A fungal polysaccharide from Trametes orientalis: Structural elucidation and multifaceted antitumor mechanisms via metastasis, angiogenesis, and immunomodulation.

Cancer remains a formidable global health challenge, underscoring the critical need for innovative and highly effective therapeutic agents. Fungal polysaccharides have gained increasing attention in anti-cancer drug development due to their remarkable structural diversity and biological activities. This study reports the isolation and comprehensive characterization of TOP60-1, a novel homogeneous polysaccharide with a molecular weight of 1.122 × 10⁴ g/mol, meticulously purified from the fruiting bodies of Trametes orientalis (Yasuda) Imaz. Structural analysis revealed TOP60-1 to be a complex heteropolysaccharide comprising various glycosidic linkages, including →4)-β-d-Glcp-(1→, →3)-β-d-Glcp-(1→, →6)-β-d-Glcp-(1→, →3,6)-β-d-Glcp-(1→, β-d-Glcp-(1→, →2,6)-α-d-Galp-(1→, →6)-α-d-Galp-(1→, →4,6)-α-d-Manp-(1→, α-l-Fucp-(1→, 3-OMe-α-l-Fucp-(1 → and →3)-α-l-Fucp-(1→. Biological evaluations demonstrated that TOP60-1 dose-dependently suppressed tumor growth, metastasis, and angiogenesis in a zebrafish xenograft model, induced tumor cell apoptosis, and significantly inhibited tumor cell migration in vitro. Furthermore, immunomodulatory investigations elucidated that TOP60-1 directly interacts with macrophage surface receptors TLR-2 and TLR-4, effectively promoting macrophage M1 polarization and upregulating the expression of critical M1-associated surface markers (CD40, CD80, CD86, MHC-II). Collectively, these findings unequivocally demonstrate that TOP60-1 possesses potent antitumor activity mediated by direct effects synergistic with profound indirect immunomodulatory mechanisms. This highlights its substantial therapeutic potential as a promising novel candidate for tumor immunotherapy.