Whole genome transcriptome profiling identifies TIGIT as a regulator of T cell exhaustion in liver cancer

PD-1 checkpoint inhibition has shown promising results in patients with hepatocellular carcinoma, inducing objective responses in approximately 20% of the treated patients. The role of other co-inhibitory molecules and their individual contribution to T cell dysfunction in liver cancer, however, remain largely elusive. Here we perform for the first time a comprehensive mRNA profiling of CD8 T cells in a murine model of autochthonous liver cancer by comparing the whole genome transcriptome of naive, functional effector and exhausted, tumor-specific CD8 T cells. Our results reveal a unique transcriptome signature of exhausted T cells and demonstrate that upregulation of the inhibitory immune receptor TIGIT represents a hallmark in the process of T cell exhaustion in liver cancer. Compared to PD-1, expression of TIGIT more reliably identified exhausted, HCC-specific T cells at different stages of their differentiation. In combination with PD-1 inhibition, targeting of TIGIT with antagonistic antibodies resulted in synergistic inhibition of liver cancer growth in immunocompetent mice. Finally, we demonstrate expression of TIGIT on tumor infiltrating CD8 T cells in tissue samples of HCC patients and identify two subsets of HCC patients based on differential expression of TIGIT on HCC-specific T cells. Our transcriptome analysis therefore provides a valuable resource for the identification of key pathways involved in T cell exhaustion in patients with hepatocellular carcinoma and identifies TIGIT as a potential target in checkpoint combination therapies. Expression profiling of OT-I cells isolated from OVA+ tumor-bearing livers (exhausted T cells) or livers of tumor-free control mice (effector T cells), respectively. As additional reference data, naive OT-I cells (naive T cells) were isolated from spleens of naive mice, that have previously received adoptive transfer of naive OT-I cells.