The aim of the present work was to study proliferation, viability, apoptosis, caspase-3, -8, and −9 activity, cytochrome c release, mitochondrial membrane potential (ΔΨm), senescence, p65 phosphorylation (NF-кB subunit), the Bcl-2 and Bcl-XL antiapoptotic proteins, and related genes induced by DOX and/or by the MG132 proteasome inhibitor in U937 leukemia cells. Here, BCL2 is linked to leukemia.