Clioquinol, a therapeutic agent for Alzheimer's disease, has proteasome-inhibitory, androgen receptor-suppressing, apoptosis-inducing, and antitumor activities in human prostate cancer cells and xenografts.
Tumor growth and metastasis depend on angiogenesis that requires the cofactor copper. Consistently, high levels of copper have been found in many types of human cancers, including prostate, breast, colon, and lung. Recent studies suggest that copper could be used as a novel selective target for cancer therapies. Clioquinol is capable of forming stable complexes with copper and currently used in clinics for treatment of Alzheimer's disease. Most recently, it has been reported that clioquinol possesses antitumor effects. However, the underlying molecular mechanism is unclear. We report here that after binding to copper, clioquinol can inhibit the proteasomal chymotrypsin-like activity, repress androgen receptor (AR) protein expression, and induce apoptotic cell death in human prostate cancer LNCaP and C4-2B cells. In addition, clioquinol alone exhibits similar effects in prostate cancer cell lines with elevated copper at concentrations similar to those found in patients. Addition of dihydrotestosterone did not affect clioquinol-mediated proteasome inhibition in both prostate cancer cell lines. However, dihydrotestosterone partially inhibited clioquinol-induced AR suppression and apoptosis only in androgen-dependent LNCaP cells. Animal studies show that clioquinol treatment significantly inhibits the growth of human prostate tumor C4-2B xenografts (by 66%), associated with in vivo proteasome inhibition, AR protein repression, angiogenesis suppression, and apoptosis induction. Our study provides strong evidence that clioquinol is able to target tumor proteasome in vivo in a copper-dependent manner, resulting in formation of an active AR inhibitor and apoptosis inducer that is responsible for its observed antiprostate tumor effect.
Chen
Di
D
Barbara Ann Karmanos Cancer Institute and Department of Pathology, School of Medicine, Wayne State University, 4100 John R Road, Detroit, MI 48201, USA.
Cui
Qiuzhi Cindy
QC
Yang
Huanjie
H
Barrea
Raul A
RA
Sarkar
Fazlul H
FH
Sheng
Shijie
S
Yan
Bing
B
Reddy
G Prem Veer
GP
Dou
Q Ping
QP
D059002:Androgen Receptor Antagonists; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D007464:Clioquinol / Q000378:metabolism / Q000494:pharmacology*; D003300:Copper / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009376:Neoplasms, Hormone-Dependent / Q000098:blood supply / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011480:Protease Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D023041:Xenograft Model Antitumor Assays
D059002:Androgen Receptor Antagonists; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D003300:Copper; D007464:Clioquinol