CXCL9 and melanoma: From the translational perspective, the findings that CXCL10lhigh/CXCL9high patients display less severe forms of several types of cancer (13–19), and that melanoma patients who are CXCL10Lhigh and/or CXCL9high tend to respond well to anti-PD-1 therapy (18, 19), suggests that the major role of the PD-1 and CTLA-4 axes is to regulate the CXCR3-CXCL9/CXCL10 interplay.