PTCH2 and central nervous system cancer: Our results corroborate those of Yang et al. [64] in the sense that Shh inhibition was produced after HDAC6 silencing, as they demonstrated that HDAC6 was upregulated in glioma stem cells compared to non-stem tumor cells, and that HDAC6 inhibition downregulated Gli1, Ptch1, and Ptch2 expression and activity in glioma stem cells.