EXPRESSION OF ALPHA-2,6-SIALYLATED SUGAR CHAINS IN NORMAL AND NEOPLASTIC COLON TISSUES - DETECTION BY DIGOXIGENIN-CONJUGATED SAMBUCUS-NIGRAAGGLUTININ

It has previously been reported that about 90% of human colon carcinom as express increased levels of the sialyltransferase which adds sialic acid in alpha2,6 linkage to galactose residues on N-linked chains of glycoproteins. To ascertain whether colon cancer tissues actually expr ess increased amounts of alpha2,6-sialylated sugar chains on their gly coconjugates, we screened tissue sections of normal colon, benign and malignant colon tumors with digoxigenin-conjugated Sambucus nigra aggl utinin (SNA), a NeuAcalpha2,6Gal/GalNAc-specific lectin. At the concen tration of lectin used, epithelial cells of all the 13 normal colon sp ecimens examined were unreactive; 3 out of 8 benign lesions showed a w eak reactivity being the remainder unreactive, while 23 out of 26 carc inomas were positive at a variable degree. Qualitative differences wer e evident among different carcinoma specimens. In some cases a large n umber of intensely stained intracytoplasmatic particles was present, t hus suggesting that reactivity may be associated with secretions, very likely of mucus droplets. In other specimens there was a more uniform distribution of the staining which suggest that reactivity is associa ted with cell membrane glycoconjugates. These data indicate that the e xpression of a2,6-sialylated sugar chains is remarkably increased in t he majority of colon cancer specimens examined.