Analysis of estrogen receptor function in vitro reveals three distinct classes of antiestrogens.

Published

Journal Article

We have developed a series of in vitro models with which to evaluate the biological activity of estrogen receptor (ER) agonists and antagonists. Using a protease digestion assay we show that the conformational changes induced within ER are distinct for agonists and antagonists. However, this assay is unable to discriminate between pure antagonists like ICI164,384 and partial agonists such as 4-OH tamoxifen or keoxifene. Using a chimeric ER-VP16 construct, we demonstrate that both pure antagonists and partial agonists deliver ER to its DNA target within cells. However, the ability of the DNA-bound receptor to activate transcription in the presence of a given antagonist is dependent on cell and promoter context. These data, suggesting functional differences among ER antagonists, were confirmed by additional experiments demonstrating that their ability to modulate the transcriptional activity of a series of ER mutants is dramatically different. Depending on the cell and promoter context and the particular ER form expressed, 4-OH tamoxifen and the related compound, keoxifene, functioned as partial agonists. Importantly, the transcriptional profiles of these two compounds were dissimilar, suggesting that they are functionally different from each other and from ICI164,384, which does not display agonist activity under any context examined. Our results reveal functional differences between these clinically important antiestrogens and suggest that the distinct biologies manifest by these compounds in vivo relate to their ability to differentially regulate ER function.

Full Text

Duke Authors

Cited Authors

  • McDonnell, DP; Clemm, DL; Hermann, T; Goldman, ME; Pike, JW

Published Date

  • June 1995

Published In

Volume / Issue

  • 9 / 6

Start / End Page

  • 659 - 669

PubMed ID

  • 8592512

Pubmed Central ID

  • 8592512

International Standard Serial Number (ISSN)

  • 0888-8809

Digital Object Identifier (DOI)

  • 10.1210/mend.9.6.8592512

Language

  • eng

Conference Location

  • United States