CXCR4 and neoplasm: Also in breast cancer, Chung and colleagues demonstrated that brain metastases-associated fibroblasts express significantly higher levels of CXCL12 and CXCL16 than fibroblasts from primary tumors or normal breast tissue, which increases tumor cell migration, with inhibition of CXCR4 or CXCL16 reducing tumor cell migration [147].