Anti-tumor and immunomodulatory activities of a novel polysaccharide from Grifola frondosa prepared by hydrogen peroxide/vitamin C-assisted extraction

Polysaccharides derived Grifola frondosa (GFP) possess diverse biological activities. In this study, a GFP fraction (coded as GFP1) purified from the crude GFP prepared by an H₂O₂/Vc-assisted extraction method was investigated for its inhibitory effects on lung cancer cells (H1975) and immunomodulatory activities in RAW264.7 macrophages. It was found that GFP1 significantly inhibited the proliferation, induced the cell apoptosis, and suppressed the migration and invasion of H1975 cells. Additionally, GFP1 increased the intracellular reactive oxygen species (ROS) levels, reduced mitochondrial membrane potential, and upregulated the expressions of caspase-3, caspase-8, and caspase-9. RT-qPCR analysis indicated that GFP1 downregulated the mRNA expression levels of PI3K, ERK2, ERK1, FAK, and RAF. GFP1 was also found to upregulate the mRNA expressions of nitric oxide synthase (iNOS), IL-1β, IL-6, and TNF-α, thereby promoting the release of nitric oxide and secretion of the corresponding cytokines. Western blot experiments indicated that GFP1 activated the NF-κB signaling pathway through the promotion of p65 phosphorylation, exerting immunomodulatory effects. Therefore, GFP1 exerted anti-tumor effect by both direct cytotoxic effects on tumor cells and modulating the body’s immune function. These findings provide new insights for the development of functional foods and effective and safe anti-tumor drugs.