Inhibition of the interaction of SDF-1 and CXCR4 using the CXCR4 inhibitor, AMD3100, or antibodies against CXCR4 prevented the radiation-induced increase of CD11b+ monocytes/macrophages and inhibited revascularisation in intracranial human GBM xenografts. Here, CXCR4 is linked to glioblastoma.