CXCL12 and cancer: The impact of the CXCL12/CXCR4 axis on promoting GBM growth has spurred the development of effective CXCR4 antagonists as potential anti-cancer drugs (Rubin et al. 2003; Kioi et al. 2010; Goffart et al. 2015; Eckert et al. 2018).