Abstract: ObjectiveTo explore the underlying mechanism responsible for formononetin-induced apoptosis of bladder cancer cells in vitro.MethodsHuman bladder cancer cells T-24 and BIU-87 were exposed to different doses of formononetin(20,40,and 80 μmol/L).Thiazolyl blue tetrazolium bromide(MTT)assay was applied to determine the effect of formononetin on proliferation of T-24 and BIU-87 cells;the apoptosis was assessed with flow cytometry and Hoechst 33258 staining.Next,the expression level of Bcl-2 mRNA in T-24 cells was analyzed with real-time reverse transcription polymerase chain reaction(RT-PCR).The expressions of p-p38 and Bcl-2 proteins in T-24 cells were determined with Western blot.ResultsCompared with the control group,the formononetin at the doses of 40 and 80 μmol/L significantly suppressed the proliferation of T-24 and BIU-87 cells,while the apoptotic rate increased significantly.The Hoechst 33258 staining results showed that T-24 cells exhibited typical apoptotic morphology.Compared with the control group,formononetin effectively reduced the expression of Bcl-2 mRNA(0.701±0.029 for 40 μmol/L group and 0.408±0.036 for 80 μmol/L group)in T-24 cells(all P<0.01).Compared with the control group,formononetin effectively increased the expression of P38 protein(0.483±0.026 for 20 μmol/L group and 0.569±0.031 for 80 μmol/L group)in T-24 cells(all P<0.01).Compared with the control group,formononetin effectively reduced expression of Bcl-2 protein(0.998±0.034 for 20 μmol/L group,0.591±0.030 for 40 μmol/L group,and 0.426±0.027 for 80 μmol/L group)in T-24 cells(all P<0.01).ConclusionFormononetin could inhibit the growth of bladder cancer cells by induction of apoptosis,which may be related to the inhibition of Bcl-2 expression and activation of P38 protein.