CCL3 and renal cell carcinoma: Aside from IL-8, additional factors including IL-1β, CCL2, CXCL5, IL-17 and IL-18 also selectively recruit subsets of MDSCs from the vasculature into renal cell carcinoma (Najjar et al., 2017; Guan et al., 2018) while CCL3 and CCL5 are important for the retention of MDSCs in tumors (Kumar et al., 2016).