Fig. 2From: The role of hedgehog signaling in gastric cancer: molecular mechanisms, clinical potential, and perspectiveMechanisms of Hh signaling pathway in cancer. a Ligand-independent mechanism: somatic mutations in PTCH1 or SMO lead to constitutive activation of Hh signaling. b-d Ligand-dependent mechanisms: autocrine regulation (b), paracrine regulation (c), and reverse paracrine regulation (d). Figure created with BioRenderBack to article page