Spatiotemporal landscape of intrahepatic cholangiocarcinoma liver metastasis at the single-cell level

Background and Aims: Intrahepatic cholangiocarcinoma (iCCA) is a highly metastatic tumor type, and iCCA with intrahepatic metastasis is associated with poor prognosis. Previous studies have confirmed that the tumor microenvironment (TME) is closely related to tumor metastasis. However, the state of the TME during iCCA liver metastasis remains unknown. Approach and Results: We profiled 28 specimens from 16 patients with iCCA (with and without intrahepatic metastasis) using integrated single-cell and spatial transcriptomics, bulk RNA sequencing, whole-exome sequencing, and in vivo and in vitro functional experiments to characterize the specific TME changes during iCCA liver metastasis. We identified the metastatic tumor cells, COL3A1 + epithelial cells, and revealed that COL3A1 + epithelial cells—endothelial-to-mesenchymal transition cells crosstalk promoted tumor invasion by inducing mesenchymal transformation of endothelial cells, while COL3A1 + epithelial cells—VEGFA + CCL4 + neutrophils crosstalk promoted tumor colonization by forming neutrophil extracellular traps. Conclusions: We revealed the key biological mechanisms involved in the invasion and colonization phases of iCCA liver metastasis. Moreover, we provide valuable data for understanding iCCA liver metastasis and a possible avenue for the treatment of advanced iCCA.