An alpha 2,3 sialyltransferase (ST3Gal I) is elevated in primary breast carcinomas

The MUC1 mucin is expressed on the luminal surface of most simple epithelia l cells but in carcinomas, especially those of the breast and ovary, MUC1 i s upregulated and aberrantly glycosylated, MUC1 contains a large amount of O-linked glycans which, in the mucin expressed by normal mammary epithelial cells, consist mainly of core 2 based structures carrying polyactosamine c hains, However, the mucin ex-pressed by breast carcinomas has shorter side- chains, often consisting of sialylated core 1 (Gal beta 1-3GalNAc). irt sit u hybridization of primary breast tissue showed that a sialyltransferase (S T3Gal I), responsible for adding sialic acid to core 1 thereby terminating chain extension, is elevated in primary breast carcinomas when compared to normal or benign tissue. Furthermore, the level of mRNA expression encoding ST3Gal I is correlated to the intensity of staining seen with the antibody SM3, which specifically recognises underglycosylated, tumour associated MU C1, Thus, the aberrant glycosylation of MUC1 seen in bl east carcinomas app ears to be due, at least in part, to the elevation of ST3Gal I.