Artemisinin induces caspase-8/9-mediated and Bax/Bak-independent apoptosis in human lung adenocarcinoma (ASTC-a-1) cells.

Artemisinin (ARTE), an antimalarial phytochemical component from the sweet wormwood plant, has been shown a potential anticancer activity by inducing cell apoptosis. The aim of this report is to explore the mechanism of ARTE-induced human lung adenocarcinoma (ASTC-a-1) cell apoptosis. Cell counting kit (CCK-8) assay showed that ARTE induced cytotoxcity in a dose- and time-dependent manner. Confocal microscopy fluorescence imaging of cells stained with Hoechst 33258 and flow cytometry (FCM) analysis of cells stained with Annexin V-FITC/propidium iodide (PI) showed that ARTE induced reactive oxygen species (ROS)-dependent apoptosis. Confocal fluorescence resonance energy transfer (FRET) imaging of single living cells expressing SCAT3, SCAT9 or CFP-Bid-YFP and fluorometic substrate assay showed that ARTE induced the activation of caspase-3, -8 and -9. Moreover, inhibition of caspase-8 or -9 completely blocked ARTE-induced apoptosis which was only partially attenuated by caspase-3 inhibitor. Interestingly, silencing Bax and Bak by RNA interference (RNAi) did not attenuate ARTE-induced apoptosis. Collectively, ARTE induces caspase-dependent but Bax/Bak-independent apoptosis in ASTC-a-1 cells.