...The aim of this study was to explore the ability of BH3 mimetics in clearing senescent A549 cells and elucidate their underlying killing mechanism. Doxorubicin-induced cell senescence was determined using augmented senescence-associated beta-galactosidase (SA-β-Gal) staining and increased P16 expression. CCK-8 and crystal violet staining demonstrated that A-1331852, BH3 mimetic, could kill senescent tumor cells without affecting the proliferating cells. A-1331852 induced caspase-dependent senescent cell death accompanied by nuclear concentration, decreased mitochondrial membrane potential, and cleavage of poly (ADP-ribose) polymerase. Most importantly, A-1331852 upregulated the expression of BID and BAX indicating their role in mediating A-1331852-induced apoptosis in senescent A549 cells. The results of fluorescence resonance energy transfer showed that A-1331852 loosened or even released the binding between BCL-xL and tBID, releasing tBID. In addition, A-1331852 also dissociated the binding between BCL-xL and BAX, eventually leading to BAX oligomerization in the mitochondria, and resulting in apoptosis via the mitochondrial pathway. In conclusion, our data demonstrate for the first time that A-1331852 promotes apoptosis of senescent A549 cells by influencing the interaction between BCL-xL and tBID and that between BCL-xL and BAX.