CXCR4 and brain neoplasm: Several reports showed that the treatment with VEGFR inhibitor determined the activation of CXCL12/CXCR4 pathway, increasing circulating CXCL12 levels and CXCR4+ cells and the infiltration of myeloid BMDC in brain tumors [85, 134] and promoting angiogenesis, tumor growth, and metastasis [135].