Oleic acid-PPAR-FABP4 loop fuels cholangiocarcinoma colonization in lymph node metastases microenvironment

Background and Aims: Lymph node metastasis is a significant risk factor for cholangiocarcinoma patients, but the mechanisms underlying cholangiocarcinoma colonization in the lymph node microenvironment remain unclear. We aimed to determine whether metabolic reprogramming fueled the adaptation and remodeling of cholangiocarcinoma cells to the lymph node microenvironment. Approach and Results: Here, we applied single-cell RNA sequencing (scRNA-seq) of primary tumor lesions and paired lymph node metastases from cholangiocarcinoma patients and revealed significantly reduced inter-tumor heterogeneity and syntropic lipid metabolic reprogramming of cholangiocarcinoma after metastasis to lymph nodes, which was verified by pan-cancer scRNA-seq analysis, highlighting the essential role of lipid metabolism in tumor colonization in lymph nodes. Metabolomics and in vivo CRISPR/Cas9 screening identified PPAR gamma as a crucial regulator in fueling cholangiocarcinoma colonization in lymph node through the oleic acid-PPAR gamma-FABP4 positive feedback loop by up-regulating fatty acid uptake and oxidation. Patient-derived organoids and animal models have demonstrated that blocking this loop impairs cholangiocarcinoma proliferation and colonization in the lymph node microenvironment and is superior to systemic inhibition of fatty acid oxidation. PPAR gamma-regulated fatty acid metabolic reprogramming in cholangiocarcinoma also contributes to the immune-suppressive niche in lymph node metastases by producing kynurenine, and was found to be associated with tumor relapse, immune-suppressive lymph node microenvironment, and poor immune checkpoint blockade response. Conclusions: Our results reveal the role of the oleic acid-PPAR gamma-FABP4 loop in fueling cholangiocarcinoma colonization in lymph nodes, and demonstrate that PPAR gamma-regulated lipid metabolic reprogramming is a promising therapeutic target for relieving cholangiocarcinoma lymph node metastasis burden and reducing further progression.