Luminescence-based cell-based primary high throughput screening assay to identify inhibitors of the Steroid Receptor Coactivator 3 (SRC3; NCOA3)
Name: Luminescence-based cell-based primary high throughput screening assay to identify inhibitors of the Steroid Receptor Coactivator 3 (SRC3; NCOA3). ..more
BioActive Compounds: 620
Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC)
Affiliation: The Scripps Research Institute, TSRI
Assay Provider: Bert O'Malley, Baylor College of Medicine
Network: Molecular Library Probe Production Centers Network (MLPCN)
Grant Proposal Number: 5U19DK062434-09
Grant Proposal PI: Bert O'Malley, Baylor College of Medicine
External Assay ID: SRC3_INH_LUMI_1536_1X%INH PRUN
Name: Luminescence-based cell-based primary high throughput screening assay to identify inhibitors of the Steroid Receptor Coactivator 3 (SRC3; NCOA3).
Chemotherapeutic agents that target estrogen receptor alpha (ERa) and growth factor signaling systems have been extensively pursued and developed for a long time (1-4]). However, one of the most pressing limitations of currently established chemotherapeutic agents for breast cancer is the fact that breast cancers frequently acquire resistance to antiestrogens (5, 6). Nuclear receptors (NR) and other hormone receptors mediate their cellular effects in part through the interaction with coactivators which increase their transcriptional activity. The best characterized coactivator family is the steroid receptor coactivator (SRC) family (7). Given the central role that SRC-3 plays in breast and other cancers, the search for small molecule agents that target SRC-1 and SRC-3 represent an innovative and potentially effective strategy to identify agents to treat hormone-refractory breast cancers and other cancers where these coactivators are overexpressed. Compounds that target the function of steroid receptor coactivator 3 (SRC-3) protein promise to be different because cancer cells are less likely to bypass the comprehensive disruption of multiple growth factor signaling systems that result from the loss of SRC-3 function. In contrast to the goal of screens that seek to interfere with NR-coactivator interactions, the work proposed here aims to identify compounds that specifically target the coactivators themselves. This approach offers to be more broadly applicable. For instance, SRC-1 or SRC-3 typically remains overexpressed in ER negative cancers or acts as a coactivator for other oncogenic transcription factors (8). SMIs that target ERa, on the other hand are largely predicted to duplicate the biological action of antiestrogens such as tamoxifen.
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steroid receptor coactivator 3, SRC3, nuclear receptor coactivator 3, NCOA3, amplified in breast cancer 1 protein, AIB1, cancer, breast cancer, inhibit, inhibitor, coactivator, primary, primary screen, lumi, luminescence, HTS, high throughput screen, 1536, Scripps Florida, The Scripps Research Institute Molecular Screening Center, SRIMSC, Molecular Libraries Probe Production Centers Network, MLPCN.
The purpose of this assay is to identify compounds that act as inhibitors of the steroid receptor coactivator 1 (SRC3), also known as nuclear receptor coactivator 3 (NCOA3). In this assay, HEK293 cells are transfected with a GAL4-responsive reporter plasmid (pGL4.31, Promega) and an expression vector encoding SRC-3 fused to the DNA-binding domain of GAL4(pBIND-SRC-3). The ability of compounds to reduce coactivator transcriptional activity is assessed by measuring luciferase expression from the reporter gene plasmid. As designed, compounds that inhibit SRC3 ability to induce transcription will lead to a decrease in expression of the luciferase gene, resulting in reduced well luminescence. Compounds are tested in singlicate at a final nominal concentration of 3.6 uM.
Seven million HEK293 cells were seeded into T-175 flasks containing 23 mLs 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 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 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 pGL4.31 reporter plasmid, 2.3 ug of pBIND-SRC3 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 (3,750 cells per well). The first two columns received cells transfected with reporter plasmid and an empty pBIND vector as a control for background luminescence. Cells were then treated with 18 nL/well of test compounds, DMSO as a negative control (final concentration 0.36%), or Gossypol as a positive control (36 uM final) 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 activity was detected by adding 5 uL per well of ONE-Glo luciferase detection reagent. After a 15 minute incubation time, light emission was measured using the ViewLux plate reader (PerkinElmer).
The percent inhibition of each test compound was calculated as follows:
%_Inhibition = ( 1 - ( median_positive_control - test_compound ) / ( median_positive_control - median_negative_control ) * 100
Test_Compound is defined as wells containing test compound treated cells.
Positive_Control is defined as wells containing Gossypol treated cells.
Negative_Control is defined as wells containing DMSO treated cells.
PubChem Activity Outcome and Score:
A mathematical algorithm was used to determine nominally active compounds. Two values were calculated: (1) the average percent inhibition of all compounds tested, and (2) three times their standard deviation. The sum of these two values was used as a cutoff parameter, i.e. any compound that exhibited greater %inhibition than the cutoff parameter was declared active.
The reported PubChem Activity Score has been normalized to 100% observed primary inhibition. Negative % inhibition values are reported as activity score zero.
The PubChem Activity Score range for active compounds is 100-64, and for inactive compounds 64-0.
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)
pGL4.31 (Promega, part C935A)
pBIND-SRC3 (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. In this case the results of each separate campaign were assigned "Active/Inactive" status based upon that campaign's specific compound activity cutoff value. 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, cytotoxic compounds, compounds that perturb the UAS/GAL4 reporter system, and compounds that quench, inhibit, stabilize, or emit luminescence within the well. All test compound concentrations reported are nominal; the specific concentration for a particular test compound may vary based upon the actual sample provided by the MLSMR.
Categorized Comment - additional comments and annotations
** Test Concentration.
Data Table (Concise)