Figures 1A, B shows that WT mice engrafted with Ret melanoma display strong antitumor responses to blockade of either PD-1 or CTLA-4 (Figure 1A; P<0.05 for CTLA-4 and P<0.01 for PD-1 blockade), whereas these effects were much reduced in CXCR3 KO mice (Figure 1B). This evidence concerns the gene CTLA4 and melanoma.