Suppression of a sialyltransferase by antisense DNA reduces invasiveness of human colon cancer cells in vitro

Transfer of terminal alpha2,6-linked sialic acids to N-glycans is catalyzed by beta -galactoside alpha2,6-sialyltransferase (ST6Gal I). Expression of STGGal I and its products is reportedly increased in colon cancers. To inve stigate directly the functional effects of ST6Gal I expression, human colon cancer (HT29) cells were transfected with specific antisense DNA. ST6Gal I mRNA and protein were virtually undetectable in six strains of transfected HT29 cells. STGGal activity was reduced to 14% of control (P<0.005) in tra nsfected cells. Expression of terminal <alpha>2,6- and alpha2,3-linked sial ic acids, and unmasked N-acetyllactosamine oligosaccharides, respectively, was assessed using flow cytometry and fluoresceinated Sambucus nigra, Maack ia amurensis and Erythrina cristagalli lectins. Results indicated a major r eduction in expression of alpha2,6-linked sialic acids and counterbalancing increase in unmasked N-acetyllactosamines in antisense DNA-transfected cel ls, without altered expression of alpha2,3-linked sialic acids or gangliosi de profiles. The ability of transfected cells to form colonies in soft agar and to invade extracellular matrix material (Matrigel), respectively, in v itro was reduced by approx. 98% (P < 0.0001) and more than 3-fold (P < 0.00 5) compared to parental HT29 cells. These results indicate that N-glycans b earing terminal alpha2,6-linked sialic acids may enhance the invasive poten tial of colon cancer cells. (C) 2001 Elsevier Science B.V. All rights reser ved.