Mucin gene expression in biliary epithelial cells

MUC5AC and MUC5B expression in canine gallbladder mucocele epithelial cells

Gallbladder mucocele (GBM) is one of the most common gallbladder diseases in dogs. Its pathogenesis has not yet been clarified, but excessive accumulation of a secretory gel-forming mucin, MUC5AC in the gallbladder has been reported. This study aimed to ascertain if MUC5AC overproduction resulted in mucus accumulation in the gallbladder during GBM development. Eleven dogs undergoing cholecystectomy who were pathologically diagnosed with GBM were included, and the expression level of mucins, particularly MUC5AC and MUC5B, in their gallbladder epithelial cells was compared with those in normal gallbladder epithelial cells. On reverse transcription-quantitative polymerase chain reaction screening, there was a significant difference (P<0.05) in the mRNA expression level of MUC1, but not of other mucins including MUC5AC and MUC5B, between mucocele and normal gallbladder epithelial cells. Protein expression levels were also evaluated for MUC5AC and MUC5B using immunohistochemistry. There was little immunoreactivity for MUC5AC, whereas MUC5B showed definitive staining in gallbladder epithelial cells. There was no difference in MUC5AC and MUC5B protein expression levels between mucocele and normal gallbladder epithelial cells. These data suggest that excessive production of mucin, especially MUC5AC and MUC5B, does not occur in canine GBM, and that abnormal mucus excretion, rather than excessive mucus production, may be the cause of GBM development.

Role of gut microbiota and bacterial metabolites in mucins of colorectal cancer

Colorectal cancer (CRC) is a major health burden, accounting for approximately 10% of all new cancer cases worldwide. Accumulating evidence suggests that the crosstalk between the host mucins and gut microbiota is associated with the occurrence and development of CRC. Mucins secreted by goblet cells not only protect the intestinal epithelium from microorganisms and invading pathogens but also provide a habitat for commensal bacteria. Conversely, gut dysbiosis results in the dysfunction of mucins, allowing other commensals and their metabolites to pass through the intestinal epithelium, potentially triggering host responses and the subsequent progression of CRC. In this review, we summarize how gut microbiota and bacterial metabolites regulate the function and expression of mucin in CRC and novel treatment strategies for CRC.

Diagnostic accuracy of HIK1083 and MUC6 as immunohistochemical markers of endocervical gastric-type adenocarcinoma: A systematic review and meta-analysis

INTRODUCTION

HIK1083 and MUC6 have been used as immunohistochemical markers to differentiate gastric-type adenocarcinoma (GTAC) from other endocervical adenocarcinomas. We aimed to assess their diagnostic accuracy through a systematic review and meta-analysis.

METHODS

Three electronic databases were searched from their inception to July 2022 for all studies assessing the expression in endocervical GTAC vs other endocervical adenocarcinomas. Diagnostic accuracy was assessed as sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-), diagnostic odds ratio (DOR), and area under the curve (AUC) on SROC curves.

RESULTS

Four studies with 343 patients were included. HIK1083 showed sensitivity= 0.64, specificity= 0.94, LR+ =8.30, LR-= 0.38, DOR= 33.36, AUC= 89.9%. MUC6 showed sensitivity= 0.51, specificity= 0.74, LR+ =1.96, LR-= 0.71, DOR= 3.48, AUC= 72.8%.

CONCLUSION

HIK1083 showed high specificity and low sensitivity as a marker of GTAC, with moderate overall accuracy; MUC6 showed moderate specificity and low sensitivity, with low overall accuracy.

Early pathogenesis of cystic fibrosis gallbladder disease in a porcine model

Hepatobiliary disease causes significant morbidity in people with cystic fibrosis (CF), yet this problem remains understudied. We previously found that newborn CF pigs have microgallbladders with significant luminal obstruction in the absence of infection and consistent inflammation. In this study, we sought to better understand the early pathogenesis of CF pig gallbladder disease. We hypothesized that loss of CFTR would impair gallbladder epithelium anion/liquid secretion and increase mucin production. CFTR was expressed apically in non-CF pig gallbladder epithelium but was absent in CF. CF pig gallbladders lacked cAMP-stimulated anion transport. Using a novel gallbladder epithelial organoid model, we found that Cl- or HCO3- was sufficient for non-CF organoid swelling. This response was absent for non-CF organoids in Cl-/HCO3--free conditions and in CF. Single-cell RNA-sequencing revealed a single epithelial cell type in non-CF gallbladders that coexpressed CFTR, MUC5AC, and MUC5B. Despite CF gallbladders having increased luminal MUC5AC and MUC5B accumulation, there was no significant difference in the epithelial expression of gel-forming mucins between non-CF and CF pig gallbladders. In conclusion, these data suggest that loss of CFTR-mediated anion transport and fluid secretion contribute to microgallbladder development and luminal mucus accumulation in CF.

The Diverse Roles of the Mucin Gene Cluster Located on Chromosome 11p15.5 in Colorectal Cancer

Colorectal cancer (CRC), the third most common malignant tumor in the world, shows multiple complex and pathologies based on the impaired structure and function of the intestinal mucosal barrier. Goblet cells secrete mucins, which are involved in the formation of the intestinal mucosal barrier and not only lubricate and protect the intestinal mucosa but also participate in the processes of cell adhesion, intercellular signal transduction, and immune regulation. It is accepted that the disordered expression and dysfunction of mucins are associated with the occurrence and development of CRC. This article focuses on the secretory mucins encoded by a gene cluster located on chromosome 11p15.5 and systematically reviews their composition, regulation, function, and role in CRC, to deepen the understanding of the pathogeneses of CRC and to provide a new basis and ideas for the treatment of CRC.

Mucins: the Old, the New and the Promising Factors in Hepatobiliary Carcinogenesis

Mucins are large O-glycoproteins with high carbohydrate content and marked diversity in both the apoprotein and the oligosaccharide moieties. All three mucin types, trans-membrane (e.g., MUC1, MUC4, MUC16), secreted (gel-forming) (e.g., MUC2, MUC5AC, MUC6) and soluble (non-gel-forming) (e.g., MUC7, MUC8, MUC9, MUC20), are critical in maintaining cellular functions, particularly those of epithelial surfaces. Their aberrant expression and/or altered subcellular localization is a factor of tumour growth and apoptosis induced by oxidative stress and several anti-cancer agents. Abnormal expression of mucins was observed in human carcinomas that arise in various gastrointestinal organs. It was widely believed that hepatocellular carcinoma (HCC) does not produce mucins, whereas cholangiocarcinoma (CC) or combined HCC-CC may produce these glycoproteins. However, a growing number of reports shows that mucins can be produced by HCC cells that do not exhibit or are yet to undergo, morphological differentiation to biliary phenotypes. Evaluation of mucin expression levels in precursors and early lesions of CC, as well as other types of primary liver cancer (PLC), conducted in in vitro and in vivo models, allowed to discover the mechanisms of their action, as well as their participation in the most important signalling pathways of liver cystogenesis and carcinogenesis. Analysis of mucin expression in PLC has both basic research and clinical value. Mucins may act as oncogenes and tumour-promoting (e.g., MUC1, MUC13), and/or tumour-suppressing factors (e.g., MUC15). Given their role in promoting PLC progression, both classic (MUC1, MUC2, MUC4, MUC5AC, MUC6) and currently tested mucins (e.g., MUC13, MUC15, MUC16) have been proposed to be important diagnostic and prognostic markers. The purpose of this review was to summarize and update the role of classic and currently tested mucins in pathogenesis of PLC, with explaining the mechanisms of their action in HCC carcinogenesis. It also focuses on determination of the diagnostic and prognostic role of these glycoproteins in PLC, especially focusing on HCC, CC and other hepatic tumours with- and without biliary differentiation.

Prognostic and clinicopathological value of MUC1 expression in colorectal cancer: A meta-analysis

BACKGROUND

Accumulating evidence supports the overexpression of mucin 1 (MUC1) in colorectal cancer (CRC), but the value of elevated MUC1 expression remains controversial. Here, we evaluated the prognostic and clinicopathological value of MUC1 expression in CRC.

MATERIALS AND METHODS

The Web of Science, PubMed, Embase, Cochrane Library, and Wanfang databases, as well as the China Biology Medicine disc (CBMdisc) and China National Knowledge Infrastructure (CNKI) were searched for studies on MUC1 expression and prognosis of CRC through July 20, 2018. The pooled relative risks (RRs) and hazard ratios (HRs) with 95% confidence intervals (95% CIs) were calculated to evaluate the prognostic and clinicopathological value of MUC1 expression in CRC. The Revman version 5.3 package and STATA, version 12 were employed for pooled analysis and analysis of publication bias.

RESULTS

This meta-analysis included 16 published studies. The combined analysis showed that CRC patients with high MUC1 expression had a worse clinical outcome in overall survival (OS) (HR = 1.51, 95% CI = 1.30-1.75, P <.00001). In addition, high MUC1 expression was associated with higher TNM stage (RR = 1.44, 95% CI = 1.17-1.77, P = .0007), greater depth of invasion (RR = 1.30, 95% CI = 1.10-1.53, P = .002), and lymph node metastasis (RR = 1.47, 95% CI = 1.20-1.80, P = .0002) of CRC. However, the elevated MUC1 expression was not related to disease-free survival/recurrence-free survival (DFS/RFS) (HR = 1.51, 95% CI = 0.78-2.89, P = .22), histological grade (RR = 1.15, 95% CI = 0.96-1.38, P = .12), gender (RR = 0.95; 95% CI = 0.83-1.08, P = .44), tumor size (RR = 1.11, 95% CI = 0.85-1.44, P = .44), tumor site (RR = 1.01, 95% CI = 0.88-1.16, P = .84), or mucinous component (RR = 0.83, 95% CI = 0.60-1.14, P = .24) in CRC.

CONCLUSION

Our findings indicated that high MUC1 expression represents a marker of poor prognosis in CRC. Meanwhile, elevated MUC1 expression was associated with advanced TNM stage, greater depth of invasion, and lymph node metastasis.

Ramifications of secreted mucin MUC5AC in malignant journey: a holistic view

Heavily glycosylated secreted mucin MUC5AC, by the virtue of its cysteine-rich repeats, can form inter- and intramolecular disulfide linkages resulting in complex polymers, which in turn craft the framework of the polymeric mucus gel on epithelial cell surfaces. MUC5AC is a molecule with versatile functional implications including barrier functions to epithelial cells, host-pathogen interaction, immune cell attraction to sites of premalignant or malignant lesions and tumor progression in a context-dependent manner. Differential expression, glycosylation and localization of MUC5AC have been associated with a plethora of benign and malignant pathologies. In this era of robust technologies, overexpression strategies and genetically engineered mouse models, MUC5AC is emerging as a potential diagnostic, prognostic and therapeutic target for various malignancies. Considering the clinical relevance of MUC5AC, this review holistically encompasses its genomic organization, domain structure, glycosylation patterns, regulation, functional and molecular connotation from benign to malignant pathologies. Furthermore, we have here explored the incipient and significant experimental tools that are being developed to study this structurally complex and evolutionary conserved gel-forming mucin.

hsa-miR-93 regulates MUCIN family gene expression via WNT/β-catenin pathway in intrahepatic stone disease

BACKGROUND

Mucin plays an essential role in the intrahepatic stone formation, but the mechanism of mucin regulation is unclear.

OBJECTIVE

To investigate the potential implication of miR-93 and WNT pathway in the regulation of intrahepatic bile duct mucin expression.

METHODS

Thirty patients with or without intrahepatic bile duct stones are involved; Reverse-transcription polymerase chain reaction was performed to evaluate the expression of MUC3, MUC4, MUC5B, MUC5AC mRNA and miR-93 levels. miR-NC or miR-93 mimics was transfected into intrahepatic biliary epithelial cells. Then mucins and Wnt pathway proteins were detected by the immunoblotting, and the target gene TCF7 were validated using the dual luciferase assay. β-catenin, wnt4, and mucins were an immunohistochemical stain of the intrahepatic biliary epithelial tissues.

RESULTS

The expression levels of MUC3, MUC4, MUC5B, and MUC5AC in patients with intrahepatic bile duct stones are higher than control, as well as Wnt pathway proteins (especially β-catenin and wnt4). Mucins levels increased in wnt4, wnt5a or SB216763-treated HIBECs, and reduced by miR-93 mimics transfection. miR-93 directly targeted TCF7 and repressed Wnt pathway protein expression, which reversed the upregulation of mucin levels induced by wnt4 or wnt5a, but not SB216763.

CONCLUSION

These results suggest a new potential mechanism in intrahepatic stones, regulating by miR-93/TCF7, non-canonical Wnt pathway, and mucins.

Prognostic Value of MUC2 Expression in Colorectal Cancer: A Systematic Review and Meta-Analysis

Background

The reliability of MUC2 as a prognostic marker in colorectal cancer (CRC) is controversial. This study evaluated the association between MUC2 expression levels in CRC tissues and prognosis.

Methods

The PubMed, Web of Science, Embase, Cochrane Library, China Biology Medicine disc (CBMdisc), Wanfang Database, and China National Knowledge Infrastructure (CNKI) databases were searched to identify studies exploring the relationship between MUC2 expression in CRC tissues and overall survival (OS). Pooled hazard ratios (HRs) and risk ratios (RRs) with 95% confidence intervals (CIs) were used to evaluate the associations between MUC2 expression levels and prognosis and MUC2 expression levels and CRC clinicopathological characteristics, respectively.

Results

The meta-analysis included 11 studies (2619 patients). Low MUC2 expression level was significantly associated with poor OS (HR, 1.67; 95% CI, 1.43–1.94; P < 0.00001) and disease-free survival (DFS)/recurrence-free survival (RFS) (HR, 1.60; 95% CI, 1.21–2.12; P = 0.001) in patients with CRC. Low MUC2 expression level was associated with advanced TNM stage (RR, 1.42; 95% CI, 1.26–1.60; P < 0.00001), lymph node metastasis (RR, 1.41; 95% CI, 1.25–1.60; P < 0.00001), lymphatic invasion (RR,1.64; 95% CI, 1.26–2.12; P = 0.0002), rectal tumor site (RR, 1.26; 95% CI, 1.09–1.46; P = 0.001), and large tumor size (RR,1.32; 95% CI, 1.02–1.70; P = 0.03). There were no associations between low MUC2 expression level and gender, histological grade, depth of invasion, and distant metastasis.

Conclusion

The low levels of MUC2 in CRC tissues are poor prognostic factor independent of stage or other well-recognized markers of later-stage disease. Large well-designed cohort studies are required to validate MUC2 as a biomarker for poor prognosis in CRC.

MUC Expression in Gallbladder Epithelial Tissues in Cholesterol-Associated Gallbladder Disease

Background/Aims

Gallstone pathogenesis is linked to mucin hypersecretion and bacterial infection. Several mucin genes have been identified in gallbladder epithelial cells (GBECs). We investigated MUC expression in cholesterol-associated gallbladder disease and evaluated the relationship between mucin and bacterial infection.

Methods

The present study involved 20 patients with cholesterol stones with cholecystitis, five with cholesterol stones with cholesterolosis, six with cholesterol polyps, two with gallbladder cancer, and six controls. Canine GBECs treated with lipopolysaccharide were also studied. MUC3, MUC5AC, MUC5B, and MUC6 antibodies were used for dot/slot immunoblotting and immunohistochemical studies of the gallbladder epithelial tissues, canine GBECs, and bile. Reverse-transcription polymerase chain reaction was performed to evaluate MUC3 and MUC5B expression.

Results

MUC3, MUC5AC, MUC5B, and MUC6 were expressed in the normal gallbladder epithelium, and of those, MUC3 and MUC5B exhibited the highest expression levels. Greatly increased levels of MUC3 and MUC5B expression were observed in the cholesterol stone group, and slightly increased levels were observed in the cholesterol polyp group; MUC3 and MUC5B mRNA was also upregulated in those groups. Canine GBECs treated with lipopolysaccharide also showed upregulation of MUC3 and MUC5B.

Conclusions

The mucin genes with the highest expression levels in gallbladder tissue in cholesterol-associated diseases were MUC3 and MUC5B. Cholesterol stones and gallbladder infections were associated with increased MUC3 and MUC5B expression.

Galectin-3 is a non-classic RNA binding protein that stabilizes the mucin MUC4 mRNA in the cytoplasm of cancer cells

Pancreatic cancer cells express high levels of MUC1, MUC4 and MUC16 mRNAs that encode membrane-bound mucins. These mRNAs share unusual features such as a long half-life. However, it remains unknown how mucin mRNA stability is regulated. Galectin-3 (Gal-3) is an endogenous lectin playing important biological functions in epithelial cells. Gal-3 is encoded by LGALS3 which is up-regulated in pancreatic cancer. Despite the absence of a RNA-recognition motif, Gal-3 interacts indirectly with pre-mRNAs in the nucleus and promotes constitutive splicing. However a broader role of Gal-3 in mRNA fate is unexplored. We report herein that Gal-3 increases MUC4 mRNA stability through an intermediate, hnRNP-L which binds to a conserved CA repeat element in the 3′UTR in a Gal-3 dependent manner and also controls Muc4 mRNA levels in epithelial tissues of Gal3^−/− mice. Gal-3 interacts with hnRNP-L in the cytoplasm, especially during cell mitosis, but only partly associates with protein markers of P-Bodies or Stress Granules. By RNA-IP plus RNA-seq analysis and imaging, we demonstrate that Gal-3 binds to mature spliced MUC4 mRNA in the perinuclear region, probably in hnRNP-L-containing RNA granules. Our findings highlight a new role for Gal-3 as a non-classic RNA-binding protein that regulates MUC4 mRNA post-transcriptionally.

Hyper Expression of Mucin 5ac Indicates Poor Cancer Prognoses: A Meta-Analysis

The aim of the study was to explore the association between mucin 5ac expression and cancer prognosis. A systematically comprehensive search was performed through PubMed, the Web of Science, and the China National Knowledge Infrastructure (CNKI). The prognostic value of mucin 5ac expression in cancer patients was evaluated. The overexpression of mucin 5ac was found to be significantly associated with a poor prognosis in cancer patients (pooled HR: 1.53, 95%CI: 1.158-2.028, P = 0.003). This association was also detected in a biliary subgroup (pooled HR: 1.83, 95%CI: 1.269-2.639, P = 0.001) and a gastrointestinal subgroup (pooled HR: 1.44, 95%CI: 1.069-1.949 P = 0.017). In the geography subgroup analysis, a statistical association was found in the Asian subgroup (pooled HR: 1.69, 95%CI: 1.200-2.384, P = 0.003). In the clinical characteristics analysis, a statistical association was found between the hyper expression of mucin 5ac and lymphatic metastasis. We indicated that mucin 5ac is a promising prognostic predictor for cancer, especially for biliary and gastrointestinal cancer, and is more suitable for predicting cancer prognoses in Asians.

Excess Secretion of Gel-Forming Mucins and Associated Innate Defense Proteins with Defective Mucin Un-Packaging Underpin Gallbladder Mucocele Formation in Dogs

Mucosal protection of the gallbladder is vital yet we know very little about the mechanisms involved. In domestic dogs, an emergent syndrome referred to as gallbladder mucocele formation is characterized by excessive secretion of abnormal mucus that results in obstruction and rupture of the gallbladder. The cause of gallbladder mucocele formation is unknown. In these first mechanistic studies of this disease, we investigated normal and mucocele-forming dog gallbladders to determine the source, identity, biophysical properties, and protein associates of the culprit mucins with aim to identify causes for abnormal mucus behavior. We established that mucocele formation involves an adoptive excess secretion of gel forming mucins with abnormal properties by the gallbladder epithelium. The mucus is characterized by a disproportionally significant increase in Muc5ac relative to Muc5b, defective mucin un-packaging, and mucin-interacting innate defense proteins that are capable of dramatically altering the physical and functional properties of mucus. These findings provide an explanation for abnormal mucus behavior and based on similarity to mucus observed in the airways of people with cystic fibrosis, suggest that abnormal mechanisms for maintenance of gallbladder epithelial hydration may be an instigating factor for mucocele formation in dogs.

Exploring the role and diversity of mucins in health and disease with special insight into non-communicable diseases

Mucins are major glycoprotein components of the mucus that coats the surfaces of cells lining the respiratory, digestive, gastrointestinal and urogenital tracts. They function to protect epithelial cells from infection, dehydration and physical or chemical injury, as well as to aid the passage of materials through a tract i.e., lubrication. They are also implicated in the pathogenesis of benign and malignant diseases of secretory epithelial cells. In Human there are two types of mucins, membrane-bound and secreted that are originated from mucous producing goblet cells localized in the epithelial cell layer or in mucous producing glands and encoded by MUC gene. Mucins belong to a heterogeneous family of high molecular weight proteins composed of a long peptidic chain with a large number of tandem repeats that form the so-called mucin domain. The molecular weight is generally high, ranging between 0.2 and 10 million Dalton and all mucins contain one or more domains which are highly glycosylated. The size and number of repeats vary between mucins and the genetic polymorphism represents number of repeats (VNTR polymorphisms), which means the size of individual mucins can differ substantially between individuals which can be used as markers. In human it is only MUC1 and MUC7 that have mucin domains with less than 40% serine and threonine which in turn could reduce number of PTS domains. Mucins can be considered as powerful two-edged sword, as its normal function protects from unwanted substances and organisms at an arm's length while, malfunction of mucus may be an important factor in human diseases. In this review we have unearthed the current status of different mucin proteins in understanding its role and function in various non-communicable diseases in human with special reference to its organ specific locations. The findings described in this review may be of direct relevance to the major research area in biomedicine with reference to mucin and mucin associated diseases.

The gallbladder of the electric ray Torpedo marmorata Risso displays excrescent cholecystocytes with merocrine and apocrine-like secretions

The gallbladder of Torpedo marmorata exhibits a mucosal surface layer of simple columnar epithelium with very tall cholecystocytes. The apical domain of each cell has few microvilli, but many mucous vesicles that are secreted by exocytosis at the cell apices. The apical regions may also elongate and undergo self-excision while shedding mucus and cell debris into the gallbladder lumen in a manner similar to that described in mammals as a result of sex steroid treatment to induce gallstones and to that found in the cholecystitis associated with cholelithiasis. Numerous small mitochondria, spherical to elongated, are distributed throughout the cells, while the nuclei are often located in the lower third of each cell. In the lower part of the cholecystocytes, large and very densely contrasted lysosomes can be found. All cells are tightly joined by junctional complexes, including long, highly contrasted desmosomes. The fibromuscular layer is made of a loose stroma with a limited muscular component and a poor blood supply. Large diameter blood vessels can only be found in the subserosal layer. It is hypothesized that the obligatorily carnivorous diet of this ureotelic fish has resulted in the evolution of a gallbladder ultrastructure resembling that found in cholecystitis but without the associated cholelithiasis.

Prognostic significance of muc4 expression in gallbladder carcinoma

Background

Mucins are high molecular glycoproteins and play protective and lubricating roles in various epithelial tissues. Deregulated expression of mucins is involved in carcinogenesis and tumor invasion. MUC4 expression has been identified as a poor prognostic factor in pancreatobiliary carcinomas. To date, the relation between MUC4 expression and prognosis in gallbladder carcinoma remains to be determined. Authors examined MUC4 expression in gallbladder carcinoma and investigated its impact on prognosis.

Methods

The expression profiles of MUC4, MUC1, MUC2 mucins in gallbladder carcinoma tissues from 63 patients were investigated using immunohistochemical staining.

Results

For gallbladder carcinoma, positive staining of MUC4, MUC1, and MUC2 was 55.6%, 81.0%, 28.6%, respectively. There was a significant correlation between the expression of MUC4 and the expression of MUC1 or MUC2 (p = 0.004, p = 0.009, respectively). Univariate analysis showed that MUC4 expression (p = 0.047), differentiation (p < 0.05), T-stage (p < 0.05) and lymph node metastasis (p < 0.001) were significantly associated with poor survival. Expression of MUC1 and MUC2 was not correlated to survival. The backward stepwise multivariate analysis showed that MUC4 expression (p = 0.039) and lymph node metastasis (p = 0.001) were significant independent risk factors. In combined assessment of MUC4 and MUC2 expression, MUC4 positive and MUC2 negative group showed a significantly worse outcome than MUC4 negative groups(MUC4-/MUC2+ and MUC4-/MUC2-) and MUC4/MUC2 co-expression group(MUC4+/MUC2+) (p < 0.05).

Conclusions

MUC4 expression in gallbladder carcinoma is an independent poor prognostic factor. Therefore, MUC4 expression may be a useful marker to predict the outcome of patients with surgically resected gallbladder carcinoma. MUC2 expression may have prognostic value when combined with MUC4 expression.

Expression of MUC1 and MUC4 in gallbladder adenocarcinoma

Background

Recent reports have indicated that overexpression of mucin (MUC) 1 and/or MUC4 correlates with the occurrence and progression of extra-hepatobiliary malignancy. In this study, we investigated the expression of MUC1 and MUC4 and their prognostic significance in gallbladder adenocarcinoma.

Methods

We examined 54 surgical gallbladder adenocarcinoma samples by immunohistochemistry for MUC1 and MUC4 expression. Staining was evaluated as a sum score of extent and intensity, dividing the samples into low and high expression groups.

Results

The low expression group for both MUC1 and MUC4 was 10 samples (18.5%), and the high expression group was 44 samples (81.5%). High MUC1 expression was significantly correlated with more differentiated tumors (p=0.033), whereas high expression of MUC4 correlated with negative nodal status (p=0.012). Other pathological features were not correlated with MUC expression. Multivariate cox regression analysis showed that neither MUC1 nor MUC4 expression correlated with survival.

Conclusions

Although there were some correlations found, a prognostic role for either MUC1 or MUC4 expression in gallbladder carcinoma was not identified in this study. Further investigation is required.

The expression of MUC mucin in cholangiocarcinoma

Cholangiocarcinoma (CC) is a highly malignant epithelial cancer of the biliary tract, the cellular and molecular pathogenesis of which remains unclear. Malignant transformation of glandular epithelial cells is associated with the altered expression of mucin. We investigated the type of mucins expressed in CC. Twenty-six patients with histologically confirmed CC were included in this study. The expression of mucin was studied by immunohistochemistry using antibodies to MUC1, MUC1 core, MUC2, MUC3, MUC4, MUC5AC, and MUC6. There was extensive (>50%) expression of mucin, mainly MUC1 in 11/25 and MUC5AC in 12/26 cases. In the case of MUC3, 6/26 cases expressed mucin extensively, whilst only 1/26 had MUC2, MUC4, and MUC6 expression. Well-differentiated tumors significantly expressed MUC3 extensively compared to poor or moderately differentiated tumors (p=0.003). Fifteen of 25 cases had metastatic disease. MUC1 was extensively expressed in 9/15 cases with metastatic disease. In contrast, MUC1 expression was present in 2/10 cases where metastases were absent. Hilar lesions were less likely to express MUC1, but this was not statistically significant. Fifteen of 25 cases had metastatic disease. Extensive MUC3 expression was significantly associated with well-differentiated tumors, whilst there was an approaching significance between the extensive expression of MUC1 and metastasis in cholangiocarcinoma.

Mucins and CD56 as markers of tumour invasion and prognosis in periampullary cancer

BACKGROUND

This study investigated the association of mucins and cluster of differentiation (CD) 56 with vascular and perineural invasion and survival in patients with periampullary cancer.

METHODS

Immunohistochemical staining was performed on formalin-fixed pancreatic tissue microarrays (cancer, chronic pancreatitis and normal pancreatic tissue) constructed from 126 pancreatic resections (cancer, 104; chronic pancreatitis, 22). Mucin (MUC) 1, MUC4 and MUC5AC expression was quantified using the immunohistochemical score (range 0-300), MUC3 expression was described as membranous or cytoplasmic, and expression of CD56, MUC2 and MUC6 as present or absent.

RESULTS

In cancers, vascular invasion correlated with overexpression (immunohistochemical score of 100 or more) of MUC1 (P = 0.003) and presence of MUC6 (P = 0.024), and perineural invasion correlated with overexpression of MUC5AC (P = 0.015). Reduced survival was observed with overexpression of MUC4 (P = 0.032) and MUC5AC (P = 0.048), membranous expression of MUC3 (P = 0.048), and presence of CD56 (P = 0.041). Perineural invasion also correlated with CD56 expression (P = 0.001). Overexpression of MUC4 and MUC5AC correlated with tumour recurrence (P = 0.001 and P = 0.034 respectively). Multivariable analysis identified membranous expression of MUC3 (P = 0.023), lymphatic invasion (P = 0.015) and perineural invasion (P = 0.004) as independent predictors of poor survival.

CONCLUSION

Mucins and CD56 may be markers of prognosis in patients with periampullary cancer.

Current status of mucins in the diagnosis and therapy of cancer

Mucins are the most abundant high molecular weight glycoproteins in mucus. Their nature and glycosylation content dictates the biochemical and biophysical properties of viscoelastic secretions, pointing out an important role in diverse biological functions, such as differentiation, cell adhesions, immune responses, and cell signaling. Mucins are expressed in tubular organs by specialized epithelial cells in the body. Their aberrant expression is well documented in a variety of inflammatory or malignant diseases. From a prognosis point of view, their expression and alterations in glycosylation are associated with the development and progression of malignant diseases. Therefore, mucins can be used as valuable markers to distinguish between normal and disease conditions. Indeed, this alteration in glycosylation patterns generates several epitopes in the oligosaccharide side chains that can be used as diagnostic and/or prognostic markers. Furthermore, these characteristic tumor-associated epitopes are extensively used as appropriate immunotargets of malignant epithelial cells. Therefore, in an effort to detect and treat cancer at the earliest stage possible, mucins are analyzed as potential markers of disease for diagnosis, progression, and for therapeutic purposes. In this review, we focused on the current status of the distribution of mucins in normal and pathologic conditions and their clinical use both in cancer diagnosis and therapeutics treatments.

The membrane-bound mucins: From cell signalling to transcriptional regulation and expression in epithelial cancers

The membrane-bound mucins belong to an ever-increasing family of O-glycoproteins. Based on their structure and localization at the cell surface they are thought to play important biological roles in cell-cell and cell-matrix interactions, in cell signalling and in modulating biological properties of cancer cells. Among them, MUC1 and MUC4 mucins are best characterized. Their altered expression in cancer (overexpression in the respiratory, gastro-intestinal, urogenital and hepato-biliary tracts) indicates an important role for these membrane-bound mucins in tumour progression, metastasis, cancer cell resistance to chemotherapeutics drugs and as specific markers of epithelial cancer cells. Some mechanisms responsible for MUC1 and MUC4 role in tumour cell properties have been deciphered recently. However, much remains to be done in order to understand the molecular mechanisms and signalling pathways that control the expression of membrane-bound mucins during the different steps of tumour progression toward adenocarcinoma and evaluate their potential as prognostic/diagnostic markers and as therapeutic tools. In this review we focus on the molecular mechanisms and signalling pathways known to control the expression of membrane-bound mucins in cancer. We will discuss the mechanisms of regulation at the promoter level (including genetic and epigenetic modifications) that may be responsible for the mucin altered pattern of expression in epithelial cancers.

Mucin gene expression in bile of patients with and without gallstone disease, collected by endoscopic retrograde cholangiography

AIM: To investigate the pattern of mucin expression and concentration in bile obtained during endoscopic retrograde cholangiography (ERC) in relation to gallstone disease.

METHODS: Bile samples obtained at ERC from 29 consecutive patients, 17 with and 12 without gallstone disease were evaluated for mucin content by gel filtration on a Sepharose CL-4B column. Dot blot analysis for bile mucin apoproteins was performed with antibodies to Mucin 1 (MUC1), MUC2, MUC3, MUC5AC, MUC5B and MUC6. Staining intensity score (0-3) was used as a measure of antigen expression.

RESULTS: MUC1, MUC2, MUC3, MUC5AC, MUC5B and MUC6 were demonstrated in 34.4%, 34.4%, 51.7%, 51.7%, 55.1% and 27.5% of bile samples, respectively. The staining intensity scores were 0.62 ± 0.94, 0.58 ± 0.90, 0.79 ± 0.97, 1.06 ± 1.22, 1.20 ± 1.26 and 0.41 ± 0.73, respectively. Mean mucin concentration measured in bile by the Sepharose CL-4B method was 22.8 ± 24.0 mg/mL (range 3.4-89.0 mg/mL). Mean protein concentration was 8.1 ± 4.8 mg/mL (range 1.7-23.2 mg/mL).

CONCLUSION: High levels of MUC3, MUC5AC and MUC5B are expressed in bile aspirated during ERC examination. A specific pattern of mucin gene expression or change in mucin concentration was not found in gallstone disease.

Expression profiles of MUC1, MUC2, and MUC4 mucins in human neoplasms and their relationship with biological behavior

Mucins are high molecular weight glycoproteins that play important roles in carcinogenesis or tumor invasion. To clarify the relationship of the expression patterns of mucins in human neoplasms with their biological behavior, we examined the expression profiles of MUC1, MUC2, and MUC4 mucins in various human neoplasms using immunohistochemistry and in situ hybridization, and compared them with clinicopathologic factors including outcome of the patients. MUC1 or MUC4 expression is related with the aggressive behavior of human neoplasms and a poor outcome of the patients. In contrast, MUC2 expression tends to be related with the indolent behavior of human neoplasms and a favorable outcome of the patients, although indolent pancreatobiliary neoplasms sometimes show invasive growth with MUC1 expression in the invasive areas. The expression of MUC2 mucin in indolent pancreatobiliary neoplasms coincided with expression of MUC2 mRNA. Our recent studies to clarify the MUC2 gene regulation mechanism disclosed that DNA methylation and histone modification in the 5' flanking region of the MUC2 promoter may play an important role. Further studies of the epigenetics also in MUC1 and MUC4 gene expression may be needed to understand the relationship between the expression of mucins in human neoplasms with their biological behavior.

Increased expression of mucin 5AC mRNA and decreased expression of epidermal growth-factor receptor mRNA in gallstone patients

Mucin, a major component of mucus, plays an important role in gallstone formation. The molecular mechanisms of mucin overproduction, however, still remain unknown. Several mucin genes (MUC) have been implicated in various diseases and gel-forming mucin genes (MUC2, MUC5AC, MUC5B, and MUC6) were recognized to be the important components of digestive mucus. Furthermore epidermal growth factor receptor (EGFR) might regulate the function of MUC5AC. The aim of this study was to investigate the expression of MUC5AC mRNA and the possible role of EGFR in the function of MUC5AC. Total twelve patients underwent elective laparoscopic cholecystectomy due to gallstone disease were enrolled (age: 64.6 +/- 15.5 years). The control group included two patients who underwent cholecystectomy without stone. The expression levels of MUC5AC and EGFR mRNAs were analyzed in gallbladder tissues using real-time reverse transcription-polymerase chain reaction assay. The expression levels of MUC5AC mRNA were increased in gallstone patients compared with those in control subjects, ranging from 2.5 to 1558 folds (mean 512.8 +/- 493.6 folds, p = 0.004). In contrast, the expression levels of EGFR mRNA were decreased in all patients (mean 0.378 +/- 0.322 fold, p = 0.002), and negative correlation was found between MUC5AC and EGFR (p = 0.02). There was no significant difference according to age, body mass index, and stone composition in the expression levels of MUC5AC and EGFR mRNAs. In conclusion, MUC5AC is over-expressed in gallstone disease, despite the decrease in the expression of EGFR mRNA. MUC5AC may be related to mucus hypersecretion.

Mucins in the mucosal barrier to infection

The mucosal tissues of the gastrointestinal, respiratory, reproductive, and urinary tracts, and the surface of the eye present an enormous surface area to the exterior environment. All of these tissues are covered with resident microbial flora, which vary considerably in composition and complexity. Mucosal tissues represent the site of infection or route of access for the majority of viruses, bacteria, yeast, protozoa, and multicellular parasites that cause human disease. Mucin glycoproteins are secreted in large quantities by mucosal epithelia, and cell surface mucins are a prominent feature of the apical glycocalyx of all mucosal epithelia. In this review, we highlight the central role played by mucins in accommodating the resident commensal flora and limiting infectious disease, interplay between underlying innate and adaptive immunity and mucins, and the strategies used by successful mucosal pathogens to subvert or avoid the mucin barrier, with a particular focus on bacteria.

Extensive lineage-specific gene duplication and evolution of the spiggin multi-gene family in stickleback

Background

The threespine stickleback (Gasterosteus aculeatus) has a characteristic reproductive mode; mature males build nests using a secreted glue-like protein called spiggin. Although recent studies reported multiple occurrences of genes that encode this glue-like protein spiggin in threespine and ninespine sticklebacks, it is still unclear how many genes compose the spiggin multi-gene family.

Results

Genome sequence analysis of threespine stickleback showed that there are at least five spiggin genes and two pseudogenes, whereas a single spiggin homolog occurs in the genomes of other fishes. Comparative genome sequence analysis demonstrated that Muc19, a single-copy mucous gene in human and mouse, is an ortholog of spiggin. Phylogenetic and molecular evolutionary analyses of these sequences suggested that an ancestral spiggin gene originated from a member of the mucin gene family as a single gene in the common ancestor of teleosts, and gene duplications of spiggin have occurred in the stickleback lineage. There was inter-population variation in the copy number of spiggin genes and positive selection on some codons, indicating that additional gene duplication/deletion events and adaptive evolution at some amino acid sites may have occurred in each stickleback population.

Conclusion

A number of spiggin genes exist in the threespine stickleback genome. Our results provide insight into the origin and dynamic evolutionary process of the spiggin multi-gene family in the threespine stickleback lineage. The dramatic evolution of genes for mucous substrates may have contributed to the generation of distinct characteristics such as "bio-glue" in vertebrates.

Expression profiles of MUC mucins and trefoil factor family (TFF) peptides in the intrahepatic biliary system: physiological distribution and pathological significance

Mucin secreted by mucosal epithelial cells plays a role in the protection of the mucosal surface and also is involved in pathological processes. So far, MUC1-4, 5AC, 5B, 6-8, 11-13 and 15-17 genes coding the backbone mucin core protein have been identified in humans. Their diverse physiological distribution and pathological alterations have been reported. Trefoil factor family (TFF) peptides are mucin-associated molecules co-expressed with MUC mucins and involved in the maintenance of mucosal barrier and the biological behavior of epithelial and carcinoma cells. Intrahepatic biliary system is a route linking the bile canaliculi and the extrahepatic bile duct for the excretion of bile synthesized by hepatocytes. Biliary epithelial cells line in the intrahepatic biliary system, secreting mucin and other molecules involved in the maintenance and regulation of the system. In this review, the latest information regarding properties, expression profiles and regulation of MUC mucins and TFF peptides in the intrahepatic biliary system is summarized. In particular, we focus on the expression profiles and their significance of MUC mucins in developmental and normal livers, various hepatobiliary diseases and intrahepatic cholangiocarcinoma.

MUC4 is a novel prognostic factor of extrahepatic bile duct carcinoma

PURPOSE

Many of the patients with extrahepatic bile duct carcinoma (EHBDC) show a poor outcome. We have reported that MUC4 is a novel prognostic factor of pancreatic adenocarcinoma and intrahepatic cholangiocarcinoma. The aim of this study is to evaluate the prognostic significance of MUC4 expression in EHBDC.

EXPERIMENTAL DESIGN

We examined the expression profile of MUC4 in EHBDC tissues from 70 patients using immunohistochemistry. MUC4 is a membrane mucin like MUC1. In addition, MUC4 is an intramembrane ligand for receptor tyrosine kinase ErbB2 and is related with regulation of p27. We compared the MUC4 expression with MUC1, ErbB2, or p27 expression in EHBDC.

RESULTS

MUC4 was expressed in 36 of the 70 patients with EHBDC. There was no significant correlation between the MUC4 expression and MUC1, ErbB2, or p27 expression. The survival of 19 patients with high MUC4 expression (>or=20% of carcinoma cells stained) was significantly worse than that of the 51 patients with low MUC4 expression (under 20% of carcinoma cells stained; P = 0.0072). The univariate analysis showed that high MUC4 expression (P = 0.0072), high MUC1 expression (P = 0.0092), histologic grading (P = 0.0029), surgical margin involvement (P = 0.0137), and nodal metastasis (P = 0.0036) were statistically significant risk factors. The backward stepwise multivariate analysis showed that high MUC4 expression (P = 0.0195) and surgical margin involvement (P = 0.0358) were statistically significant independent risk factors.

CONCLUSIONS

MUC4 expression in EHBDC is a new independent factor for poor prognosis and predicts the outcome of patients with EHBDC.

Prognostic value of mucins in the classification of ampullary carcinomas

The ampulla of Vater is of high clinical relevance with regard to influx of chyme, ascending inflammation, intubation during diagnostic and therapeutic endoscopic investigation, therapeutic papillotomy, and especially to malignant transformation. Little is known about the distribution of mucins in the ampulla. In this study, we have investigated the mucin distribution in the normal ampulla of Vater and compared it to duodenal mucosa and Brunner glands. Expression of mucins in the ampulla of Vater and duodenum was monitored by reverse transcription-polymerase chain reaction and localization of the products by immunohistochemistry. The samples investigated originated from 30 autopsy cases. Mucins MUC1, MUC3, MUC4, MUC5AC, MUC5B, MUC6, MUC7, and MUC8 were expressed in the ampulla of Vater. Immunohistochemistry revealed production of MUC4, MUC5AC, MUC5B, and MUC6. The mucin composition varied in comparison with the duodenum referring to MUC2, MUC7, and MUC8. Detected mucins contribute to innate immunity, epithelial restitution, and protection against the aggressive secretions of the liver, gall bladder, and pancreas. By cross-linking, they influence the rheological properties of the secretions in the ampulla and facilitate unidirectional flow into the duodenum. Knowledge of their pattern of expression has prognostic value with regard to the detection of malignancy. The observed differences in the mucin distribution between the duodenum and the ampulla of Vater support the use of MUC2, MUC7, and MUC8 as useful tool in the classification of ampullary carcinomas.

MUC4 expression is a novel prognostic factor in patients with invasive ductal carcinoma of the pancreas

BACKGROUND

Many patients with invasive ductal carcinoma of the pancreas (IDC) have a poor outcome. MUC4 expression has been implicated as a marker for diagnosis and progression of IDC, but there are no studies of the relation between MUC4 expression and patient prognosis in IDC.

AIMS

To investigate the prognostic significance of MUC4 expression in IDC.

METHODS

The expression profiles of MUC4, ErbB2, p27, and MUC1 were investigated in IDC tissues from 135 patients by means of immunohistochemistry.

RESULTS

MUC4 was expressed in 43 of the 135 patients with IDC (31.9%). The survival of 21 patients with high MUC4 expression (>20% of neoplastic cells stained) was significantly worse than that of the 114 patients with low MUC4 expression (<20% of neoplastic cells stained) (p = 0.0043). Univariate analysis showed that high MUC4 expression (p = 0.0061), large primary tumour status (>T2) (p = 0.0436), distant metastasis (p = 0.0383), lymphatic invasion (p = 0.0243), and surgical margins (p = 0.0333) were significant risk factors affecting the outcome of patients with IDC. Backward stepwise multivariate analysis showed that MUC4 expression (p = 0.0121), lymph node metastasis (p = 0.0245), and lymphatic invasion (p = 0.0239) were significant independent risk factors. ErbB2, p27, and MUC1 were not independent risk factors.

CONCLUSIONS

This study shows that MUC4 expression in IDC is a new independent factor for poor prognosis and predicts the outcome of patients with IDC.

Characterization of the PCR inhibitory effect of bile to optimize real-time PCR detection of Helicobacter species

The inhibitory effect of human and porcine bile samples to detect Helicobacter DNA was studied by adding different concentrations of bile samples to PCR mixtures of six thermostable DNA polymerases containing cagA specific primers and Helicobacter pylori DNA. PCR products were amplified by using the Rotorgene system and SYBR Green I. Among the six DNA polymerases tested, rTth had the lowest sensitivity to bile inhibitors, whereas Taq and Tfl had the highest sensitivity. Bile proteins did not inhibit AmpliTaq DNA polymerase, whereas the fraction containing mainly bile acids and their salts inhibited the amplification capacity of AmpliTaq. Heating human bile at 98 degrees C and adding casein and formamide to the reaction mixture reduced the PCR inhibitory effect of bile. Therefore, a pre-PCR treatment based on dilution and heating of bile, adding casein and formamide to the reaction mixture of rTth DNA polymerase was found efficient to amplify DNA directly in bile.

MUC1 and MUC5AC mucin expression in liver fluke-associated intrahepatic cholangiocarcinoma

AIM: To investigate the expressions of MUC1 and MUC5AC in intrahepatic cholangiocarcinoma (ICC). Association of expressions of mucins MUC1 and MUC5AC with clinical findings, metastasis, and survival of the liver fluke-associated ICC patients was determined.

METHODS: The expressions of MUC1 and MUC5AC mucins were examined by immunohistochemical staining in 87 cases of histologically-proven ICC. The expressions of mucins in relationship between clinicopathological significance and prognosis of the patients were evaluated.

RESULTS: Fifty-two patients (60%) exhibited both MUC1 and MUC5AC expressions, whereas 31% expressed either MUC1 or MUC5AC, and 9% expressed neither. High MUC1 immunoreactivity displayed a significant correlation with tumor progression as reflected by vascular invasion (P<0.001), whereas high expression of MUC5AC significantly correlated with neural invasion (P = 0.022) and advanced ICC stage (P = 0.008). Patients with high expression of MUC1 had a significantly shorter survival (P = 0.0002). According to multivariate analyses, MUC1 reactivity (P = 0.026), histological grading and stage of tumor represented the least probability of survival.

CONCLUSION: MUC1 is overexpressed in liver fluke-associated cholangiocarcinoma and relates to vascular invasion and poor prognosis, whereas MUC5AC mucin is neoexpressed and relates to neural invasion and advanced ICC stage. High MUC1 expression in tumor may be useful for predicting the poor outcome of ICC patients.

Regulation and function of trefoil factor family 3 expression in the biliary tree

Microarray analysis identified trefoil factor family 3 (TFF3) as a gene expressed in biliary epithelial cells (BECs), regulated by interleukin (IL)-6, and potentially involved in biliary pathophysiology. We therefore studied the regulation and function of BEC TFF3, in vitro and in vivo in IL-6(+/+) and IL-6(-/-) mice subjected to chronic bile duct ligation for 12 weeks. In vitro studies showed that IL-6 wild-type (IL-6(+/+)) BECs expressed higher TFF3 mRNA and protein levels than IL-6-deficient (IL-6(-/-)) BECs. BEC TFF3 expression is dependent primarily on signal transducer and activator of transcription (STAT3) signaling, but the reciprocal negative regulation known to exist between the intracellular IL-6/gp130 signaling pathways, STAT3 and mitogen-activated protein kinase (MAPK), importantly contributes to BEC TFF3 expression. Specifically blocking STAT3 activity with a dominant-negative molecule or treatment with a growth factor such as hepatocyte growth factor, which increases MAPK signaling, decreases BEC TFF3 expression. In contrast, specifically blocking MAPK activity with PD98059 significantly increased BEC TFF3 expression. Higher BEC TFF3 levels in IL-6(+/+) BECs were associated with significantly better migration than IL-6(-/-) BECs in a wound-healing assay and defective IL-6(-/-) BEC migration was reversed with exogenous TFF3. In vivo, hepatic TFF3 mRNA and protein expression was limited to BECs and dependent significantly on STAT3 signaling, but was influenced by other factors present after bile duct ligation. Comparable results were obtained in normal and diseased human tissue samples. In conclusion the regulation and function of BEC TFF3 expression is similar to the colon. BEC TFF3 expression depends primarily on gp130/STAT3 and contributes to BEC migration and wound healing. Therefore, use of recombinant IL-6 or TFF3 peptides should exert a therapeutic role in preventing biliary strictures in liver allografts.

Intracellular liposomes and cholesterol deposits in chronic cholecystitis and biliary sludge

Ultrastructural study of a group of selected specimens of chronic cholecystitic gallbladders reveals cholecystocyte changes characterized by abraded and altered microvilli accompanied by mitochondrial damages in the apical regions as well as mucus accumulation with aggregated, angulated lysosomes and heterogeneous liposomes. These liposomes contain needle-like crystals, probably rich in cholesterol. Many fragments of cholecystocystes and damaged organelles or contents can be found in the biliary sludge. These data support previous reports suggesting that there is an association between cholecystitis and the presence of cholelithiasis, subsequent to the production of altered bile. The present data suggest that disintegrating, sloughed cholecystocyte contents also contribute to the bile sludge, a complex milieu enriched by lipids, cholesterol deposits, altered mucus due in part to changes in expression of apomucins. The instability of prolonged storage of such modified bile, caused and/or accompanied by other associated metabolic defects, including gallbladder sluggishness, would favor the nucleation and the enlargement of gallstones. Based on the aforementioned data, a comprehensive sequence for cholecystocyte ultrastructural alterations and pathologies is proposed, as a result of chronic cholecystitis.

MUC4 mucin expression in human pancreatic tumours is affected by organ environment: the possible role of TGFbeta2

MUC4 is highly expressed in human pancreatic tumours and pancreatic tumour cell lines, but is minimally or not expressed in normal pancreas or chronic pancreatitis. Here, we investigated the aberrant regulation of MUC4 expression in vivo using clonal human pancreatic tumour cells (CD18/HPAF) grown either orthotopically in the pancreas (OT) or ectopically in subcutaneous tissue (SC) in the nude mice. Histological examination of the OT and SC tumours showed moderately differentiated and anaplastic morphology, respectively. The OT tumour cells showed metastases to distant lymph nodes and faster tumour growth (P<0.01) compared to the SC tumours. The MUC4 transcripts in OT tumours were very high compared to the undetectable levels in SC tumours. The SC tumour cells regained their ability to express MUC4 transcripts after in vitro culture. Immunohistochemical analysis using MUC4-specific polyclonal antiserum confirmed the results obtained by Northern blot analysis. Interestingly, the OT tumours showed expression of TGFβ2 compared to no expression in SC, suggesting a possible link between MUC4 and TGFβ2. The MUC4 expression, morphology, and metastasis of human pancreatic tumour cells are regulated by a local host microenvironment. TGFβ2 may serve as an interim regulator of this function.

The mouse secreted gel-forming mucin gene cluster

Using genomic cosmid and BAC clones and genome shotgun supercontigs available in GenBank, we determined the complete gene structure of the four mouse secreted gel-forming mucin genes Muc2, Muc5ac, Muc5b and Muc6 and the organization of the genomic locus harboring these genes. The mouse secreted gel-forming mucin gene is 215 kb on distal chromosome 7 to 69.0 cM from the centromere and organized as: Muc6-Muc2-Muc5ac-Muc5b with Muc2, Muc5ac and Muc5b arranged in the same orientation and Muc6 in opposite. Mouse mucin genes have highly similar genomic organization to each other and to their respective human homologues indicating that they have been well conserved through evolution. Deduced peptides showed striking sequence similarities in their N- and C-terminal regions whereas the threonine/serine/proline-rich central region is specific for each other and for species. Expression studies also showed that they have expression patterns similar to human mucin genes with Muc2 expressed in small and large intestines, Muc5ac and Muc6 in stomach, and Muc5b in laryngo-tracheal tract. These data constitute an important initial step for investigation of mucin gene regulation and mucin function through the use of animal models.

MUC4 is a novel prognostic factor of intrahepatic cholangiocarcinoma-mass forming type

Complete surgical resection of the tumor is the sole approach to improve the cure rate of patients with intrahepatic cholangiocarcinoma-mass forming type (ICC-MF). Although patients are treated by curative resection, many of them show poor outcome. Mucin (MUC)4 expression has been implicated as a marker for diagnosis and progression of pancreatic adenocarcinomas, but there is no study of the relationship between MUC4 expression and patient's prognosis in ICC-MF. In the present study, we examined the expression profile of MUC4 in ICC-MF tissue from 27 patients using immunohistochemistry. MUC4 was expressed in the carcinoma tissues of 10 (37%) of the 27 ICC-MF tumors, whereas it was not expressed in normal liver tissue. Because MUC4 is an intramembrane ligand for receptor tyrosine kinase ErbB2 and is related with regulation of p27, we also compared the MUC4 expression with ErbB2 and p27 expressions in ICC-MFs. The patients with MUC4 and ErbB2 double positive expression showed a short survival period compared to non-expressing patients. MUC4 and p27 showed no relationship. The univariate analysis showed that tumor size, intrahepatic metastasis, lymph node metastasis, MUC4 expression, and MUC1 expression were statistically significant risk factors affecting the outcome of the patients with ICC-MF. The multivariate analysis demonstrated that MUC4 expression, as well as surgical margin, were statistically significant independent risk factors. In conclusion, the results suggest that expression of MUC4 in ICC-MF is a new independent factor for poor prognosis and is a useful marker to predict the outcome of the patients with ICC-MF.

Prognostic value of serum MUC5AC mucin in patients with cholangiocarcinoma

BACKGROUND

The authors recently showed that MUC5AC mucin, which is expressed aberrantly in tumor tissue, is present in significant concentrations in serum from patients with cholangiocarcinoma. Subsequently, determination of serum MUC5AC had high sensitivity and specificity for cholangiocarcinoma. In this study, the possible association between serum MUC5AC mucin and the clinical findings of the patients and their prognostic value were explored.

METHODS

The expression of MUC5AC mucin in serum samples from 179 patients with histologically confirmed cholangiocarcinoma were determined using immunoblotting.

RESULTS

Detection of serum MUC5AC was associated with patients with blood group Type A, larger-sized tumors (> 5 cm), and advanced-stage disease. Patients who had positive serum MUC5AC status had a significantly poorer prognosis (median survival, 127 days; 95% confidence interval [95% CI], 107-180 days) compared with patients who had negative serum MUC5AC status (median survival, 329 days; 95% CI, 199-458 days; P < 0.001). Multivariate analysis with adjustment for all covariates showed that patients who had positive serum MUC5AC status had a 2.5-fold higher risk of death compared with patients who had negative serum MUC5AC status (P < 0.001).

CONCLUSIONS

Serum MUC5AC was associated with tumor burden. The determination of serum MUC5AC may be predictive of poor patient outcome and may be useful in selecting possible treatment options for patients with cholangiocarcinoma. Cancer 2003;98:1438-43.

PEA3 transactivates the Muc4/sialomucin complex promoter in mammary epithelial and tumor cells

Sialomucin complex (SMC, rat Muc4) is a heterodimeric glycoprotein composed of two subunits, the mucin component ascites sialoglycoprotein ASGP-1 and the transmembrane subunit ASGP-2, which is aberrantly expressed on the surfaces of a variety of tumor cells. Up-regulation of the Muc4/SMC gene in the 13762 sublines of the rat mammary adenocarcinoma correlates with the overexpression of transcription factor PEA3 and the receptor tyrosine kinase ErbB2. Here we report that PEA3 is capable of transactivating the Muc4/SMC promoter in a dose-dependent manner via direct attachment to a PEA3 binding site. ERM and ER81, the other two members of the PEA3 subfamily of transcription factors, could not transactivate the Muc4/SMC promoter. Transcriptional activation of Muc4/SMC by PEA3 is potentiated by Ras and MEKK1 kinases. These data suggest that expression of PEA3 in mammary tumors leads to up-regulation of Muc4/SMC transcription, the gene product of which may contribute to the metastatic potential of mammary tumors.

Serum MUC5AC mucin as a potential marker for cholangiocarcinoma

Aberrant expression of MUC5AC mucin is obvious in cholangiocarcinoma tissues, however, this mucin has never been detected in the serum. Using immunoblotting marked with antibody vs. MUC5AC core protein, we could detect MUC5AC mucin in the serum of 112 from 179 cholangiocarcinoma patients (62.6% sensitivity), two of the 62 with benign hepatobiliary diseases, six of the 60 with hepato-gastrointestinal cancer, and none in either the 60 active opisthorchiasis or 74 healthy persons. Detection of serum mucin in the serum of cholangiocarcinoma patients corresponded well to the MUC5AC expressed in individual tissues. Serum MUC5AC may be used to enhance the diagnostic accuracy of cholangiocarcinoma.

Lipopolysaccharide induces overexpression of MUC2 and MUC5AC in cultured biliary epithelial cells: possible key phenomenon of hepatolithiasis

Bacterial infection, bile stasis, mucin hypersecretion, and an alteration of the mucin profile such as an aberrant expression of gel-forming apomucin (MUC2 and MUC5AC) in the intrahepatic biliary tree are thought to be important in the lithogenesis of hepatolithiasis. So far, there have been no detailed studies linking bacterial infection to altered mucus secretion of biliary epithelium. In this study, the influence of lipopolysaccharide (LPS), a bacterial component, on apomucin expression in cultured murine biliary epithelial cells was examined with emphasis on the participation of tumor necrosis factor (TNF)-alpha. It was found that LPS up-regulated the expression of MUC2 and MUC5AC in cultured murine biliary epithelial cells. LPS also induced the expression of TNF-alpha in biliary epithelial cells and its secretion into the culture medium. The up-regulation of these apomucins was inhibited by pretreatment with TNF-alpha antibody. TNF-alpha alone also induced the overexpression of MUC2 and MUC5AC in cultured biliary epithelial cells. This overexpression was inhibited by pretreatment with calphostin C, an inhibitor of protein kinase C. These findings suggest that LPS can induce overexpression of MUC2 and MUC5AC in biliary epithelial cells via synthesis of TNF-alpha and activation of protein kinase C. This mechanism might be involved in the lithogenesis of hepatolithiasis.

Genomic organization of MUC4 mucin gene. Towards the characterization of splice variants

The human MUC4 gene encodes a large membrane-associated mucin, characterized by a mucin tandem repeat domain and a growth factor-like transmembrane domain. In addition to the originally published sequence (sv0-MUC4), several MUC4 cDNA sequences (called sv1-MUC4 to sv21-MUC4, MUC4/X, MUC4/Y) from various tissues and cell lines have been recently described. They differ from sv0-MUC4 by deletions and/or insertions located in the 3' region or, for two of them, by deletion of the central repetitive domain. To establish the nature of the mechanisms responsible for the diversity of MUC4 transcripts, the genomic structure of the 3' region of the human MUC4 gene was determined. Our results show that it spans approximately 30.8 kb of genomic DNA and is composed of 24 exons, including one alternative exon which was exclusively reported for sv1-MUC4. Moreover, we have shown that the different MUC4 transcripts are generated by several mechanisms, including the alternative use of cassette exons, exon skipping or use of cryptic splice donor/acceptor sites.

The mouse Muc5b mucin gene: cDNA and genomic structures, chromosomal localization and expression

We report here the isolation and characterization of the mouse Muc5b mucin gene (mMuc5b). We determined its complete cDNA sequence, its genomic organization, and chromosomal localization. Moreover, we analyzed the expression of this gene by reverse-transcription PCR and in situ hybridization. The structure of the gene was determined from a genomic cosmid clone that encompasses the entire mMuc5b gene, including the 5'-flanking region. The mMuc5b gene spans approximately 36 kb and contains 49 exons. It is located on mouse distal chromosome 7. mMuc5b encodes at least two transcripts by alternative splicing of the second exon, the longest one being 14.9 kb in length. The deduced peptide contains 4782 amino acids. Its central region can be subdivided into 10 imperfect repeats, each composed of a cysteine-rich domain followed by a threonine, serine, and proline-rich mucin-type domain. It is flanked by cysteine-rich domains similar to cysteine-rich domains of pre-pro-von Willebrand factor. Comparison with its human homologue MUC5B revealed common features including high sequence similarities in the 5' and 3' regions, and the conservation of the genomic organization. In contrast, mMuc5b differs from its human homologue, since no highly tandemly repeated sequences could be identified within its central region. mMuc5b is expressed mainly in laryngeal mucous glands, and at a lesser extend in stomach and duodenum.

Interacting QTLs for cholesterol gallstones and gallbladder mucin in AKR and SWR strains of mice

We employed quantitative trait locus (QTL) mapping in a backcross between gallstone-susceptible SWR/J and gallstone-resistant AKR/J inbred mice to identify additional susceptibility loci for cholesterol gallstone formation. After 12 wk of feeding the mice a lithogenic diet, we phenotyped 330 backcross progeny for gallstones, gallbladder mucin accumulation, liver weight, and body weight. Marker-based regression analysis revealed significant single QTLs associated with gallstone formation on chromosome 9 and the liver weight/body weight ratio on chromosomes 5 and X. A search for gene pairs detected significant gene-gene interactions for mucin accumulation between loci on chromosomes 5 and 11 and suggestive gene-gene interactions linked to gallstone formation between the QTL on chromosome 9 and loci on chromosomes 6 and 15. These findings uncover new QTLs for cholesterol gallstones, reveal independent loci for mucin accumulation, and demonstrate the importance of considering gene-gene interactions in cholesterol cholelithiasis. According to standard nomenclature, the gallstone QTL on chromosome 9 is named Lith5.

Characterization of human mucin gene MUC4 promoter: importance of growth factors and proinflammatory cytokines for its regulation in pancreatic cancer cells

The human mucin gene MUC4 encodes a large transmembrane mucin that is thought to play important roles in tumor cell biology and that is overexpressed in human pancreatic carcinomas. In this report, we describe the structure and functional activity of the 5'-flanking region, including 1.0 kilobase of the promoter. The long 5'-untranslated region (2.7 kilobases) is characterized by a high content of GC in its 3'-end. The first TATA box was located at -2672/-2668. Multiple transcription start sites and a high density of putative binding sites for Sp1 (GC and CACCC boxes), AP-1/-2/-4, cAMP-responsive element-binding protein, GATA, GR, and STAT transcription factors were found within the 5'-flanking region. Transcriptional activity of the promoter was assessed using pGL3-luciferase deletion mutants in two MUC4-expressing (CAPAN-1 and CAPAN-2) and one nonexpressing (PANC-1) pancreatic cancer cell line. Two highly active fragments (-219/-1 and -2781/-2572) that drive MUC4 transcription in CAPAN-1 and CAPAN-2 cells were identified. Gel retardation assays indicated that Sp1 and Sp3 bind to cognate cis-elements found in the 5'-flanking region and that Sp1 transactivates, whereas Sp3 inhibits the GC-rich region (-464/-1) in CAPAN-2 cells. Activation of protein kinase C with phorbol ester and treatment of cells with epidermal growth factor and transforming growth factor-alpha resulted in up-regulation of the promoter. Tumor necrosis factor-alpha and interferon (IFN)-gamma inflammatory cytokines had no or mild effect on MUC4 transcriptional activity when used alone. However, a very strong synergistic effect (10-12-fold activation) between IFN-gamma and tumor necrosis factor-alpha or IFN-gamma and transforming growth factor-alpha was obtained in CAPAN-2 cells. Altogether these results demonstrate that the 5'-flanking region of MUC4 contains epithelial cell-specific, positive, and negative regulatory cis-elements, that Sp1/Sp3 are important regulators of MUC4 basal expression, and that its regulation in pancreatic cancer cells involves complex interplay between several signaling pathways.

Aberrant expression of human mucin gene MUC5B in gastric carcinoma and cancer cells. Identification and regulation of a distal promoter

In gastric cancer, altered expression of MUC1, MUC2, MUC5AC, and MUC6 mucin genes has already been described. We show in this report by the means of in situ hybridization, reverse transcriptase-polymerase chain reaction, and transfection assays that MUC5B is also abnormally expressed in gastric carcinomatous tissues and cell lines. We thus undertook to elucidate the molecular mechanisms that regulate the transcription of MUC5B in gastric cancer cells. To this end, high expressing (KATO-III) and low expressing (AGS) gastric cancer cell lines were chosen to study human mucin gene MUC5B expression and promoter activity. Sequencing of the promoter region revealed a distal TATA box located 1 kilobase upstream of the proximal TATA box. Functional activity of the promoter was addressed by using deletion mutants covering 2044 nucleotides upstream of the MUC5B transcription start site. We identified a distal promoter 10 times more active than the proximal promoter in KATO-III cells. In AGS cells, both promoters, much less active, showed the same range of activity. Binding assays allowed us to show that the transcription factor ATF-1 binds to a cis-element present in the distal promoter. Sp1, which binds to both promoters specifically transactivates the proximal promoter. Treatment of transfected cells with PMA, cholera toxin A subunit, and calcium ionophore showed that only PMA led to a substantial activation of the distal promoter. MUC5B 5'-flanking region having a high GC content, influence of methylation on the MUC5B expression was assessed. Our results indicate that repression of MUC5B expression visualized in AGS cells is due in part to the presence of numerous methylated cytosine residues throughout the 5'-flanking region. Altogether these results demonstrate that MUC5B expression in gastric cancer cells is governed by a highly active distal promoter that is up-regulated by protein kinase C and that repression is under the influence of methylation.