Tumor-associated blood group antigen expressions and immunoglobulins associated with tumors

As outlined in Figures 1 and 2, the biosynthetic pathways for the expression of the A, B and H, and the Lewis determinant carbohydrate sequence structures, as well as sialylated structures, involves both type 1 and type 2 precursor chains (which may be present as glycolipids and N- or O-linked glycoproteins), and many glycosyltransferases. For tumor cells, there appears to be increased expressions of fucosyl- and sialyltransferases yielding such structures as the Le(x), sialyl-Le(a), and many other similar determinants, which are not found on the normal cell progenitor of the tumor. The types of structures expressed on tumor cells is dependent on the particular fucosyl-, sialyl- and other glycosyltransferase genes activated in the transformation and tumor progression events, the availability of the substrates for the glycosyltransferases (both the precursor sequences and the nucleotide-sugar substrates) which is partly dependent on metabolites available to the tumor mass, and on the genotype of the individual regarding particular glycosyltransferases. Both the loss of A, B and/or H blood group antigen expressions of tumor cells and the relative expressions of the Lewis and sialylated-oligosaccharide determinants may be a consequence of the competing biosynthetic pathways and the glycosyltransferases for common substrate sequences, as well as due to the loss of particular glycosyltransferases concomitant with transformation. All of these factors probably account for the variable expressions of the complex of carbohydrate sequence determinants when comparing tumor sections of different individuals as well as the heterogeneity of expression of particular determinants within a single tumor tissue section. As described above, the A, B and/or H determinants, and the precursor sequences, are also expressed to differing extents on epithelial cells depending on the tissue type and cellular location in the tissue. Thus, the differentiation state of the particular epithelial cell also determines the quantity and types of carbohydrate sequences expressed. However, because of the complex nature of the competing biosynthetic pathways for the carbohydrate sequences of glycolipids and glycoproteins, and the relative activations of fucosyl- and sialyltransferases of tumor cells, it would seem that simple deductions as to the state of differentiation of particular tumors with A, B, H and precursor sequence expressions is not warranted.(ABSTRACT TRUNCATED AT 400 WORDS)