We analyzed gliomas for expression of CXCL12 and CXCR4 and found abundant expression of CXCL12 in both Ntv-a- and Gtv-a Arf−/− gliomas (Figure 4; left panel) and there was also a clear expression of CXCR4 in the same samples (Figure 4; middle panel). This evidence concerns the gene CXCL12 and central nervous system cancer.