Disulfiram/Copper induces Bak-mediated caspase-independent apoptosis in MCF-7 cells

Abstract

Abstract Disulfiram (DSF) and copper (Cu2+) in combination exhibit powerful anti-cancer effects on a variety of cancer cell lines.Here, we report the capacity of DSF/Cu2+ to induce both reactive oxygen species (ROS)-dependent and caspase-independent apoptosis in MCF-7 cells. DSF/Cu2+ facilitated the accumulation of intracellular reactive oxygen species (ROS), and induced ROS-dependent apoptosis accompanied by chromatin condensation and phosphatidylserine externalization. Most importantly, DSF/Cu2+ caused caspase-independent apoptosis by promoting the translocation of AIF from the mitochondria to the nucleus. Besides, the cytotoxicity of DSF/Cu2+ was inhibited in AIF knockout cells, suggesting the indispensability of AIF. The pro-apoptotic protein Bak instead of Bax was upregulated and activated upon DSF/Cu2+ treatment, and Bak knockout cells exhibited high resistance to DSF/Cu2+, indicating the importance of Bak in DSF/Cu2+-induced apoptosis. Additionally, both co-immunoprecipitation and live-cell quantitative fluorescence resonance energy transfer (FRET) analysis revealed that DSF/Cu2+ unlocked the binding of Mcl-1 to Bak, and subsequent Bak homo-oligomerization. Overall, our data demonstrate for the first time that DSF/Cu2+ triggers Bak oligomerization and AIF nucleus translocation to mediate caspase-independent apoptosis in MCF-7 cells.