Evidence indicates that the presence of aberrant α1→2fucosylation pathways is responsible for the accumulation of large quantities of Leb and Y antigens in human colorectal carcinoma. Significantly higher activities of α1→2 as well as α1→3 and α1→4fucosyltransferases were found in most of the tissues from carcinoma than in the adjacent normal tissues and in healthy subjects. α1→2Fucosyl‐transferases associated with the synthesis of Leb (Fucal→2Galβ1→3[Fucc1→4]GlcNAcβ) and Y (Fucα1→2Ga1β→4[Fucα1→3]GlcNAcβ) structures from Le→ (GaIβ1→3[Fucal→4]GlcNAcβ) and X (Galβ1→4[Fucα 1→3]GlcNAcβ) ones, respectively, were demonstrated in colorectal carcinomas and in colorectal carcinoma cell lines (COLO201, LS174T and SW1116). The activation of α1→2fucosyltransferase with such new substrate specificities in colorectal carcinoma might result in the preferential synthesis of Leb and Y structures from Le→ and X rather than from H type 1 and H type 2 structures.

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