Alpinia katsumadai Hayata induces growth inhibition and autophagy-related apoptosis by regulating the AMPK and Akt/mTOR/p70S6K signaling pathways in cancer cells

Alpinia katsumadai Hayata (AKH), a widely used traditional Chinese medicine, exerts various biological functions, including anti-inflammatory, antioxidant, anti-microbial and anti-asthmatic effects. However, studies on its anticancer activity and associated mechanisms are limited. The present study investigated the effects of ethanol extract from AKH on the viability of various human cancer and normal liver LX-2 cells using Cell Counting Kit-8 assay. Apoptosis was detected by Hoechst 33342/PI staining and Annexin-V-FITC/PI double staining. Autophagy was examined by Ad-GFP-LC3B transfection. The association between AKH-induced autophagy and apoptosis was investigated by pre-treatment of the cells with the autophagy inhibitors, 3-methyladenine (3MA) and bafilomycin A1 (Baf-A1), followed by treatment with AKH. The expression levels of cleaved poly(ADP-ribose) polymerase (PARP), caspase-8, caspase-3, caspase-9, phosphorylated (p-)AMP-activated protein kinase (AMPK), Akt, mTOR and p70S6K were examined using western blot analysis. The in vivo antitumor activity of AKH was investigated in nude mice bearing A549 lung cancer xenografts. The components of AKH were detected by liquid chromatography mass spectrometry-ion trap-time-of-flight mass spectrometry. The results revealed that AKH significantly inhibited the proliferation of various cancer cells with the half maximal inhibitory concentration (IC(50)) values of 203–284 µg/ml; however, its inhibitory effect was much less prominent against normal liver LX-2 cells with an IC(50) value of 395 µg/ml. AKH markedly induced apoptosis and autophagy, and upregulated the protein expression of cleaved-caspase-3, caspase-8, caspase-9 and cleaved PARP in a concentration-dependent manner. Of note, the autophagy inhibitors (3MA and Baf-A1) significantly attenuated its pro-apoptotic effects on human pancreatic cancer Panc-28 and lung cancer A549 cells. Furthermore, AKH significantly increased the levels of p-AMPK, and decreased those of p-Akt, p-mTOR and p-p70S6K in Panc-28 and A549 cells. AKH markedly inhibited the growth of A549 tumor xenografts in vivo. In addition, a total of nine compounds were detected from AKH. The present study demonstrates that AKH markedly inhibits the growth and induces autophagy-related apoptosis in cancer cells by regulating the AMPK and Akt/mTOR/p70S6K signaling pathways. AKH and/or its active fractions may thus have potential to be developed as novel anticancer agents for clinical use.