CXCL12 and breast cancer: Moreover, the bone resident chemokine stromal derived factor-1 (SDF-1, Figure 4), known to mediate HSC homing and breast cancer migration through ligation of CXCR4, has been shown to regulate miRNAs in breast cancer cells and stromal cells that control breast cancer cell tumorigenicity and quiescence (Lim et al., 2011; Rhodes et al., 2011a,b).