Plumbagin-induced Apoptosis in Human Prostate Cancer Cells is Associated with Modulation of Cellular Redox Status and Generation of Reactive Oxygen Species

PURPOSE: To investigate the mechanism of human prostate cancer cell growth inhibition by plumbagin, a constituent of the widely used medicinal herb Plumbago zeylanica L. MATERIALS AND METHODS: Cell viability was determined by trypan blue dye exclusion assay. Apoptosis induction was assessed by analysis of cytoplasmic histone-associated DNA fragmentation. Cell cycle distribution and generation of reactive oxygen species (ROS) were determined by flow cytometry. The effect of plumbagin treatment on cellular redox status was determined by analysis of intracellular glutathione (GSH) levels and expression of genes involved in ROS metabolism. RESULTS: Plumbagin treatment decreased viability of human prostate cancer cells (PC-3, LNCaP, and C4-2) irrespective of their androgen responsiveness or p53 status. Plumbagin-mediated decrease in cell viability correlated with apoptosis induction, which was accompanied by ROS generation and depletion of intracellular GSH levels. Pretreatment of cells with the antioxidant N-acetylcysteine inhibited plumbagin-mediated ROS generation and apoptosis. Plumbagin treatment also resulted in altered expression of genes responsible for ROS metabolism, including superoxide dismutase 2 (Mn-SOD). CONCLUSION: The present study points towards an important role of ROS in plumbagin-induced apoptosis in human prostate cancer cells.