Sialyl LewisA, also known as sialyl LeA and SLeA, is a tetrasaccharide carbohydrate that is usually attached to O-glycans on the surface of cells. It is known to play a vital role in cell-to-cell recognition processes. Occurrence of the Sialyl Lewis A antigen, detected with the CA19-9 antibody, is highly correlated advanced epithelial cancers, such as stage III and stage IV colorectal cancers. Neoplastic transformation is often associated with characteristic changes in the expression of the sialyl Lewis(a) and sialyl Lewis(x) antigens, representing typical tumor-associated carbohydrate antigens. High amounts of sialyl Lewis(a) are present in human adenocarcinomas of the colon, pancreas and stomach. Sialylated Lewis structures present on the surface of tumor cells are carried by the carbohydrate chains of glycoproteins and glycolipids.
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