Inhibition of Foxp3 in cancer cells induces apoptosis of thyroid cancer cells.

Foxp3+ regulatory T cells (Tregs) in lymphocytes facilitate the thyroid tumor growth and invasion. Very limited information is available on Foxp3 expression in thyroid cancer cells and its function is totally unknown. This study demonstrated that Foxp3 expression was increased in thyroid cancer cells. Inhibition of Foxp3 decreased cell proliferation and migration, but increased apoptosis, suggesting a positive role of Foxp3 in cancer growth. Interestingly, Foxp3 inhibition enhanced PPARγ expression and activity. In addition, Foxp3 inhibition downregulated NF-κB subunit p65 and cyclin D1 but upregulated caspase-3 levels. These molecular changes are in line with Foxp3 shRNA-mediated alteration of cell functions. Collectively, our study demonstrates that thyroid cancer cells express a high level of functional Foxp3 and that the inhibition of the Foxp3 suppresses the proliferation and migration but promotes apoptosis, suggesting that targeting Foxp3 in thyroid cancer cells may offer a novel therapeutic option for thyroid cancer.