Low O‐acetylation of sialyl‐LEx contributes to its overexpression in colon carcinoma metastases

• Published in: International journal of cancer 1997-07, Vol.72 (2), p.258-264
• Main Authors: Mann, Benno, Klussmann, Enno, Vandamme‐Feldhaus, Valérie, Iwersen, Matthias, Hanski, Marie‐Luise, Riecken, Ernst‐Otto, Buhr, Heinz Johannes, Schauer, Roland, Kim, Young S., Hanski, Christoph
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Gastroenterology. Liver. Pancreas. Abdomen; Medical sciences; Stomach. Duodenum. Small intestine. Colon. Rectum. Anus; Tumors
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/(SICI)1097-0215(19970717)72:2<258::AID-IJC10>3.0.CO;2-C

Two factors potentially determining the consistent over‐expression of sialyl‐Lex antigen in colon carcinoma and metastases were investigated: (i) the expression of the mucins MUC1 and MUC2, known to carry sialyl‐Lex, by Northern blotting; (ii) the extent of sialic acid O‐acetylation, by Western blotting and HPLC. RNA and sialyl‐Lex‐positive mucins were purified from normal colonic mucosa (N), primary carcinomas (T) and their liver metastases (M). Northern blots showed that mRNA expression both of MUC1 and of MUC2 decreases during the progression of the disease, and is lowest in metastatic tissue. The expression of mucin‐bound sialyl‐Lex increased strongly from N to T and, to a lesser extent, to M. After alkali treatment of the mucins these differences disappeared, indicating that the total amount of mucin‐bound sialyl‐Lex is the same in the 3 types of tissues. The O‐acetylation of mucin‐bound sialyl‐Lex gradually decreased from N to M. HPLC analysis showed that in N about 70%, in T 45% and in M only 20% of mucin‐bound sialic acids are O‐acetylated. Thus, the increase of sialyl‐Lex detectable during colon‐carcinoma progression is due to diminished O‐acetylation and not to increased expression of mucin protein cores. The decrease of O‐acetylation is therefore the primary chemical alteration contributing to colon carcinoma‐associated overexpression of sialyl‐Lex. Int. J. Cancer 72:258–264, 1997. © 1997 Wiley‐Liss, Inc.