CXCL9 and melanoma: The major chemokine/chemokine receptor interactions occurring in melanoma development and progression include the CXCR4/CXCR7/CXCL12, CXCR3/CXCL9,10,11, CXCR1,2/CXCL8, CCR2/CCL2, CCR4/CCL17,22, CCR5/CCL5, CCR7/CCL21 and CCR10/CCL27 axes.