Extract from the branches of Rhamnus yoshinoi exerts anti-cancer effects on human prostate cancer cells through Wnt/β-catenin proteasomal degradation and identification of compounds by GC/MS

We evaluated the anti-cancer activity against human prostate cancer cells and the associated molecular mechanism of extracts from the branches of Rhamnus yoshinoi (RYB). Treatment with RYB suppressed viability of human prostate cancer cells (PC-3) and decreased protein levels of both β -catenin and T-cell factor 4 (TCF4). This was reflected in reduced TCF4 mRNA, but not decreased β catenin mRNA. PC-3 cells were pretreated with the pro-teosome inhibitor MG132 before treatment with RYB, which blocked RYB-mediated down regulation of β -catenin in PC-3 cells, thus confirming that RYB promotes the proteasomal degradation of β -catenin. RYB induced β -catenin phosphorylation, and GSK-3 β inhibition by LiCl blocked the phosphorylation and proteasomal degradation of β catenin by RYB. These results suggest that GSK-3 β may be an important upstream kinase for RYB-mediated regulation of β -catenin. Finally, GC/MS analysis of RYB identified 18 compounds. Based on these findings, RYB shows potential for development as a therapeutic agent for prostate cancer.