CXCL12 and breast cancer: CXCR4 is highly expressed in BC metastases; thus, I.X. found that suppressed CXCL12/CXCR4 signaling pathway or silenced CXCR4 in BCSCs sensitizes BC to immune checkpoint blockers, inhibiting metastasis reversing drug-resistance in BC (Chen I. X. et al., 2019).