CCR1 and retinoblastoma: While Ly6G identified both PMN-MDSCs and neutrophils, LAMP2 and retinoblastoma allow the discrimination of these two polymorphonuclear subsets.22 Ly6G+ cells in the tumor of control mice were mostly RB1 and LAMP2 negative (figure 3E) suggesting a PMN-MDSC phenotype.22 In sharp contrast, Ly6G+ cells in the tumor of mice silenced for CCR1 and CCR5 had a high expression of RB1 and LAMP2 consistent with a ‘classical’ neutrophil phenotype.