Background: Sorafenib is the most widely used first-line treatment for patients with advanced hepatocellular carcinoma (HCC), but such treatment provides only limited survival benefits that might be related to the immune status of distinct tumor microenvironments. A fundamental understanding of the distribution and phenotypes of T lymphocytes in tumors will undoubtedly lead to the development of novel immunotherapeutic strategies that could possibly enhance the efficacy of sorafenib treatments.
Methods: Flow cytometry, immunohistochemistry and immunofluorescence analyses were performed to detect the infiltration and distribution of various leukocyte populations, and the expression of different immune checkpoint molecules in fresh HCC tumor tissues. Correlations among indicating genes were calculated in 365 patients with HCC from The Cancer Genome Atlas (TCGA) data set, and the cumulative overall survival time was calculated using the Kaplan-Meier method. Moreover, role of adenosinergic pathway on sorafenib anti-tumor efficacy was investigated using both subcutaneous and orthotopic transplantation tumor model in immune competent C57BL/6 mice.
Results: We revealed that levels of CD3+ and CD8+ T cells were significantly downregulated in HCC tumor tissue, so were the infiltration of CD169+ cells (a Mφ subpopulation with T cell activation capacities) and their contact with CD8+ cells in tumor milieus. Moreover, levels of PD-1 and CD39 expression were significantly upregulated in human HCC-infiltrating CD4+ and CD8+ T cells, and CD39+CD8+ T cells exhibited a CD69+PD-1+perforinlowIFNγlow "exhausted" phenotype. Levels of both CD39+ T cells infiltration and adenosine receptor ADORA2B expression in tumor tissues were negatively correlated with overall survival of patients with HCC. Accordingly, mice treated with sorafenib in combination with adenosine A2B receptor blockage reagents exhibited significantly reduced tumor progression compared with control groups.
Conclusions: These results suggest that adenosinergic pathway might represent an applicable target for sorafenib-combined-therapies in human HCC.
Keywords: Adenosinergic pathway; Hepatocellular carcinoma; Immunotherapy; Sorafenib; T cells exhaustion.