CCL2 and central nervous system cancer: Importantly, CCL2 then recruits regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) through CCR4 and CCR2 as significant contributors to the potently immunosuppressive glioma microenvironment (Carrillo-de et al., 2012; Braganhol et al., 2015; Chang et al., 2016; Lu et al., 2017).