Anticancer effects of imperatorin isolated from Angelica dahurica: induction of apoptosis in HepG2 cells through both death-receptor- and mitochondria-mediated pathways.

Imperatorin (IM) is a furanocoumarin isolated from the root of Angelica dahurica, which is reported to have anticonvulsant and anticancer effects. In this study, the antiproliferative effect of IM on 9 human cancer cell lines was examined, and human hepatoma HepG2 cells were chosen as the target for preferential killing by IM. Particularly, the mechanism of IM-induced apoptosis and in vivo animal effects were also studied. Cell viability was measured using MTT assay, and apoptosis was detected by Hoechst staining, annexin V-PI staining, and DNA laddering assay. Mitochondrial membrane potential was detected by JC-1 staining. Western blot analysis was employed to detect the expression of apoptosis-related proteins. In addition, the in vivo anticancer effect of IM was examined in nude mice bearing HepG2 cells. IM inhibited the proliferation of HepG2 cells through apoptosis induction in a time- and dose-dependent manner by observation of the nuclear morphology, DNA fragmentation, phosphatidylserine externalization, loss of mitochondrial membrane potential, release of cytochrome c into cytosol, and activation of caspase-3, caspase-8, caspase-9, and poly(ADP-ribose) polymerase cleavage. As cell death could partly be prevented by the caspase-8 or caspase-9 inhibitor and was evidenced by the results of Western blot analysis, our results also suggest that IM-induced apoptosis is mediated through both death receptor and mitochondrial pathways. In the animal model, IM was found to effectively suppress tumor growth by 31.93 and 63.18% at dosages of 50 and 100 mg/kg, respectively, after treatment for 14 days. No significant weight loss or toxicity to the hosts was found. IM can function as a cancer suppressor by inducing apoptosis in HepG2 cells through both death-receptor- and mitochondria-mediated pathways. Furthermore, the in vivo antitumor activities of IM are significant with negligible weight loss and damage to the host.