We found that pharmacologic inhibition of STAT3 by S31-201 (S31-201 inhibits the STAT3 transcription factor by blocking the phosphorylation and dimerization events necessary for its activation) significantly reduced the CXCL12-induced migration of 4T1 cells as compared with control (Additional file 5: Figure S5), highlighting the role of CXCR7/STAT3 signaling in CXCL12-dependent migration of breast cancer cells. Here, STAT3 is linked to breast cancer.