CXCL12 and breast cancer: For example, CXCR7-activation can block CXCR4-driven transendothelial migration of lymphoma cells (Zabel et al. 2009), can impair CXCL12-induced tube formation of endothelial progenitor cells (Yan et al. 2012), facilitate CXCR4-mediated neuronal migration (Sanchez-Alcaniz et al. 2011) and enhance CXCR4-promoted chemotaxis in vitro but decreases matrix degradation and invasion in vivo in CXCR4-overexpressing MTLn3 breast cancer cells (Herandez et al. 2011).