Scutellaria barbata D. Don extract inhibits the tumor growth through down-regulating of Treg cells and manipulating Th1/Th17 immune response in hepatoma H22-bearing mice

BACKGROUND: Previous studies showed Scutellaria barbata D. Don extract (SBE) is a potent inhibitor in hepatoma and could improve immune function of hepatoma H22-bearing mice. However, the immunomodulatory function of SBE on the tumor growth of hepatoma remains unclear. This study aimed to investigate the anti-tumor effects of SBE on hepatoma H22-bearing mice and explore the underlying immunomodulatory function. METHODS: The hepatoma H22-bearing mice were treated by SBE for 30 days. The effect of SBE on the proliferation of HepG2 cells in vitro, the growth of transplanted tumor, the cytotoxicity of natural killer (NK) cells in spleen, the amount of CD4(+)CD25(+)Foxp3(+) Treg cells and Th17 cells in tumor tissue, and the levels of IL-10, TGF-β, IL-17A, IL-2, and IFN-γ in serum of the hepatoma H22-bearing mice was observered. IL-17A was injected to the SBE treated mice from day 9 post H22 inoculation to examine its effect on tumor growth. RESULTS: SBE treatment inhibited the proliferation of HepG2 cells in vitro with a dose-dependent manner and significantly suppressed the tumor growth of hepatoma H22-bearing mice. Meanwhile, it increased NK cells’ cytotoxicity in spleen, down-regulated the amount of CD4(+)CD25(+)Foxp3(+) Treg cells and Th17 cells in tumor tissue, and decreased IL-10, TGF-β, and IL-17A levels (P < 0.01) whereas increased IL-2 and IFN-γ levels (P < 0.01) in the serum of hepatoma H22-bearing mice. Moreover, administration of recombinant mouse IL-17A reversed the anti-tumor effects of SBE. CONCLUSION: SBE could inhibit the proliferation of HepG2 cells in vitro. Meanwhile, SBE also could inhibit the growth of H22 implanted tumor in hepatoma H22-bearing mice, and this function might be associated with immunomodulatory activity through down-regulating of Treg cells and manipulating Th1/Th17 immune response.