Glycobiology Advance Access originally published online on September 26, 2003
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Glycobiology vol 14 no 1 pp. 39-49, 2004
© Oxford University Press 2004; all rights reserved.
Expression of ß-galactoside
2,6 sialyltransferase and of
2,6-sialylated glycoconjugates in normal human liver, hepatocarcinoma, and cirrhosis
2 Department of Experimental Pathology, F. Addarii Institute of Oncology, University of Bologna, Via S. Giacomo 14, 40126 Bologna, Italy; and 3 Pathology Unit, F. Addarii Institute of Oncology, University of Bologna, Bologna, Italy
Received on July 22, 2003; revised on September 2, 2003; accepted on September 2, 2003
ß-Galactoside
2,6-sialyltransferase (ST6Gal.I) mediates the addition of
2,6-linked sialic acid to glycoproteins. ST6Gal.I is strongly expressed by the liver and is up-regulated in several cancers, but little is known of its regulation in human liver diseases. We have investigated the expression of ST6Gal.I and its product, the
2,6-sialylated lactosamine, in normal human liver, hepatocarcinoma (HCC), and cirrhosis. We found that both ST6Gal.I activity and mRNA can undergo up- or down-regulation in different HCC patients. At the mRNA level, the groups of specimens showing the highest expression were HCC of grade 2, HCC developed without preexisting cirrhosis, and HCC of male patients. The lectin from Sambucus nigra (SNA) reveals a significative overexpression of
2,6-sialylated glycoconjugates in HCC tissue homogenates and their intracellular accumulation in HCC histological sections, even though in a few cases the extent of
2,6-sialylation dramatically decreases. Transcription of the gene occurs through at least two different promoters, resulting in two differentially expressed mRNA species. RNA in situ hybridization reveals that the ST6Gal.I mRNA can be expressed at a quantitatively heterogeneous level among the neoplastic cells. Neither ST6Gal.I expression nor
2,6-sialylation are altered in cirrhosis. These data indicate that neoplastic transformation but not cirrhosis can alter the process of
2,6-sialylation of liver glycoproteins.
1 To whom correspondence should be addressed; e-mail: dallolio{at}alma.unibo.it
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