PamGene and it's collaborators presented the following posters at the Society of Toxicology's 54th Annual Meeting in San Diego, California (March 22nd to 26th 2015). 
You can directly download PDF copies of the Posters:
2478 Functional characterization of compounds by their ability to modulate Farnesoid X receptor interaction with a coregulator motif peptide array reveals multiple modes of action
Poster Session: Late-Breaking Poster Session 1, Poster Board: 110, Date & Time: March 26th, 08:30-12:00
René Houtman1, Chia-Wen Hsu2, Menghang Xia2, Rinie van Beuningen1 & John P. Groten1
1 PamGene, Den Bosch, The Netherlands and 2 NCATS, NIH, Bethesda, MD, USA

The nuclear receptor (NR) Farnesoid X receptor (FXR) regulates the homeostasis of bile acids, lipids, and glucose. Because endogenous chemicals bind and activate FXR, it is important to examine which xenobiotic compounds would disrupt normal receptor function and cause potential toxicity effects including cholestasis and cancer. Upon compound binding, NR-dependent gene expression is dictated by the nature of, a multitude of, recruited coregulators that regulate the chromatin accessibility at the target gene locus. Therefore compounds that induce similar FXR-coregulator interaction profiles are expected to display similar pharmacology, while differential interactions are indicative for a different mode of action. In the current study, a set of 12 FXR antagonists (i.e. (Z)-guggulsterone, ivermectin, chlorophacinone and their analogs) identified previously from the Tox21 10K library screening using a cell-based human FXR β-lactamase (Bla) reporter gene assay were characterized for their ability to modulate the coregulator interaction of CDCA-activated FXR using a peptide micro array with 154 coregulator-derived motifs. We found that chlorophacinone and ivermectin (100 and 90% efficacy resp.) are the most efficacious inhibitors of FXR-SRC2-2 interactions, consistent with the results measured from an orthogonal coactivator assay. All of the identified FXR antagonists showed significant modulation of all CDCA-induced FXR-coregulator interactions, i.e. displacement of coactivators (gene transcription enhancers), and profiles allowed us to sub-classify the chemically related compounds. Interestingly, the ivermectin analogs distinctively displayed enhancement of corepressor interaction, which may explain their superior antagonism over the other compounds. These results suggest that FXR-coregulator interaction profiling provides a novel method to classify the mechanism of action for the structure related compounds.

2322 (Ant)agonist-Induced Modulation of ERα and ERβ Cointeraction
Poster Session: Receptors, Poster Board: 616, Date & Time: March 25th, 13:00-16:30
L. de Haan1, N. Evers1, S. Wang1, J. H. van den Berg1, R. Houtman2,
J. P. Groten2,1 and I. Rietjens1.
1 Toxicology, Wageningen University, Wageningen, Netherlands and 2 Toxicology, Pamgene International B.V., ‘s Hertogenbosch, Netherlands.

The aim of the present study was to investigate the ligand-induced interactions of the estrogen receptor (ER)α and ERβ with nuclear coregulators. To this end, two agonists (estradiol and genistein) and two antagonists (4-hydroxytamoxifen and fulvestrant) were characterized for intrinsic relative potencies and efficacy towards ERα and ERβ using ER selective U2OS reporter gene assays. Ligand-dependent modulation of ERα and ERβ interaction with 154 unique coregulator-derived peptides was characterised using MARCoNI (Microarray Assay for Real-time Coregulator- Nuclear Receptor Interaction). Modulation of the interaction of ERα and ERβ with co-regulators by a specific agonist are very similar indicating only a limited number of differences between both receptor subtypes upon activation by a specific ligand. Differences in modulation of the interaction of the ERs with coregulators by different (ant)agonists were more pronounced, enabling a qualitative discrimination between different agonists and antagonists for the same receptor (1-4). 1. N.M. Evers, S. Wang, J.H.J. van den Berg, R. Houtman, D. Melchers, L.H.J. de Haan, A.G.H. Ederveen, J.P. Groten, I.M.C.M. Rietjens. Chemico-Biol. Interactions 220 (2014) 222–230. 2 N.M. Evers, J.H.J. van den Berg, S. Wang, D. Melchers, R. Houtman, L.H.J. de Haan, A.G.H. Ederveen, J.P. Groten, I.M.C.M. Rietjens. J. of Steroid Biochemistry & Molecular Biology 143 (2014) 376–385. 3. S. Wang, R. Houtman, D. Melchers, J.M.M.J.G. Aarts, A.A.C.M. Peijnenburg, R.M.G.J. van Beuningen, I.M.C.M. Rietjens, and T.F.H. Bovee. Altex 30 (2013) 145-157. 4. J.M.M.J.G. Aarts, S. Wang, R. Houtman, R.M.G.J. van Beuningen, W. M.A. Westerink, B.J. van de Waart, I.M.C.M. Rietjens, T.F.H. Bovee. Chem. Res. Tox. 26 (2013) 336-346.