SHH and medulloblastoma: To determine whether CD15+ population isolated from SmoA1 PTEN+/+ tumors resembled human SHH-driven MB at a molecular level, we performed gene expression analysis on CD15+ and CD15- tumor cells isolated from SmoA1 PTEN+/+ tumors and compared the resulting gene expression profiles with the gene expression profiles of recently identified 6 molecular subgroups of human medulloblastoma tumor samples (c1-c6) defined by Cho et al [4].