Late stage Counterscreen for the probe development effort to identify inhibitors of the Steroid Receptor Coactivator 3 (SRC3; NCOA3): Luminescence-based cell-based dose response assay to identify cytotoxic compounds
Name: Late stage Counterscreen for the probe development effort to identify inhibitors of the Steroid Receptor Coactivator 3 (SRC3; NCOA3): Luminescence-based cell-based dose response assay to identify inhibitors of the Steroid Receptor Coactivator 2 (SRC2; NCOA2). ..more
BioActive Compounds: 4
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: HEK293Cytox_INH_LUMI_1536_4XIC50 MDCSRUN for SRC3
Name: Late stage Counterscreen for the probe development effort to identify inhibitors of the Steroid Receptor Coactivator 3 (SRC3; NCOA3): Luminescence-based cell-based dose response assay to identify inhibitors of the Steroid Receptor Coactivator 2 (SRC2; NCOA2).
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.
1. Arteaga, C.L., A.K. Tandon, D.D. Von Hoff, and C.K. Osborne, Transforming growth factor beta: potential autocrine growth inhibitor of estrogen receptor-negative human breast cancer cells. Cancer Res, 1988. 48(14): p. 3898-904.
2. Ciardiello, F., T. Troiani, F. Caputo, M. De Laurentiis, G. Tortora, G. Palmieri, F. De Vita, M.R. Diadema, M. Orditura, G. Colantuoni, C. Gridelli, G. Catalano, S. De Placido, and A.R. Bianco, Phase II study of gefitinib in combination with docetaxel as first-line therapy in metastatic breast cancer. Br J Cancer, 2006. 94(11): p. 1604-9.
3. Goldstein, D., S.M. Bushmeyer, P.L. Witt, V.C. Jordan, and E.C. Borden, Effects of type I and II interferons on cultured human breast cells: interaction with estrogen receptors and with tamoxifen. Cancer Res, 1989. 49(10): p. 2698-702.
4. Riggins, R.B., A. Zwart, R. Nehra, and R. Clarke, The nuclear factor kappa B inhibitor parthenolide restores ICI 182,780 (Faslodex; fulvestrant)-induced apoptosis in antiestrogen-resistant breast cancer cells. Mol Cancer Ther, 2005. 4(1): p. 33-41.
5. Chen, F.L., W. Xia, and N.L. Spector, Acquired resistance to small molecule ErbB2 tyrosine kinase inhibitors. Clin Cancer Res, 2008. 14(21): p. 6730-4.
6. Riggins, R.B., M.M. Mazzotta, O.Z. Maniya, and R. Clarke, Orphan nuclear receptors in breast cancer pathogenesis and therapeutic response. Endocr Relat Cancer, 2010. 17(3): p. R213-31.
7. Lonard, D.M., R. Kumar, and B.W. O'Malley, Minireview: the SRC family of coactivators: an entree to understanding a subset of polygenic diseases? Mol Endocrinol, 2010. 24(2): p. 279-85.
8. Xu, J., R.C. Wu, and B.W. O'Malley, Normal and cancer-related functions of the p160 steroid receptor co-activator (SRC) family. Nat Rev Cancer, 2009. 9(9): p. 615-30.
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The purpose of this assay is to determine whether powder samples of compounds identified as SRC3 inhibitor probe candidates are cytotoxic to HEK293 cells. This assay determines dose response curves.
In this assay, HEK293 cells are incubated with potential SRC3 inhibitors identified during the primary screening campaing. As designed, compounds that affect HEK293 cell viability will lead to a decrease in cellular ATP levels , resulting in reduced well luminescence as detected using a luciferase-based assay that quantifies ATP . Compounds are tested in quadruplicate using a 10-point 1:3 dilution series starting at a nominal test concentration of 36 uM.
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 and resuspended at a concentration of 100,000 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. 500 cells per well). The first two columns received medium only 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 Doxycycline 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 was detected by adding 5 uL per well of CellTiter Glo reagent. After a 15 minutes incubation time, light emission was measured with the ViewLux reader (PerkinElmer). The percent cytotoxicity of each test compound was calculated as follow:
%_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 cell culture medium only.
Negative_Control is defined as wells containing DMSO treated cells.
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 (Symyx Technologies Inc). The reported IC50 values were generated from fitted curves by solving for the X-intercept value at the 50% inhibition level of the Y-intercept value. In cases where the highest concentration tested (i.e. 36 uM) did not result in greater than 50% inhibition, 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 100-71, and for inactive compounds 47-0.
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)
CellTiter Glo reagent (Promega, part G7573)
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, 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.
Categorized Comment - additional comments and annotations
From BioAssay Depositor:
Assay: CurveFit : Equation: =( ( [Maximal Response] * [Concentration]^[Hill Slope] ) / ( [Inflection Point Concentration]^[Hill Slope] + [Concentration]^[Hill Slope] ) ) + [Baseline Response]
Assay: CurveFit : Mask: Excluded Points
Assay: Dictionary: Version: 0.1
Assay Format: Cell-based
Assay Cell Type: HEK293
* Activity Concentration. ** Test Concentration.
Data Table (Concise)