Peptides extracted from edible mushroom: Lentinus squarrosulus induces apoptosis in human lung cancer cells.

Context: Lentinus squarrosulus Mont. (Polyporaceae) is an interesting source of diverse bioactive compounds. Objective: This is the first study of the anticancer activity and underlying mechanism of peptides extracted from Lentinus squarrosuls. Materials and methods: Peptides were isolated from the aqueous extract of L. squarrosulus by employing solid ammonium sulphate precipitation. They were further purified by ion-exchange chromatography on diethylaminoethanol (DEAE)-cellulose and gel filtration chromatography on Sephadex G25. Anticancer activity was investigated in human lung cancer H460, H292 and H23 cells cultured with 0-40 mu g/mL of peptide extracts for 24h. Cell viability and mode of cell death were evaluated by MTT and nuclear staining assay, respectively. Western blotting was used to investigate the alteration of apoptosis-regulating proteins in lung cancer cells treated with peptide extracts (0-20 mu g/mL) for 24h. Results: The cytotoxicity of partially-purified peptide extracts from L. squarrosulus was indicated with IC50 of similar to 26.84 +/- 2.84, 2.80 +/- 2.14 and 18.84 +/- 0.30 mu g/mL in lung cancer H460, H292 and H23 cells, respectively. The extracts at 20 mu g/mL induced apoptosis through the reduction of anti-apoptotic Bcl-2 protein (similar to 0.5-fold reduction) and up-regulation of BAX (similar to 4.5-fold induction), a pro-apoptotic protein. Furthermore, L. squarrosulus peptide extracts (20 mu g/mL) also decreased the cellular level of death receptor inhibitor c-FLIP (similar to 0.6-fold reduction). Conclusions and discussion: This study provides the novel anticancer activity and mechanism of L. squarrosulus peptide extracts, which encourage further investigation and development of the extracts for anti-cancer use.