Single-cell transcriptome analysis revealed the immune profile of PD-1 blockade in gallbladder carcinoma liver metastasis

Gallbladder carcinoma is the most common cancer of the biliary tract, and the immune checkpoint blockade showed promising efficacy in the treatment of advanced gallbladder carcinoma. However, the underlying mechanisms remain unknown. METHODS: Single-cell RNA sequencing was used to reveal immune cell dynamics in an anti-PD-1 responder with gallbladder carcinoma liver metastases. Gene set variation analysis, pseudotime analysis, single-cell regulatory network inference and clustering analysis, and CellChat analysis were used to identify the functions of each cell cluster. Immunohistochemistry and multicolored immunohistochemistry analysis were applied to confirm the intratumoral cell types, and the prognostic value of CXCL13+CD8+T cells in patients with gallbladder carcinoma liver metastases with immunotherapy was evaluated. Four biliary tract carcinoma and 3 immunotherapy bulk RNA-seq datasets were analyzed to investigate the prognostic value of CXCL13+CD8+T cells and SPP1+TAMs. RESULT: A total of 19,648 high-quality single-cell transcriptome data were obtained from liver metastasis before and after aPD-1 therapy. We discovered improved cytotoxic activity in CD8+T cells and enhanced proinflammatory phenotypes in myeloid cells. The identified SPP1+TAMs were related to poor prognosis. The increased effector/memory T cells represented characteristics similar to exhausted T cells in transitory status after aPD-1therapy, which may play a crucial role in the antitumor immune response. We further revealed that CXCL13+T cells in a high subtype of biliary tract carcinoma were characterized as a ‘hot tumor’ profile with high immune scores, correlated to the immunostimulatory context with favorable survival, and can predict effective responses to immunotherapy. CONCLUSIONS: Our study provided an overview of immune cell dynamics in gallbladder carcinoma liver metastases after aPD-1 treatment and highlighted the importance of CXCL13+T cells in biliary tract carcinoma and effective responses to immunotherapy, which would advance the understanding and treatment of the disease.