Alpha-2,6-sialylation of L-PHA reactive oligosaccharides and expression of N-acetylglucosaminyltransferase V in human diffuse large B cell lymphoma.

Cell surface sialylation and beta1-6 branching of L-PHA reactive oligosaccharides play an important role in metastatic capacities of various tumor cell lines. We analyzed the expression and sialylation of L-PHA reactive oligosaccharides in human diffuse large B cell lymphoma (DLBCL). DLBCL was grouped into three types; i). Group A, non-reactive type with no expression of L-PHA reactive oligosaccharides, ii). Group B, sialylated type with expression of sialylated L-PHA reactive oligosaccharides and iii). Group C, non-sialylated type with expression of non-sialylated L-PHA reactive oligosaccharides. To clarify the linkage of sialic acid residues in L-PHA reactive oligosaccharides of Group B cases, L-PHA lectin histochemistry after treatment with two different neuraminidases was performed. In all Group B cases, L-PHA binding reactivity was found after treatment with Vibrio cholerae neuraminidase. But not after treatment with Newcastle disease virus neuraminidase. These data indicate that alpha2,6-linked sialic acid residues were predominantly involved in sialylation of L-PHA reactive oligosaccharides of Group B. To clarify the relationship between expression of N-acetylglucosaminyltransferase V (GnT-V), which catalyzes beta1-6 branching of L-PHA reactive oligosaccharides, and L-PHA reactivities in DLBCL, we investigated the expression of GnT-V using immunohistochemical methods. Most of the Group B and C cases expressed GnT-V while 33% of Group A cases showed no expression of GnT-V. These data suggest that expression of GnT-V is not always correlated with the expression of L-PHA reactive glycoconjugates. Furthermore, survival of patients in Group A which showed no expression of GnT-V was significantly shorter than that of patients in Group C which expressed GnT-V. Therefore, loss of non-sialylated L-PHA reactive oligosaccharides due to lack of expression of GnT-V in lymphoma cells may be associated with aggressiveness of DLBCL.