| In Vitro | In vitro activity: In neuroblastoma cell lines, GSK1324726A inhibits cell growth and induces cytotoxicity. GSK1324726A also modulates expression of genes involved in apoptosis, signaling, and MYC-family pathways, including the direct suppression of BCL2 and MYCN.
Kinase Assay: For determination of binding affinities to BET protein bromodomains, I-BET726 is titrated against truncates containing both BD1 and BD2 of BRD2 (10 nM), BRD3 (10 nM), and BRD4 (10 nM) in 50 mM HEPES pH7.5, 150 mM NaCl, 5% Glycerol, 1 mM DTT and 1 mM CHAPS in the presence of an Alexa 647 derivative (50 nM) of fluorescent ligand. After equilibrating for 1 h, the bromodomain protein: ligand interaction is detected using Time Resolved Fluorescence Resonance Energy Transfer (TR-FRET) following the addition of 1.5 nM europium chelate labeled anti-6His antibody. Plates are read using an Envision Plate reader (λEX = 337 nm, λEM = 615 nm, λEM = 665 nm; dual dichroic = 400 nm & 630 nm). These data are fitted to a four parameter IC50 model using Graphit data analysis software.
Cell Assay: Briefly, cells (LA-N-1, Kelly, LA1-55n, BE(2)-M17, BE(2)-C, KanTS, IMR32, LA-N-2, SK-N-SH, SK-N-BE(2), CHP-134, SK-N-AS, SH-SY5Y, SK-N-FI, CHP-212, LA1-5s, SK-N-DZ cells) are seeded into 384-well or 96-well plates at a density optimized for 6 days of growth. The following day, T0 measurements are taken using CellTiter-Glo, CellTiter-Fluor, or CyQuant Direct, following the manufacturer’s instructions. Plates are read on an Envision, Safire 2, or SpectraMax Gemini EM plate reader. Remaining plates are treated with DMSO or a titration of I-BET726. Cells are incubated for 6 days and developed as described above. Results are plotted as a percentage of the T0 value, normalized to 100%, versus concentration of compound. A 4-parameter equation is used to generate concentration response curves. Growth IC50 (gIC50) values are calculated at the mid-point of the growth window (between DMSO and T0 values). Ymin-T0 values are calculated by subtracting the T0 value (100%) from the Ymin value on the curve, and are a measure of net population cell growth or death. |
|---|