CCR6 and breast cancer: The effects of the CCL20/CCR6 axis in chemotaxis have been proven in in vitro and in vivo experiments.[28,38] A study has shown that tumor cells can not only express CCR6 and CCL20 but inhibiting CCL20 expression can also reduce the proliferation, migration, and invasion of cancer cells.[39] Studies found that CCR6+ Tregs are present in human peripheral blood and human breast cancer, nonsmall cell lung cancer, and hepatocytes.[40–42] CCR6 expression can be used to identify effector/memory Tregs in mice.[43]