The indicated cell lines were seeded in 96-well (3×103 cells/well) plates and cultured in 100 ul medium containing 10% serum. After 24 hours, cells were treated with or without various concentrations of compounds in 50 μl medium for 24 to 48 hours and the cell viability was measured using the Cell Titer Glo (Promega) according to the manufacturer’s instructions. The cell viability assay for the human prostate organoid MSK-PCaX cells were performed as described previously 35 (link), 39 (link). For 2-D culture, 5,000 organoids cells per well of a collagen coated 96-well cell culture were plated in 100 ul complete human media with vehicle (DMSO) control or JQ1 (10–3000 nM). Viable cells were counted using CellTiter-Glo (Promega) Luminescent Cell Viability Assay after 72 hours treatment. All cell viability experiments were conducted in triplicate. For 3-D culture, 5,000 organoids cells in 10 ul Matrigel per well were plated in 96-well cell culture plate. Viable cells under 3-day-treatment of 100 ul complete human media with vehicle (DMSO) control or JQ1 (10–3000 nM) were counted using CellTiter-Glo (Promega) Luminescent Cell Viability Assay. Data was shown as mean ± SD from three independent experiments.