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

The chemical compound δ-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 δ-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 δ-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 Δψm 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 δ-elemene was through a mitochondrial-mediated pathway.