CCL17 and neoplasm: Knockdown FOXP3 with siRNA in vitro can promote the migration and invasion of human breast cancer MCF-7 cells; In addition, CCL22 and CCL17 released by tumor cells and tumor associated macrophages can attract CCR4+Tregs to the tumor site, and FOXP3 and HAT1 can together epigenetically alter the promoter on CCR4+Tregs, providing space for FOXP3 binding and CCR4 gene activation.