Deoxyelephantopin impairs growth of cervical carcinoma SiHa cells and induces apoptosis by targeting multiple molecular signaling pathways

Deoxyelephantopin, a sesquiterpene lactone extracted and purified from Elephantopus scaber, has been shown to exhibit antitumor and hepatoprotective activities. The purpose of this study was to investigate the antiproliferative and apoptosis-inducing properties of deoxyelephantopin in SiHa cells and to elucidate the underlying molecular mechanisms. Deoxyelephantopin inhibited growth of SiHa cells and triggered apoptosis. Apoptosis was accompanied by sequential activation of caspases (8, 9, 3, and 7) and reactive oxygen species (ROS) production. Downregulation of antiapoptotic proteins (Bcl2 and Bcl-x(L)) and upregulation of apoptotic protein (bax) were also detected. Our results demonstrated that deoxyelephantopin-induced G2/M phase arrest was associated with a marked increase in the levels of p53 and p21 and a decrease in phospho-signal transducer and activator of transcription 3 (pSTAT3-Tyr705), cyclin-dependent kinase 1 (cdc2), and cyclin B1. The expression of p-Akt and p-mTOR was downregulated. p-ERK was inhibited while p-JNK and p-p38 was activated on deoxyelephantopin treatment. Our findings provided the first evidence that STAT3/p53/p21 signaling, MAPK pathway, PI3k/Akt/mTOR pathway, caspase cascades, and ROS play critical roles in deoxyelephantopin-induced G2/M phase arrest and apoptosis of SiHa cells.