CD4 regulatory T cells in hepatocellular carcinoma with different etiologies

Background & Aims:

Foxp3 CD25 CD4 regulatory T cells (Tregs) are expanded in patients with hepatocellular carcinoma (HCC) and their number correlates with disease progression and poor prognosis. During chronic hepatitis C virus (HCV) infection, Tregs inhibit antiviral immune response, promote fibrosis and thus may ultimately facilitate liver cancer. Here, we compared Tregs in HCV-infected patients versus patients with non-viral liver diseases both with and without HCC.

Methods:

Using multi-color flowcytometry we analyzed frequency and phenotype of Foxp3 CD25 CD4 Tregs and CD3 T effector cells in the blood of 89 individuals: 42 HCV-infected patients, 20 patients with non-alcoholic steatohepatitis, 10 patients with alcoholic liver disease and 17 healthy blood donors. 31 of our patients had HCC (16 HCV-assoiated and 21 of non-viral etiologies).

Results:

Our analysis showed that patients with HCV-associated HCC had the highest frequencies of PD-1 CD8 and PD-1 CD4 T effector cells among our study groups (p < 0.01 each). Although increased over healthy controls, frequencies of Foxp3 CD25 CD4 Tregs were not conspicuously altered in HCC: a minor difference was only noted, when patients with non-viral HCC were compared to their corresponding non-viral disease controls without HCC (p < 0.05). However, numbers of Foxp3 CD25 CD4 Tregs expressing inhibitory checkpoint molecules (CTLA-4, PD-1, PD-L1, and GITR) were significantly more enhanced in patients with HCV-associated HCC than in non-viral HCC (p < 0.05 each). Moreover, unlike non-viral liver diseases, Tregs with expression of CTLA-4, PD-1, and PD-L1 were also significantly higher when patients with HCV-associated HCC were compared to their HCV-positive disease controls without HCC (p < 0.05 each).

Conclusions:

HCV-induced HCC differ from non-viral HCC by expressing enriched numbers of exhausted PD1 T effector cells and enhanced frequencies of Tregs with upregulated expression of checkpoint inhibitor molecules. High expression of checkpoint molecules on Tregs is likely to contribute to enhanced inhibition of the immune response in HCV-associated HCC. Thus, interfering with checkpoint inhibitor molecules on Tregs may offer new treatment options in HCV-associated HCC.