Artemisinin enhances the anti-tumor immune response in 4T1 breast cancer cells in vitro and in vivo

Background: Breast cancer is a prominent cause of death among women worldwide. Recent studies have demonstrated that artemisinin (ART) displays anti-tumor activity. Using a mouse breast cancer model, we investigated the effects of ART in vitro and in vivo to determine how it influences the anti-tumor immune response. Methods: We measured the proliferation and apoptosis of 4T1 cells in vitro after ART treatment by MTT assay and FACS. To examine the effects of ART in vivo, tumor volumes and survival rates were measured in 4T1 tumor-bearing mice. FACS was used to determine the frequencies of Tregs, MDSCs, CD4(+) IFN-gamma(+) T cells, and CTLs in the tumors and spleens of the mice. mRNA levels of the transcription factors T-bet and FOXP3 and cytokines IFN-gamma, TNF-alpha, TGF-beta, and IL-10 were also determined by real-time RT-PCR. ELISA was used to measure TGF-beta protein levels in the cell culture supernatants. Results: ART supplementation significantly increased 4T1 cell apoptosis and decreased TGF-beta levels in vitro. ART also impeded tumor growth in 4T1 TB mice and extended their survival. MDSC and Treg frequencies significantly decreased in the 4T1 TB mice after ART treatment while CD4(+) IFN-gamma(+) T cells and CTLs significantly increased. ART significantly increased T-bet, IFN-gamma, and TNF-alpha mRNA levels within the tumor and significantly decreased TGF-beta mRNA levels. Conclusion: ART supplementation hindered 4T1 tumor growth in vivo by promoting T cell activation and quelling immunosuppression from Tregs and MDSCs in the tumor.