PTCH1 and myeloid leukemia: As the Hh receptor Ptch1 is an Hh target gene, this receptor has been shown to be overexpressed in many cancers such as lung, breast, prostate, ovary, colon, brain, melanoma [21,37,38], and myeloid leukemia [15,39] (see the Human Protein Atlas website http://www.proteinatlas.org/ENSG00000185920-PTCH1/cancer, [40]) (Figure 1).