3,3-diindolyimethane enhances the inhibitory effect of idarubicin on the growth of human prostate cancer cells

Objective To study the effects of idarubicin(IDA)combined with 3,3-diindolylmethane(DIM)on the growth inhibition of human prostate cancer cells. Methods Human prostate cancer cells of the line PC-3M were cultured and then divided into the following groups: control group with solvent added into the culture fluid: IDA groups, with IDA of the terminal concentrations of 0.5,1 or 5 mg/L added into the culture fluid; DIM groups, with DIM of the terminal concentrations of 30,60 or 100 μmol/L added into the culture fluid; and DIM+IDA groups, with 0.5 mg/L IDA and DIM 30,60 or 100 μmol/L added into the culture fluid.48 h later the cell growth inhibition rate was detected by MTT assay. Flow cytometry and acridine orange staining were used to detect the cell cycle and apoptosis. RT-PCR and Western blotting were used to detect the mRNA and protein expression of caspase 9,an apoptosis gene. Results Both IDA and DIM dose-dependently inhibited the growth of the PC-3M cells. The growth inhibition rate of the 60 μmol/L DIM+0.5 mg/L IDA group was 69.9%,almost 10 times as that of the 0.5 mg/L IDA group. The apoptosis rate of the 60 μmol/L DIM+0.5 mg/L IDA group was 47.0%,significantly higher than that of the 0.5 mg/L IDA group(3.2%,P＜0.05).RT-PCR and Western blotting showed- that the combination of DIM and IDA significantly enhanced the mRNA and protein expression of caspase 9. Conclusion DIM enhances the growth inhibition effect of IDA on human prostate cancer cells by the mechanism of induction of apoptosis. Key words: Prostatic neoplasms; Apoptosis; DIM; IDA