For example, in ovarian cancer, tumor cells secrete CCL28 to recruit Tregs [34]; hypoxia-inducible factor-1 (HIF-1) induced by hypoxia directly downregulates Foxp3 expression by combining with the Foxp3 promoter region, inducing Treg formation [35], and regulates the function and differentiation of MDSCs [36]. Here, FOXP3 is linked to ovarian cancer.