CXCL12 and central nervous system cancer: To investigate the mechanisms underlying Notch1 regulation of GICs invasion and self-renewal, stable Notch1-knockdown glioma initiation cells (U87-shNotch1 and U251-shNotch1) were established (Additional file 3: Figure S3a-b) and western blot showed that inhibition of Notch1 pathway through shRNA or MK0752 in U87 and U251 derived GICs could quantitatively decrease the expression of CXCR4, but the expression of CXCL12 made no difference in the shNC and shNotch1 groups (Additional file 3: Figure S3c-d).