The control of sialyltransferase activity in tumor‐cell lines derived from different tissues is multifactorial

Abstract

The activities of the sialyltransferase enzymes and the resulting expression of sialoglycoproteins were examined in tumor cells derived from different tissues in order to gain a greater understanding of the factors controlling the cell glycosylation state. Cell-cell contact, which is dependent on cell confluency state, was shown to influence glycosylation in the neurallyderived mouse neuro-2A neuroblastoma and the C6 glioma cell lines. Both showed a relatively high level of cell sialyltransferase activity under sub-confluent conditions with activity decreasing upon the formation of cell-cell contacts associated with confluency. A parallel decrease in the expression of sialoglycoproteins, as determined by lectin blot analysis, was also observed under these conditions. In contrast, the H411e hepatoma cell line showed an increase in enzyme activity with confluency with the susceptibility of the enzyme in this cell line to glucocorticoid induction only being detected in sub-confluent cell cultures. The number of trypsinisation cycles of the cells was also shown to affect the enzyme activity of the neuro-2A and C6 cells with an increase in enzyme activity coincident with passage number being observed in the neuro-2A cells, and a decrease in the C6 glioma cell line. Trypsinisation had no effect on enzyme activity in the H411e cells. These results demonstrate that the control of sialyitransferase activity in tumor cells is multifactorial with the tissue of origin playing a key role.Key words: Sialyltransferase; Glycoprotein; Neuroblastoma; Hepatoma; Glioma; Sialic acid each transfer being catalysed by an individual sialyl-T isozyme [4]. Sialic acid can in addition be transferred to sialic acid residues in c~2,8 linkages to form polysialic acid chains (PSA) of up to 50 residues in length, which are expressed in a developmentally regulated manner on the neural cell adhesion molecule, NCAM [5]. The expression of protein-bound sialic acid is altered in certain tumor cell lines where it acts to influence cell adhesivity and consequently the invasive or metastatic potential of the cell [6]. Tumor cells with significant metastatic potential tend to have a high sialyl-T activity [7], and treatment of adenocarcinoma cells with an enzyme inhibitor was demonstrated to decrease metastasis [8].While the role of cellular transcription factors and oncogenes [9], and also external agents such as glucocorticoids and cytokines [10][11][12] in the control of sialyl-T activity have been well characterised, the role of cell-cell interaction in this process has not been addressed. As cell adhesion molecule (CAM) mediated cell-cell contact can activate a cellular signalling mechanism [13] and has previously been demonstrated to influence the expression of cell surface adhesion ligands [14], it was of interest to examine the effect of cell-cell contact on both basal sialyl-T expression in cell lines derived from different tissues and also to observe the enzyme susceptibility to regulation by external factors such as corticosteroids u...

Differential carbohydrate binding and cell surface glycosylation of human cancer cell lines

“…What is clearly evident from the comparison of glycosylation signatures generated in our study and that previously reported [Tao et al, 2008] is that the glycosylation status of commonly used cell lines cultured in different laboratories varies significantly. Many factors may influence the glycans displayed on cell surfaces, including sugar concentration in the growth media [Hossler et al, 2009], passage number [Coughlan and Breen, 1995], cell density [Senechal et al, 1983; Coughlan and Breen, 1995] and the serum used [Hossler et al, 2009]. Given that changes in cell surface glycosylation may significantly impact on the validity of data generated from cell‐based assays using common laboratory cell lines, we suggest that regular evaluation of glycosylation signatures be undertaken, either using lectin array technology or flow cytometry.…”

Stabilization of lysosomal membrane and cell membrane glycoprotein profile bySemecarpus anacardium Linn. nut milk extract in experimental hepatocellular carcinoma

“…The precipitate was hydrolysed with 3N HCl for 4 h at 100°C. Similarly, a known amount of delipidized residues of tissues prepared according to the method of Folsch et al (1951) were hydrolysed with 3 N HCl as above. The hydrolysed materials were neutralized and aliquots were used for the estimation of hexose (Niebus, 1972), hexosamine (Wagner, 1979) and sialic acid (Warren, 1959).…”

“…Increased activity of sialyl transferase leads to increased expression of sialic acid in hepatoma (Coughlan and Breen, 1995) which may be one of the requisites of neoplastic cells helping malignancy. O'Kennedy et al (1991) suggested that the shedding of sialic acid from the surface of tumour cells may be involved in the blockage of the immune system.…”