p53 signaling plays an important role in cell death. Zerumbone, a natural cyclic sesquiterpene, has shown cytotoxic activity against many cancers. This study was done to investigate the anticancer effects of zerumbone on non-small cell lung cancer (NSCLC) cells and explored the involvement of p53 signaling. Cell viability was assessed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium assay. Apoptosis was confirmed by annexin-V/propidium iodide staining and caspase activity assay. Mitochondrial membrane potential (Δφm) and reactive oxygen species (ROS) production were measured by flow cytometry. Depletion of p53 was achieved by transfection of specific small interfering RNA. Gene expression changes were determined by Western blot analysis. Zerumbone treatment caused a dose-dependent inhibition of A549 and H460 NSCLC cell viability. Zerumbone-induced mitochondrial apoptosis of NSCLC cells, evidenced loss of Δφm, release of mitochondrial cytochrome c, and activation of caspase-9 and -3. There was increased p53 and Bax expression and ROS production in zerumbone-treated cells. Downregulation of p53 or scavenging ROS interfered with the pro-apoptotic action of zerumbone. Combinational treatment with zerumbone and cisplatin significantly accelerated apoptosis and promoted p53 expression and ROS production in NSCLC cells, compared with each alone. These findings demonstrate that zerumbone induces mitochondrial apoptosis and enhances the susceptibility to cisplatin in NSCLC cells, which are, at least partially, mediated through activation of p53 signaling and promotion of ROS generation. This study may provide a rationale for the potential clinical application of zerumbone as a chemotherapeutic agent against NSCLC.
Keywords: Apoptosis; Chemosensitivity; Combination therapy; Natural products; p53.
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