Characterization of a water-soluble polysaccharide from Boletus edulis and its antitumor and immunomodulatory activities on renal cancer in mice

A polysaccharide (BEP, Mw = 113,432 Da) was purified from Boletus edulis, which had a backbone consisting of (1→6)-linked-α-d-glucopyranosyl, (1→2,6)-linked-α-d-galactopyranosyl, (1→6)-linked-α-d-galactopyranosyl, and (1→3)-linked-α-d-rhamnopyranosyl residues, which were branched at O-2 position of (1→2,6)-linked-α-d-galactopyranosyl residue with a single terminal (1→)-linked-α-l-arabinofuranosyl residue. After 32 days’ BEP administration to Renca tumor bearing mice, the tumor mass of Renca transplanted in mice was significantly repressed. Furthermore, BEP could significantly increase the spleen and thymus indices, stimulate splenocytes proliferation, augment NK cell and CTL activities in spleen, and promote the secretion of the cytokines IL-2 and TNF-α in Renca tumor bearing mice. Meanwhile oral administration of BEP (100 and 400 mg/kg) restored all the altered hematological and biochemical parameters of tumor-bearing mice to normal levels. Thus, these data demonstrate that BEP possesses potential immunomodulatory activity and might be employed as effective therapeutic agents for the prevention of renal caner.