Differential expression of N-linked oligosaccharides in methotrexate-resistant primary central nervous system lymphoma cells

Abstract

Background: Oligosaccharides of glycoprotein, particularly negatively-charged sialylated N-glycans, on the surface of lymphomas play important roles in cell-cell interactions and bind immunoglobulin-like lectins, causing inflammatory responses and bioregulation. However, their characterizations have largely been unknown in central nervous system (CNS) lymphoma. Methods: Here, we investigated expression patterns of N-linked oligosaccharides of glycoproteins in cells derived from CNS lymphomas and clinical specimens. Results: We first generated methotrexate (MTX)-resistant cells derived from HKBML and TK as CNS lymphoma, and RAJI as non-CNS lymphoma and determined N-linked oligosaccharide structures in these cells and other non-CNS lymphoma-derived cells including A4/FUK, OYB, and HBL1. Major components of the total oligosaccharides were high-mannose type N-glycans, whose level increased in MTX-resistant HKBML and TK but decreased in MTX-resistant RAJI. We also detected sialylated biantennary galactosylated N-glycans with α1,6-fucosylation, A2G2F, and A2G2FB from HKBML, TK, and RAJI. Sialylated A4G4F was specifically isolated from RAJI. However, the ratios of these sialylated N-glycans slightly decreased against MTX-resistant compared to non-resistant cells. Interestingly, almost all complex-type oligosaccharides were α2,6-sialylated. Discussion: This is the first study for the expression profile of N-oligosaccharides on MTX-resistant primary CNS lymphoma-derived cells HKBML and TK, and tumor tissues resected from patients with CNS lymphoma, Conclusion: These results propose a possibility that the differential expression of high-mannose types and sialylated A2G2F, A2G2FB, and A4G4F on the surface of CNS lymphomas may provide a hint for targets for diagnoses and treatments of the oligosaccharide type-specific lymphomas.