Among the signaling pathways that include platelet-derived growth factor (PDGF), tumor growth factor beta (TGF-β), and sonic hedgehog (SHH) signaling pathways, we pay particular attention to the Hippo-YAP/TAZ signaling pathway in this review and introduce recent findings of new roles of YAP/TAZ signaling in hepatic fibrosis and cancer. Here, WWTR1 is linked to cancer.