Understanding the Clinical Significance of MUC5AC in Biliary Tract Cancers.

Simple Summary: Biliary tract cancers (BTC) are tumors arising from cells lining ducts in the liver that facilitate the transport of bile into the gastrointestinal tract. They are often divided into two broad groups, cholangiocarcinoma and gallbladder cancers. They are aggressive tumors with limited treatment options that are often ineffective and have bad outcomes. In current clinical practice, there are no good tests to identify these cancers in early stages and predict their aggressiveness or response to the available treatments. We shed light on the role of a glycoprotein, MUC5AC, in BTC including its potential impact on biliary cancer development. We discuss the clinical evidence surrounding the use of MUC5AC when detected in BTC patients' tumor tissue and blood and its potential use in managing these cancers. Biliary tract cancers (BTC) arise from biliary epithelium and include cholangiocarcinomas or CCA (including intrahepatic (ICC) and extrahepatic (ECC)) and gallbladder cancers (GBC). They often have poor outcomes owing to limited treatment options, advanced presentations, frequent recurrence, and poor response to available systemic therapy. Mucin 5AC (MUC5AC) is rarely expressed in normal biliary epithelium, but can be upregulated in tissues of benign biliary disease, premalignant conditions (e.g., biliary intraepithelial neoplasia), and BTCs. This mucin's numerous glycoforms can be divided into less-glycosylated immature and heavily-glycosylated mature forms. Reported MUC5AC tissue expression in BTC varies widely, with some associations based on cancer location (e.g., perihilar vs. peripheral ICC). Study methods were variable regarding cancer subtypes, expression positivity thresholds, and MUC5AC glycoforms. MUC5AC can be detected in serum of BTC patients at high concentrations. The hesitancy in developing MUC5AC into a clinically useful biomarker in BTC management is due to variable evidence on the diagnostic and prognostic value. Concrete conclusions on tissue MUC5AC are difficult, but serum detection might be relevant for diagnosis and is associated with poor prognosis. Future studies are needed to further the understanding of the potential clinical value of MUC5AC in BTC, especially regarding predictive and therapeutic value. [ABSTRACT FROM AUTHOR]