Cell Apoptosis Induced by δ-Elemene in Colorectal Adenocarcinoma Cells via a Mitochondrial-mediated Pathway

The chemical compound delta-elemene, isolated from the Chinese herbal medicine plant Curcuma Wenyujin, has been known to exert antitumor activity. In this study we demonstrated that apoptotic cell death induced by delta elemene in DLD-1 cells was concentration-and time-dependent, and had little inhibition of the normal human liver cell line WRL-68. Apoptosis was further confirmed and quantified by DNA fragmentation ELISA, Annexin V (AnV) binding of externalized phosphatidylserine and the mitochondrial probe JC-1 using flow cytometry. The rapid increase in intracellular reactive oxygen species (ROS) levels was involved in the mechanism of cell death. Western blot analysis demonstrated that delta-elemene activated the caspase-signaling pathway, leading to the proteolysis conversion of pro-caspase-3 to activate caspase-3, and the subsequent cleavage of the caspase substrate PARP. In the process of the induction of apoptotic cell death, Bax translocated into mitochondria, a reduction in Delta psi m was observed and a release of cytochrome c and apoptosis inducing factor (AIF) from mitochondria into the cytosol occurred, indicating that cell death induced by delta-elemene was through a mitochondrial-mediated pathway.