CXCR4 and breast cancer: First, we verified that CXCL12wt, CXCL12-L29C, CXCL12M, and CXCL12D, but not CXCL4-S26C or CXCL12wt mixed with the specific CXCR4 inhibitor AMD3100 led to the increase of cytoplasmic Ca2+ in MDA-MB-231 breast cancer cells (Supplementary Fig. S5).