Atractylodes macrocephala polysaccharide orchestrates anti-tumor immunity via a dual-network mechanism targeting the gut microbiota and spleen.

Colorectal cancer (CRC) is a common global malignancy, and its advanced stage is closely linked to a gut microbiota-metabolism-immunity vicious cycle requiring early intervention. In this study, anti-CRC effects of PAMK in CT26 tumor-bearing mice were explored. Results showed that PAMK significantly inhibited tumor growth and improved the quality of life of tumor-bearing mice by enhancing antitumor immunity, including increased NK cell infiltration and NKG2D expression, elevated CD4⁺:CD8⁺ ratios, and higher serum IFN-γ levels. However, therapeutic effects of PAMK were not observed in antibiotic‑induced microbiota depletion (AIMD) mice. Notably, following fecal microbiota transplantation (FMT), therapeutic effects of PAMK were largely restored. PAMK alleviated tumor-induced gut microbiota dysbiosis characterized by enriched g_Alistipes, and remodeled fatty acid and steroid metabolism, which was closely associated with enhanced antitumor immunity and a potential microbiota-metabolism-immunity axis. Meanwhile, PAMK modulated multiple metabolic, circadian and immune pathways in the spleen as verified by transcriptomics and qPCR. Integrative multi-omics analysis indicated that the gut microbiota-metabolite-spleen gene axis may act synergistically to mediate anti-CRC effects of PAMK in tumor-bearing mice. This study highlights the potential of PAMK in CRC tumor immune adjuvants, providing experimental and theoretical support for its clinical translation and novel tumor immunotherapies.