Mucoepidermoid carcinoma-associated expression of MUC5AC, MUC5B and mucin-type carbohydrate antigen sialyl-Tn in the parotid gland

Expression and localisation of MUC1 modified with sialylated core-2 O-glycans in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most frequent of the rare salivary gland malignancies. We previously reported high expression of Mucin 1 (MUC1) modified with sialylated core-2 O-glycans in MEC by using tissue homogenates. In this study, we characterised glycan structures of MEC and identified the localisation of cells expressing these distinctive glycans on MUC1. Mucins were extracted from the frozen tissues of three patients with MEC, and normal salivary glands (NSGs) extracted from seven patients, separated by supported molecular matrix electrophoresis (SMME) and the membranes stained with various lectins. In addition, formalin-fixed, paraffin-embedded sections from three patients with MEC were subjected to immunohistochemistry (IHC) with various monoclonal antibodies and analysed for C2GnT-1 expression by in situ hybridisation (ISH). Lectin blotting of the SMME membranes revealed that glycans on MUC1 from MEC samples contained α2,3-linked sialic acid. In IHC, MUC1 was diffusely detected at MEC-affected regions but was specifically detected at apical membranes in NSGs. ISH showed that C2GnT-1 was expressed at the MUC1-positive in MEC-affected regions but not in the NSG. MEC cells produced MUC1 modified with α2,3-linked sialic acid-containing core-2 O-glycans. MUC1 containing these glycans deserves further study as a new potential diagnostic marker of MEC.

Characterization of tumor-associated MUC1 and its glycans expressed in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is one of the most frequently misdiagnosed tumors. Glycans are modulated by malignant transformation. Mucin 1 (MUC1) is a mucin whose expression is upregulated in various tumors, including MEC, and it has previously been investigated as a diagnostic and prognostic tumor marker. The present study aimed to reveal the differences in the mucin glycans between MEC and normal salivary glands (NSGs) to discover novel diagnostic markers. Soluble fractions of salivary gland homogenate prepared from three MEC salivary glands and 7 NSGs were evaluated. Mucins in MEC and NSGs were separated using supported molecular matrix electrophoresis, and stained with Alcian blue and monoclonal antibodies. The glycans of the separated mucins were analyzed by mass spectrometry. MUC1 was found in MEC but not in NSGs, and almost all glycans of MUC1 in MEC were sialylated, whereas the glycans of mucins in NSGs were less sialylated. The core 2 type glycans, (Hex)₂(HexNAc)₂(NeuAc)₁ and (Hex)₂(HexNAc)₂(NeuAc)₂, were found to be significantly abundant glycans of MUC1 in MEC. MEC markedly produced MUC1 modified with sialylated core 2 glycans. These data were obtained from the soluble fractions of salivary gland homogenates. These findings provide a basis for the utilization of MUC1 as a serum diagnostic marker for the preoperative diagnosis of MEC.

Regulation of mucin 1 expression and its relationship with oral diseases

OBJECTIVE

The aim of this study is to describe the polymorphic mucin 1 (MUC1), and to provide an overview of the known complex and multiple functions of MUC1 in normal oral mucosa and oral mucosal lesions in compromised situations as well as exploring the challenges associated with the heterogeneous nature of MUC1. We will review the current knowledge and provide insights into the future management possibilities of using MUC1 as a therapeutic agent.

METHODS

A literature search of the electronic databases included MEDLINE (1966 -December 2019) and hand searches of cross-references were undertaken using terms related to mucins, MUC1.

RESULTS

MUC1 is a large transmembrane glycoprotein expressed on the apical surface of most of epithelial cell surfaces. Not only is it involved in lubrication, cell surface hydration, and protection against degrading enzymes, MUC1 also promotes abnormal cellular signalling, angiogenesis, anti-adhesion and tumorigenesis. Aberrant glycosylation, overexpression, loss of apical constraint are characteristics of the transformation of a normal cell to a cancerous cell. This review summarizes studies of MUC1 expression and function with a special emphasis on oral epithelial cells in normal and abnormal conditions. In addition, current knowledge of MUC1 and unexplored areas of MUC1 are presented.

CONCLUSION

MUC1 is an archetypical transmembrane protein, the presence of MUC1 in ectopic regions may lead to dysregulation of certain enzymes and activation of various pathways, favouring the development of inflammatory responses and tumour formation. This review examines the potential of MUC1 in the development of future therapeutics.

mRNA and P-element-induced wimpy testis-interacting RNA profile in chemical-induced oral squamous cell carcinoma mice model

P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs), a novel class of noncoding RNAs, are involved in the carcinogenesis. However, the functional significance of piRNAs in oral squamous cell carcinoma (OSCC) remains unknown. In the present study, we used chemical carcinogen 4-nitroquinoline-1-oxide (4NQO) induced OSCC mouse model. piRNAs and mRNAs were profiled using next-generation sequencing in the tongue tumor tissues from 4NQO induction and healthy tongue tissues from control mice. Furthermore, we analyzed the differential gene expression of human OSCC in Gene Expression Omnibus (GEO) database. According to the common differentially expressed genes in the 4NQO model and human OSCC tissues, piRNAs and mRNAs network were established based on informatics method. A total of 14 known piRNAs and 435 novel predicted piRNAs were differently expressed in tumor tissue compared to healthy tissue. Among differently expressed piRNAs 260 were downregulated, and 189 were upregulated. The mRNA targets for the differentially expressed piRNAs were identified using RNAhybrid software. Primary immunodeficiency and herpes simplex infection were the most enriched pathways. A total of 22 mRNAs overlapped in human and mice OSCC. Moreover, we established the regulatory network of 11 mRNAs, including Tmc5, Galnt6, Spedf, Mybl2, Muc5b, Six31, Pigr, Lamc2, Mmp13, Mal, and Mamdc2, and 11 novel piRNAs. Our data showed the interaction between piRNAs and mRNAs in OSCC, which might provide new insights in the development of diagnostic biomarkers and therapeutic targets of OSCC.