CCL2 and glioma: In glioma, MDSCs are expanded and recruited by a variety of inflammatory cytokines and chemokines secreted by glioma cells and other immune cells, such as GM-CSF (Horikawa et al., 2020), S100A8/9 (Gabrilovich and Nagaraj, 2009; Kwak et al., 2020), prostaglandin-E2 (PGE2) (Mao et al., 2014), CCL2 (Chang et al., 2016) and IL-8 (Alfaro et al., 2016).