*2.4. Cell Cycle Analysis*

LNCaP or PC-3 cells (1.5 × 10<sup>5</sup> cells) were seeded into 100-mm culture dishes (Sumitomo Bakelite Co., Ltd., Tokyo, Japan). Twenty-four hours after seeding, the cells were treated with 0.1 or 0.3 mg/mL PFD or vehicle (0.1% DMSO) for 24 h. After treatment, the cells were isolated, and the nuclei were stained using the BD Cycletest Plus DNA Reagent Kit (BD Biosciences, San Jose, CA, USA). To determine the cell cycle distribution, the DNA content of the stained cells was analyzed using the BD FACS Canto II flow cytometer (BD Biosciences), as described previously [28].
