Abstract: Objective To explore inhibitive effect of juglone on prostate cancer PC-3 cells.Methods The 3-(4,5 dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide(MTT)assay was used to determine the growth of PC-3 cells treated with different concentrations of juglone.The induction of apoptosis was detected by flow cytometry with annexin V-FITC/PI staining.Western blot was used to detect the expression of apoptosis-associated protein of B-cell lymphoma(Bcl-2)and Bcl-2-associated X protein(Bax).Results Juglone could significantly inhibit the growth of PC-3 cells in dose-dependent manner with the inhibition ratios of 20.6%,39.7%,57.3%,and 66.2%,respectively.Flow cytometry detection showed that the early and late apoptosis rates of PC-3 cells treated with juglone of 25,50,and 100 μmol/L were 7.37% and 2.07%,11.03% and 5.8%,and 18.62% and 8.54%,respectively,and higher than those of the control group(P<0.05).High dose of juglone(≥50 μmol/L)could reduce the expression of apoptosis-regulated protein Bcl-2 and increase the expression of apoptosis-regulated protein Bax(P<0.05).ConclusionJuglone can suppress the growth of PC-3 prostate cancer cells.