Physicochemical characterization and antitumor activity in vitro of a selenium polysaccharide from Pleurotus ostreatus.

Selenium-enriched polysaccharides have been gaining great attention for their antitumor activity in recent years. In this study, a novel selenium polysaccharide fraction (Se-POP-3) produced by Pleurotus ostreatus was characterized and its antitumor activity explored at cellular level. Results showed that Se-POP-3 has 25.9 μg/g of selenium, an average molecular weight of 16,106 Da, and is mainly composed of mannose, glucose and galactose with a molar ratio of 1.7:49.6:2.4. Spectra analysis revealed Se-POP-3 as a pyranopolysaccharide linked by α-glycoside bonds in the main chain, and selenium may occur in the form of COSe and SeO. A single sphere of Se-POP-3 has 50-60 nm in aqueous solution, even though it can agglomerate to form larger spherical structures. In vitro experiments with cancer and normal cell lines showed that Se-POP-3 can induce apoptosis and inhibit migration of cancer cells. Potential anticancer mechanism is that Se-POP-3 can disrupt the Bax/Bcl-2 protein ratio and inhibit the epithelial-to-mesenchymal transition (EMT) in cancer cells. Se-POP-3 showed no significant effect on the growth of normal cell lines. Se-POP-3 showed great potential as a broad-spectrum antitumor agent and dietary supplement.