Small Molecule Inhibitors as Probes for Estrogen and Androgen Receptor Action

Shapiro, David J.; Mao, Chengjian; Cherian, Milu T.

doi:10.1074/jbc.r110.203026

Cited by 31 publications

(24 citation statements)

References 50 publications

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“…Blocking ERα functioning is the major treatment modality in luminal breast cancer (33)(34)(35). Most efforts to modulate the ERα activity have focused on a single pocket buried in the ERα protein, where agonists, antagonists, and selective modulators interact with ERα: the ligand-binding pocket.…”

Section: Discussionmentioning

confidence: 99%

Interaction of 14-3-3 proteins with the Estrogen Receptor Alpha F domain provides a drug target interface

Leeuwen

Pereira

Flach

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

126

180

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Estrogen receptor alpha (ERα) is involved in numerous physiological and pathological processes, including breast cancer. Breast cancer therapy is therefore currently directed at inhibiting the transcriptional potency of ERα, either by blocking estrogen production through aromatase inhibitors or antiestrogens that compete for hormone binding. Due to resistance, new treatment modalities are needed and as ERα dimerization is essential for its activity, interference with receptor dimerization offers a new opportunity to exploit in drug design. Here we describe a unique mechanism of how ERα dimerization is negatively controlled by interaction with 14-3-3 proteins at the extreme C terminus of the receptor. Moreover, the small-molecule fusicoccin (FC) stabilizes this ERα/14-3-3 interaction. Cocrystallization of the trimeric ERα/ 14-3-3/FC complex provides the structural basis for this stabilization and shows the importance of phosphorylation of the penultimate Threonine (ERα-T 594 ) for high-affinity interaction. We confirm that T 594 is a distinct ERα phosphorylation site in the breast cancer cell line MCF-7 using a phospho-T 594 -specific antibody and by mass spectrometry. In line with its ERα/14-3-3 interaction stabilizing effect, fusicoccin reduces the estradiol-stimulated ERα dimerization, inhibits ERα/chromatin interactions and downstream gene expression, resulting in decreased cell proliferation. Herewith, a unique functional phosphosite and an alternative regulation mechanism of ERα are provided, together with a small molecule that selectively targets this ERα/14-3-3 interface.T he estrogen receptor alpha (ERα) is a ligand-dependent transcription factor and the driving force of cell proliferation in 75% of all breast cancers. Current therapeutic strategies to treat these tumors rely on selective ER modulators (SERMs), like tamoxifen (TAM) (1) or aromatase inhibitors (AIs) that block estradiol synthesis (2). Although the benefits of treating hormone-sensitive breast cancers with SERMs and AIs are evident, resistance to treatment is commonly observed (3, 4). To overcome resistance, selective ERα down-regulators (SERDs) can for instance be applied that inhibit ERα signaling through receptor degradation (5, 6). Approaches that target the ERα/ DNA or ERα/cofactor interactions are explored as well (5, 7), but other essential steps in the ERα activation cascade are currently unexploited in drug design, also due to a lack of molecular understanding of the processes at hand.One such step that is crucial for many aspects of ERα functioning is ligand-driven receptor dimerization (8, 9). 17β-Estradiol (E2) association with the ERα ligand binding domain (LBD) drives large conformational changes (10) resulting in ERα dissociation from chaperones (11, 12), unmasking of domains for receptor dimerization, and DNA binding (13,14). Whereas the LBD contains the main dimerization domain (15), the extreme C-terminal domain of the receptor (F domain) imposes a restraint on dimerization (15, 16), although the regulation of this remain...

show abstract

Section: Discussionmentioning

confidence: 99%

Interaction of 14-3-3 proteins with the Estrogen Receptor Alpha F domain provides a drug target interface

Leeuwen

Pereira

Flach

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

126

180

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show abstract

“…Targeting other portions of the hormone receptors themselves has also evoked interest. Small molecule inhibitors target alternative binding sites on the estrogen and androgen receptor, which may result in improved selectivity or novel interactions (Shapiro et al, 2011). Likewise, while estrogen and progesterone receptor expression does correlate with response to antihormonal therapy, those patients without receptor expression also experience some benefit.…”

Section: Discussionmentioning

confidence: 99%

Steroid Hormones and Ovarian Cancer

King¹,

Wong²

2011

Steroids - Clinical Aspect

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“…Although ERa is a well-validated drug target for treating estrogenopathies including breast cancers, it is far from being fully exploited Shapiro et al, 2011). In particular, the target sites on this protein are far from exhaustively defined.…”

Section: Discussionmentioning

confidence: 99%

“…Currently, almost all ER modulators in clinical use interact with the classical ligand-binding pocket (Dai et al, 2008), which is well characterized (Eiler et al, 2001). But therapeutics that target ER by means other than those currently available may be useful in the treatment of endocrine resistant breast cancers (Moore et al, 2010;Shapiro et al, 2011). In particular, we are interested in finding new ligands whose interaction with ER is not affected by the presence or absence of other known ligands (i.e., estrogens, DNA, or other factors).…”

mentioning

confidence: 99%

In Search of Novel Drug Target Sites on Estrogen Receptors Using RNA Aptamers

Chatakonda²,

Kourtidis³

et al. 2014

Nucleic Acid Therapeutics

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Estrogen receptor a (ERa) is a well-validated drug target for a majority of breast cancers. But the target sites on this receptor are far from exhaustively defined. Almost all ER antagonists in clinical use function by binding to the ligand-binding pocket to occlude agonist access. Resistance to this type of drugs may develop over time, not caused by the change of ERa itself, but by changes in ER associated proteins. This observation is fueling the development of reagents that downregulate ER activity through novel binding sites. However, it is challenging to find general ER antagonists that act independently from other known ER ligands. In this report, we describe the utility of RNA aptamers in the search for new drug target sites on ERa. We have identified three high affinity aptamers and characterized one of them in detail. This aptamer interacted with ERa in a way not affected by the presence or absence of either the steroidal ligands or the estrogen response DNA elements, and effectively inhibited ER-mediated transcriptional activation in a breast cancer cell line. Serving as a novel drug lead, it may also be used to guide the rational chemical synthesis of small molecule drugs or to perform screens of small molecule libraries for those that are able to displace the aptamer from its binding site.

show abstract

Small Molecule Inhibitors as Probes for Estrogen and Androgen Receptor Action

Cited by 31 publications

References 50 publications

Interaction of 14-3-3 proteins with the Estrogen Receptor Alpha F domain provides a drug target interface

Interaction of 14-3-3 proteins with the Estrogen Receptor Alpha F domain provides a drug target interface

Steroid Hormones and Ovarian Cancer

In Search of Novel Drug Target Sites on Estrogen Receptors Using RNA Aptamers

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