Cell surface N-acetylneuraminic acid α2,3-galactoside-dependent intercellular adhesion of human colon cancer cells

Sialoglycans on the cell surface of human colon cancer (HCC) cells have been 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 surface of HCC cells, we studied the intercellular adhesion of HCC cell lines expressing increasing NeuAc alpha 2,3Gal-R. Our model system consisted of the HCC SW48 cell. line, which inherently possesses low levels of cell surface 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 the expression vector, pcDNA3, containing either rat liver cDNA encoding Gal beta 1,3(4)GlcNAc alpha 2,3 sialyltransferase (ST3Gal III) or human placental cDNA encoding Gal beta 1,3GalNAc/Gal beta 1,4GlcNAc alpha 2,3 sialyltransferase (ST3Gal TV) into SW48 cells. Selection of neomycin-resistant clones (600 mu g G418/ml) having a higher percentage of cells expressing NeuAc alpha 2,3Gal-R (up to 85% positive Maackia amurenis agglutinin staining compared with 30% for wild type cells) was performed. These ST3Gal III and ST3Gal TV clonal variants demonstrated increased adherence to IL-lp-activated human umbilical vein endothelial cells (HUVEC) (up to 90% adherent cells compared with 63% for wild type cells). Interestingly, ST3Gal III and ST3Gal IV clonal variants also bound non-activated HUVEC up to C-fold more effectively than wild type cells. Cell surface NeuAc alpha 2,3Gal-R expression within the various SW48 clonal variants correlated directly with increased adhesion 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 GalNAc Lewis X structures were found to specifically inhibit intercellular adhesion. At 1.0 mM, NeuAc alpha 2,3Gal beta 1,3 (Fuc alpha 1,4)-GlcNAc-OH and Gal 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-methyl 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, these studies demonstrated that cell surface NeuAc alpha 2,3Gal-R expression is involved in HCC cellular adhesion to HUVEC. These specific carbohydrate-mediated intercellular adhesive events may play an important role in tumor angiogenesis, metastasis and growth control. (C) 1999 Academic Press.