Cell cytotoxicity assay

The RWPE-1 cells were seeded (3 × 10⁴ cells per well) on 96-well plates and incubated in RPMI plus 10% FBS for 24 h. The cells were then incubated in fresh media containing various concentrations of PGWE (0–5 mg/mL) for an additional 24 h. Cell viability was measured using a Quanti-MAX^™ WST-8 cell viability assay kit from Biomax Corporation (Seoul, Korea). Before measuring the viability, the media were removed, replaced with 200 µL of fresh RPMI plus 10% FBS medium, and 10 µL of Quanti-MAX^™ (WST-8) was added to each well. The cells were then incubated for 1 h. The absorbance was measured at 490 nm in a VERSAmax microplate reader (Molecular Devices, Sunnyvale, CA, United States) to determine the formazan concentration, which is proportional to the number of live cells.