Patient-derived organoid cultures regain partial sensitivity to targeted therapies in culture.A, pathology and treatment regiments of indicated patients. B and C, representative confocal images (B) and quantifications (C) of 5-ethynyl-2′-deoxyuridine (EdU) positive cells (red) in PDOs treated with vehicle, 500 nM fulvestrant, 1 μM palbociclib, or combination of fulvestrant and palbociclib for 96 h. The scale bar represents 40 μm. Proliferation was assessed by pulsing PDOs with EdU for 4 h and quantifying the ratio of EdU+ cells per total (DAPI+) number of cells in 20 to 30 PDOs from one experiment (#7 and #27) or three independent experiments (#8, #10, and #26). Each data point represents the percentage of EdU+ cells in one PDO, red line indicates the mean ratio of EdU+ cells per treatment group. Student’s t test was used to assess significance comparing each treatment group to vehicle sample. DAPI, 4′,6-diamidino-2-phenylindole; EdU, 5-ethynyl-2′-deoxyuridine; PDOs, patient-derived organoids.