CCR4 and melanoma: The conclusion that the CCR4/CCL17,22 axis promotes melanoma metastasis to the brain was previously substantiated by a variety of findings, including the fact that: (1) CCR4 expression is upregulated in melanoma metastasis, which elevates its tumorigenicity and potential to form brain metastasis; (2) CCR4 upregulation elevated that malignancy phenotype of melanoma cell populations and (3) a CCR4 antagonist (AF‐399/42018025) in melanoma‐bearing mice inhibited local tumorigenicity and metastasis formation.98