Unraveling the anti-colorectal cancer mechanisms of polysaccharide: a multi-omics investigation into gut microbiota-metabolism-immunity crosstalk.

[BACKGROUND] This study aimed to systematically investigate the anti-colorectal cancer efficacy and the underlying mechanisms of polysaccharide with a focus on its role in modulating the gut microbiota-metabolism-immune axis.

[METHODS] A homogeneous ASP fraction was structurally characterized using HPSEC, monosaccharide composition analysis, SEM, and FT-IR. Its anti-tumor activity was evaluated in a CT-26 tumor-bearing mouse model through histopathology, tumor inhibition rate, immune organ indices, and serum cytokine (IFN-γ, TNF-α, IL-2) assays. The potential mechanisms of action were elucidated by integrating 16S rDNA sequencing of gut microbiota, determination of short-chain fatty acids (SCFAs), untargeted serum metabolomics using UPLC-Q-TOF/MS, molecular docking studies, Western blot analysis of key signaling proteins, and validation through cell experiments.

[RESULTS] ASP demonstrated significant dose-dependent anti-tumor activity, with the medium dose showing the highest efficacy (50.84% inhibition). It induced tumor cell apoptosis, normalized tumor-associated immune organ hypertrophy, and rebalanced pro- and anti-tumor cytokines. Metabolomics identified 12 key biomarkers, revealing that ASP primarily reversed CRC-induced disruptions in glycerophospholipid and tryptophan metabolism. Concurrently, ASP restored gut microbiota diversity, suppressed pro-inflammatory genera, and promoted beneficial bacteria and some SCFAs. Integrated correlation analysis established a robust link between microbiota remodeling and metabolic correction. Molecular docking, Western blot validation and cell experiments confirmed that ASP and its regulated metabolites could inhibit the activity of PLA2/TLR4/MyD88/NF-κB signaling pathway.

[CONCLUSION] The results indicate that anti-CRC effect of ASP may be jointly regulated through multiple pathways: correcting abnormal glycerophospholipid and tryptophan metabolism in the host, restoring the homeostasis of the intestinal microbiota, increase the content of some SCFAs, and inhibiting the TLR4/NF-κB signaling pathway.