Quercetin-exposed MCF-7 breast cancer cells showed apoptotic cell death with a reduction in mitochondrial membrane potential, down-regulation of Bcl-2 protein, and activation of the initiator caspases, caspase-8 and caspase-9, and the effector caspase, caspase-6, which were attributed to the binding of quercetin to the Fas/CD95 receptor [273]. Here, CASP9 is linked to breast cancer.