Characterization and Antitumor Effect of a Novel Polysaccharide from Grifola frondosa

A novel polysaccharide, MZF, with a molecular mass of 23 kDa was isolated from Grifola frondosa. Results from methylation and H-1 NMR led to the conclusion that MZF is a heteropolysaccharide consisting of -> 6)-alpha-D-Galp-(1 -> (36.2%), -> 3)-alpha-L-Fucp-(1 -> (14.5%), -> 6)-alpha-D-Manp-(1 -> (9.4%), -> 3)-beta-D-Glcp-(1 -> (10.1%), alpha-D-Manp-(1 -> (23.2%), and -> 3,6)-beta-D-Glcp-(1 -> (6.5%). Although MZF did not affect the proliferation of colon-26 cells in vitro, it significantly inhibited tumor growth in BALB/CA mice inoculated with colon-26 cancer cells. Moreover, MZF significantly induced the proliferation of splenocytes and peritoneal macrophages. The mRNA expression of IL-12p40, IL-2 and IFN-gamma were increased significantly in MZF-treated spleen. Furthermore, MZF augmented the percentage of IFN-gamma-producing cells in both splenic CD4(+) and CD8(+) T cells and tumor infiltrating CD4(+) and CD8(+) cells and enhanced the cytotoxic activity of NK cells and CTLs. These results indicate that MZF is a novel effective immunomodulator that has antitumor activity associated with induced cell-mediated immunity.