First, to examine differential expression of oligosaccharides of glycoproteins on the surface of the cells, we generated MTX-resistant lymphoma cells (Fig. 1), including HKBML and TK as PCNSL, and RAJI as non-CNS lymphoma, in addition to HBL, OYB, and A4/FUK as other non-CNS lymphoma references (Additional file 1: Table S1, and Additional file 2: Figure S1A). Here, TKT is linked to primary central nervous system lymphoma.