Single-cell RNA-seq reveals transcriptional landscape and intratumor heterogenicity in gallbladder cancer liver metastasis microenvironment.

Background: Gallbladder cancer (GBC) is a highly aggressive biliary epithelial malignancy. The median survival time of GBC patients was less than 1 year. Tumor invasion and metastasis are the major cause of high mortality of GBC patients. However, the molecular mechanisms involved in GBC metastases are still unclear.

Methods: We performed 10X genomics single-cell RNA sequencing (scRNA-seq) on GBC liver metastasis tissue to evaluate the characteristics of the GBC liver metastasis microenvironment.

Results: In this study, 8 cell types, a total of 7,788 cells, including T cells, B cells, malignant cells, fibroblasts, endothelial cells, macrophages, dendritic cells (DCs), and mast cells were identified. Malignant cells displayed a high degree of intratumor heterogenicity, while neutrophils were found to promote GBC cell proliferation, migration, and invasion. Furthermore, cytotoxic cluster of differentiation (CD8) T cells became exhausted and CD4 regulatory T cells (Tregs) exhibited immunosuppressive characteristics. Macrophages played an important role in the tumor microenvironment (TME). We identified three distinct macrophage subsets and emergent M2 polarization. We also found that cancer-associated fibroblasts exhibited heterogeneity and may be associated with GBC metastasis.

Conclusions: Although preliminary in nature, our study provides a landscape view at the single-cell level. These results offer a unique perspective into understanding the liver metastasis of GBC.