Studies Of The Anti-tumor Activity In Vivo Or In Vitro And Mechanisms Of δ-elemene Induced Tumor Cell Apoptosis

Elemene is a naturally occurring compound that can be isolated from the traditional Chinese medicinal herb, Curcuma Wenyujin, which was used to treat tumors in Chinese folk medicine. Elemene exists as an essential oil mixture ofβ-,γ- andδ-elemene.δ-elemene is another isomeric compound ofβ-elemene with a different site of double bond.The antitumor effect ofδ-elemene was investigated in vitro and in vivo, and the mechanism ofδ-elemene induced apoptosis in HeLa, NCI-H292, HL-60 or DLD-1 cell lines were reported in this dissertation.In vitro, we examined the inhibition ofδ-elemene on 7 tumor cell lines. There were five cell lines sensitive toδ-elemene, the values of IC₅₀ were 157.9, 233.2, 231.6, 222.4, 154.5μM in HeLa, NCI-H292, HepG₂, DLD-1 and HL-60, respectively. We examined the effect ofδ-elemene on normal bone marrow and normal liver cell lines WRL68, it was suggested thatδ-elemene posseed no signs of bone marrow suppression and WRL68. In vivo, the HepG₂ cells were transplanted subcutaneously to BALB/c nude mice to produe solid tumors. The result was shown that the inhibition of HepG₂ treated withδ-elemene was in dose-dependent manner. There was no significant difference betweenδ-elemene andβ-elemene with the concentration of 75 mg/kg (p>0.05). And no significant reduction in body weight was found inδ-elemene treated mice, it meant that the inhibition to the growth of tumor was not cytotoxicity. Scanning electron micrographs further certificated thatδ-elemene inhibited the growth of HepG₂ by apoptosis in vivo.Therefore, the mechanism ofδ-elemene induced apoptosis in HeLa, NCI-H292, HL-60 or DLD-1 cell lines were investigated. Induction of early apoptosis byδ-elemene in a time-dependent manner was confirmed by morphology, DNA fragmentation ELISA assay, Annexin-V and JC-1 labeled flow cytometry analysis, and active caspase-3 assay.δ-elemene increased the expression of pro-apoptotic protein, Bax and decreased the expression of anti-apoptotic mitochondrial protein, Bcl-2. Activation of ERK1/2 and p38 and inhibition of JNK increased the ration of Bax/Bcl-2 protein expression. And the reduction in the mitochrome membrane potential was observed, and a release of cytochrome c and apoptosis inducing factor (AIF) from mitochrome into the cytosol occurred. And the activation of caspase-3 and cleaved PARP which prevented the DNA repair. These results indicated that the apoptosis induced byδ-elemene was through the mitochrome-mediated pathway. The rapid increase in intracellular reactive oxygen species (ROS) levels was involved in the mechanism of apoptosis. In addition, the G₂ block was involved in HL-60 cell death induced byδ-elemene.