Single-Cell Dissection of the Immune Microenvironment in Intrahepatic Metastasis of Multifocal Hepatocellular...

Intrahepatic metastasis in multifocal hepatocellular carcinoma is associated with poor prognosis and therapeutic resistance, yet the immune mechanisms driving disease progression remain unclear. Here, we analyzed genetic and immune differences between primary tumors and intrahepatic metastatic lesions using sequencing approaches and spatial validation methods. We found that metastatic lesions shared key genomic features with primary tumors but exhibited a distinct immunosuppressive environment enriched in myeloid and T cell populations. In particular, a subset of macrophages expressing glycoprotein nonmetastatic melanoma protein B (GPNMB) was consistently enriched in metastatic niches across multiple independent cohorts. These macrophages were spatially colocalized with CD8⁺ T cells exhibiting features of terminal exhaustion. Mechanistically, integrated multiomics and functional analyses revealed that GPNMB overexpression triggers lipid metabolic rewiring via the phosphatidylinositol 3-kinase/AKT-cyclooxygenase-2 cascade, leading to elevated prostaglandin E2 secretion, which directly suppresses CD8⁺ T cell cytotoxicity. Specific silencing of this subset using a dual-targeted, lipid-polymer nanoparticle (APL_siGpnmb) effectively reversed T cell exhaustion, inhibited metastasis, and synergized with anti-programmed death 1 immunotherapy in mouse models without inducing systemic toxicity. These findings identify GPNMB-positive macrophages as key metabolic and immune regulatory hubs, suggesting that targeting the GPNMB-prostaglandin E2 axis provides a promising precision therapeutic strategy for intrahepatic metastasis in multifocal hepatocellular carcinoma.