[3,3-diindolylmethane 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 micromol/L added into the culture fluid; and DIM + IDA groups, with 0. 5 mg/L IDA and DIM 30, 60 or 100 micromol/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 micromol/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 micromol/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.