Abstract
Introduction: Normal colonic epithelial cells produce mucins which are more than 50% carbohydrate and have characteristic terminal sugars on the oligosaccharide chains that can be recognized by lectins. A goblet cell in the upper portion of the colonic crypt makes mucin with a terminal sugar which binds the lectins Dolichos biflorus agglutinin (DBA) and soybean agglutinin (SBA). The lower portion of the crypt has mucin with a terminal sugar residue which binds to Ricinus communis agglutinin-1 (RCA-1). Colon cancer produces mucin that binds peanut agglutinin (PNA). The goal of this study was to use lectin binding patterns in order to differentiate mucins secreted by low grade neoplasms from mucins produced by adenocarcinomas in the colon causing pseudomyxoma peritonei. Methods: Normal and diseased colon specimens were obtained from 31 patients with mucinous lesions and prepared for fluorescent lectin microscopy using fluorescein isothicyanate (FITC)-conjugated lectins: DBA, SBA, RCA-1 and PNA. The FITC-lectin labeling and pathological interpretations were performed independently. Results: 23/23 of the adenocarcinoma cases were positive for FITC PNA labeling versus 3/7 of the low grade neoplasm cases, a difference that was statistically significant (p=0.001 by chi-square). Conclusion: PMP is a disease characterized by a mucinous fluid collection in the abdomen and pelvis caused by mucus-producing adenomas or adenocarcinomas. The disease can behave very aggressively clinically. In this study, PNA binds to the mucins in all tumor sections that are adenocarcinomas. It was expected that SBA and DBA would bind similarly to the same tumor section but that was not always the case. This might be due to subtle differences in what these two GalNAc-binding lectins recognize and has an undetermined significance. It is reasonable to theorize that a tumor section with strong PNA binding and weaker SBA, DBA, or RCA-1 binding could represent increased dysplasia within the tumor and it will be interesting to compare this data with clinical outcomes. Further work will include more cases of low grade neoplasms as well as long-term clinical outcomes in order to strengthen the hypothesis that the absence of PNA binding predicts improved outcomes. This information could be valuable in determining the best treatment strategy for different patients.
Published Version
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