SmoA1 tumor cells express high levels of surface-localized CXCR4. A, qPCR measured CXCR4 expression in RNA derived from P6 cerebellum (n = 3), 2-month-old adult mice (n = 5), and spontaneous medulloblastomas from SmoA1 mice (n = 25). *, P < 0.05; ***, P < 0.001, unpaired t test. B, Surface CXCR4 was measured by flow cytometry. Representative histograms are shown. Gray histogram, control IgG staining (SmoA1 medulloblastoma cells); blue histogram, thymocytes; red histogram, SmoA1 medulloblastoma cells. C, CXCR7 gene expression from mouse brain and tumor tissue was analyzed as in A. ***, P < 0.001, unpaired t test.