CCL7 and neoplasm: High CCL7 expression evokes the recruitment of tumor-associated macrophages (TAMs) that express CCR2 on the surface, resulting in the persistence of increased vascular permeability (de Vries et al., 2006; Medioni et al., 2007); therefore, tumor cells can cross the blood–brain barrier and move toward brain tissues (Wyler et al., 2014).