Identification of carbohydrates and functional groups involved in the adhesion of neoplastic cells

Modifications of glycosphingolipid profile and synthesis in normal rat fibroblasts and in syngeneic neoplastic cells at different subculture stages

Glycosphingolipids are plasma membrane macromolecules involved in diversified recognition functions on the cell surface resulting in modulation of cell adhesion and differentiation. As the in vitro cellular system of the neoplastic cell line SGS/4A and syngeneic normal fibroblasts (FG) represents a useful tool for studies on molecular mechanisms regulating cell adhesion, neoplastic transformation and cellular ageing, we studied the changes of glycosphingolipid and of the enzymes involved in their metabolism in both cultured cells at different subculture stages. The FG subculture progression induces a drastic decrease of total glycosphingolipid content with consistent alterations in the molecular composition. In particular, a significant decrease of GM(3), a slight increase of GD(1a), the disappearance of 'b'-series gangliosides and the drastic reduction of triosylceramides were observed. On the contrary, the increasing number of SGS/4A subcultures, characterized by a specific and different glycosphingolipid composition as compared with FG cells, does not cause modifications. Although glycosyltransferase activity levels quite well parallel the glycosphingolipid patterns and can account for the noted variations, the mRNA expression analysis of two glycosyltransferases suggests that the in vitro cell ageing of normal rat fibroblasts causes drastic changes in the glycosphingolipid profile through the regulation, at either the transcriptional or post-translational level, of some biosynthetic enzymes.

Modifications of adhesion properties and proteoglycan structure in rat embryo fibroblast cultures with increasing passages

Adhesion properties of rat embryo fibroblast cultures and proteoglycans (PGs) produced both in the growth medium and in the cell layer were investigated with increasing passages. Both cell-cell and cell-substrate adhesion increased with increasing subculture number. Cell adhesion properties were improved by cell treatment with chondroitinase ABC. The increase in subculture number was coupled with a constant increase of PG molecular size, which was particularly evident in cell layer extracts. The ratio HS-PGs/DS-PGs increased with increasing passages. PG modifications are likely to represent evidence of changes in extracellular matrix organization and could play a role in the increase of cell adhesion properties.

Recognition sites involved in the adhesive processes of neoplastic and normal homogeneic cells

Cross-adhesion experiments between neoplastic and normal homogeneic cells show that trypsin-sensitive recognition sites are involved in cell-cell adhesion of neoplastic cells and that the affinity between heterologous recognition sites is higher then between homologous ones.

Determination of adhesive rate constant in normal and neoplastic homogeneic cells

The adhesive rate constant (ARC) of neoplastic SGS-2 cells which have a low contact inhibition, is remarkably higher than that of normal homogeneic fibroblasts. This is in contrast with the mutual adhesion theory which states that the loss of contact inhibition is strictly related to the loss of cell recognition and consequently to the loss of cell adhesion capacity.