Host metadherin coordinates hepatic lipid metabolism and CD8+ T cell immunity to promote tumor progression.

Cancer progression is systemically influenced by distant organ dysfunction induced by primary tumors, yet how long-distance tumor-organ crosstalk regulates antitumor immunity remains unclear. Here, we identify host metadherin (MTDH) as a critical regulator of tumor-induced immunosuppression and metabolic reprogramming via tumor-liver interactions. Using Mtdh knockout mouse models, we show that concurrent MTDH loss in hepatocytes and CD8+ T cells enhances effector T cell function and suppresses tumor growth and metastasis. Mechanistically, tumor-derived extracellular vesicles and particles (EVPs) activate Kupffer cells to secrete tumor necrosis factor α (TNF-α) and TGF-β, which suppress hepatic PPARα-mediated lipid oxidation via nuclear factor κB (NF-κB) signaling. MTDH loss restores hepatic lipid catabolism, reduces systemic lipid levels, and promotes mitochondrial metabolic reprogramming in CD8+ T cells under lipid-reduced conditions, thereby boosting antitumor immunity. Genetic or pharmacological targeting of MTDH synergizes with anti-PD-1 therapy. These findings establish host MTDH as a key mediator of tumor-liver crosstalk through metabolic and immune interactions, driving systemic cancer progression.