CXCL12 and central nervous system cancer: Analysis of the brain tumor model with increased tissue expression of CXCL12 after exposure to the radiation of glioma cells implanted in the brain compared with tumors implanted in the brain that did not receive radiation showed higher MIB1 expression, as a marker of proliferative activity (Fig. 3A), and higher infiltration in the periphery of tumor tissue (Fig. 3D).