Celastrol, a triterpene extracted from the Chinese "Thunder of God Vine," is a potent proteasome inhibitor and suppresses human prostate cancer growth in nude mice.
Interest in the use of traditional medicines for cancer prevention and treatment is increasing. In vitro, in vivo, and clinical studies suggest the potential use of proteasome inhibitors as novel anticancer drugs. Celastrol, an active compound extracted from the root bark of the Chinese medicine "Thunder of God Vine" (Tripterygium wilfordii Hook F.), was used for years as a natural remedy for inflammatory conditions. Although Celastrol has been shown to induce leukemia cell apoptosis, the molecular target involved has not been identified. Furthermore, whether Celastrol has antitumor activity in vivo has never been conclusively shown. Here, we report, for the first time, that Celastrol potently and preferentially inhibits the chymotrypsin-like activity of a purified 20S proteasome (IC(50) = 2.5 micromol/L) and human prostate cancer cellular 26S proteasome (at 1-5 micromol/L). Inhibition of the proteasome activity by Celastrol in PC-3 (androgen receptor- or AR-negative) or LNCaP (AR-positive) cells results in the accumulation of ubiquitinated proteins and three natural proteasome substrates (IkappaB-alpha, Bax, and p27), accompanied by suppression of AR protein expression (in LNCaP cells) and induction of apoptosis. Treatment of PC-3 tumor-bearing nude mice with Celastrol (1-3 mg/kg/d, i.p., 1-31 days) resulted in significant inhibition (65-93%) of the tumor growth. Multiple assays using the animal tumor tissue samples from both early and end time points showed in vivo inhibition of the proteasomal activity and induction of apoptosis after Celastrol treatment. Our results show that Celastrol is a natural proteasome inhibitor that has a great potential for cancer prevention and treatment.
Yang
Huanjie
H
The Prevention Program, Barbara Ann Karmanos Cancer Institute, and Department of Pathology, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA.
Chen
Di
D
Cui
Qiuzhi Cindy
QC
Yuan
Xiao
X
Dou
Q Ping
QP
D059002:Androgen Receptor Antagonists; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology; D045786:Diterpenes, Kaurane; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D053978:Pentacyclic Triterpenes; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011817:Rabbits; D011944:Receptors, Androgen / Q000096:biosynthesis; D029757:Tripterygium / Q000737:chemistry; D014315:Triterpenes / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
D059002:Androgen Receptor Antagonists; D004224:Diterpenes; D045786:Diterpenes, Kaurane; D053978:Pentacyclic Triterpenes; D061988:Proteasome Inhibitors; D011944:Receptors, Androgen; D014315:Triterpenes; C011959:oridonin; D002918:Chymotrypsin; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; C050414:celastrol