Previous studies revealed that a mutation of the PSMB5 gene at nucleotide position 322 (G322A), which corresponds to the substitution of Ala49 to Thr (Ala49Thr), induced conformational changes in the bortezomib-binding pocket of ß5 subunit and was responsible for acquired bortezomib resistance in T-cell acute lymphoblastic leukemia and myeloid leukemia cells [14]–[16]. Here, PSMB5 is linked to T-cell acute lymphoblastic leukemia.