated MUC13 may hold significant potential in the screening, diagnosis and treatment of CRC.

Chemokine-mucinome interplay in shaping the heterogeneous tumor microenvironment of pancreatic cancer

Pancreatic cancer (PC) is exemplified by a complex immune-suppressive, fibrotic tumor microenvironment (TME), and aberrant expression of mucins. The constant crosstalk between cancer cells, cancer-associated fibroblasts (CAFs), and the immune cells mediated by the soluble factors and inflammatory mediators including cytokines, chemokines, reactive oxygen species (ROS) promote the dynamic temporal switch towards an immune-escape phenotype in the neoplastic cells and its microenvironment that bolsters disease progression. Chemokines have been studied in PC pathogenesis, albeit poorly in the context of mucins, tumor glycocalyx, and TME heterogeneity (CAFs and immune cells). With correlative analysis from PC patients' transcriptome data, support from available literature, and scientific arguments-based speculative extrapolations in terms of disease pathogenesis, we have summarized in this review a comprehensive understanding of chemokine-mucinome interplay during stromal modulation and immune-suppression in PC. Future studies should focus on deciphering the complexities of chemokine-mediated control of glycocalyx maturation, immune infiltration, and CAF-associated immune suppression. Knowledge extracted from such studies will be beneficial to mechanistically correlate the mucin-chemokine abundance in serum versus pancreatic tumors of patients, which may aid in prognostication and stratification of PC patients for immunotherapy.

α1,4-linked N-acetylglucosamine suppresses gastric cancer development by inhibiting MUC1-mediated signaling

Gastric cancer is the second leading cause of cancer deaths worldwide, and more understanding of its molecular basis is urgently needed. Gastric gland mucin secreted from pyloric gland cells, mucous neck cells, and cardiac gland cells of the gastric mucosa harbors unique O‐glycans carrying terminal α1,4‐linked N‐acetylglucosamine (αGlcNAc) residues. We previously reported that αGlcNAc loss correlated positively with poor outcomes for patients with differentiated‐type gastric cancer. However, the molecular mechanisms underlying these outcomes remained poorly understood. Here, we examined the effects of upregulated αGlcNAc expression on malignant phenotypes of the differentiated‐type gastric cancer cell lines, AGS and MKN7. Upregulation of αGlcNAc following ectopic expression of its biosynthetic enzyme attenuated cell proliferation, motility, and invasiveness of AGS and MKN7 cells in vitro. Moreover, AGS cell tumorigenicity was significantly suppressed by αGlcNAc overexpression in a xenograft model. To define the molecular mechanisms underlying these phenotypes, we investigated αGlcNAc binding proteins in AGS cells and identified Mucin‐1 (MUC1) and podocalyxin. Both proteins were colocalized with αGlcNAc on human gastric cancer cells. We also found that αGlcNAc was bound to MUC1 in murine normal gastric mucosa. When we assessed the effects of αGlcNAc binding to MUC1, we found that αGlcNAc blocked galectin‐3 binding to MUC1, phosphorylation of the MUC1 C‐terminus, and recruitment of Src and β‐catenin to that C‐terminus. These results suggest that αGlcNAc regulates cancer cell phenotypes by dampening MUC1 signal transduction.

Intracellular MUC20 variant 2 maintains mitochondrial calcium homeostasis and enhances drug resistance in gastric cancer

BACKGROUND

Signet ring cell carcinoma (SRCC) is a particular histologic variant of gastric cancer (GC). However, the critical factor related to the aggressive characteristics of SRCC has not been determined.

METHODS

We collected surgically resected tissues from 360 GC patients in the Kumamoto University cohort and generated survival curves via the Kaplan-Meier method. In vitro, we identified the specific transcript variant of MUC20 in SRCC cells by direct sequencing and investigated the role of MUC20 in GC progression using GC cells with MUC20 silencing and forced expression. In vivo, we examined chemoresistance using MUC20 variant 2 (MUC20v2)-overexpressing non-SRCC cells to construct a xenograft mouse model.

RESULTS

We analyzed a comprehensive GC cell line database to identify the specifically expressed genes in gastric SRCC. We focused on MUC20 and investigated its role in GC progression. Survival analysis revealed that GC patients with high MUC20 expression exhibited a poor prognosis and that MUC20 expression was significantly correlated with SRCC histological type. Moreover, we found that gastric SRCC cells specifically expressed MUC20v2, which was dominantly expressed in the cytoplasm. Silencing MUC20v2 caused cell death with characteristic morphological changes in gastric SRCC cells. To further determine the types of cell death, we examined apoptosis, pyroptosis and ferroptosis by detecting cleaved PARP, gasdermin E-N-terminal (GSDME-N), and lipid reactive oxygen species (ROS) levels, respectively. We found that apoptosis and pyroptosis occurred in MUC20-silenced gastric SRCC cells. In addition, MUC20v2-overexpressing GC cells exhibited chemoresistance to cisplatin (CDDP) and paclitaxel (PTX). RNA sequencing revealed that the pathways involved in intracellular calcium regulation were significantly upregulated in MUC20v2-overexpressing GC cells. Notably, forced expression of MUC20v2 in the cytoplasm of GC cells led to the maintenance of mitochondrial calcium homeostasis and mitochondrial membrane potential (MMP), which promoted cell survival and chemoresistance by suppressing apoptosis and pyroptosis. Finally, we investigated the significance of MUC20v2 in a xenograft model treated with CDDP and showed that MUC20v2 overexpression caused chemoresistance by inhibiting cell death.

CONCLUSION

These findings highlight the novel functions of MUC20v2, which may confer cell survival and drug resistance in GC cells.

SIGNIFICANCE

MUC20v2 protects GC cells from apoptosis and pyroptosis by maintaining mitochondrial calcium levels and mitochondrial membrane potential and subsequently induces drug resistance.

A SPLUNC1 Peptidomimetic Inhibits Orai1 and Reduces Inflammation in a Murine Allergic Asthma Model

Orai1 is a plasma membrane Ca2+ channel that mediates store-operated Ca2+ entry (SOCE) and regulates inflammation. Short palate lung and nasal epithelial clone 1 (SPLUNC1) is an asthma gene modifier that inhibits Orai1 and SOCE via its C-terminal α6 region. SPLUNC1 levels are diminished in asthma patient airways. Thus, we hypothesized that inhaled α6 peptidomimetics could inhibit Orai1 and reduce airway inflammation in a murine asthma model. To evaluate α6-Orai1 interactions, we used fluorescent assays to measure Ca2+ signaling, Förster resonance energy transfer, fluorescent recovery after photobleaching, immunostaining, total internal reflection microscopy, and Western blotting. To test whether α6 peptidomimetics inhibited SOCE and decreased inflammation in vivo, wild-type and SPLUNC1-/- mice were exposed to house dust mite (HDM) extract with or without α6 peptide. We also performed nebulization, jet milling, and scanning electron microscopy to evaluate α6 for inhalation. SPLUNC1-/- mice had an exaggerated response to HDM. In BAL-derived immune cells, Orai1 levels increased after HDM exposure in SPLUNC1-/- but not wild-type mice. Inhaled α6 reduced Orai1 levels in mice regardless of genotype. In HDM-exposed mice, α6 dose-dependently reduced eosinophilia and neutrophilia. In vitro, α6 inhibited SOCE in multiple immune cell types, and α6 could be nebulized or jet milled without loss of function. These data suggest that α6 peptidomimetics may be a novel, effective antiinflammatory therapy for patients with asthma.

An efficient and safe MUC1-dendritic cell-derived exosome conjugate vaccine elicits potent cellular and humoral immunity and tumor inhibition in vivo

Antitumor vaccines are a promising strategy for preventing or treating cancers by eliciting antitumor immune responses and inducing protective immunity against specific antigens expressed on tumor cells. Vaccine formulations that enhance the humoral and cellular immune responses of vaccine candidates would be highly beneficial but are still limited. Here we developed an antitumor vaccine candidate by conjugating a MUC1 glycopeptide antigen to dendritic cell-derived exosomes (Dex). In vivo, the MUC1-Dex construct induced high MUC1-specific IgG antibody titers with strong binding affinities for MUC1-positive tumor cells and promoted cytokine secretion. Moreover, CD8⁺ T cells from immunized mice exhibited strong cytotoxicity against MUC1-positive tumor cells. Importantly, in both preventative and therapeutic tumor-bearing mouse models, the construct inhibited tumor growth and prolonged survival. Collectively, these results demonstrate that Dex is a promising vaccine carrier that can be used as adjuvant to enhance the immunological efficacy of tumor vaccines. STATEMENT OF SIGNIFICANCE.

Effects of Baicalein and Chrysin on the Structure and Functional Properties of β-Lactoglobulin

Two flavonoids with similar structures, baicalein (Bai) and chrysin (Chr), were selected to investigate the interactions with β-lactoglobulin (BLG) and the influences on the structure and functional properties of BLG by multispectral methods combined with molecular docking and dynamic (MD) simulation techniques. The results of fluorescence quenching suggested that both Bai and Chr interacted with BLG to form complexes with the binding constant of the magnitude of 10⁵ L·mol⁻¹. The binding affinity between BLG and Bai was stronger than that of Chr due to more hydrogen bond formation in Bai–BLG binding. The existence of Bai or Chr induced a looser conformation of BLG, but Chr had a greater effect on the secondary structure of BLG. The surface hydrophobicity and free sulfhydryl group content of BLG lessened due to the presence of the two flavonoids. Molecular docking was performed at the binding site of Bai or Chr located in the surface of BLG, and hydrophobic interaction and hydrogen bond actuated the formation of the Bai/Chr–BLG complex. Molecular dynamics simulation verified that the combination of Chr and BLG decreased the stability of BLG, while Bai had little effect on it. Moreover, the foaming properties of BLG got better in the presence of the two flavonoids compounds and Bai improved its emulsification stability of the protein, but Chr had the opposite effect. This work provides a new idea for the development of novel dietary supplements using functional proteins as flavonoid delivery vectors.

Characterization of recombinant β subunit of human MUC4 mucin (rMUC4β)

MUC4 is a transmembrane mucin expressed on various epithelial surfaces, including respiratory and gastrointestinal tracts, and helps in their lubrication and protection. MUC4 is also aberrantly overexpressed in various epithelial malignancies and functionally contributes to cancer development and progression. MUC4 is putatively cleaved at the GDPH site into a mucin-like α-subunit and a membrane-tethered growth factor-like β-subunit. Due to the presence of several functional domains, the characterization of MUC4β is critical for understanding MUC4 biology. We developed a method to produce and purify multi-milligram amounts of recombinant MUC4β (rMUC4β). Purified rMUC4β was characterized by Far-UV CD and I-TASSER-based protein structure prediction analyses, and its ability to interact with cellular proteins was determined by the affinity pull-down assay. Two of the three EGF-like domains exhibited typical β-fold, while the third EGF-like domain and vWD domain were predominantly random coils. We observed that rMUC4β physically interacts with Ezrin and EGFR family members. Overall, this study describes an efficient and simple strategy for the purification of biologically-active rMUC4β that can serve as a valuable reagent for a variety of biochemical and functional studies to elucidate MUC4 function and generating domain-specific antibodies and vaccines for cancer immunotherapy.

Purified mucins in drug delivery research

One of the main challenges in the field of drug delivery remains the development of strategies to efficiently transport pharmaceuticals across mucus barriers, which regulate the passage and retention of molecules and particles in all luminal spaces of the body. A thorough understanding of the molecular mechanisms, which govern such selective permeability, is key for achieving efficient translocation of drugs and drug carriers. For this purpose, model systems based on purified mucins can contribute valuable information. In this review, we summarize advances that were made in the field of drug delivery research with such mucin-based model systems: First, we give an overview of mucin purification procedures and discuss the suitability of model systems reconstituted from purified mucins to mimic native mucus. Then, we summarize techniques to study mucin binding. Finally, we highlight approaches that made use of mucins as building blocks for drug delivery platforms or employ mucins as active compounds.

MUC1: Structure, Function, and Clinic Application in Epithelial Cancers

The transmembrane glycoprotein mucin 1 (MUC1) is a mucin family member that has different functions in normal and cancer cells. Owing to its structural and biochemical properties, MUC1 can act as a lubricant, moisturizer, and physical barrier in normal cells. However, in cancer cells, MUC1 often undergoes aberrant glycosylation and overexpression. It is involved in cancer invasion, metastasis, angiogenesis, and apoptosis by virtue of its participation in intracellular signaling processes and the regulation of related biomolecules. This review introduces the biological structure and different roles of MUC1 in normal and cancer cells and the regulatory mechanisms governing these roles. It also evaluates current research progress and the clinical applications of MUC1 in cancer therapy based on its characteristics.

Structural Alterations of Mucins Are Associated with Losses in Functionality

Commercial mucin glycoproteins are routinely used as a model to investigate the broad range of important functions mucins fulfill in our bodies, including lubrication, protection against hostile germs, and the accommodation of a healthy microbiome. Moreover, purified mucins are increasingly selected as building blocks for multifunctional materials, i.e., as components of hydrogels or coatings. By performing a detailed side-by-side comparison of commercially available and lab-purified variants of porcine gastric mucins, we decipher key molecular motifs that are crucial for mucin functionality. As two main structural features, we identify the hydrophobic termini and the hydrophilic glycosylation pattern of the mucin glycoprotein; moreover, we describe how alterations in those structural motifs affect the different properties of mucins-on both microscopic and macroscopic levels. This study provides a detailed understanding of how distinct functionalities of gastric mucins are established, and it highlights the need for high-quality mucins-for both basic research and the development of mucin-based medical products.

The role of mucin 1 in respiratory diseases

Recent evidence has demonstrated that mucin 1 (MUC1) is involved in many pathological processes that occur in the lung. MUC1 is a transmembrane protein mainly expressed by epithelial and hematopoietic cells. It has a receptor-like structure, which can sense the external environment and activate intracellular signal transduction pathways through its cytoplasmic domain. The extracellular domain of MUC1 can be released to the external environment, thus acting as a decoy barrier to mucosal pathogens, as well as serving as a serum biomarker for the diagnosis and prognosis of several respiratory diseases such as lung cancer and interstitial lung diseases. Furthermore, bioactivated MUC1-cytoplasmic tail (CT) has been shown to act as an anti-inflammatory molecule in several airway infections and mediates the expression of anti-inflammatory genes in lung diseases such as chronic rhinosinusitis, chronic obstructive pulmonary disease and severe asthma. Bioactivated MUC1-CT has also been reported to interact with several effectors linked to cellular transformation, contributing to the progression of respiratory diseases such as lung cancer and pulmonary fibrosis. In this review, we summarise the current knowledge of MUC1 as a promising biomarker and drug target for lung disease.

Mucin Secretion in Cystic Fibrosis: A Systematic Review

BACKGROUND

Mucus protects the epithelium against invaders and toxic materials. Sticky and thick mucus is characteristic of CF.

OBJECTIVE

The aim of this systematic review is to characterize the specific mucins secreted in the lung and intestinal tract of CF patients.

METHODS

A systematic literature search was conducted up to December 31, 2019. The following terms were used: "cystic fibrosis" AND "mucin." Case-control studies comparing mucin expression in CF patients to healthy controls were included.

RESULTS

We found 741 eligible studies, 694 studies were rejected because they were performed in animals and not in full text, and 32 studies were excluded being editorials, duplications, review articles, meta-analysis, or not in English. Fifteen studies were eligible for our study, including 150 CF patients compared to 82 healthy controls, all fulfilled the inclusion criteria. The main mucin types expressed in the sinus submucosal glands, sputum, tracheobronchial surface epithelium, and lung submucosal glands were MUC5AC and MUC5B. Increase in the number of sinusoidal submucosal glands and expression of MUC5B was found in CF patients, but no such difference from healthy controls was found for the number of goblet cells in the surface epithelium nor in the expression of -MUC5AC. The opposite was found in the tracheobronchial surface epithelium and in the lungs.

CONCLUSIONS

Increased expression of MUC5AC in the surface epithelium and of MUC5B in the subepithelial glands may be the result of higher secretion rate of mucin into the lumen of the respiratory tract, causing mucus plaque, infection, and inflammation.

Dual-Probe Approach for Mass Spectrometric Quantification of MUC1-Specific Terminal Gal/GalNAc In Situ

Protein glycosylation is a prevalent post-translational modification that mediates a variety of cellular processes. For membrane proteins, glycosylation at their terminal motif is usually more functional. Among the various glycosylation types found in membrane proteins, O-glycosylation is the most common and is closely correlated with a variety of cancer types, including breast cancer. Slightly aberrant expression of certain O-glycans can significantly affect cancer progression, especially at the cancer-related membrane protein level. To collect biological information on protein-specific glycosylation and further explore clinical applications, quantitative detection of glycosylation is essential. However, few assays have been reported for the in situ detection of protein-specific glycosylation to date. Herein, we developed a dual-probe approach for mass spectrometric quantification of protein-specific glycosylation using the terminal galactose/N-acetylgalactosamine (Gal/GalNAc) of MUC1 as a model. The dual-probe (i.e., protein probe and glycan probe) system was first designed and built. The protein probe contained an aptamer for MUC1 protein recognition and a capture DNA sequence. Correspondingly, the glycan probe had a DNA sequence complementary to that of the capture DNA, a substrate peptide containing a reporter peptide, and a tryptic cleavage site, and could be covalently linked with the terminal Gal/GalNAc. Exonuclease III enabled recycling of the hybridization-dehybridization process in a restricted space. Finally, the reporter peptide was tryptically released and quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The mass response of the reporter peptide represented the amount of MUC1-specific terminal Gal/GalNAc. This dual-probe approach was applied for in situ detection of MUC1-specific terminal Gal/GalNAc in three human breast cancer cell lines and 32 pairs of matched breast cancer tissue samples. The relationship between MUC1-specific terminal Gal/GalNAc expression and breast cancer diagnosis/prognosis was also assessed.

Role of MUC1 rs4072037 polymorphism in gastric cancer: a meta-analysis

Background and objective: To further determine the association between mucin 1 (MUC1) rs4072037 polymorphism and gastric cancer risk on the basis of previously published studies. Methodology: PubMed and Embase were used to search all the available publications. The relative risk of the correlation was shown as odds ratio (OR) with 95% confidence interval (95% CI) under all the genetic comparisons. Subgroup analyses based on ethnicity, study design and HWE were also executed to detect effects of specific factors on the risk of gastric cancer. Results: MUC1 rs4072037 polymorphism was observed to reduce the risk of gastric cancer under the five genetic comparisons [(GG versus AA: OR (95% CI)=0.72 (0.61, 0.84); GG + GA versus AA: OR (95% CI)=0.82 (0.76, 0.88); GG versus AA + GA: OR (95% CI)=0.83 (0.71, 0.96); G versus A: OR (95% CI)=0.78 (0.72, 0.84); GA versus AA: OR (95% CI)=0.80 (0.74, 0.87)]. This decreased risk of gastric cancer was also detected in subgroup analyses based on ancestry (Asian and Caucasian), study design (population-based and hospital-based) and HWE (P _HWE>0.05). Conclusions: MUC1 rs4072037 polymorphism may have an important role in gastric cancer, and this protective effect may vary among different ethnic populations and control subjects.

Mucin glycoproteins block apoptosis; promote invasion, proliferation, and migration; and cause chemoresistance through diverse pathways in epithelial cancers

Overexpression of mucin glycoproteins has been demonstrated in many epithelial-derived cancers. The significance of this overexpression remains uncertain. The aim of this paper was to define the association of mucin glycoproteins with apoptosis, cell growth, invasion, migration, adhesion, and clonogenicity in vitro as well as tumor growth, tumorigenicity, and metastasis in vivo in epithelial-derived cancers by performing a systematic review of all published data. A systematic review of PubMed, Embase, and the Cochrane Central Register of Controlled Trials was performed to identify all papers that evaluated the association between mucin glycoproteins with apoptosis, cell growth, invasion, migration, adhesion, and clonogenicity in vitro as well as tumor growth, tumorigenicity, and metastasis in vivo in epithelial-derived cancers. PRISMA guidelines were adhered to. Results of individual studies were extracted and pooled together based on the organ in which the cancer was derived from. The initial search revealed 2031 papers, of which 90 were deemed eligible for inclusion in the study. The studies included details on MUC1, MUC2, MUC4, MUC5AC, MUC5B, MUC13, and MUC16. The majority of studies evaluated MUC1. MUC1 overexpression was consistently associated with resistance to apoptosis and resistance to chemotherapy. There was also evidence that overexpression of MUC2, MUC4, MUC5AC, MUC5B, MUC13, and MUC16 conferred resistance to apoptosis in epithelial-derived cancers. The overexpression of mucin glycoproteins is associated with resistance to apoptosis in numerous epithelial cancers. They cause resistance through diverse signaling pathways. Targeting the expression of mucin glycoproteins represents a potential therapeutic target in the treatment of epithelial-derived cancers.

Presence and structure-activity relationship of intrinsically disordered regions across mucins

Many members of the mucin family are evolutionarily conserved and are often aberrantly expressed and glycosylated in various benign and malignant pathologies leading to tumor invasion, metastasis, and immune evasion. The large size and extensive glycosylation present challenges to study the mucin structure using traditional methods, including crystallography. We offer the hypothesis that the functional versatility of mucins may be attributed to the presence of intrinsically disordered regions (IDRs) that provide dynamism and flexibility and that the IDRs offer potential therapeutic targets. Herein, we examined the links between the mucin structure and function based on IDRs, posttranslational modifications (PTMs), and potential impact on their interactome. Using sequence-based bioinformatics tools, we observed that mucins are predicted to be moderately (20%-40%) to highly (>40%) disordered and many conserved mucin domains could be disordered. Phosphorylation sites overlap with IDRs throughout the mucin sequences. Additionally, the majority of predicted O- and N- glycosylation sites in the tandem repeat regions occur within IDRs and these IDRs contain a large number of functional motifs, that is, molecular recognition features (MoRFs), which directly influence protein-protein interactions (PPIs). This investigation provides a novel perspective and offers an insight into the complexity and dynamic nature of mucins.

Mucins and Pathogenic Mucin-Like Molecules Are Immunomodulators During Infection and Targets for Diagnostics and Vaccines

Mucins and mucin-like molecules are highly O-glycosylated proteins present on the cell surface of mammals and other organisms. These glycoproteins are highly diverse in the apoprotein and glycan cores and play a central role in many biological processes and diseases. Mucins are the most abundant macromolecules in mucus and are responsible for its biochemical and biophysical properties. Mucin-like molecules cover various protozoan parasites, fungi and viruses. In humans, modifications in mucin glycosylation are associated with tumors in epithelial tissue. These modifications allow the distinction between normal and abnormal cell conditions and represent important targets for vaccine development against some cancers. Mucins and mucin-like molecules derived from pathogens are potential diagnostic markers and targets for therapeutic agents. In this review, we summarize the distribution, structure, role as immunomodulators, and the correlation of human mucins with diseases and perform a comparative analysis of mucins with mucin-like molecules present in human pathogens. Furthermore, we review the methods to produce pathogenic and human mucins using chemical synthesis and expression systems. Finally, we present applications of mucin-like molecules in diagnosis and prevention of relevant human diseases.

Mucins as a New Frontier in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common idiopathic interstitial pulmonary disease with a median survival of 3–5 years after diagnosis. Recent evidence identifies mucins as key effectors in cell growth and tissue remodeling processes compatible with the processes observed in IPF. Mucins are classified in two groups depending on whether they are secreted (secreted mucins) or tethered to cell membranes (transmembrane mucins). Secreted mucins (MUC2, MUC5AC, MUC5B, MUC6-8 and MUC19) are released to the extracellular medium and recent evidence has shown that a promoter polymorphism in the secreted mucin MUC5B is associated with IPF risk. Otherwise, transmembrane mucins (MUC1, MUC3, MUC4, MUC12-17 and MUC20) have a receptor-like structure, sensing the external environment and activating intracellular signal transduction pathways essential for mucosal maintenance and damage repair. In this context, the extracellular domain can be released to the external environment by metalloproteinase action, increased in IPF, thus activating fibrotic processes. For example, several studies have reported increased serum extracellular secreted KL6/MUC1 during IPF acute exacerbation. Moreover, MUC1 and MUC4 overexpression in the main IPF cells has been observed. In this review we summarize the current knowledge of mucins as promising druggable targets for IPF.

Induction of Trop-2 expression through the binding of galectin-3 to MUC1

Both mucin 1 (MUC1) and trophoblast cell surface antigen 2 (Trop-2) are overexpressed in various epithelial tumor cells, and their high expression is correlated with a poor prognosis. Both proteins were expressed in a human breast cancer cell line, MCF-7 cells, but neither was in a human colon cancer cell line, HCT116 cells. When MUC1 cDNA was introduced into HCT116 cells (HCT116/MUC1), expression of Trop-2 was induced. Reciprocally, treatment of MCF-7 cells with MUC1 siRNA reduced the level of Trop-2. Mithramycin A, an inhibitor of specificity protein 1 (Sp1) transcription factor, effectively inhibited the expression of Trop-2. Consistently, treatment with Sp1 siRNA reduced the expression of Trop-2. To reveal the relationship between MUC1 and Sp1, coimmunoprecipitation assays were performed. Sp1 was coimmunoprecipitated with MUC1 and the level of coimmunoprecipitated Sp1 increased in relation to the level of induced Trop-2. It is known that galectin-3 is an endogenous ligand of MUC1. Binding of galectin-3 to MUC1 elevated the recruitment of Sp1 to MUC1, and knockdown of galectin-3 reduced the level of Trop-2. These results suggest that the binding of galectin-3 to MUC1 enhances the recruitment of Sp1, leading to promotion of the transcription of Trop-2.

Acquired Enamel Pellicle Modification with Casein and Mucin in Different Concentrations and its Impact on Initial Dental Erosion

Casein and mucin have been shown to improve the erosion-protective properties of the pellicle when applied in combination. The aim of this in vitro study was to optimize the concentrations of these 2 proteins to achieve a maximum protective effect. For the 2 parts of this study, we prepared a total of 195 human enamel specimens and randomly assigned them to 13 groups, corresponding to 11 different casein-mucin concentration-combinations tested and 2 negative control groups (humid chamber). They underwent 5 cycles, consisting of pellicle formation from human whole saliva (2 h, 30°C), modification of the pellicle with casein and mucin in different concentrations (immersion in protein solutions for 2 h, 30°C), and erosion for 1 min in citric acid (0.65%, pH 3.5, 30°C). Surface microhardness (SMH), surface reflection intensity (SRI), and in the first part also calcium release were monitored during the cycling process, and analyzed with Kruskal-Wallis and post hoc Dunn’s tests. The results suggest that the best concentrations to achieve the highest erosion-protective effect are 3.0% casein and 0.81% mucin, which lead to a significant protection as measured by SMH as well as SRI compared to the unmodified pellicle. For the calcium release, no significant differences were found. This concentration combination corresponds to a general raise of the protein concentrations and a change in the molar ratio of the proteins as compared to earlier studies. Casein and mucin could now be incorporated at the determined concentration as natural ingredients in oral care products designed to protect against erosion.

Structure-Based Design of Potent Tumor-Associated Antigens: Modulation of Peptide Presentation by Single-Atom O/S or O/Se Substitutions at the Glycosidic Linkage

GalNAc-glycopeptides derived from mucin MUC1 are an important class of tumor-associated antigens. α- O-glycosylation forces the peptide to adopt an extended conformation in solution, which is far from the structure observed in complexes with a model anti-MUC1 antibody. Herein, we propose a new strategy for designing potent antigen mimics based on modulating peptide/carbohydrate interactions by means of O → S/Se replacement at the glycosidic linkage. These minimal chemical modifications bring about two key structural changes to the glycopeptide. They increase the carbohydrate-peptide distance and change the orientation and dynamics of the glycosidic linkage. As a result, the peptide acquires a preorganized and optimal structure suited for antibody binding. Accordingly, these new glycopeptides display improved binding toward a representative anti-MUC1 antibody relative to the native antigens. To prove the potential of these glycopeptides as tumor-associated MUC1 antigen mimics, the derivative bearing the S-glycosidic linkage was conjugated to gold nanoparticles and tested as an immunogenic formulation in mice without any adjuvant, which resulted in a significant humoral immune response. Importantly, the mice antisera recognize cancer cells in biopsies of breast cancer patients with high selectivity. This finding demonstrates that the antibodies elicited against the mimetic antigen indeed recognize the naturally occurring antigen in its physiological context. Clinically, the exploitation of tumor-associated antigen mimics may contribute to the development of cancer vaccines and to the improvement of cancer diagnosis based on anti-MUC1 antibodies. The methodology presented here is of general interest for applications because it may be extended to modulate the affinity of biologically relevant glycopeptides toward their receptors.

Interactions of salivary mucins and saliva with food proteins: a review

Mucins are long glycoprotein molecules responsible for the gel nature of the mucous layer that covers epithelial surfaces throughout the body. Mucins, as the major salivary proteins, are also important proteins for the food oral processing and digestion. The interactions of salivary mucins and saliva with several food proteins and food protein emulsions, as well as their functional properties related to the food oral processing were reviewed in this paper. The target food proteins of focus were whey proteins (lactoferrin and beta-lactoglobulin) and non-whey proteins (casein, gelatin, galectin/lectin, and proline-rich proteins). Most of the studies suggest that electrostatic attraction (between positively charged food proteins with negatively charged moieties of mucin mainly on glycosylated region of mucin) is the major mode of interaction between them. On the other hand, casein attracts the salivary proteins only via non-covalent interactions due to its naturally self-assembled micellar structure. Moreover, recent studies related to β-lactoglobulin (BLG)-mucin interactions have clarified the importance of hydrophobic as well as hydrophilic interactions, such as hydrogen bonding. Furthermore, in vitro studies between protein emulsions and saliva observed a strong aggregating effect of saliva on caseinate and whey proteins as well as on surfactant-stabilized emulsions. Besides, the sign and the density of the charge on the surface of the protein emulsion droplets contribute significantly to the behavior of the emulsion when mixed with saliva. Other studies also suggested that the interactions between saliva and whey proteins depends on the pH in addition to the flow rate of the saliva. Overall, the role of interactions of food proteins and food protein emulsions with mucin/saliva-proteins in the oral perception, as well as the physicochemical and structural changes of proteins were discussed.

Commercial Porcine Gastric Mucin Preparations, also Used as Artificial Saliva, are a Rich Source for the Lectin TFF2: In Vitro Binding Studies

Mucous gels (mucus) cover internal body surfaces. The secretory mucins MUC5AC and MUC6 and the protective peptide TFF2 are characteristic constituents of gastric mucus; TFF2 is co-secreted with MUC6. Herein, we investigated two commercial mucin preparations by FPLC and proteomics, because they are model systems for studying the rheology of gastric mucins. One preparation is also used as a saliva substitute, for example, after radiation therapy. We show that both preparations contain TFF2 (≈0.6 to 1.1 %, w/w). The majority of TFF2 is strongly bound noncovalently to mucin in a manner that is resistant to boiling in SDS. First overlay assays with ¹²⁵ I-labeled porcine TFF2 revealed that mucin binding is modulated by Ca²⁺ and can be blocked by the lectin GSA-II and the antibody HIK1083, both recognizing the peripheral GlcNAcα1→4Galβ1→R moiety of MUC6. TFF2 binding was also inhibited in the presence of Me-β-Gal but less so by the α anomer. TFF2 may play a role in the oligomerization and secretion of MUC6, the rheology of gastric mucus, and the adherence of gastric microbiota. TFF2 in artificial saliva may be of benefit. TFF2 might also interact with the sugar moiety of various receptors.

The Impact of Mesothelin in the Ovarian Cancer Tumor Microenvironment

Ovarian cancer is the deadliest gynecological disease among U.S. women. Poor 5-year survival rates (<30%) are due to presentation of most women at diagnosis with advanced stage disease with widely disseminated intraperitoneal metastasis. However, when diagnosed before metastatic propagation the overall 5-year survival rate is >90%. Metastasizing tumor cells grow rapidly and aggressively attach to the mesothelium of all organs within the peritoneal cavity, including the parietal peritoneum and the omentum, producing secondary lesions. In this review, the involvement of mesothelin (MSLN) in the tumor microenvironment is discussed. MSLN, a 40kDa glycoprotein that is overexpressed in many cancers including ovarian and mesotheliomas is suggested to play a role in cell survival, proliferation, tumor progression, and adherence. However, the biological function of MSLN is not fully understood as MSLN knockout mice do not present with an abnormal phenotype. Conversely, MSLN has been shown to bind to the ovarian cancer antigen, CA-125, and thought to play a role in the peritoneal diffusion of ovarian tumor cells. Although the cancer-specific expression of MSLN makes it a potential therapeutic target, more studies are needed to validate the role of MSLN in tumor metastasis.

"Do We Know Jack" About JAK? A Closer Look at JAK/STAT Signaling Pathway

Janus tyrosine kinase (JAK) family of proteins have been identified as crucial proteins in signal transduction initiated by a wide range of membrane receptors. Among the proteins in this family JAK2 has been associated with important downstream proteins, including signal transducers and activators of transcription (STATs), which in turn regulate the expression of a variety of proteins involved in induction or prevention of apoptosis. Therefore, the JAK/STAT signaling axis plays a major role in the proliferation and survival of different cancer cells, and may even be involved in resistance mechanisms against molecularly targeted drugs. Despite extensive research focused on the protein structure and mechanisms of activation of JAKs, and signal transduction through these proteins, their importance in cancer initiation and progression seem to be underestimated. This manuscript is an attempt to highlight the role of JAK proteins in cancer biology, the most recent developments in targeting JAKs, and the central role they play in intracellular cross-talks with other signaling cascades.

Tn Antigen Mimics by Ring-Opening of Chiral Cyclic Sulfamidates with Carbohydrate C1- S- and C1- O-Nucleophiles

Starting from commercially available ( S)-isoserine and effectively accessible ( S)-α-methylserine, enantiopure cyclic sulfamidates have been prepared as chiral building blocks for the synthesis of various S- and O-glycosylated amino acid derivatives, including unnatural variants of the Tn antigen, through highly chemo-, regio-, and stereoselective nucleophilic ring-opening reactions with carbohydrate C1- S- and C1- O-nucleophiles.

Triple-negative and HER2-overexpressing breast cancer cell sialylation impacts tumor microenvironment T-lymphocyte subset recruitment: a possible mechanism of tumor escape

Introduction

Breast cancers develop different patterns of sialylation to modulate their tumor-infiltrating lymphocyte (TIL) environment. We studied the relationship between α-2,6 sialyltransferases and the TIL in different breast cancer molecular subgroups.

Materials and methods

Immunohistochemical preparations were made from 39 luminal (LUM), 13 human epidermal growth factor receptor 2-overexpressing (HER2) and 47 triple-negative (TN) breast carcinomas. Targeted proteins included ST6Gal-I, ST6Gal-II, ST6GalNac-I, CD8, CD4 and granzyme-B in both cytotoxic T lymphocytes and NK lymphocytes (CTL/NK).

Results

CTL/NK populations were significantly more frequent in TN than LUM (P <0.001). TN showed a lower level of ST6Gal-I expression than LUM or HER2 (both P > 0.001). ST6GalNac-I expression was lower in LUM than in TN or HER2 (P = 0.002 and P = 0.02, respectively). In HER2, a significant association was found between a low level of ST6Gal-I expression and a high TIL level. In TN, a significant association was observed between a high level of ST6Gal-II expression and a high TIL level.

Conclusion

An increase in infiltrating lymphocytes could be influenced by low expression of ST6Gal-I in HER2 and by high expression of ST6Gal-II in TN breast cancers. Thus, targeting these sialylation pathways could modulate the levels of TIL.

Principles of mucin structure: implications for the rational design of cancer vaccines derived from MUC1-glycopeptides

Cancer is currently one of the world's most serious public health problems. Significant efforts are being made to develop new strategies that can eradicate tumours selectively without detrimental effects to healthy cells. One promising approach is focused on the design of vaccines that contain partially glycosylated mucins in their formulation. Although some of these vaccines are in clinical trials, a lack of knowledge about the molecular basis that governs the antigen presentation, and the interactions between antigens and the elicited antibodies has limited their success thus far. This review focuses on the most significant milestones achieved to date in the conformational analysis of tumour-associated MUC1 derivatives both in solution and bound to antibodies. The effect that the carbohydrate scaffold has on the peptide backbone structure and the role of the sugar in molecular recognition by antibodies are emphasised. The outcomes summarised in this review may be a useful guide to develop new antigens for the design of cancer vaccines in the near future.

Mucin Expression in the Esophageal Malignant and Pre-malignant States: A Systematic Review and Meta-analysis

BACKGROUND

Mucins are heavily glycosylated glycoproteins, synthesized by mucosal surfaces and have an important role in healthy state and malignant diseases. Change in mucins synthesis or secretion may be primary event or secondary to inflammation or carcinogenesis.

AIM

The aim of this study is to assess the current knowledge about mucin expression in esophageal lesions, and to establish a role for different mucin expressions as prognostic markers.

METHOD

English Medical literature searches were conducted for "mucin" and "esophagus." Observational studies were included. Meta-analysis was performed using comprehensive meta-analysis software. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated.

RESULTS

In the random-effect model, mucin expression was significantly higher in esophageal lesions than in normal esophageal mucosa with OR=5.456 (95% CI, 1.883-15.807, P=0.002). Measure of heterogeneity, demonstrated in the included studies, was high: Q=287.501, df (Q)=44.00, P<0.0001, I=84.696%. There is a gradient of mucin expression and complexity in esophageal premalignant to malignant lesions, lower in Barrett's mucosa with low grade dysplasia (LGD), increased in high grade dysplasia (HGD), and highest in esophageal adenocarcinoma (EAC). MUC2, MUC3, MUC5AC, and MUC6 expression was higher in EAC than HGD, and higher in HGD than in LGD mucosa. The opposite was found for MUC1 and MUC4.

CONCLUSION

Increased expression of certain mucin genes in esophageal mucosa may be further studied as a potential diagnostic tool, and this may add important information in the surveillance of Barrett's esophagus.

Mucins as multifunctional building blocks of biomaterials

Mucins glycoproteins are emerging as a multifunctional building block for biomaterials with diverse applications in chemistry and biomedicine.

Anti-cancer effects of F16: A novel vascular endothelial growth factor receptor-specific inhibitor

Vascular endothelial growth factor receptor-2 is a dynamic target for therapeutic intervention in various types of cancers. This study was aimed to explore the anti-angiogenic activity of a novel vascular endothelial growth factor receptor-specific inhibitor named F16 in both in vitro and in vivo experimental models. This compound effectively reduced cell proliferation, tube formation, and migration of human umbilical vein endothelial cells in a concentration-dependent manner by directly inhibiting vascular endothelial growth factor binding and subsequent vascular endothelial growth factor receptor-2 phosphorylation. The F16 was also able to inhibit the phosphoinositide 3-kinase/protein kinase B-mediated survival and migration pathways in cancer in addition to inhibiting the focal adhesion kinase and mitogen-activated protein kinases-mediated signaling in GI-101A cancer cells. The chorioallantoic membrane assay followed by tumor growth inhibition measurements with GI-101A breast cancer xenograft implanted athymic nude mice confirmed the in vivo tumor reductive effects of F16. It was interesting to observe a decrease in tumor burden after F16 treatment which correlated very well with the decrease in the plasma levels of mucin-1 (MUC-1). Our studies so far have confirmed that F16 is a specific inhibitor of angiogenesis in both in vitro and in vivo models. The F16 also works very efficiently with Taxol in combination by limiting the tumor growth that is better than the monotherapy with any one of the drugs that were tested individually. Thus, F16 offers a promising anti-proliferative and anti-angiogenic effects with better specificity than some of the existing multi-kinase inhibitors.