Antitumor activity of a polysaccharide from Pleurotus eryngii on mice bearing renal cancer

One water-soluble polysaccharide (PEPw), with an average molecular weight of 2.5 × 104 Da, was isolated from the fruiting bodies of Pleurotus eryngii and subjected to composition analysis and evaluated for the antitumor and immunomodulatory activity. PEPw was composed of arabinose, mannose and galactose in a molar ratio of 1.2:2.3:6.2 and had a backbone mainly consisting of 1,6-linked-Galp, 1,2,6-linked-Galp and 1,4-linked-Manp residues, which was occasionally terminated with terminal-Araf attached to O-2 of 1,2,6-linked-Galp residue. The animal experiment results showed that PEPw significantly increased relative thymus and spleen indices, promoted the spleen lymphocytes proliferation induced by ConA or LPS, elevated the activities of NK cell and CTL in spleen, and increased the serum concentration of TNF-α and IL-2 in Renca tumor-bearing mice. As a result, the tumor growth was significantly inhibited by PEPw treatment at the doses of 50, 100 and 200 mg/kg in a dose-dependent manner. These data indicated that the anti-tumor activity of PEPw may be related to the activation of the immune response in tumor-bearing mice.