SAG is a potent Smoothened (Smo) receptor agonist (Kd = 59 nM); sag antagonizes cyclopamine action at the Smo receptor. SAG potently activates the Hedgehog signaling pathway in Shh-light 2 cells (EC50 ~ 3 nM). SAG induces pathway activation independently of Ptch proteins. The Smoothened receptor (SMO) mediates signal transduction in the hedgehog pathway, which is implicated in normal development and carcinogenesis. SMO antagonists can suppress the growth of some tumours.