[Mechanism of polyphyllin A in inhibition of proliferation and induction of apoptosis of gastric cancer cells by directly targeting ETS-1].

The present study investigated the mechanism of polyphyllin A(PPA) in inhibiting gastric cancer(GC) cells. GC cells(SGC7901 and MGC803 cell lines) were treated with PPA at different concentrations. The effect of PPA on the proliferation of GC cells was detected by MTT assay, real-time cell analysis(RTCA) assay, and clone-forming assay, respectively. Reactive oxygen species(ROS) of GC cells was detected by flow cytometry. The change of mitochondrial membrane potential was detected by JC-1 assay. The expression and phosphorylation levels of apoptosis-related proteins(caspase-9, caspase-3, and PARP) and proteins related to the signaling pathway(ETS-1, CIP2 A, and Akt) were detected by Western blot. The binding sites of PPA to ETS-1 were analyzed by molecular docking. The affinity of PPA and ETS-1 was detected by drug affinity responsive target stability(DARTS) assay. PPA had a significant inhibitory effect on the proliferation and colony formation of GC cells at a low concentration. The PPA groups showed increased ROS and decreased mitochondrial membrane potential. PPA down-regulated the precursor expression of caspase-9 and caspase-3 and promoted the cleavage of PARP, suggesting that PPA induced the apoptosis of GC cells through the mitochondrial pathway. PPA significantly reduced expression levels of CIP2 A and the phosphorylation of downstream Akt. Molecular docking showed that PPA bound to the ETS domain of ETS-1, the transcription factor of CIP2 A, and formed hydrogen bonds with Pro319 and Asp317. DARTS assay further confirmed that PPA significantly prevented the hydrolysis of ETS-1 by pronase, which was inductive of the direct binding effect of PPA and ETS-1. PPA inhibits the proliferation and induces the apoptosis of GC cells by directly targeting ETS-1 to down-regulate the ETS-1/CIP2 A/Akt signaling pathway.