Because a higher percentage of PMN-MDSCs expressed the receptors for IL-8 and because it has previously been shown that these cells are associated with poor clinical outcomes in melanoma patients (21), we isolated splenic PMN-MDSCs and performed transwell chemotaxis assays to determine if IL-8 attracts peripheral MDSCs to the tumor microenvironment. This evidence concerns the gene CXCL8 and melanoma.