The Role of Mucin Expression in the Diagnosis of Oesophago-Gastric Cancer: A Systematic Literature Review.

Simple Summary: Oesophago-gastric cancers are associated with poor survival due to late diagnosis. By the time patients present to their doctor, there is a high chance the disease has spread around the body. Currently, less than 40% of patients with oesophago-gastric cancer can be treated with potentially curative intent. Non-invasive testing of patients who are at higher risk of oesophago-gastric cancer may help to identify these cancers earlier, before they have spread around the body, potentially increasing chances of cure. Mucins are proteins that are found throughout the digestive system and involved in the development of this disease. In this study, the literature on the role of mucins in the diagnosis of oesophago-gastric cancer has been reviewed. Mucins MUC1, MUC2, MUC5AC and MUC6 were the most frequently implicated in oesophago-gastric cancer. Further study of these mucins in high-risk populations may reveal new markers for non-invasive early diagnostic testing for oesophago-gastric cancer. Survival in oesophago-gastric cancer (OGC) is poor due to early diagnostic challenges. Non-invasive risk stratification may identify susceptible patients with pre-malignant or benign disease. Following diagnostic confirmation with endoscopic biopsy, early OGC may be treated sooner. Mucins are transmembrane glycoproteins implicated in OGC with potential use as biomarkers of malignant transformation. This systematic review defines the role of mucins in OGC diagnosis. A literature search of MEDLINE, Web of Science, Embase and Cochrane databases was performed following PRISMA protocols for studies published January 1960–December 2022. Demographic data and data on mucin sampling and analysis methods were extracted. The review included 124 studies (n = 11,386 patients). Gastric adenocarcinoma (GAc) was the commonest OG malignancy (n = 101) followed by oesophageal adenocarcinoma (OAc, n = 24) and squamous cell carcinoma (OSqCc, n = 10). Mucins MUC1, MUC2, MUC5AC and MUC6 were the most frequently implicated. High MUC1 expression correlated with poorer prognosis and metastases in OSqCc. MUC2 expression decreases during progression from healthy mucosa to OAc, causing reduced protection from gastric acid. MUC5AC was upregulated, and MUC6 downregulated in GAc. Mucin expression varies in OGC; changes may be epigenetic or mutational. Profiling upper GI mucin expression in OGC, with pre-malignant, benign and healthy controls may identify potential early diagnostic biomarkers. [ABSTRACT FROM AUTHOR]