PTCH1 and medulloblastoma: In our study, we have silenced expression of GLI1 using a small interfering RNA (siRNA), followed by the determination of gene expression patterns of PTCH1, Cyclin D2, Plakoglobin, NKX2.2 and PAX6 in 14 cell lines and 41 primary medulloblastoma and astrocytoma tumor samples.