The resultant cells including MTX-resistant TK, MTX-resistant HKBML, and MTX-resistant RAJI obtained resistances against MTX with 5.43-fold (inhibitory concentration 50 (IC50) = 1.88 × 10− 7 M), 9.36-fold (IC50 = 6.24 × 10− 9 M), and 37.72-fold (IC50 = 4.56 × 10− 7 M), respectively (Fig. 1a–c), indicating that acquired resistances to MTX in PCNSL-derived TK and HKBML cells are weak than that in non-CNS lymphoma-derived RAJI cells. Here, TKT is linked to primary central nervous system lymphoma.