The Cancer Cell Killing Effects of Gynura procumbens, Toleaf Are Associated with CD4+ T Lymphocyte Activation

Background: Toleaf is a cold abstraction extract from the Gynura procumbens (Lour.) Merr. plant. Compounds extracted from G. procumbens exert anti-cancer effects against various cancers. However, detailed mechanisms underlying these actions remain unclear. Previous research indicated that G. procumbens ethanol extracts also have immunomodulatory properties. Therefore, we examined the relationship between Toleaf’s anti-cancer effects and immune system responses in vitro and ex vivo. Methods: Effects of Toleaf on immune response were assessed using ELISA, RT-PCR, and flow cytometry to measure IFN-γ, IL-2, IL-4, and IL-12 expression in primary splenic cells obtained from 6-week-old male BALB/c or C57BL/6 mice and in T lymphocytes isolated from mouse splenic cells. Toleaf’s anti-cancer and T-cell activation effects were evaluated by determining CT-26, EL-4, and B16 cancer cell viability. Results: Toleaf treatment increased splenic cell IFN-γ production and CD4+ T lymphocyte IL-2, IL-4, and IL-12-mRNA levels. All three cancer cell lines exhibited decreased viability after exposure to Toleaf-treated T lymphocytes. However, Toleaf did not exert direct cytotoxic effects on these cells. Conclusions: Toleaf activates type 1 and 2 T helper responses, suggesting that its anti-cancer effects are associated with CD4+ T lymphocyte activation.