Interleukin (IL)-24 is a multifunction cytokine in infectious diseases and cancers. IL-17-secreting CD4+ T (Th17) and CD8+ T (Tc17) cells promotes pathogenesis of hepatitis B virus (HBV)-associated liver disorders. However, the regulatory role of IL-24 to Th17/Tc17 cell response was not fully elucidated during HBV infection and HBV-hepatocellular carcinoma (HCC). In this study, plasma and peripheral blood mononuclear cells were isolated from 27 chronic hepatitis B (CHB) patients, 42 HBV-HCC patients and 17 normal controls (NC). Liver-infiltrating lymphocytes (LILs) were prepared from tumor and para-tumor tissues of 17 HBV-HCC patients, whereas CD4+ T cells in LILs were purified. LILs were stimulated with recombinant human IL-24. CD3+CD4+IL-17+ Th17 cells and CD3+CD8+IL-17+ Tc17 cells were investigated by flow cytometry. IL-24 level was measured by enzyme-linked immunosorbent assay. Purified CD4+ T cells were polarized for Th17 cells, and the regulatory role of IL-24 to liver-infiltrating Th17 polarization was assessed. There were no significant differences of peripheral Th17 or Tc17 cell percentage among NC, CHB, and HBV-HCC patients. Liver-infiltrating Th17 and Tc17 cell proportion was reduced in tumor tissues compared with para-tumor tissues. In contrast, plasma IL-24 level was increased in CHB and HBV-HCC patients. Exogenous IL-24 stimulation (10 or 100 ng/mL) in vitro downregulated of Th17 frequency and IL-17 secretion in LILs from both para-tumor and tumor tissues without affecting cellular proliferation or Tc17 percentage. Only 100 ng/mL of IL-24 inhibited tumor-infiltrating Th17 polarization, and this process was accompanied by suppression of nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase phosphorylation. In conclusion, IL-24 might dampen Th17 cell response through NF-κB pathway in HBV-HCC tumor microenvironment. Elevated IL-24 might enhance anti-tumor immune response in HBV-HCC patients.
Keywords: Tc17 cells; Th17 cells; hepatitis B virus; hepatocellular carcinoma; interleukin-24.