Sclareol Reduces CD4+ CD25+ FoxP3+ T-reg Cells in a Breast Cancer Model in Vivo

Background: Sclareol is a phytochemical used in people's diet in Southeast Asia. Objective: To investigate the immunotherapeutic effectiveness of Sclareol against breast cancer by direct intraperitoneal injection. Methods: Sclareol was isolated and purified from Salvia sclarea. Effect of Sclareol on cell growth inhibition was evaluated by MTT assay. Intraperitoneally injected Sclareol effects on reducing the tumor volume and shifting the cytokine profile were investigated. We also assessed if intraperitoneally injected Sclareol could improve the outcome of cancer therapy through suppressing the regulatory T cells. Results: The results confirmed a significant decrease in the tumor size. Furthermore, a significant decrease in the level of IL-4 and an increase in the level of IFN-γ were noticed in the intraperitoneally injected Sclareol group (p<0.05). It was also observed that the splenocytes of treated animals significantly increase in cell proliferation assay. Moreover, measurements of splenic T regulatory cell indicated that intraperitoneally injected Sclareol significantly decreased the number of splenic T regulatory cell. Conclusion: Our results suggest that Sclareol, by reducing T-reg cells frequency and also tumor size can enhance the effect of cancer therapy as an immunostimulant.