Hippo signaling pathway, also known as the Salvador/Warts/Hippo (SWH) pathway, controls organ size in animals through the regulation of cell proliferationand apoptosis. The Hippo pathway consists of a core kinase cascade in which Hpo phosphorylates the protein kinase Warts (Wts) Hpo (MST1/2 in mammals) is a member of the Ste-20 family of protein kinases. This highly conserved group of serine/threonine kinases regulates several cellular processes, including cell proliferation, apoptosis, and various stress responses.