The incidence rate of intrahepatic cholangiocarcinoma (ICC), which has a poor prognosis, is rapidly increasing. To investigate the intratumor heterogeneity in ICC, we analyzed single-cell RNA sequencing data from the primary tumor and adjacent normal tissues of 14 treatment-naïve patients. We identified 10 major cell types, along with 45 subclusters of cells. Notably, we identified a fibroblast cluster, Fibroblast_LUM+, which was preferably enriched in tumor tissues and actively interacted with cholangiocytes. LGALS1 was verified as a marker gene of Fibroblast_LUM+, contributing to the malignant phenotype of ICC. Higher amount of LGALS1+ fibroblasts was associated with poorer overall survival of ICC patients. Mechanistically, LGALS1+ fibroblasts activated the proliferation and migration of tumor cells by upregulating the expression levels of CCR2, ADAM15, and β-integrin. Silencing LGALS1 in cancer-associated fibroblasts (CAFs) suppressed CAF-augmented tumor cell migration and invasion in vitro as well as tumor formation in vivo, suggesting that blockade of LGALS1 serves as a potential therapeutic approach for ICC. Taken together, our single-cell analysis provides insight into the interaction between malignant cells and specific subtypes of fibroblasts, which contributes to better understanding of the intratumor heterogeneity in ICC and the development of novel strategies for the treatment of ICC by targeting fibroblasts in the tumor microenvironment.
