A major repressor of YAP function is the tumor-suppressive Hippo pathway,154,158 which is represented by a serine/threonine kinase cascade in which the mammalian sterile 20-like kinase 1 or 2 (MST1 or MST2) binds and phosphorylates the scaffold protein Salvador homolog 1 (SAV1). This evidence concerns the gene SAV1 and neoplasm.