Inhibition on Proteasome β1 Subunit Might Contribute to the Anti-Cancer Effects of Fangchinoline in Human Prostate Cancer Cells.

Dong Li,Xiao-Bo Qu,Yu Lu,Li-Xing Feng,Peng Sun,Xuan Liu,De-An Guo,Min Yang,Li-Hong Hu,Bao-Hong Jiang,Wan-Ying Wu,Miao Liu,Chih-Pin Chuu

doi:10.1371/journal.pone.0141681

Abstract

Fangchinoline is a bisbenzylisoquinoline alkaloid isolated from Radix Stephaniae tetrandrae S. Moore. Fangchinoline and its structure analogue, tetrandrine, exhibited direct binding affinity with recombinant human proteasome β1 subunit and also inhibited its activity in vitro. In cultured prostate PC-3 cells and LnCap cells, fangchinoline could dose-dependently inhibit cell proliferation and caspase-like activity of cellular proteasome which was mediated by proteasome β1 subunit. The inhibitive effect of fangchinoline on caspase-like activity of proteasome was also observed in purified human erythrocyte 20S proteasome. In PC-3 cells, fangchinoline induced cell cycle arrest at G0/G1 phase and apoptosis. Treatment of PC-3 tumor-bearing nude mice with fangchinoline inhibited tumor growth, induced apoptosis and also caused decrease in proteasome activities in tumor xenografts. Dose-dependent and time-dependent accumulation of ubiquitinated proteins and important proteasome substrates such as p27, Bax and IκB-α were observed in fangchinoline-treated cells. Over-expression of proteasome β1 subunit by plasmid transfection increased sensitivity of cells to the cytotoxicity of fangchinoline while knockdown of proteasome β1 subunit ameliorated cytotoxicity of fangchinoline in PC-3 cells. Results of the present study suggested that proteasome inhibition was involved in the anti-cancer effects of fangchinoline. Fangchinoline and its structure analogues might be new natural proteasome inhibitors targeting β1 subunit.

Highlights

Proteasome has emerged as an important and effective target for anti-cancer therapy[1]
The results suggested that fangchinoline and tetrandrine exhibited similar binding affinity to proteasome β1 subunit
The results indicated that fangchinoline dose-dependently and time-dependently induced increase in ubiquitinated IκBα (Ub-IκBα), Ub-p27 and Ub-Bax in PC-3 cells treated with fangchinoline

Summary

Introduction

Proteasome has emerged as an important and effective target for anti-cancer therapy[1]. In our screening of natural proteasome inhibitors, fangchinoline and tetrandrine, two bisbenzylisoquinoline alkaloids isolated from dried root of Stephaniae tetrandrine S. Proteasome-Inhibiting Effects of Fangchinoline decision to publish, or preparation of the manuscript. Nanjing Tianyi Bioscience Co. Ltd, provided support in the form of salaries for authors YL, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section

Methods

Results

Conclusion