Localization of transmembrane mucin MUC1 on the apical surface of oral mucosal cells

Analysis of the association between salivary proteins and oral mucositis in patients with head and neck cancer undergoing IMRT: a longitudinal study

INTRODUCTION

This longitudinal study assessed the association between salivary protein composition and the clinical onset/severity of oral mucositis (OM) in patients with head and neck tumours treated with intensity-modulated-radiotherapy (IMRT).

METHODS

Saliva samples/clinical data were obtained from 40 head and neck cancer patients treated at Guy's Hospital before -IMRT(T0) and after-IMRT (T1 = 6 m, T2 = 12 m) (ethics approval/consent). Salivary flow rate, total protein concentration, and secretion rate were determined from saliva samples and compared with pre-treatment values. OM was assessed, total/specific salivary proteins, including mucin 5B and 7, IgA, cystatin-S, albumin, and α-amylase, were quantified.

RESULTS

95% patients experienced OM during IMRT, with 33 subjects reaching grade 2&3. At T1, there was a significant reduction in salivary flow rate, total protein secretion rate, α-amylase and cystatin-S compared to baseline. Remarkably IMRT did not significantly alter mucin 5B and 7, or the IgA secretion rate at any time point. At T1, all the analyzed proteins were associated with the OM outcomes. In addition, there was a significant inverse correlation between IgA concentration at T0 and the severity of OM during IMRT.

CONCLUSION

This study revealed significant associations between several salivary proteins and OM in patients with head and neck cancer undergoing IMRT. Further longitudinal studies are needed to confirm these results.

CLINICAL SIGNIFICANCE

The study contributes to the understanding of certain salivary proteins association with OM. This could be the first step towards identifying potential salivary markers that could offer perspectives for personalized medicine approaches to improve their quality of life (QoL).

RESEARCH QUESTION

What is the association between salivary proteins and the occurrence and severity of OM in head and neck cancer patients?

AIM

To assess the association between salivary protein composition with the clinical onset/severity of oral mucositis (OM) in head and neck cancer patients treated with intensity modulated radiotherapy.

NULL HYPOTHESIS

There is no association between salivary proteins and onset/severity of OM in HNC patients.

Glycocalyx Curving the Membrane: Forces Emerging from the Cell Exterior

Morphological transitions are typically attributed to the actions of proteins and lipids. Largely overlooked in membrane shape regulation is the glycocalyx, a pericellular membrane coat that resides on all cells in the human body. Comprised of complex sugar polymers known as glycans as well as glycosylated lipids and proteins, the glycocalyx is ideally positioned to impart forces on the plasma membrane. Large, unstructured polysaccharides and glycoproteins in the glycocalyx can generate crowding pressures strong enough to induce membrane curvature. Stress may also originate from glycan chains that convey curvature preference on asymmetrically distributed lipids, which are exploited by binding factors and infectious agents to induce morphological changes. Through such forces, the glycocalyx can have profound effects on the biogenesis of functional cell surface structures as well as the secretion of extracellular vesicles. In this review, we discuss recent evidence and examples of these mechanisms in normal health and disease.

From Anti-PD-1/PD-L1 to CTLA-4 and to MUC1-Is the Better Response to Treatment in Smokers of Cancer Patients Drug Specific?

Whether smokers respond to anti-cancer drugs differently than non-smokers remains controversial. The objective of this study is to explore whether the better response of the smokers is specific to therapy of anti-PD-1/PD-L1, anti-checkpoint inhibitor, individual drugs on the cell surface, or lung cancer. Our results showed that among all non-small cell lung cancer (NSCLC) patients, when the data from anti-PD-1/PD-L1, anti-CTLA-4, and anti-MUC1 drugs are combined, the mean hazard ratios (HR) of smokers and non-smokers were 0.751 and 1.016, respectively. A meta-analysis with a fixed effect (FE) model indicated that the smokers have an HR value of 0.023 lower than that of the non-smokers. A stratified subgroup meta-analysis indicated that when treated with anti-CTLA-4 drugs, smokers had reduced HR values of 0.152 and 0.165 on average and FE model meta-analysis, respectively. When treated with an anti-MUC1 drug, smokers had reduced HR values of 1.563 and 0.645, on average and FE model meta-analysis, respectively. When treated with a combination of nivolumab and ipilimumab drugs, smokers had, on average, reduced HR and FE model meta-analysis values (0.257 and 0.141), respectively. Smoking is a clinical response predictor for anti-PD/PD-L1 monotherapy or first-line treatment in lung, urothelial carcinoma, and head and neck cancer. Smokers treated with other drugs have shown worse responses in comparison to non-smokers. These data suggest that, along with the progress in the development of new drugs for cancer, drugs acting on specific genotypes of smokers likely will arise.

Oral mucosal pellicle as an immune protection against micro-organisms in patients with recurrent aphthous stomatitis: A hypothesis

Recurrent Aphthous Stomatitis (RAS) is the most common ulcerative diseases of oral mucosa affecting an estimate of 20% of the world's population. Majority of the people affected by RAS are under 30 years of age. RAS is located on the lining (non-keratinized) oral mucosa, i.e. buccal mucosa, lateral side of the tongue, soft palate, lip mucosa, or the floor of mouth. An aphthous ulcer develops when lymphocytic cells infiltrate into the epithelium and cause an edema due to transient inflammatory stimuli. Bacteria, viruses and fungi have been suggested to cause aphthous lesions, but findings regarding oral pathogens are conflicting. Prior consensus has been that RAS is a multifactorial condition, with microbes, allergies, nutritional deficiencies, genetic factors, certain illnesses, immunodeficiency, hormonal changes, trauma and stress among others, contributing to the condition. In spite of many suggestions and investigations, the etiology and pathophysiology of RAS remains uncertain. Our hypothesis focuses on mucin proteins that have been shown to play a role in the formation of protective mucosal pellicle, which serves as the first line of defense between oral epithelium and pathogens within the oral cavity. Mucins, including transmembrane mucin 1 (MUC1), and salivary mucins MUC5B and MUC7 form a protein network that is strongly retained to oral epithelium. The role of the mucosal pellicle in pathophysiology of RAS is unknown. Structural variations have been found in the salivary MUC7 terminal end oligosaccharides in RAS patients, rendering the protein unable to agglutinate pathogens. Furthermore, low levels of MUC1 fail to provide a scaffold for assembly of salivary mucins. We introduce a new hypothesis, the alterations in the structure of these glycoproteins could have a profound impact on the oral mucosal barrier function. On the other hand, micro-organisms secreting their mucolytic enzymes destroy the mucosal pellicle causing oral ulcers.

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.