Sphere formation assay. RWPE-2, CWR-R1, and DU-145 prostate cells were treated in the presence of DEAB at 5, 10 and 20 μM or Ko143 at 1 and 5 μM concentration or vehicle control. Spheres were counted in each well after 10 to 14 days of growth. Sphere forming ability of RWPE-2 cells did not decrease upon treatment with DEAB (A). Sphere formation was decreased in RWPE-2 cells upon treatment with Ko143 at 5 μM concentration (B). Sphere formation was decreased in CWR-R1 cells upon treatment with DEAB (C) or Ko143 (D). Sphere forming ability of DU-145 cells did not decrease upon treatment with DEAB (E) or Ko143 (F).