CXCL12 and breast cancer: Since chemokine receptor C‐X‐C chemokine receptor type 4 (CXCR4) on MDA‐MB‐231 and its ligand C‐X‐C motif chemokine ligand 12 (CXCL12) from bone cells play a crucial role in MDA‐MB‐231 bone metastasis [32], we explored the impact of GW405833 exposure on the expression of these two genes in breast cancer and osteoblasts, respectively.