Title: Kavalactone yangonin induces autophagy and sensitizes bladder cancer cells to flavokawain A and docetaxel via inhibition of the mTOR pathway


Authors: Zhongbo Liu1, U-Syn Ha1, Ke Yu, Chunli Wu1, Noriko Yokoyama1, Xiaolin Zi1,2,3


Institutions: 1 Departments of Urology, 2 Pharmacology and 3 Chao Family Comprehensive Cancer Center, University of California, Irvine, Orange, CA 92868, USA.


Abstract: Consumption of kava (Piper methysticum Forst) has been linked to reduced cancer risk in the South Pacific Islands. Kavalactones are major bioactive components in kava root extracts, which have recently demonstrated anti-cancer activities. However, molecular mechanisms of kavalactones' anti-cancer action remain largely unknown. We have identified two kavalactones, yangonin and 5 6'-dehydrokawain, as potent inducers of autophagic cell death in bladder cancer cells. The effect of yangonin inducing autophagy is associated with increased expression of beclin and ATG5. In addition, yangonin increases the expression of LKB1 and decreases the phosphorylation of Akt, PRAS40, rpS6, p70S6K and 4E-BP1, leading to increased binding of 4E-BP1 to m7 GTP. The growth inhibitory effects of yangonin were attenuated in TSC1 or LKB1 knockout mouse embryonic fibroblasts, suggesting that TSC1 and LKB1 expression may contribute to optimal growth inhibition by yangonin. Furthermore, yangonin reduces the viability of bladder cancer cell lines derived from different stages of human bladder cancer, and acts synergistically with apoptosis-inducing agents such as docetaxel and flavokawain A. Our results support a novel anti-bladder cancer mechanism by yangonin and further studies are needed to assess the potential use of yangonin for bladder cancer prevention and treatment


Keywords: yangonin, bladder cancer, autophagy, mTOR


Full text: JBR-2016-0160.pdf


J biomed Res published on 20 April, 2017, doi:10.7555/JBR.31.20160160