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Paeonol induces cytoprotective autophagy via blocking the Akt/mTOR pathway in ovarian cancer cells.

ABSTRACT: Paeonol (Pae), a phenolic acid compound isolated from the Moutan Cortex, was previously demonstrated to exert multiple anticancer effects. The rational control of autophagy has been considered a potential treatment strategy for epithelial ovarian cancer. However, whether Pae induces autophagy and the relationship between its antitumour activities and autophagy in epithelial ovarian cancer are still unclear. In this study, we found that Pae induced not only antiproliferation activity and apoptosis but also autophagy, and complete autophagic flux was observed in A2780 and SKOV3 cells. In addition, combination treatment with Pae and an autophagy inhibitor (3-methyladenine and hydroxychloroquine) showed significant synergetic effects on inhibiting cell viability and promoting apoptosis in vitro and in the A2780 xenograft model, without severe side effects, which was often had by cisplatin. These results indicate that autophagy induced by Pae has a cytoprotective role in both A2780 and SKOV3 cells. Mechanistically, we found that Pae inhibited the protein kinase B(Akt)/mammalian target of rapamycin (mTOR) pathway. Furthermore, when combined with the inhibitors MK2206 and rapamycin to inhibit Akt and mTOR kinase activity, Pae-induced autophagy was increased. Taken together, our results demonstrate that Pae induced cytoprotective autophagy by inhibiting the Akt/mTOR pathway in ovarian cancer cells. Thus, the strategy of combining Pae with an autophagy inhibitor to block Akt/mTOR-dependent autophagy could enhance the antitumour activity of Pae and warrants further application for the treatment of ovarian cancer.

SUBMITTER: Gao L

PROVIDER: S-EPMC6690917 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Rationale: Cardenolides have potential as anticancer drugs. 3'-epi-12?-hydroxyfroside (HyFS) is a new cardenolide structure isolated by our research group, but its molecular mechanisms remain poorly understood. This study investigates the relationship between its antitumor activities and autophagy in lung cancer cells. Methods: Cell growth and proliferation were detected by MTT, lactate dehydrogenase (LDH) release, 5-ethynyl-20-deoxyuridine (EDU) and colony formation assays. Cell apoptosis was detected by flow cytometry. Autophagic and signal proteins were detected by Western blotting. Markers of autophagy and autophagy flux were also detected by immunofluorescence, transmission electron microscopy and acridine orange staining. Real time RT-PCR was used to analyze the gene expression of Hsp90. Hsp90 ubiquitination was detected by coimmunoprecipitation. The antitumore activities of HyFS were observed in nude mice. Results: HyFS treatment inhibited cell proliferation and induced autophagy in A549 and H460 lung cancer cells, but stronger inhibition of cell proliferation and induction of cell apoptosis were shown when HyFS-mediated autophagy was blocked. The Hsp90/Akt/mTOR axis was found to be involved in the activation of HyFS-mediated autophagy. Evidence of direct interaction between Hsp90 and Akt was observed. HyFS treatment resulted in decreased levels of heat shock protein 90 (Hsp90) and phosphorylated Akt, overexpression of Hsp90 increased activation of autophagy, and inhibition of Hsp90 expression decreased autophagy. In addition, ubiquitin-mediated degradation of Hsp90 and subsequent dephosphorylation of its client protein Akt were also found in HyFS-treated lung cancer cells. Moreover, combination treatment with HyFS and chloroquine showed remarkably increased tumor inhibition in both A549- and H460-bearing mice. Conclusion: Our results demonstrate that HyFS induced cytoprotective autophagy through ubiquitin-mediated degradation of Hsp90, which further blocked the Akt/mTOR pathway in lung cancer cells. Thus, a combination of a HyFS-like cardenolide and an autophagic inhibitor is a potential alternative approach for the treatment of lung cancer.

Project description:Non-small cell lung cancer (NSCLC) is a globally scaled disease with a high incidence and high associated mortality rate. Autophagy is one of the important physiological activities that helps to control cell survival, influences the dynamics of cell death, and which plays a crucial role in the pathophysiology of NSCLC. Sotetsuflavone is a naturally derived and occurring flavonoid, and previous studies have demonstrated that sotetsuflavone possesses potential anti-cancer activities. However, whether or not sotetsuflavone induces autophagy, as well as has effects and influences cell death in NSCLC cells remains unclear. Thus, in our study, we examined and elucidated the roles and underlying mechanisms of sotetsuflavone upon the dynamics of autophagy in NSCLC in vivo and in vitro. The results indicated that sotetsuflavone was able to inhibit proliferation, migration, and invasion of NSCLC cells. Mechanistically, sotetsuflavone was able to induce apoptosis by increasing the levels of expression of cytochrome C, cleaved-caspase 3, cleaved-caspase 9, and Bax, and contrastingly decreased levels of expression of Bcl-2. In addition, we also found that decreased levels of expression of cyclin D1 and CDK4 caused arrest of the G0/G1 phases of the cell cycle. Furthermore, we also found that sotetsuflavone could induce autophagy which in turn can play a cytoprotective effect on apoptosis in NSCLC. Sotetsuflavone-induced autophagy appeared related to the blocking of the PI3K/Akt/mTOR pathway. Our in vivo study demonstrated that sotetsuflavone significantly inhibited the growth of xenograft model inoculated A549 tumor with high a degree of safety. Taken together, these findings suggest that sotetsuflavone induces autophagy in NSCLC cells through its effects upon blocking of the PI3K/Akt/mTOR signaling pathways. Our study may provide a theoretical basis for future clinical applications of sotetsuflavone and its use as a chemotherapeutic agent for treatment of NSCLC.

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Paeonol induces cytoprotective autophagy via blocking the Akt/mTOR pathway in ovarian cancer cells.

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