CXCL12 and brain neoplasm: The autocrine/paracrine loop of the CXCL12/CXCR4 pair has been deeply investigated in brain tumors in both in vitro and in vivo models: CXCL12 stimulates proliferation and migration of glioblastoma cells and xenografted tumors inducing ERK1/2 and Akt phosphorylation [147–149].