A Paradoxical Tumor Antigen Specific Response in the Liver

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• Functional tumor-specific CD8+ T cells are critical for anti-tumor immunity and immunotherapy success.
• Liver metastases exhibit higher numbers of CD8+ T cells compared to other sites, but these cells often display an exhausted phenotype.

Purpose of the Study:

• To investigate the phenotype and function of CD8+ T cells in liver tumors.
• To elucidate the mechanisms by which extrahepatic tumors promote liver metastasis and impair anti-tumor immunity.

Main Methods:

• Murine tumor models and patient-derived single-cell RNA sequencing (scRNA-seq) data analysis.
• High-dimensional multi-omic analysis integrating proteomic CODEX and scRNA-seq.
• Functional CD8+ T cell depletion experiments and Spp1 knockout mouse models.

Main Results:

• Liver tumor-infiltrating CD8+ T cells are abundant yet exhausted, failing to control tumor growth locally but effective against distant tumors.
• SPP1+ macrophages interact with CD8+ T cells in profibrotic liver regions, contributing to T cell exhaustion.
• Spp1 deficiency ameliorates T cell exhaustion and reduces liver tumor growth.
• Extrahepatic signaling induces an intermediate cell (IC) population in the liver, characterized by specific surface markers, which predicts liver metastasis.

Conclusions:

• Extrahepatic tumors create a pro-metastatic liver microenvironment by inducing an IC population that suppresses CD8+ T cell function.
• This mechanism contributes to liver metastasis and may limit the effectiveness of immune checkpoint inhibitor therapy in liver cancer.