Promotion of Ros-mediated Bax/Cyt-c apoptosis by polyphyllin II leads to suppress growth and aggression of glioma cells

BACKGROUND: Gliomas remain among the most difficult cancers to treat, with a 5-year overall survival no greater than 5%. Many saponins showed a wide spectrum of anti-cancer activities at low concentration. Polyphyllin II is one of the common saponins from Paris polyphylla. However, the effect of Polyphyllin II on glioma cells has not been evaluated. Objective of the present study was to investigate whether Polyphyllin II have inhibition on glioma cells, and the possible mechanisms. METHODS: The viability of U87 and U251 cells was detected by cell counting kit-8, cell counting real time cellular analysis and cell clone formation methods. Transwell was used to estimate the aggression of U87 and U251. The cell apoptosis rate was tested by flow cytometry. The morphological change was determined by transmission electron microscopy. The levels of AKT, phosphorylation of AKT, Bax, Bcl-2, cytochrome c, and cleaved caspase 3 proteins were assessed by Western blot. N-acetyl-L-cysteine was used to check the role of ROS in polyphyllin II inhibition to glioma cells. RESULTS: Polyphyllin II showed significant suppress to proliferation and aggression of U87 and U251 in a dose- and time- dependent manner. Result of flow cytometry confirmed that Polyphyllin II induced apoptosis to U87 and U251 cells. Transmission electron microscopy observation revealed majority of the glioma cells treated with Polyphyllin II had turgidity of mitochondrion, disarrangement, diminution and vacuolization, those refer to mitochondrial apoptosis. Western blot indicated that Polyphyllin II promoted cyt-c, Bax, caspase 3 and cleaved-caspase 3, and decreased Bcl-2, AKT and p-AKT. Rescue experiments using N-acetyl-L-cysteine, a reactive oxygen species scavenger, reversed the levels of Bax and cyt-c, and the inhibition in Polyphyllin II-treated U87 and U251 cells. CONCLUSIONS: The present findings revealed that polyphyllin II may be a potential drug against glioma.