β-Elemene, a novel plant-derived antineoplastic agent, increases cisplatin chemosensitivity of lung tumor cells by triggering apoptosis

β-Elemene, a new plant-derived anticancer agent with low toxicity, has been reported to be effective in the treatment of leukemia and solid tumors. In the current study, we explored the therapeutic application of β-elemene in sensitizing lung cancer cells to cisplatin. β-Elemene considerably enhanced the inhibitory effect of cisplatin on cell proliferation in a time- and dose-dependent manner in the human non-small cell lung cancer (NSCLC) cell lines H460 and A549. Furthermore, this effect of β-elemene on cisplatin activity occurred through the induction of apoptosis in NSCLC cells, as assessed by an ELISA-based assay, TUNEL assay and annexin V binding assay. Consistent with these results, the protein levels of Bax and phospho-Bcl-2 increased and those of Bcl-2 and XIAP decreased in cells treated with β-elemene in combination with cisplatin, compared with the levels in cells treated with either agent alone. Finally, β-elemene augmented the cisplatin-induced increases in caspase-3, -7, -9 and -10 activities and cleaved caspase-3, -9 and poly(ADP-ribose) polymerase levels in NSCLC cells. These observations suggest that β-elemene sensitizes NSCLC cells to cisplatin via a mitochondria-mediated intrinsic apoptosis pathway involving Bcl-2 family proteins and IAPs (inhibitor of apoptosis proteins). Our data provide a rationale for developing a combination of β-elemene and cisplatin as a regimen for the treatment of lung carcinoma and other cisplatin-resistant tumors.