β-Elemene Induces Apoptosis in Human Renal-cell Carcinoma 786-0 Cells through Inhibition of MAPK/ERK and PI3K/Akt/mTOR Signalling Pathways

Background: Renal-cell carcinoma (RCC) is resistant to almost all chemotherapeutics and radiation therapy. beta-Elemene, a promising anticancer drug extracted from a traditional Chinese medicine, has been shown to be effective against various tumors. In the present study, anti-tumor effects on RCC cells and the involved mechanisms were investigated. Methods: Human RCC 786-0 cells were treated with different concentrations of beta-elemene, and cell viability and apoptosis were measured by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry, respectively. Protein expression was assayed by western blotting. Autophagy was evaluated by transmission electron microscopy. Results: beta-Elemene inhibited the viability of 786-0 cells in a dose- and time-dependent manner. The anti-tumor effect was associated with induction of apoptosis. Further study showed that beta-elemene inhibited the MAPK/ERK as well as PI3K/Akt/mTOR signalling pathways. Moreover, robust autophagy was observed in cells treated with beta-elemene. Combined treatment of beta-elemene with autophagy inhibitors 3-methyladenine or chlorochine significantly enhanced the anti-tumor effects. Conclusions: Our data provide first evidence that beta-elemene can inhibit the proliferation of RCC 786-0 cells by inducing apoptosis as well as protective autophagy. The anti-tumor effect was associated with the inhibition of MAPK/ERK and PI3K/Akt/mTOR signalling pathway. Inhibition of autophagy might be a useful way to enhance the anti-tumor effect of beta-elemene on 786-0 cells.