Carcinogenesis Advance Access originally published online on June 15, 2005
Carcinogenesis 2005 26(11):1896-1904; doi:10.1093/carcin/bgi155
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Carcinogenesis vol.26 no.11 © Oxford University Press 2005; all rights reserved.
Indole-3-carbinol inhibition of androgen receptor expression and downregulation of androgen responsiveness in human prostate cancer cells
Department of Molecular and Cell Biology and The Cancer Research Laboratory and 1 Department of Nutritional Sciences and Toxicology, The University of California at Berkeley, Berkeley, CA 94720, USA
* To whom correspondence and reprints should be addressed at: Department of Molecular and Cell Biology, 591 LSA, University of California at Berkeley, Berkeley, CA 94720-3200, USA. Tel: +1 510 642 8319; Fax: +1 510 643 6791; Email: glfire{at}berkeley.edu
Indole-3-carbinol (I3C), a naturally occurring compound found in vegetables of the Brassica genus, such as broccoli and cabbage, is a promising anticancer agent previously shown to induce a G1 cell-cycle arrest in the cells of human lymph node carcinoma of prostate (LNCaP) through regulation of specific G1-acting cell-cycle components. Since the androgen receptor (AR) mediates proliferation and differentiation in the prostate and is expressed in nearly all human prostate cancers, the effects of I3C on AR expression and function were examined in LNCaP cells. Immunoblot and quantitative RT–PCR assays revealed that I3C inhibited the expression of AR protein and mRNA levels within 12 h of indole treatment. I3C downregulated the reporter activity of LNCaP cells transiently transfected with an AR promoter-luciferase plasmid, demonstrating that a unique response to I3C is the inhibition of AR promoter activity. In contrast to I3C, the natural I3C dimerization product 3,3'-diindolylmethane, which acts as an androgen antagonist, had no effect on AR expression. To determine the functional significance of the I3C-inhibited expression of AR, the AR-regulated prostate specific antigen (PSA) was utilized as a downstream indicator. I3C downregulated the expression of PSA transcripts and protein levels and inhibited PSA promoter activity, as well as that of a minimal androgen responsive element containing reporter plasmid. Expression of exogenous AR prevented the I3C disruption of androgen-induced PSA expression. Taken together, our results demonstrate that I3C represses AR expression and responsiveness in LNCaP cells as a part of its antiproliferative mechanism.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  L.G. Wang, X.M. Liu, and J.W. Chiao Repression of androgen receptor in prostate cancer cells by phenethyl isothiocyanate Carcinogenesis, October 1, 2006; 27(10): 2124 - 2132. [Abstract] [Full Text] [PDF]
|
|