Cloning, expression, and characterization of a novel UDP-galactose:β- N-acetylglucosamine β1,3-galactosyltransferase (β3Gal-T5) responsible for synthesis of type 1 chain in colorectal and pancreatic epithelia and tumor cells derived therefrom

Abstract

The sialyl Lewis a antigen is a well known tumor marker, CA19-9, which is frequently elevated in the serum in gastrointestinal and pancreatic cancers. UDP-galactose:N-acetylglucosamine β1,3-galactosyltransferase(s) (β3Gal-Ts) are required for the synthesis of the sialyl Lewis a epitope. In the present study, a novel β3Gal-T, named β3Gal-T5, was isolated from a Colo205 eDNA library using a degenerate primer strategy based on the amino acid sequences of the four human β3Gal-T genes cloned to date. Transfection experiments demonstrated that HCT-15 cells transfected with the β3Gal-T5 gene expressed all the type 1 Lewis antigens. In gastrointestinal and pancreatic cancer cell lines, the amounts of β3Gal-T5 transcripts were quite well correlated with the amounts of the sialyl Lewis a antigens. The β1,3Gal-T activity toward agalacto-lacto-N-neotetraose was also well correlated with the amounts of β3Gal-T5 transcripts in a series of cultured cancer cells, and in Namalwa and HCT-15 cells transfected with the β3Gal-T5 gene. Thus, the β3Gal-T5 gene is the most probable candidate responsible for the synthesis of the type 1 Lewis antigens in gastrointestinal and pancreatic epithelia and tumor cells derived therefrom. In addition, β3Gal-T5 is a key enzyme that determines the amounts of the type 1 Lewis antigens including the sialyl Lewis a antigen.