1.Yueyang Hospital of Integrated Traditional Chinese and Western Medicine， Shanghai University of Traditional Chinese Medicine， Shanghai 200437， China;2.Shanghai Putuo District Central Hospital， Shanghai 200062，China
Objective To investigate the effect and mechanism of saikosaponin A （SSA） on the reversal of cisplatin （DDP） resistance in human lung cancer cell line A549/DDP.Methods The resistance of A549 and A549/DDP cells to DDP and the inhibitory effects of SSA against the proliferation of A549 and A549/DDP cells were detected using cell counting kit-8 （CCK-8）. The apoptosis rates of A549/DDP cells treated with SSA or DDP or SSA combined with DDP and the changes in reactive oxygen species （ROS） were determined by flow cytometry. The mRNA expression levels of C-myc， B-cell lymphoma 2 （Bcl-2） and cysteinyl aspartate-specific protease-3 （Caspase-3） were detected by real-time polymerase chain reaction （Real-time PCR）， followed by the determination of β-catenin transcriptional activity using the TopFish dual-luciferase reporter assay system and the measurement of β-catenin protein expression in A549/DDP cells by Western blot.Results The results of CCK-8 assay showed that the DDP resistance of A549/DDP cells was 12.82 times that of A549 cells （P<0.05）. SSA inhibited the viability of A549 cells with the half maximal inhibitory concentration （IC50） being 34.9 μmol·L-1， and also suppressed the viability of A549/DDP cells in a concentration-dependent manner. Since the inhibition rate of 20 μmol/L SSA against A549/DDP cells was less than 10%， the reversal concentration was set at 20 μmol/L. Flow cytometry revealed that compared with the control， DDP alone increased the apoptosis rate of A549/DDP cells （P<0.05）， stimulated the accumulation of intracellular ROS （P<0.05）， down-regulated the mRNA expression levels of C-myc and Bcl-2 in A549/DDP cells， up-regulated Caspase-3 mRNA expression， and reduced the transcriptional activity of β-catenin （P<0.05）. Compared with the DDP group， the SSA+DDP group exhibited obviously increased apoptosis of A549/DDP cells， enhanced accumulation of intracellular ROS， down-regulated C-myc and Bcl-2 mRNA expression， up-regulated Caspase-3 mRNA expression （P<0.05）， and weakened β-catenin transcription （P<0.05）. DDP combined with SSA better decreased the β-catenin protein expression in contrast to that of control or DDP （P<0.05）.Conclusions SSA enhances the sensitivity of A549/DDP cells to DDP possibly by inhibiting the activation of Wnt/β-catenin pathway.
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