The Akt/mammalian target of the rapamycin (mTOR) pathway is activated in the majority of human cancers. Activation of the Akt/mTOR pathway confers resistance to many types of cancer therapy. In this study, we evaluated the apoptotic effect of ethanol extract of Artemisia annua L. through down-regulation of Akt signal pathways and the mitochondrial pathway in hepato-carcinoma cells (HepG2). A. annua extract is known as a medicinal herb that is effective against cancer. We evaluated anti-proliferative activity by MTT-based viability assay and apoptotic effect by Annexin-V/PI staining, mitochondrial membrane potential (MMP), and caspase-3/7 activity as determined by flow cytometry. A. annua treatment led to loss of MMP, resulting in cytochrome c-inducible activation of caspase-3/7. Treatment with A. annua extract reduced activities of Akt/mTOR/anti-apoptotic proteins (such as Bcl-2 and Bcl-XL), leading to increased activation of tumor suppressor p53 and pro-apoptotic proteins (such as Bax and Bak). We applied LY294002 (inhibitor of Akt) and rapamycin (inhibitor of mTOR) to determine the relationship between signal transduction of proteins associated with apoptosis. LY294002 and rapamycin significantly reduced cell viability and increased apoptosis. These results indicate that Bcl-2 and caspase-3 are key regulators in A. annua extract-induced apoptosis in HepG2 cells and are controlled through the Akt/mTOR signaling pathway.

Keywords: HepG2, Akt, mTOR, Artemisia annua L., apoptosis