Breast cancer is the second cause of cancer death among women.Current therapies for breast cancer have several adverse side-effects.Many studies have suggested that polysaccharides have multiple health benefits to humans.The objective of our study was to assess the anticancer effect of the extract of polysaccharides from selenium-enriched P.fortuneana fruiting bodies.Our extract contained 93.7%(w/w)of carbohydrate,2.1%(w/w)of uronic acid and 3.7 μg/g of selenium,and thus considered as Se-conjugated polysaccharides(Se-PFPs).In vitro studies showed that Se-PFPs inhibited the growth of MDAMB-231 human breast cancer cells in a concentration dependent manner by arresting the cells at the G2 phase of the cell cycle.Treatment with Se-PFPs also caused cell death with increased P53,Bax,Puma and Noxa,decreased Bcl2 but increased Bax/Bcl2 ratio,and increased activities of caspases 3 and 9,suggesting an effect on the P53-mediated cytochrome c-caspase pathway of apoptosis.Treatment of nude mice that bear MDA-MB-231-derived xenograft tumors with Se-PFPs significantly reduced the tumor weight and tumor volume,confirming in vivo antitumor activity,while the animal body weight remained unchanged.Collectively,these results suggest that Se-PFPs may have therapeutic and some chemo-sensitizer effects on breast cancer cells.