In this study,we investigated the molecular mechanism of dandelion polysaccharide (DP) inhibition of breast cancer cells by observing the effects of DP on the proliferation,migration and invasion of human triple-negative breast cancer MDA-MB-231 cells.After treating human breast cancer MDA-MB-231 cells and normal breast epithelial cells MCF-10A with DP,the effect of different concentrations of DP (0,100,200,400,800 μg/mL) on cell viability was detected by CCK-8 method. The effect of DP on the clonogenic ability of breast cancer cells was detected by plate cloning assay.the effect of DP on the migration and invasion ability of breast cancer cells was examined by the scratch assay and Transwell assay.Western blotting was performed to detect phosphatidylinositol 3 kinase (PI3K),phosphorylated phosphatidylinositol 3 kinase (p-PI3K),protein kinase B (Akt),phosphorylated protein kinase B (p-Akt),glycogen synthase kinase-3β (GSK-3β),phosphorylated glycogen synthase kinase-3β (p-GSK-3β) protein expression,epithelial mesenchymal transition (EMT)-related marker proteins E-cadherin,N-cadherin and vimentin expression.The results showed that compared with the blank group,the DP group (100,200,400,800 μg/mL) was able to significantly inhibit the viability of MDA-MB-231 cells (P < 0.05 or P < 0.01),and there was no significant effect on the viability of MCF-10A cells.compared with the blank group,the DP group (200,400 μg/mL) was able to significantly reduce the ability of cell clone formation (P < 0.01).the DP group (200,400 μg/mL) showed significantly reduced migration and invasion ability (P  < 0.01).the DP group (200,400 μg/mL) showed significantly reduced p-PI3K,p-Akt and p-GSK-3β protein expression levels were decreased in the DP group (200,400 μg/mL) compared with the blank group (P < 0.01),while no significant changes were observed in PI3K,Akt and GSK-3β total proteins.E-cadherin expression levels were upregulated,but N-cadherin and Vimentin expression levels were downregulated in the DP group (200,400 μg/mL) compared with the blank group,and the differences were statistically significant (P  < 0.05 or P < 0.01).In conclusion,DP can effectively inhibit the proliferation,migration,invasion and EMT process of human breast cancer MDA-MB-231 cells,and the mechanism may be related to the inhibition of PI3K/Akt/GSK-3β signaling pathway activity.