PTCH1 and medulloblastoma: The role of epigenetic regulation of Ptch1 expression seemed to be crucial in heterozygous Ptch1 mice, since a combined treatment with the DNA-methyltransferase1 inhibitor 5-aza-2′deoxycytidine and the histone deacetylase inhibitor valproic acid efficiently prevented RMS and medulloblastoma formation in this model [29].