An interesting hypothesis came from a study by Topalian's group which found that chemokines CCL5 and CXCL1 were upregulated in PD-L1-positive melanoma tumors along with IFNγ and several IFNγ-regulated genes based on the analysis of 49 archived melanoma specimens that were either PD-L1 positive or negative (121). Here, CXCL1 is linked to melanoma.