Human colonic
adenocarcinoma tissue and derived cell lines have been characterized by an abundance of different type 1 and 2 lacto series
glycolipid antigens which are either low or not found in normal colonic mucosa. The enzymatic basis for the expression of contrasting
glycolipid compositions between
adenocarcinomas and normal colonic mucosa, as well as between derived cell lines, has been studied. The following results were of particular interest. (i) Abundant activities of beta 1----4galactosyltransferase associated with synthesis of both
lactosylceramide and
lactoneotetraosylceramide, beta 1----3galactosyltransferase for synthesis of
lactotetraosylceramide, and an alpha 1----3/4fucosyltransferase responsible for synthesis of Lex and Lea
antigens were found in normal colonic mucosa or in a normal mucosal epithelial cell line HCMC, or in both. Variable levels of these activities were found in
adenocarcinoma tissues and in various established
adenocarcinoma cell lines. In striking contrast, significant activity of a beta 1----3N-acetylglucosaminyltransferase responsible for synthesis of
lactotriaosylceramide (Lc3) was found in various cases of colonic
adenocarcinoma and cell lines, but was undetectable in normal colonic epithelial cells. (ii) In situ transfer of
galactose to Lc3 was performed on histologic sections by preincubation of the tissue with acceptor
glycolipid followed by incubation with
UDP-galactose. The biosynthesized
glycolipid was revealed by indirect immunofluorescence with the
monoclonal antibody 1B2 which defines
lactoneotetraosylceramide antigen. In these studies, histologic sections prepared from frozen normal proximal colon tissue were shown to lack native type 2 chain structures. However, transfer of
galactose from
UDP-galactose could be demonstrated in the epithelial cells of normal proximal colon after incorporation of Lc3 into the membranes, indicating the ability of normal colonic epithelial cells to synthesize type 2 chain core structures if the precursor Lc3 is available. In contrast,
adenocarcinoma tissues showed significant native immunofluorescence with the antibody. These data suggest that an accumulation of both type 1 and 2 chain lacto series
glycolipids with alpha 1----3- or alpha 1----4fucosyl substitution in human
adenocarcinoma is due to enhanced beta 1----3N-acetylglucosaminyltransferase rather than enhancement of other
enzymes. This
enzyme may play a key role in regulating the level of various types of lacto series
tumor-associated
antigens with the lacto type 1 or 2 chain.