Proteasome subunit beta 2 (PSMB2), one of the two proteins of the PSM which we found, was predominant in ALL with t(12;21) (p < 0.01) while PSM beta 6 (or P42 i.e., PSMB6) predominated in the other group of pre-B2 ALL (p < 0.01). Here, PSMB6 is linked to acute lymphoblastic leukemia.