SPP1⁺ macrophage-FADS1⁺ tumor cell crosstalk via the PDGFB-PDGFRB axis drives liver metastasis in colorectal cancer.

Liver metastasis is the predominant cause of mortality among individuals diagnosed with colorectal cancer (CRC). However, the mechanisms underlying the tumor-microenvironment interactions that promote this process remain poorly defined. Here, we developed an integrative multiomics framework to dissect the cellular and molecular determinants of colorectal cancer liver metastasis (CRLM). By analyzing 1,156 metastasis-associated genes, we identified three molecular subtypes with distinct prognostic and immunometabolic features: C1 with mixed phenotypes and favorable survival, C2 with metabolic activation and immune suppression, and C3 with immune activation and signaling dysregulation, which had the poorest outcomes. Mechanistically, we discovered that SPP1⁺ macrophages secrete PDGFB, which activates PDGFRB signaling in FADS1⁺ tumor cells to trigger epithelial-mesenchymal transition (EMT) and promote liver metastasis. This macrophage-tumor crosstalk was validated by single-cell transcriptomics, genetic perturbation, and coculture experiments. Collectively, our findings define a macrophage-derived PDGFB-PDGFRB axis that drives CRC liver metastasis and highlight a potential therapeutic target for overcoming metastatic progression and immune resistance.