BCL2 and leukemia: In addition to the involvement of BCL-2, XIAP, and MCL-1 (13), p53 mutant leukemia remains a challenge to treat because p53 positively regulates apoptosis by upregulating PUMA and NOXA, the pro-apoptotic BH3 (BCL-2 homology 3)-only members of the BCL-2 family (14), and these pathways may also play a role in disease progression.