To establish the importance of CXCR2 ligands in the recruitment of PMN-MDSC to the primary tumors, bone marrow cells from Rosa mT/mG reporter mice expressing tdTomato (used as fluorescently tagged wild-type [wt] cells) and CXCR2 knockout mice expressing GFP (IL8rb-KO crossed with mice expressing EGFP under the lysozyme M promoter [Il8rb-KO]) were mixed at a 1∶1 ratio and adoptively transferred into tumor-bearing RETAAD mice. This evidence concerns the gene CXCR2 and neoplasm.