Mechanism ofPolygonum multiflorum R50 on apoptosis of human colorectal cancer cells

OBJECTIVE To investigate the mechanism of 50% ethanol eluted extract of raw Polygonum multiflorum( R50) on cell cycle and apoptosis of human colorectal cancer cells. METHODS Cell viability was detected by MTT assay after HT29 and HCT116 cells were treated with R50 50-300 mg·L-1for 24,48 and 72 h,respectively. Cell cycle and apoptosis were assayed by flow cytometry after the cells were treated with R50 50,100 and 200 mg·L- 1for 48 h. The morphological changes of cells and nuclei were observed under a light microscope in Giemsa staining and the expression of procaspase-3 and Pdcd4proteins was detected by Western blotting after the cells were treated with R50 100 mg·L- 1for 48 h.RESULTS HCT116 and HT29 cells were inhibited by R50 in a time- and concentration-dependent manner. There was no significant change was observed in cell cycle in the two human colorectal cancer cells treated with R50. R50 induced cell apoptosis in a concentration-dependent manner with R50 50,100 and200 mg·L- 1for 48 h. The apoptotic rate of HCT116 cells in R50 200 mg·L- 1group increased to( 27. 65± 1. 62) % from( 5. 85 ±0. 35) % of control group( P 0. 05),and that of HT29 cells in R50 200 mg·L- 1group increased to( 35. 35 ± 0. 35) % from( 10. 25 ± 0. 77) % of control group( P 0. 05). Cell shinkage,nuclear condensation and apoptotic bodies were observed. Procaspase-3 and Pdcd4 proteins were down-regulated in HCT116 and HT29 cells after R50 100 mg·L- 1was treated for 48 h. CONCLUSION R50 inhibits the viability of HCT116 and HT29 cells largely by inducing cell apoptosis through the caspase pathway. The down-regulation of Pdcd4 may be related to cell apoptosis.