Pipernonaline from Piper Longum Linn. Induces ROS-mediated Apoptosis in Human Prostate Cancer PC-3 Cells

The antiproliferation effects of pipernonaline, a piperine derivative, were investigated on human prostate cancer PC-3 cells. It inhibited growth of androgen independent PC-3 and androgen dependent LNCaP prostate cells in a dose-dependent (30-90 μM) and time-dependent (24-48 h) manner. The growth inhibition of PC-3 cells was associated with sub-G(1) and G(0)/G(1) accumulation, confirmed by the down-regulation of CDK2, CDK4, cyclin D1 and cyclin E, which are correlated with G(1) phase of cell cycle. Pipernonaline up-regulated cleavage of procaspase-3/PARP, but did not change expression of proapoptotic bax and antiapoptotic bcl-2 proteins. Its caspase-3 activation was confirmed by the caspase-3 assay kit. In addition, pipernonaline caused the production of reactive oxygen species (ROS), increase of intracellular Ca(2+), and mitochondrial membrane depolarization, which these phenomena were reversed by N-acetylcysteine, a ROS scavenger. The results suggest that pipernonaline exhibits apoptotic properties through ROS production, which causes disruption of mitochondrial function and Ca(2+) homeostasis and leads to its downstream events including activation of caspase-3 and cleavage of PARP in PC-3 cells. This is the first report of pipernonaline toward the anticancer activity of prostate cancer cells, which provides a role for candidate agent as well as the molecular basis for human prostate cancer.