To achieve our goal, cell death (apoptosis or necrosis), cell cycle, mitochondrial transmembrane potential, ROS formation, caspase activities, apoptotic regulating proteins (Bcl-2 and Bcl-XL), invasion and expression of its regulators, matrix metalloproteinase-2 (MMP-2), and MMP-9 were examined in MDA-MB-231 breast cancer cells. This evidence concerns the gene BCL2L1 and breast cancer.