Furthermore there were no thiopurine S-methyltrasferase gene (TPMT) [9], phosphoribosyl pyrophosphate synthetase 1 gene (PRPS1) [10] and cytosolic 5’-nucleotidase II gene (NT5C2) [11] mutations in Reh-6MPR and Reh-6TGR cells (Supplementary Tables 1 and 2), which previously shown to be associated with thiopurine resistance in ALL. The gene discussed is PRPS1; the disease is acute lymphoblastic leukemia.