Abstract: ObjectiveEffect of polysaccharides from the Undaria Pinnatifida on the inhibition of gastric carcinoma cell BGC-823 and its mechanism were studied. MethodsAfter treatment with polysaccharides from the Undaria Pinnatifida at different concentrations (25, 50, 100 μg/ml)for 24 h, 48 h, 72 h, the inhibitory effect on proliferation of BGC-823 cells was analyzed by MTT method. After treatment with polysaccharides from the Undaria Pinnatifida under different concentrations (2.5, 50, 100 μg/ml) for 48 h, the cell structures were observed by transmission electron microscope.The cell apoptotic ratio of BGC-823 cells was measured with flow cytometry (FCM) and the expression of survivin mRNA was detected by RT-PCR. ResultsPolysaccharides from the Undaria Pinnatifida inhibited the proliferation of BGC-823 cells significantly in a concentration-depending manner (P<0.05).The IC50 was 38.13μg/ml,after treatment with polysaccharides from the Undaria Pinnatifida in different concentrations for 24 h.The cell apoptosis of BGC-823 cells were induced significantly and have a characteristic structure changes of apoptosis. The apoptotic ratio is 69.91% treated with 100 μg/ml of PUP,and the expression level of survivin mRNA were decreased significantly (P<0.01). ConclusionPUP can inhibit the proliferation, inducing apoptosis of BGC-823 cell. This effect was associated with the down-regulation expression of survivin gene.