CASP9 and esophageal cancer: As the mitochondrial pathway and the death receptor pathway are reported to mediate caspases activation, and caspase-9 and caspase-8 belonged to the two pathways respectively21,22, we predicted SFE induced mitochondrial apoptosis in esophageal cancer cells and then measured the mitochondrial membrane potential, the decrease of which was a characteristic performance in mitochondrial apoptosis.