Objective: To explore how safflower polysaccharide (SPS) induce apoptosis of human liver cancer cell line SMMC-7721 through observing the influence of SPS on proliferation

apoptosis and expression of apoptosis gene and protein Bax and Bcl-2 of SMMC-7721. Method: SMMC-7721 cells were treated with different concentrations(0

0.02

0.04

0.08

0.16

0.32

0.64

1.28 g·L-1) of SPS. The cells growth inhibitory rate was measured by methyl thiazolyl tetrazolium(MTT) assay. The morphological changes of apoptosis were observed by AnnexinⅤ-FITC/PI staining. The mitochondrial membrane potential(Δψm) was assayed by fluorescent microscopy using Rhodamine 123(Rho123). Quantitative real-time RT-PCR and Western blot analysis were used to detect the mRNA and protein expressions of Bcl-2 and Bax. Result: SPS could inhibit the proliferation of SMMC-7721 cells in a dose and time dependent manner. After treated with SPS

SMMC-7721 cells presented typical apoptosis under fluorescence microscope.Fluorescence intensity of Rho123 were significantly decreased in SMMC-7721 cells. The mRNA and protein expression of Bcl-2 expression were down-regulated while those of Bax were up-regulated and both changes had good time-dependent tendency. The ratio of Bcl-2/Bax decreased significantly in a time-dependent manner. Conclusion: SPS could inhibit the proliferation of SMMC-7721 and enhance apoptosis of SMMC-7721 and its mechanism maybe relate with its up-regulation of Bax expression as well as down-regulation of Bcl-2 expression and decline of Δψm.