Cell surface N-acetylneuraminic acid alpha 2,3-galactoside-dependent intercellular adhesion of human colon cancer cells

Sialoglycans on the cell surface of human colon cancer (HCC) cells have bee n implicated in cellular adhesion and metastasis. To clarify the role of N- acetyl-neuraminic acid (NeuAc) linked alpha 2,3 to galactose (Gal) on the s urface of HCC cells, we studied the intercellular adhesion of HCC cell line s expressing increasing NeuAc alpha 2,3Gal-R. Our model system consisted of the HCC SW48 cell. line, which inherently possesses low levels of cell sur face alpha 2,3 and alpha 2,6 sialoglycans. To generate SW48 clonal variants with elevated cell surface NeuAc alpha 2,3Gal-R linkages, we transfected t he expression vector, pcDNA3, containing either rat liver cDNA encoding Gal beta 1,3(4)GlcNAc alpha 2,3 sialyltransferase (ST3Gal III) or human placen tal cDNA encoding Gal beta 1,3GalNAc/Gal beta 1,4GlcNAc alpha 2,3 sialyltra nsferase (ST3Gal TV) into SW48 cells. Selection of neomycin-resistant clone s (600 mu g G418/ml) having a higher percentage of cells expressing NeuAc a lpha 2,3Gal-R (up to 85% positive Maackia amurenis agglutinin staining comp ared with 30% for wild type cells) was performed. These ST3Gal III and ST3G al TV clonal variants demonstrated increased adherence to IL-lp-activated h uman umbilical vein endothelial cells (HUVEC) (up to 90% adherent cells com pared with 63% for wild type cells). Interestingly, ST3Gal III and ST3Gal I V clonal variants also bound non-activated HUVEC up to C-fold more effectiv ely than wild type cells. Cell surface NeuAc alpha 2,3Gal-R expression with in the various SW48 clonal variants correlated directly with increased adhe sion to HUVEC (r=0.84). Using HCC HT-29 cells, which express high levels of surface NeuAc alpha 2,3Gal-R, addition of synthetic sialyl, sulfo or GalNA c Lewis X structures were found to specifically inhibit intercellular adhes ion. At 1.0 mM, NeuAc alpha 2,3Gal beta 1,3 (Fuc alpha 1,4)-GlcNAc-OH and G al beta 1,4(Fuc alpha 1,3)GlcNAc beta 1,6(SE-6Gal beta 1,3)GalNAc alpha 1-O -methyl inhibited HT-29 cell adhesion to IL-1 beta-stimulated HUVEC by 100% and 68%, respectively. GalNAc beta 1,4(Fuc alpha 1,3)GlcNAc beta 1-O-methy l and GalNAc beta 1,4(Fuc alpha 1,3)GlcNAc beta 1,6Man alpha 1,6Man beta 1- O-C30H61, however, did not possess inhibitory activity. In conclusion, thes e studies demonstrated that cell surface NeuAc alpha 2,3Gal-R expression is involved in HCC cellular adhesion to HUVEC. These specific carbohydrate-me diated intercellular adhesive events may play an important role in tumor an giogenesis, metastasis and growth control. (C) 1999 Academic Press.