To determine the effect of irradiation, a treatment for malignant glioma, on CXCR4 down regulated GL26-Cit-Sh2CXCR4 cells, we implanted GL26-Cit-NT (N=10) and CXCR4 knock-down GL26-Cit-Sh2CXCR4 cells intracranially into Rag1−/− mice (N=10). Here, RAG1 is linked to malignant glioma.