Within HH signaling pathway, Smo protein is often utilized as the drug target because of (1) the ability to transduce downstream signaling pathways in cancers with a loss of function of Ptch1, (2) cancer-causing capacity in the presence of aberrant expression, and (3) the hydrophobic structural transmembrane helical domain capable of binding a variety of small-molecule drugs. This evidence concerns the gene PTCH1 and cancer.