Heterogeneity of exhausted T cells in the tumor microenvironment is linked to patient survival following resection in hepatocellular carcinoma.

Despite the success of monotherapies based on blockade of programmed cell death 1 (PD-1) in human melanoma, most patients do not experience durable clinical benefit. T-cell infiltration and/or the presence of PD-L1 in tumors may be used as indicators of clinical response; However, recent studies reported that preexisting tumor-specific T cells may have limited reinvigoration capacity. Therefore, evaluating status of T cells of tumor-adjacent area and its impact on the prognosis are very important. Here, we examined 117 surgical samples from HCC patients for infiltration of exhausted T cell (Tex) including CD4+-Tex, CD8+-Tex and regulatory T cell (FOXP3+-Treg) in tumor and adjacent tissue. CD3+CD45RO+T cells were sorted from adjacent area or tumor core, then the clusters and heterogeneity of T cells were further interrogated by single-cell RNA sequencing. As a result, we suggested that abundance or location of T cell subsets is differentially correlate with long-term clinical outcome of HCC. In contrast with CD4+T or CD4+-Tex, the infiltration of CD8+T or CD8+-Tex cells was closely linked to overall or recurrence-free survival. FOXP3+-Treg is more predictive of early recurrence. Single-cell transcriptional analysis demonstrates the composition of CD4+-Tex, CD8+-Tex, and FOXP3+-Treg is shifted in tumor and adjacent tissue. Molecular profiles including genes coding checkpoint receptors, effector molecules are distinct between CD4+-Tex, CD8+-Tex, though some common features of CD4+ and CD8+ T cell exhaustion are revealed. In conclusion, we underline the heterogeneity and clinical relevance of Tex cells in HCC patients. A better understanding of Tex is critical for HCC monitoring and treatment.