CXCR4 and medulloblastoma: The tumor-specific E1 cells, showed increased expression of genes likely to contribute to malignancy, including the VEGF receptor Flt1, the p-Glycoprotein Abcb1a (aka Mdr1), and the CXCR4 ligand Cxcl12 (aka Sdf1), which has been shown to promote medulloblastoma growth and glioblastoma–endothelial interactions31–34.