ALPHA-2,6 SIALYLATION OF N-ACETYLLACTOSAMINIC SEQUENCES IN HUMAN COLORECTAL-CANCER CELL-LINES - RELATIONSHIP WITH NONADHERENT GROWTH

In a previous work we found that human colorectal cancer tissues express increased levels of an alpha-2,6 sialyltransferase (alpha-2,6 ST) acting on N-acetyllactosaminic sequences (E.C. 2.4.99.1). In this study we have taken advantage of the known specificity of elderberry bark lectin (Sambucus nigra agglutinin, SNA) for NeuAc-alpha2, 6Gal/GalNAc structures to investigate the relationship between expression of alpha-2,6-sialyltransferase activity and occurrence of alpha-2,6-sialylated oligosaccharide sequences in human colorectal cancer cell lines. Three cell lines with opposite adhesion properties were used in this study: SW 948 cells grow adherent to the culture flask surface and express very low levels of enzyme activity; COLO 205 cell grow in non-adherent form and express the highest levels of alpha-2,6 ST activity; A non-adherent subline of SW 948 cells (SW 948 FL) was isolated and found to express high levels of alpha-2,6 ST activity. By using SNA-Sepharose chromatography we found that expression of alpha-2,6 ST activity correlates with the extent of alpha-2,6-sialylation of N-linked chains of glycoproteins but not with the presence of alpha-2,6-sialylated glycolipids.