1. Volume 135, Issue 1, Pages 305-309 (July 2008)
Aberrant Expression of Carbohydrate Antigens in Cancer: The Role of Genetic and Epigenetic Regulation 
Young S. Kim, Guoren Deng 
Gastroenterology 
Volume 135, Issue 1, Pages (July 2008)
DOI: /j.gastro
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2. Figure 1
Biosynthesis of the determinants of blood group antigens. (A) A and H determinants are composed of fucose (Fuc), galactose (Gal) and N-acetylgalactosamine (GalNAc) with minimal antigenic determinant structures. R, underlying glycoprotein or glycolipid substructure. The α1,3-GalNAc transferase (A3GALNT) encoded by A gene transfers a GalNAc residue from UDP-GalNAc to the Gal residue of the precursor H substrate in α1,3 glycosidic linkage, producing A antigen as defined by the trisaccharide structure. In cancers, this process is blocked, resulting in the loss of A antigen and the increased expression of H antigen. The minimal antigenic determinant structure of H antigen is a disaccharide consisting of Fuc linked in α1,2 glycosidic linkage to Gal. (B) Genetic and epigenetic changes that inactivate AB blood group antigens. Aberrant promoter hypermethylation in one copy of the gene (the first hit) is associated with either the loss of other copy of the gene by the loss of the chromosomal region/LOH, or by promoter methylation of the other copy (biallelic methylation), which represent the second hit. (C) Biosynthesis of Sda and sialyl Lex/a antigenic determinants. Sda and sialyl Lex/a antigenic determinants are formed by the addition of GalNAc or Fuc to the precursor trisaccharide substrate by the action of B4GALT and FUT3 respectively. In cancers, the loss of Sda antigen and the expression of sialyl Lex/a antigens occur. As mentioned by Kawamura et al,9 there is a reciprocal relationship between the expression of Sda antigen and sialyl Lex/a antigens.
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2008 AGA Institute Terms and Conditions