[Frontiers in Bioscience E3, 1315-1325, June 1, 2011]

Sanggenon C decreases tumor cell viability associated with proteasome inhibition

Hongbiao Huang1, Ningning Liu1, Kai Zhao1, Chenchen Zhu3, Xiaoyu Lu1, Shujue Li1,4, Wen Lian1, Ping Zhou1, Xiaoxian Dong1, Canguo Zhao1, Haiping Guo1, Change Zhang1, Changshan Yang1, Guanmei Wen1, Li Lu1, Xiaofen Li1, Lixia Guan1, Chunjiao Liu1, Xuejun Wang1,4, Qing Ping Dou1,2, Jinbao Liu1

Protein Modification and degradation Lab, 1Department of Pathophysiology; 4Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical College, Guangzhou Guangzhou Medical College. Guangzhou, Guangdong, People's Republic of China, 2The Developmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute, and Departments of Oncology, Pharmacology and Pathology, School of Medicine, Wayne State University. Detroit, Michigan, USA, 3School of Chinese Medicine, Guangzhou University of Traditional Chinese Medicine. Guangzhou, Guangdong, People's Republic of China, 4Division of Biomedical Sciences, University of South Dakota Sanford School of Medicine, Vermillion, South Dakota, USA.

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and methods
3.1. Materials
3.2. Extraction and isolation of Sanggenon C
3.3. Peptidase activity assay and cell-based proteasome activity assay
3.4. Cell culture
3.5. LDH assay
3.6. Cell viability assay
3.7. Cell death assay
3.8. Cell cycle analysis
3.9. Western blot analysis
4. Results
4.1. Determination of Sanggenon C Structure
4.2. Cytotoxicity of Sanggenon C in murine hepatoma H22 and leukemic P388 cells
4.3. Sanggenon C induces cell cycle arrest at G0/G1 phase in H22 and P388 cells
4.4. Sanggenon C causes cell death in H22 and P388 cells
4.5. Sanggenon C inhibits the chymotrypsin-like activity of a purified rabbit 20S proteasome and H22 cell lysate
4.6. Sanggenon C causes proteasome inhibition in murine H22 and P388 cell lines
4.7. Sanggenon C-induced tumor cell death occurs after proteasome inhibition
4.8. Sanggenon C decreases cell viability, and induces cell death and proteasome inhibition in human leukemia cells
5. Discussion
6. Acknowledgements
7. References

1. ABSTRACT

Several flavonoids have been reported to be proteasome inhibitors, but whether prenylated flavonoids are able to inhibit proteasome function remains unknown. We report for the first time that Sanggenon C, a natural prenylated flavonoid, inhibits tumor cellular proteasomal activity and cell viability. We found that (1) Sanggenon C inhibited tumor cell viability and induced cell cycle arrest at G0/G1 phase; (2) Sanggenon C inhibited the chymotrypsin-like activity of purified human 20S proteasome and 26S proteasome in H22 cell lysate, and Sanggenon C was able to dose-dependently accumulate ubiquitinated proteins and proteasome substrate protein p27; (3) Sanggenon C-induced proteasome inhibition occurred prior to cell death in murine H22 and P388 cell lines; (4) Sanggenon C induced death of human K562 cancer cells and primary cells isolated from leukemic patients. We conclude that Sanggenon C inhibits tumor cell viability via induction of cell cycle arrest and cell death, which is associated with its ability to inhibit the proteasome function and that proteasome inhibition by Sanggenon C at least partially contributes to the observed tumor cell growth-inhibitory activity.