*2.3. Cell Viability Assay*

To assess cell viability after the PFD treatments, LNCaP, E9, F10, AIDL, and PC-3 cells were plated in 12-well plates at 5 × 10<sup>4</sup> to 1 × 10<sup>5</sup> cells/well. PFD (0.1 and 0.3 mg/mL) or vehicle-only (0.1% dimethyl sulfoxide [DMSO]) was added on day two, and the cells were cultured for an additional three days. The cells were detached by trypsinization and counted using the Countess II Automated Cell Counter (Thermo Fisher Scientific Inc., Waltham, MA, USA). Cell viability was assessed by trypan blue exclusion assay.
