Enhanced sialylation represents one of the most frequently occurring alterations of the
sugar chain structure in various
cancers. However, up to now, sialylation of intracellular
proteins of
thyroid carcinomas has never been investigated. The aim of this study was comparative analysis of cytoplasmic and nuclear
sialoglycoproteins isolated from thyroid benign and malignant
tumors as well as non-neoplastic lesions. The sialylation level and types of
sialic acid linkages were analysed by
lectin blotting and
enzyme linked lectino-solid-phase assay (ELLSA) using Sambucus nigra (SNA) and Maakia amurensis (MAA)
agglutinins. The presence of alpha2,6 and alpha2,3 linked
sialic acid residues was detected in all types of thyroid lesion specimens but there were some differences in the banding and intensity patterns. Analysis of SNA and MAA binding by ELLSA method showed that in the majority of
cancer samples the level of
sialic acid residues was lower than in non-neoplastic lesions and
adenomas. Our present results suggest that decrease in sialylation rather than increase is a characteristic feature of malignant transformation in the thyroid.