A Gastric Glycoform of MUC5AC Is a Biomarker of Mucinous Cysts of the Pancreas

Abstract

Molecular indicators to specify the risk posed by a pancreatic cyst would benefit patients. Previously we showed that most cancer-precursor cysts, termed mucinous cysts, produce abnormal glycoforms of the proteins MUC5AC and endorepellin. Here we sought to validate the glycoforms as a biomarker of mucinous cysts and to specify the oligosaccharide linkages that characterize MUC5AC. We hypothesized that mucinous cysts secrete MUC5AC displaying terminal N-acetylglucosamine (GlcNAc) in either alpha or beta linkage. We used antibody-lectin sandwich assays to detect glycoforms of MUC5AC and endorepellin in cyst fluid samples from three independent cohorts of 49, 32, and 66 patients, and we used monoclonal antibodies to test for terminal, alpha-linked GlcNAc and the enzyme that produces it. A biomarker panel comprising the previously-identified glycoforms of MUC5AC and endorepellin gave 96%, 96%, and 87% accuracy for identifying mucinous cysts in the three cohorts with an average sensitivity of 92% and an average specificity of 94%. Glycan analysis showed that MUC5AC produced by a subset of mucinous cysts displays terminal alpha-GlcNAc, a motif expressed in stomach glands. The alpha-linked glycoform of MUC5AC was unique to intraductal papillary mucinous neoplasms (IPMN), whereas terminal beta-linked GlcNAc was increased in both IPMNs and mucinous cystic neoplasms (MCN). The enzyme that synthesizes alpha-GlcNAc, A4GNT, was expressed in the epithelia of mucinous cysts that expressed alpha-GlcNAc, especially in regions with high-grade dysplasia. Thus IPMNs secrete a gastric glycoform of MUC5AC that displays terminal alpha-GlcNAc, and the combined alpha-GlcNAc and beta-GlcNAc glycoforms form an accurate biomarker of mucinous cysts.

Loss of stomach, loss of appetite? Sequencing of the ballan wrasse (Labrus bergylta) genome and intestinal transcriptomic profiling illuminate the evolution of loss of stomach function in fish

“…Furthermore, a gene like mammalian MUC5AC , neighboring mucin 2 ( muc2 ), was identified in the wrasse genome assembly. The mammalian MUC5AC protein is a gel-forming mucin protein secreted in the gastrointestinal tract [ 27 ]. Orthologues of muc5ac were identified in most teleost species, including several agastric fish species (Ensembl database, release 86).…”

Multi-lectin Affinity Chromatography and Quantitative Proteomic Analysis Reveal Differential Glycoform Levels between Prostate Cancer and Benign Prostatic Hyperplasia Sera

“…A strategy for future validation of any glycoproteins of interest may include the use of antibody-lectin assays built to target specific protein glycoforms, such as those use by Sinha, J. et al . 63 . Additionally, further experiments for analysis of intact glycopeptides may also provide more detailed annotation of protein glycosylation status and reveal more specific alterations in glycan structure between PCa and BPH, as lectins, although useful tools for separation, provide limited information regarding glycan structure.…”

Early Detection of Pancreatic Cancer: Opportunities and Challenges

“…[92][93][94][95] Moreover, carbohydrate alterations to mucins detected in PCF have shown high sensitivity and high specificity in differentiating mucinous from nonmucinous pancreatic cysts and early detection of IPMN-associated PDACs. 96,97 In fact, MUC4 and MUC16 are reported to be 100% specific for PDAC, with associated sensitivities of 63% and 67%, respectively. 98 Promising biomarker results with PCF have also been reported for differentially methylated DNA, telomerase activity, protease expression, and the overexpression of Das-1.…”