YAP1 and cancer: Accumulated evidence shows that Hippo signaling is a key regulator, and activation of the Hippo pathway acts as a tumor-suppressive in several human cancers, for example, gastric cancer [15], lung cancer [16], and HCC [17–20], etc. YAP and TAZ, the effectors of the Hippo pathway, are transcription co-activators that serve as oncogenes in tumorigenesis and development in several cancers [21].