SMO and acute myeloid leukemia: Wellbrock et al. [8], in their work on the Hedgehog (Hh) pathway, observed the expression of the Smoothened (SMO) and Patched-1 (PTCH1) receptors, as well as their downstream mediators, GLI1, GLI2, and GLI3, but did not detect any expression of Hedgehog ligands in AML cells.