Orlistat induces apoptosis and protective autophagy in ovarian cancer cells: involvement of Akt-mTOR-mediated signaling pathway
Orlistat possesses anti-tumor capacity by inducing apoptosis in ovarian cancer cells. However, the mechanism is not clearly understood. Emerging evidence indicates the overlaps between autophagy and apoptosis. In this study, we have investigated the role of autophagy in orlistat-induced apoptosis in ovarian cancer (OC) cells.
The effect of orlistat on apoptosis was evaluated in SKOV3 and A2780 cell lines by MTT and TUNEL assay. The formations of autophagosomes were observed by acridine orange and GFP-LC3 fluorescence. In addition, conversions of LC3-I to LC3-II were analyzed by western blot, as well as other autophagy-related proteins. 3-Methyladenine (3-MA) was used as an autophagy inhibitor in combined treatment with orlistat. Western blot was further conducted to investigate the molecular mechanisms of orlistat-affected apoptosis and autophagy on protein level.
The proliferation activities of OC cells were inhibited by orlistat in a dose-dependent manner. The expressions of cleaved-caspase 3 and 9 in orlistat-treated cells were increasing, which suggested that orlistat-induced apoptosis was caspase-dependent. At the same time, the average number of GFP-LC3 dots per cell was increased after 48 h of orlistat treatment. The expression levels of LC3-II were significantly up-regulated, as well as other autophagy-related proteins such as Vsp34, Atg7 and UVRAG. These results suggested orlistat-induced autophagy flux, which was further found involved in inhibiting the Akt/mTOR/p70S6K signaling pathway. However, combined treatment of orlistat and 3-MA significantly suppressed the cell viability, which indicated a pro-survival role of autophagy in OC cells.
We suggested that orlistat had anti-cancer effect in OC cells. In addition, autophagy played a pro-survival role, suppressing which the orlistat-induced anti-cancer effect would be more significant.
KeywordsOvarian cancer Orlistat Autophagy mTOR
HLP and QW contributed equally to this work. HLP and QW conducted the experiment and wrote the original draft. XZ assisted with study design, methodology design, and reviewed and edited the original draft. XRQ helped conduct the experiment. XW helped in analysis of data and preparation of tables and figures. All authors reviewed the manuscript.
This work was supported by the key research and development program of Sichuan Province (Grant No. 2017SZ0002).
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Conflict of interest
All authors declare there is no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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