Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC)
Affiliation: The Scripps Research Institute, TSRI
Assay Provider: Patrick Griffin, TSRI
Network: Molecular Library Probe Production Centers Network (MLPCN)
Grant Proposal Number: CA134873
Grant Proposal PI: Patrick Griffin, TSRI
External Assay ID: SF1_INH_LUMI_1536_3XIC50 DCSRUN for LRH1 IAG

Name: Counterscreen for inverse agonists of the liver receptor homolog-1 (LRH-1; NR5A2): Luminescence-based cell-based high throughput dose response assay to identify inverse agonists of the Steroidogenic Factor 1 Nuclear Receptor (SF1; NR5A1).

Description:

The goal of this project is to identify modulators (inverse agonists) of the orphan nuclear receptor LRH-1, which has been implicated in cancer by enhancing proliferation and cell cycle progression and metabolic disorders through its regulation of genes involved cholesterol and bile acid homeostasis.

NR5A2 or Liver receptor homologue-1 (LRH-1) is a member of the NR5A, or Ftz-F1, subfamily V nuclear receptors for which there are four members (1). Murine LRH-1 was originally identified due to its sequence homology to the Drosophila Fushi tarazu factor-1 but orthologs have been subsequently identified in several other species including rat, chicken, horse, zebrafish and human (2-7). LRH-1, and its closest family member steroidogenic factor-1 (SF-1, NR5A1), bind to identical DNA consensus sequences (response elements or REs) and both have the ability to bind phospholipids in their ligand binding domains (LBDs) (8-10). However, LRH-1 and SF-1 are expressed in different tissues and thus are considered likely to have non-overlapping, non-redundant functions. SF-1 expression is confined to steroidogenic tissues and adrenals where it regulates development, differentiation, steroidogenesis and sexual determination (5, 7, 11). LRH-1 is highly expressed in tissues of endodermal origin and its expression is essential for normal liver, intestine, and pancreas function. LRH-1 has also been shown to be expressed in the ovary and adipose tissue.

In a recent report, Chand and colleagues investigated the mechanism of action of LRH-1 in invasive breast cancer cells. They found that LRH-1 promotes motility and cell invasiveness in both ER-positive (MCF-7) and ER-negative (MDA-MB-231) breast cancer cells and similar effects were observed in non-tumorigenic mammary epithelial cells. Interestingly, both remodeling of the actin cytoskeleton and E-cadherin processing were observed when LRH-1 was over-expressed. These findings implicate LRH-1 in promotion of migration and invasion in breast cancer independent of estrogen sensitivity. Together these findings provided strong evidence that LRH-1 plays a significant role in tumor formation both in vitro and in vivo. Therefore, the identification of potent and selective LRH-1 inverse agonists may provide new approaches for the treatment of cancer.

References:

1. Fayard, E., J. Auwerx, and K. Schoonjans, LRH-1: an orphan nuclear receptor involved in development, metabolism and steroidogenesis. Trends Cell Biol, 2004. 14(5): p. 250-60.
2. Galarneau, L., J.F. Pare, D. Allard, D. Hamel, L. Levesque, J.D. Tugwood, S. Green, and L. Belanger, The alpha1-fetoprotein locus is activated by a nuclear receptor of the Drosophila FTZ-F1 family. Mol Cell Biol, 1996. 16(7): p. 3853-65.
3. Kudo, T. and S. Sutou, Molecular cloning of chicken FTZ-F1-related orphan receptors. Gene, 1997. 197(1-2): p. 261-8.
4. Boerboom, D., N. Pilon, R. Behdjani, D.W. Silversides, and J. Sirois, Expression and regulation of transcripts encoding two members of the NR5A nuclear receptor subfamily of orphan nuclear receptors, steroidogenic factor-1 and NR5A2, in equine ovarian cells during the ovulatory process. Endocrinology, 2000. 141(12): p. 4647-56.
5. Broadus, J., J.R. McCabe, B. Endrizzi, C.S. Thummel, and C.T. Woodard, The Drosophila beta FTZ-F1 orphan nuclear receptor provides competence for stage-specific responses to the steroid hormone ecdysone. Mol Cell, 1999. 3(2): p. 143-9.
6. Ellinger-Ziegelbauer, H., A.K. Hihi, V. Laudet, H. Keller, W. Wahli, and C. Dreyer, FTZ-F1-related orphan receptors in Xenopus laevis: transcriptional regulators differentially expressed during early embryogenesis. Mol Cell Biol, 1994. 14(4): p. 2786-97.
7. Lavorgna, G., H. Ueda, J. Clos, and C. Wu, FTZ-F1, a steroid hormone receptor-like protein implicated in the activation of fushi tarazu. Science, 1991. 252(5007): p. 848-51.
8. Li, Y., M. Choi, G. Cavey, J. Daugherty, K. Suino, A. Kovach, N.C. Bingham, S.A. Kliewer, and H.E. Xu, Crystallographic identification and functional characterization of phospholipids as ligands for the orphan nuclear receptor steroidogenic factor-1. Mol Cell, 2005. 17(4): p. 491-502.
9. Solomon, I.H., J.M. Hager, R. Safi, D.P. McDonnell, M.R. Redinbo, and E.A. Ortlund, Crystal structure of the human LRH-1 DBD-DNA complex reveals Ftz-F1 domain positioning is required for receptor activity. J Mol Biol, 2005. 354(5): p. 1091-102.
10. Krylova, I.N., E.P. Sablin, J. Moore, R.X. Xu, G.M. Waitt, J.A. MacKay, D. Juzumiene, J.M. Bynum, K. Madauss, V. Montana, L. Lebedeva, M. Suzawa, J.D. Williams, S.P. Williams, R.K. Guy, J.W. Thornton, R.J. Fletterick, T.M. Willson, and H.A. Ingraham, Structural Analyses Reveal Phosphatidyl Inositols as Ligands for the NR5 Orphan Receptors SF-1 and LRH-1. Cell, 2005. 120(3): p. 343-355.
11. Luo, X., Y. Ikeda, and K.L. Parker, A cell-specific nuclear receptor isa essential for adrenal and gonadal development and sexual differentiation. Cell, 1994. 77(4): p. 481-90.

Keywords:

DCSRUN, counterscreen, SF-1, StAR, NR5A1, dose response, dose, titration, crc, triplicate, HTS, high throughput, 1536, Nuclear receptor, NR, CYP7A promoter-binding factor; alpha-1-fetoprotein transcription factor; b1-binding factor, hepatocyte transcription factor which activates enhancer II of hepatitis B virus; fetoprotein-alpha 1 (AFP) transcription factor; hepatocytic transcription factor; liver receptor homolog 1; liver receptor homolog-1; nuclear receptor NR5A2; nuclear receptor subfamily 5 group A member 2, LRH1, liver, activator, inverse agonist, transcriptional assay, luciferase, luminescence, Scripps Florida, The Scripps Research Institute Molecular Screening Center, SRIMSC, Molecular Libraries Probe Production Centers Network, MLPCN.

Assay Overview:

The purpose of this assay is to determine dose response curves of compounds deemed promising after beeing evaluated in single-dose, triplicate experiments in the LRH-1, SF-1, VP16 and StAR promoter assays (AIDs 651613, 651614, 651615 and 651611, respectively).

This assay is specifically designed to determine whether or not previously selected compounds are strictly selective towards LRH-1, by assesing their inhibition potency again its closest homolog, SF-1.

This assay determines dose response SF-1 inhibition curves for compounds. This cell-based assay employs HEK293 cells co-transfected with an SF-1 expression vector (to activate expression of the StAR reporter), and a luciferase reporter driven by the promoter of the SF-1 target gene, Steroidogenic acute regulatory protein (StAR). As designed, compounds that inhibit SF-1 activity will prevent SF-1-mediated activation of the 5xSFRE StAR-luciferase reporter, leading to a decrease in well luminescence. Compounds are tested in triplicate using a 10-point 1:3 dilution series starting at a maximum nomimal test concentration of 36 uM.

Protocol Summary:

Seven million HEK293 cells were seeded in T-175 flasks 23 mL of DMEM media supplemented with 10% v/v fetal bovine serum and 1% v/v Anti-Anti. Flasks were then incubated for 48 hours at 37 C, 5% CO2 and 95% relative humidity (RH). The day prior to run the assay, cells were harvested using TrypLE, resuspended in fresh media at a density of 1 million cells per mL and seeded into new T-175 flasks (23 mL per flask). After being allowed to attach for one hour at 37 C, 5% CO2 and 95% RH, cells were transfected with 1 mL of preincubated mix of serum-free OptiMEM containing 23 ug of the StAR-Luc reporter plasmid, 11.5 ug of the SF-1 expression vector and 80 uL of transfection reagents. Twenty four hours post transfection, cells were harvested using 5 mL of TrypLE and resuspended at a concentration of 750,000 cells per mL in phenol-red free DMEM media supplemented as described above.

The assay was started by dispensing 5 uL of cell suspension into each well of a white, solid-bottom 1536-well plate using a flying reagent dispenser (i.e. 3,750 cells per well). The first two columns received cells transfected with the reporter plasmid only (no cotransfection with the SF-1 expressing vector) as a control for background luminescence (no SF-1 cells). Cells were then treated with 18 nL/well of test compounds or DMSO as a negative control (final concentration 0.36%) using a PinTool transfer unit (GNF). Plates were then placed in the incubator at 37 C, 5% CO2 and 95%RH. Twenty four hours later, plates were removed from the incubator and equilibrated to room temperature for 10 minutes. Luciferase was detected by adding 5 uL per well of ONE-Glo luciferase detection reagent. After a 15 minutes incubation time, light emission was measured with the ViewLux reader (PerkinElmer).

The percent inhibition for each compound was calculated as follows:

%_Inhibition = ( 1 - ( Median_Positive_Control - Test_Compound ) / ( Median_Positive_Control - Median_Negative_Control ) * 100

Where:

Test_Compound is defined as wells containing test compound.
Low_Control is defined as wells containing DMSO.
High_Control is defined as wells containing cells transfected with the reporter only (no SF-1 expressed).

For each test compound, percent inhibition was plotted against compound concentration. A four parameter equation describing a sigmoidal dose-response curve was then fitted with adjustable baseline using Assay Explorer software (Accelrys Inc). The reported IC50 values were generated from fitted curves by solving for the X-intercept value at the 50% activation level of the Y-intercept value. In cases where the highest concentration tested (i.e. 36 uM) did not result in greater than 50% activation, the IC50 was determined manually as greater than 36 uM.

PubChem Activity Outcome and Score:

Compounds with an IC50 greater than 10 uM were considered inactive. Compounds with an IC50 equal to or less than 10 uM were considered active.

Any compound with a percent activity value < 50% at all test concentrations was assigned an activity score of zero. Any compound with a percent activity value >= 50% at any test concentration was assigned an activity score greater than zero.

Activity score was then ranked by the potency of the compounds with fitted curves, with the most potent compounds assigned the highest activity scores.

The PubChem Activity Score range for active compounds is 100-70, and for inactive compounds 70-0.

List of Reagents:

HEK-293 cells (ATCC, part CRL-1573)
DMEM media (Invitrogen, part 11965)
Fetal Bovine Serum (Hyclone, part SH30088.03)
Anti-Anti (Gibco, part 15240)
TrypLE (Invitrogen, part 12604)
T-175 flasks (Falcon, part 353112)
StAR-Luc plasmid (Assay Provider)
SF-1 expression vector (Assay Provider)
TransIT 293 transfection reagent (Mirus Corporation, part MIR-2700)
ONE-Glo luciferase reagent (Promega, part E6130)
White, solid-bottom 1536-well plates (Greiner, part 789173)

Due to the increasing size of the MLPCN compound library, this assay may have been run as two or more separate campaigns, each campaign testing a unique set of compounds. All data reported were normalized on a per-plate basis. Possible artifacts of this assay can include, but are not limited to: dust or lint located in or on wells of the microtiter plate, and compounds that modulate well luminescence. All test compound concentrations reported above and below are nominal; the specific test concentration(s) for a particular compound may vary based upon the actual sample provided by the MLSMR. The MLSMR was not able to supply all compounds selected for testing in this assay.

Assay: Dictionary: Version: 0.1

Assay: CurveFit [1]: Equation: =( ( [Maximal Response] * [Concentration]^[Hill Slope] ) / ( [Inflection Point Concentration]^[Hill Slope] + [Concentration]^[Hill Slope] ) ) + [Baseline Response]

Assay: CurveFit [1]: Mask: Excluded Points

Grant Number: CA134873