Abrogation of MUC5AC Expression Contributes to the Apoptosis and Cell Cycle Arrest of Colon Cancer Cells

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.

Clinicopathological and prognostic value of CD44 gene polymorphism (rs187115) in Swedish patients with colorectal cancer

Cluster of differentiation (CD) 44 plays a crucial role in apoptosis, cell-cell interactions, angiogenesis, metastasis and proliferation. The aim of the present study was to examine the influence of CD44 gene polymorphism rs187115 on colorectal cancer (CRC) susceptibility and the association with various clinical features including long-term survival in Swedish patients with CRC. Genotypes were screened, using TaqMan single nucleotide polymorphism (SNP) assays based on polymerase chain reaction, in 612 CRC patients and 575 healthy controls.The carriers of G allele, genotypes (AG + GG), were found to be associated with an increased risk of CRC with an odds ratio (OR) of 1.35 (95% confidence interval (CI) = 1.01-1.81; p = 0.039) and found to be more common in patients with mucinous cancer compared with non-mucinous cancer, OR = 1.69 (95% CI = 1.02-2.80; p = 0.011). By using Kaplan-Meier analysis, the patients with genotype GG showed shorter cancer-specific and recurrence free survival with a hazard ratio (HR) of 1.25 (95% CI = 1.02-1.54; p = 0.036) and 1.52 (95% CI = 1.12-2.06; p = 0.007), respectively, in comparison with the carriers of A allele (AG + AA). The present findings demonstrated that the variant G allele of CD44 gene polymorphism rs187115 was related to risk for CRC and associated to mucinous cancer and predict worse prognosis in Swedish patients with CRC.

Mucin 16 Promotes Colorectal Cancer Development and Progression Through Activation of Janus Kinase 2

BACKGROUND

Mucin 16 (MUC16), a cell surface-associated mucin, has been implicated to be upregulated in a large repertoire of malignances. However, its function in the pathogenesis of colorectal cancer (CRC) is unknown.

AIMS

Here, we explored the regulatory role of MUC16 in CRC.

METHODS

First, tumor and paracancerous tissues, and serum samples from 162 CRC patients, peripheral blood samples from 48 healthy volunteers and 72 benign colorectal patients were collected. The correlation between the MUC16 expression and the clinical phenotypes of the patients was analyzed. Subsequently, HCT116 and SW480 cells with deletion of MUC16 were established to detect changes in the growth and metastatic capacities of CRC cells. The genes with the highest correlation with MUC16 were predicted by bioinformatics, and their binding relationships were detected by Co-IP and double-labeled immunofluorescence, followed by functional rescue experiments.

RESULTS

Overexpression of MUC16 in CRC patients was positively correlated with serum biomarkers and poor prognosis of patients. It was demonstrated by in vitro and in vivo experiments that knocking-down the expression of MUC16 could significantly inhibit the growth and metastasis of CRC cells. MUC16 activated janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) by interacting with JAK2. Further overexpression of JAK2 in cells with poor expression of MUC16 revealed a significant increase in the proliferative and metastatic capacities of CRC cells.

CONCLUSIONS

MUC16 contributes to the development and progression of CRC by binding to JAK2, thereby promoting phosphorylation of JAK2 and further activating STAT3 phosphorylation.

Identification of Key Histone Modifications and Hub Genes for Colorectal Cancer Metastasis

Background:

Epithelial-Mesenchymal Transition (EMT) and its reverse Mesenchymal- Epithelial Transition (MET) are essential for tumor cells metastasis. However, the effect of epigenetic modifications on this transition is unclear.

Objective:

We aimed to explore the key histone modifications and hub genes of EMT/MET during Colorectal Cancer (CRC) metastasis.

Method:

The differentially expressed genes and differentially histone modified genes were identified. Based on the histone modification features, the up- and down-regulated genes were predicted by Random Forest algorithm. Through protein-protein interaction network and Cytoscape analysis, the hub genes with histone modification changes were selected. GO, KEGG and survival analyses were performed to confirm the importance of the hub genes.

Results:

It was found that H3K79me3 plays an important role in EMT/MET. And the 200-300bp and 400-500bp downstream of TSS may be the key regulatory regions of H3K79me3. Moreover, we found that the expression of the hub genes was down-regulated in EMT and then up-regulated in MET. And the changes of the hub genes expression were consistent with the changes of H3K79me3 signal in the specific regions of the genome. Finally, the hub genes KRT8 and KRT18 were involved in the metastasis process and were significantly related to the survival time.

Conclusion:

H3K79me3 may be crucial for EMT/MET, and the hub genes KRT8 and KRT18 may be the key genes in this process.

Mucin 5AC expression is common but unrelated to tumor progression in pancreatic adenocarcinoma

Introduction: Mucin 5AC (MUC5AC) belongs to the family of secreted gel-forming mucins. It is physiologically expressed in some normal mucin producing epithelial cells but also in pancreatic, ovarian, and colon cancer cells. The role of MUC5AC expression in cancer is not fully understood. This study was designed to explore the role of MUC5AC for pancreatic cancer progression, its association to microsatellite instability, and its diagnostic utility. Methods: Mucin 5AC expression was studied immunohistochemically in a tissue microarray (TMA) from 532 pancreatic cancers, 61 cancers of the ampulla Vateri, six acinar cell carcinomas and 12 large sections of pancreatitis. Results: Mucin 5AC staining was interpretable in 476 of 599 (79%) arrayed cancers. Staining was completely absent in normal pancreas and pancreatitis, but frequent in pancreatic cancer. Membranous and cytoplasmic MUC5AC expression was most common in pancreatic adenocarcinomas (71% of 423), followed by carcinomas of the ampulla Vateri (43% of 47), and absent in six acinar cell carcinomas. Mucin 5AC expression was unrelated to tumor phenotype (tumor stage, tumor grade, lymph node, and distant metastasis), and microsatellite instability in ductal adenocarcinomas and carcinomas of the ampulla Vateri. Conclusion: Our study indicates that MUC5AC is an excellent biomarker for pancreatic cancer diagnosis, especially to support the sometimes-difficult diagnosis on small biopsies. Mucin 5AC expression is unrelated to pancreatic cancer aggressiveness.

Resistance to Cell Death in Mucinous Colorectal Cancer-A Review

Mucinous colorectal cancer (CRC) is estimated to occur in approximately 10-15% of CRC cases and is characterized by abundant extracellular mucin. Mucinous CRC is frequently associated with resistance to apoptosis. Inferior prognosis is observed in mucinous CRC, particularly in rectal cancer and metastatic cases. Mucins are heavily glycosylated secretory or transmembrane proteins that participate in protection of the colonic epithelium. MUC2 overexpression is a hallmark of mucinous CRCs. Mucinous CRC is associated with KRAS and BRAF mutation, microsatellite instability and the CpG island methylator phenotype. Mutations of the APC gene and p53 mutations which are characteristic non-mucinous colorectal adenocarcinoma are less common in mucinous CRC. Both physical and anti-apoptotic properties of mucin provide mechanisms for resistance to cell death. Mucin glycoproteins are associated with decreased expression of pro-apoptotic proteins, increased expression of anti-apoptotic proteins and increased cell survival signaling. The role for BCL-2 proteins, including BCL-X_L, in preventing apoptosis in mucinous CRC has been explored to a limited extent. Additional mechanisms opposing cell death include altered death receptor expression and altered mutation rates in genes responsible for chemotherapy resistance. The roles of alternate cell death programs including necroptosis and pyroptosis are not well understood in mucinous CRC. While the presence of MUC2 is associated with an immunosuppressive environment, the tumor immune environment of mucinous CRC and the role of immune-mediated tumor cell death likewise require further investigation. Improved understanding of cell death mechanisms in mucinous CRC may allow modification of currently used regimens and facilitate targeted treatment.

MUC1 and MUC5AC implication in Tunisian colorectal cancer patients

Background/aim

Mucins, such as MUC1 and MUC5AC, are known for their protective and moisturizing role in intestinal epithelium. Their expression is tightly controlled given their essential role in normal tissue homeostasis, whereas their deregulation leads to chronic inflammation, and even cancer. This study aimed to assess the expression profiles of MUC1 and MUC5AC and their implications in colorectal carcinogenesis.

Materials and methods

A retrospective study of 202 patients who underwent colorectal cancer (CRC) surgery was conducted. The expression of MUC1 and MUC5AC was investigated by immunohistochemistry and reverse-transcription polymerase chain reaction (RT-PCR). Statistical analysis of mucin expression pattern, as well as the clinicopathological criteria of the patients, was performed using the chi-square test, survival curves were plotted using the Kaplan—Meier product-limit method, and differences between the survival curves were tested using the log-rank test.

Results

The expression of both mucins was abnormally high in the tumor tissues for both mRNA and protein. MUC1 expression was correlated with advanced cancer stages and lymph node metastases for both the mRNA (P < 0.016 and P < 0.002, respectively) and protein level (P < 0.006 and P < 0.001, respectively). However, MUC5AC expression did not pinpoint any significant association between the clinicopathological criteria, but patients who expressed MUC5AC showed an increase in overall survival (P < 0.009).

Conclusion

The expression of MUC1 might be a poor prognostic biomarker in CRC and could play a role in tumor transformation and metastasis. However, MUC5AC expression might be a good prognostic in the Tunisian cohort.

Elevated MUC5AC expression is associated with mismatch repair deficiency and proximal tumor location but not with cancer progression in colon cancer

Mucin 5AC (MUC5AC) is a secreted gel-forming mucin expressed by several epithelia. In the colon, MUC5AC is expressed in scattered normal epithelial cells but can be abundant in colorectal cancers. To clarify the relationship of MUC5AC expression with parameters of tumor aggressiveness and mismatch repair deficiency (dMMR) in colorectal cancer, a tissue microarray containing 1812 colorectal cancers was analyzed by immunohistochemistry. MUC5AC expression was found in 261 (15.7%) of 1,667 analyzable colorectal cancers. MUC5AC expression strongly depended on the tumor location and gradually decreased from proximal (27.4% of cecum cancers) to distal (10.6% of rectal cancers; p < 0.0001). MUC5AC expression was also strongly linked to dMMR. dMMR was found in 21.3% of 169 cancers with MUC5AC positivity but in only 4.6% of 1051 cancers without detectable MUC5AC expression (p < 0.0001). A multivariate analysis showed that dMMR status and tumor localization predicted MUC5AC expression independently (p < 0.0001 each). MUC5AC expression was unrelated to pT and pN status. This also applied to the subgroups of 1136 proficient MMR (pMMR) and of 84 dMMR cancers. The results of our study show a strong association of MUC5AC expression with proximal and dMMR colorectal cancers. However, MUC5AC expression is unrelated to colon cancer aggressiveness.

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.

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.

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.