Human prostate cancer cell lines PC3 (A) and LNCaP (B), and the mouse prostate cancer cell line TRAMP-C2 (C) were treated with multiple concentrations of SLE for 72 h. Total protein was then measured and normalized to vehicle-treated controls (CTL). A dose-dependent inhibition was observed with an IC50 of 167 μg/mL in PC3, 200 μg/mL in LNCaP, and 100 μg/mL in TRAMP-C2, respectively. Each experiment was conducted at least thrice in duplicate. Error bars indicate standard deviation (SD). * P<0.05, ** P<0.01.