Triptolide downregulates treg cells and the level of IL-10, TGF-β, and VEGF in melanoma-bearing mice

Regulatory T cells play a key role in suppressing tumor immunity. Triptolide, a major active component isolated from the Chinese medicinal herb Tripterygium wilfordii, has been proven to possess multiple antitumor activities. Here, we investigated the effect of triptolide on regulatory T cells and on the level of IL-10, transforming growth factor-β, and vascular endothelial growth factor in tumor-bearing mice. Fifty male C57BL/6 mice were randomly grouped as follows: normal control group, model group with B16-F10 cells implanted, and three treatment groups with cyclophosphamide, triptolide-high dose, triptolide-low dose. The proportion of regulatory T cells in the spleen and axillary lymph nodes was evaluated by flow cytometric analysis. Production of cytokines IL-10, transforming growth factor-β, and vascular endothelial growth factor in serum was measured using enzyme-labeled immunosorbent assay kits. The mRNA levels of Foxp3, IL-10, and transforming growth factor-β in the spleen and vascular endothelial growth factor in tumor tissue were detected by real-time PCR. The results showed that triptolide significantly decreased the proportion of regulatory T cells and lowered the Foxp3 level in the spleen and axillary lymph nodes of tumor-bearing mice. Production of IL-10 and transforming growth factor-β in peripheral blood, and the mRNA level of IL-10 and transforming growth factor-β in the spleen were also decreased. Additionally, triptolide could remarkably inhibit production of vascular endothelial growth factor in tumor-bearing mice. In conclusion, our study demonstrated that triptolide might inhibit tumor growth by inhibiting regulatory T cells and some cytokines such as IL-10 and transforming growth factor-β, as well as production of vascular endothelial growth factor.