We have precisely analyzed the structures of
glycosphingolipids of human
cancer cells and normal epithelial cells using several methods, including enzymatic release of
carbohydrate moieties, fluorescent labeling, and identification using 2D mapping, enzymatic digestion, and mass spectrometry. These analyses enabled the identification of novel
tumor-associated carbohydrate antigens that can be used to elucidate the involvement of
carbohydrates in
cancer malignancy and could act as candidate
tumor markers. In our previous study, we identified a novel
glycosphingolipid that accumulates in
colon cancer cells, NeuAcα2-6(Fucα1-2)Galβ1-4GlcNAcβ1-3Galβ1-4Glc (α2-6 sialylated type 2H, ST2H). Here, structural analyses of
cancer cells and normal epithelial cells from 60 colorectal and five
pancreatic cancer patients, including four and two Lewis-negative individuals, respectively, reveal the presence of an additional novel
glycosphingolipid, NeuAcα2-6(Fucα1-2)Galβ1-3GlcNAcβ1-3Galβ1-4Glc (α2-6 sialylated type 1H, ST1H). ST2H was found in colorectal and
pancreatic cancer cells from about half of the cases. Unlike ST2H, ST1H was found in
cancer cells from three out of six Lewis-negative patients (i.e., two cases of colorectal and one case of
pancreatic cancer). However, the moiety was not found in normal epithelial cells or
cancer cells from 59 Lewis-positive patients. These findings suggest that the accumulation of this
carbohydrate antigen occurs predominantly in
cancer cells of Lewis-negative patients. When the ST1H
epitope is also carried on
mucins as well as
glycosphingolipids, this
epitope is a promising
tumor marker candidate, especially for Lewis-negative individuals.