Lectin histochemistry of galactose and N-acetyl-galactosamine glycoconjugates in normal gastric mucosa and gastric cancer and the relationship with ABO and secretor status.

Abstract

The histochemical binding of four lectin-peroxidase conjugates to normal human gastric mucosa and gastric carcinoma is described. The lectins were peanut agglutinin (PNA) which is specific for galactose residues and soy bean agglutinin (SBA), Dolichos biflorus agglutinin (DBA) and Helix pomatia agglutinin (HPA) which are specific for N-acetylgalactosamine. Binding of PNA to surface mucous cells or normal gastric mucosa occurred in non-secretors but not secretors and was independent of ABO blood group at all sites. PNA binding was unrelated to the immunohistochemical demonstration of Thomsen-Friedenreich (T) antigen. DBA and HPA bound selectively to surface mucous cells in normal gastric mucosa from group A secretors but binding at other sites was independent of ABO status. SBA binding showed no relationship with blood group or secretor status. In gastric cancers the major finding was the occurrence of extensive masking of lectin binding sites by sialic acid which was not seen in normal mucosa. Sialic acid masking was most marked with PNA and least marked with DBA. There was no correlation between lectin binding patterns and the stage or differentiation of tumours. Results are consistent with in vitro studies demonstrating increased sialation of membrane glycoproteins following malignant transformation. Difficulties in interpreting the histochemical demonstration of lectin binding in terms of specific glycoconjugates are discussed.