Over-expression of beta-1,4-galactosyltransferase I, II, and V in human astrocytoma

Purpose: beta -1.4-Galactosyltransferase (beta -1,4-GaIT) I. II. and V are the enzymes responsible for the biosynthesis of N-acetyllactosamine on N-gl ycans by transferring UDP-galactose to the terminal N-acetylglucosamine (N- GlcNAc) residues with the formation of a beta -1.4-linkage. Neoplasms under go various changes in the carbohydrate of their glycoconjugates, indicating the possible changes in glycosyltransferases themselves. Method: Therefore . we compared the expression of beta -1,4-GalTs between astrocytoma and nor mal brain tissues. Results: Our reverse-transcription polymerase chain reac tion (RT-PCR) results showed that beta -1,4-GaIT I transcript was absent in normal adult brain but detectable in grade II, III, and IV astrocytomas; t he level of beta -1,4-GAIT II transcript was increased in grade II. III, an d IV astrocytomas while only a trace amount was found in normal brain; beta -1,4-GalT V transcript existed in normal brain and increased in the proces s of astrocytoma progress, with the highest level in grade IV astrocytoma. By Ricinus communis agglutinin-1 (RCA-1) lectin blot assay, we also found t he more extensive galactosylated bands in astrocytomas compared with normal brain. A major 61kD protein was galactosylated in astrocytoma but not in n ormal brain tissues. Conclusion: These results indicate that the increase o f galactosylation in astrocytomas may be caused by the alterations of gene expression of beta -1,4-GaIT I. II, and V and that the malignant degree of astrocytoma is correlated with the expression of beta -1,4-GalT V.