In vitro studies revealed that the chemokine (C-X-C motif) ligand CX3CL1 and CXCL13 levels were elevated in the serum of breast cancer patients with brain metastases, indicating that the presence of these chemokines may disrupt the integrity of the BBB and thus are implicated in the process of BM [72]. This evidence concerns the gene CXCL13 and breast carcinoma.