Neutral Inonotus obliquus polysaccharide (IOP-W): Structural characterization and p53/MAPK-mediated apoptotic...

Inonotus obliquus is a medicinal fungus growing on birch bark. A neutral polysaccharide (IOP-W, M_w = 8.222 kDa) was isolated from its crude polysaccharides via sequential DEAE DE-52 cellulose column and Sephadex G-200 gel filtration column chromatography. IOP-W, composed primarily of galactose, glucose, and mannose, was structurally characterized by UV-Vis, FT-IR, GC-MS, and NMR as a glucan containing →4)-α-D-Glcp-(1→, →6)-β-D-Glcp-(1→, →3)-β-D-Glcp-(1→, →4,6)-α-D-Glcp-(1→, terminal α-D-Glcp, and β-D-Glcp reducing end. AFM confirmed its aggregated spherical morphology. IOP-W exerted antitumor activity against MIA PaCa-2 cells by modulating apoptosis and migration. Metabolomics revealed effects on amino acids, alkaloids, lipids, and nucleotides involving 20 pathways, while transcriptomic KEGG analysis showed regulation of MAPK, TNF, and p53 signaling. In vivo investigations employing small animal MRI technology have validated that tumor growth is significantly suppressed in animal models, accompanied by elevated spleen index and improved physiological parameters. Western blotting and immunohistochemistry revealed altered expression of Parp-1, p53, Bax/Bcl-2, p-ERK1/2, p-JNK1, NF-κB, vimentin, and MMP-9. These findings indicate that IOP-W inhibits pancreatic cancer via the p53/MAPK pathway, highlighting its potential as a fungal polysaccharide-based therapeutic candidate.