CXCR4 and central nervous system cancer: To study the regulatory mechanism of the Notch1 pathway and CXCR4 in GICs, we applied Magnetic Activated Cell Sorting (MACS) to enrich CD133+ cells from U87 and U251 glioma cells, both CD133 and Nestin were stained to assess the stem cell phenotype, CD133 positive cells exhibited a high Notch1 activity (Fig. 3a).