Functional polysaccharide Lentinan suppresses human breast cancer growth via inducing autophagy and caspase-7-mediated apoptosis

The aim of this study was to evaluate the direct antitumor activity of edible fungal polysaccharide Lentinan, rather than as a host defence potentiator, on human breast cancer and investigate its underlying mechanisms. The present results revealed that there were 45.46% and 59.16% of inhibitory rate after Lentinan treatment in MCF-7 cells and tumor-bearing athymic nude mice, respectively. Annexin V-FITC/PI, H&E staining and TUNEL assay showed that Lentinan induced cell apoptosis which accompanied with abundant activated caspase-7, increased cytosol cytochrome c and Bax/Bcl-2. Unexpectedly, we firstly demonstrated that Lentinan could stimulate cell autophagy according to the detection of autophagosomes and autophagic flux. Pretreatment with autophagy inhibitors decreased Lentinan-induced cells death. These findings provided new insight into the mechanisms of Lentinan-antitumor effect and contributed to its development in functional foods and cancer therapy.