Previously, deoxycytidine kinase (dCK), a salvage pathway enzyme of nucleotide biosynthesis, was reported as an alternative molecular target for MTX by affinity purification using styrene glycinemethacrylate (SG) beads from cytoplasmic extracts of the human acute monocytic leukemia cell line THP-1 [3]. The gene discussed is DCK; the disease is acute monocytic leukemia.