SMO and chronic myelogenous leukemia, BCR-ABL1 positive: In fact, the Hh pathway in CML LSCs is triggered by attaching a ligand, sonic hedgehog (SHH), to the PTCH receptor, which removes PTCH-mediated suppression of SMO, and a conformational change of SMO, which stimulates the glioma-linked oncogene (GLI1 and GLI2) transcription factor, leading to reduced apoptosis [133, 134].