The immunosuppressive tumor microenvironment in hepatocellular carcinoma

Increasing evidence indicates the immunosuppressive nature of the local environment in tumor. The present study was focused on analyzing the immune status within hepatocellular carcinoma. In contrast to the increasing number of CD4⁺ T cells, CD8⁺, CD3⁻CD56⁺, CD3⁺CD56⁺, and γδT cells were all found to be under-represented in tumor infiltrating lymphocytes. Notably, the relative abundance of CD3⁺CD56⁺ cells appeared to be correlated with patient survival. Functional analysis demonstrated that CD4⁺ cells in the tumor tended to produce more IL-10 but less IFN-γ, whereas CD8⁺ cells showed impaired capacity for the production of both IFN-γ and perforin. Consistent with previous reports, we observed a significant increase of Foxp3⁺ cells in the tumor tissue. Intriguingly, although over 90% of CD4⁺CD25^high cells were found to be Foxp3⁺, the majority of Foxp3⁺ cells were identified in the CD4⁺CD25^medium and CD4⁺CD25⁻ subsets. In support of its role as a negative regulator, CD4⁺CD25^high cells suppressed the proliferation of CD4⁺CD25⁻ cells isolated from the same tissues in an APC dependent manner. In conclusion, the tumor microenvironment of hepatocellular carcinoma is featured by the presence of multiple immunosuppressive factors.