g(m2)-ganglioside and Stomach-Neoplasms

The content of the GM2 ganglioside and the activity of UDP-GalNAc: GM3 beta-1,4N-acetylgalactosaminyltransferase (beta-1,4GalNAcT), which synthesizes GM2, increased in gastric cancer tissues and gastric cancer cell lines as compared with that in normal gastric mucosa.. Expression of beta-1,4GalNAcT mRNA and a concentration of GM2 in the human gastrointestinal tissues were examined. Beta-1,4GalNAcT mRNA in human surgical specimens, which was not detectable with Northern blotting because of the paucity of absolute amounts expressed, was detected with competitive reverse transcription-polymerase chain reaction (PCR) method using an internal standard cRNA that could be amplified by the same primers as target mRNA in PCR. The quantification of GM2 was examined using immunostaining of thin-layer chromatography.. In 10 of 10 gastric carcinomas and 6 of 13 colonic carcinomas, mRNA expression was more enhanced than that in the normal mucosa of each patient. The alteration of GM2 content in carcinoma from normal tissue generally was correlated to the change in the expression of beta-1,4GalNAcT mRNA with a few exceptions. One gastric cancer sample had a higher level of mRNA with a lower GM2 content than the corresponding normal tissue, and two colonic carcinoma tissue specimens had a lower level of mRNA with a higher GM2 content.. These results suggest that expression of the beta-1,4GalNAcT gene is a key step in the molecular mechanisms underlying the regulation of cancer-associated GM2 expression in the stomach and the colon.

Topics: Adenocarcinoma; Base Sequence; Blotting, Northern; Colonic Neoplasms; G(M2) Ganglioside; Gastric Mucosa; Gene Expression; Humans; Intestinal Mucosa; Molecular Sequence Data; N-Acetylgalactosaminyltransferases; Polymerase Chain Reaction; Polypeptide N-acetylgalactosaminyltransferase; RNA-Directed DNA Polymerase; RNA, Messenger; RNA, Neoplasm; Stomach Neoplasms

A glycolipid detected in human gastric mucosa with anti-GM2 monoclonal antibody was characterized to be GalNAc beta 1-4[NeuAc alpha 2-3]Gal beta 1-4GlcNAc beta 1-3Gal 1-4Glc-Cer (NGM-1), which was lost in gastric cancer tissue with complementary increase of GM2 sharing the same terminal carbohydrate structure as NGM-1 (Dohi, T., Ohta, S., Hanai, N., Yamaguchi, K., and Oshima, M. (1990) J. Biol. Chem. 265, 7880-7885). The study on differential expression of NGM-1 in gastric fundic mucosa, pyloric mucosa, gastric cancer, and various other tissues indicated that NGM-1 existed specifically in fundic mucosa. The content of GM3 and sialylparagloboside (SPG), which are the substrates for the synthesis of GM2 and NGM-1, respectively, were not significantly different in these tissues. Therefore, the presence of two kinds of beta 1,4GalNAc transferases having different substrate specificity was considered to be critical for the expression of NGM-1 and GM2. The activity of beta 1,4GalNAc transferase which synthesizes GM2 or NGM-1 was determined by detecting the products with specific monoclonal antibodies. The activity of beta 1,4GalNAc transfer to SPG was high in fundic mucosa, while it was absent in pyloric mucosa or cancer. On the other hand, the increased activity of beta 1,4GalNAc transfer to GM3 was observed in cancer tissues and cancer cell lines which were rich in GM2. Our conclusion is that the limited expression of NGM-1 in fundic mucosa and the increase of GM2 in cancer are attributed to two types of beta 1,4GalNAc transferases localized in each region with different substrate specificity; the one in fundic mucosa transfers GalNAc to SPG but not to GM3, and the other one enhanced in cancer transfers GalNAc to GM3 but not to SPG.

Topics: Antibodies, Monoclonal; Cell Line; Chromatography, Thin Layer; Colonic Neoplasms; G(M2) Ganglioside; Galactosyltransferases; Gangliosides; Gastric Fundus; Gastric Mucosa; Humans; Kinetics; N-Acetylgalactosaminyltransferases; Organ Specificity; Polypeptide N-acetylgalactosaminyltransferase; Pyloric Antrum; Stomach Neoplasms

The ganglioside fraction of human gastric mucosa was analyzed with a newly established anti-GM2 monoclonal antibody KM531. Using this antibody, accumulation of GM2 was observed in all of four cases of gastric carcinoma. In all ganglioside fractions extracted from normal gastric mucosa obtained from eight cases of peptic ulcer GM2 itself was not detected, but three kinds of glycolipid showing slower mobility than GM2 on thin-layer plates were detected by immunostaining with KM531. These glycolipids were assigned as NGM-1, -2, and -3. They were completely lost in all carcinoma tissues and in non-cancerous gastric mucosa from two cases of gastric cancer, and they were also not detected in the ganglioside fraction of small or large intestine. Of these glycolipids, the major one, NGM-1, was isolated from the pooled ganglioside fraction of normal gastric mucosa obtained from cases of peptic ulcer. The structure was determined by proton nuclear magnetic resonance, negative ion fast atom bombardment-mass spectrometry, gas chromatography-mass spectrometry, and treatment with exoglycosidases and mild acid hydrolysis. The structure was GalNAc beta 1----4(NeuAc alpha 2----3) Gal beta 1----4GlcNAc beta 1----3 Gal beta 1----4Glc beta 1----1Cer, which has the same terminal sequence as GM2 but has internal neolacto series structure. This epitope was previously identified as Cad blood group antigen. The decrease of this glycolipid and the increase of GM2 was considered to be a cancer-associated change in gastric mucosa.

Topics: Antibodies, Monoclonal; beta-N-Acetylhexosaminidases; Carbohydrate Conformation; Carbohydrate Sequence; G(M2) Ganglioside; Gangliosides; Gas Chromatography-Mass Spectrometry; Gastric Mucosa; Humans; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Sequence Data; Stomach Neoplasms; Stomach Ulcer