FASN-mediated fatty acid biosynthesis remodels immune environment in Clonorchis sinensis infection-related intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver cancer with high lethality. Clonorchis sinensis (C. sinensis) infection is an important risk factor for ICC. Here we investigated the clinical impact and underlying molecular characteristics of C. sinensis-infected ICC.We performed single-cell RNA sequencing, whole exome sequencing, RNA-sequencing, metabolomics and spatial transcriptomics in 251 ICC patients from three medical centers. The alterations of metabolic and immune microenvironment of C. sinensis-infected ICCs were validated through in vitro co-culture system and hydrodynamic injection ICC mouse model.We revealed that C. sinensis infection was significantly associated with ICC patients' overall survival and immunotherapy response. Fatty acid biosynthesis and the expression of FASN, a key enzyme catalyzing long-chain fatty acid synthesis, were significantly enriched in C. sinensis-infected ICCs. ICC cell lines treated with C. sinensis-produced excretory/secretory products (ESPs) displayed an elevation of FASN and free fatty acid. The metabolic alteration of tumor cells was closely correlated with the enrichment of tumor-associated macrophage-like (TAM-like) macrophages and the impairment function of T cells, which led to the immunosuppressive microenvironment formation and tumor progression. Spatial transcriptomics analysis revealed that malignant cells were in closer juxtaposition with TAM-like macrophages in C. sinensis-infected ICCs than non-C. sinensis-infected ICCs. Importantly, FASN inhibitor significantly reversed immunosuppressive microenvironment and enhanced anti-PD-1 efficacy in ICC mouse models treated with ESPs from C. sinensis.We uncover the metabolic signature and immune microenvironment of C. sinensis-infected ICCs and highlight the combination of FASN inhibitors with immunotherapy as a promising strategy for treating C. sinensis-infected ICCs.C. sinensis-infected ICC patients have a poorer prognosis and worse response to immunotherapy than non-C. sinensis-infected ICCs. The underlying molecular characteristics of C. sinensis-infected ICCs remains unclear. Herein, we demonstrate that up-regulation of FASN and free fatty acids in C. sinensis-infected ICCs leads to immunosuppressive microenvironment formation and tumor progression. Thus, administration of FASN inhibitors could significantly reverse immunosuppressive environment and further enhance anti-PD-1 efficacy in combating C. sinensis-infected ICCs.