YAP, TAZ, and Hippo-Dysregulating Fusion Proteins in Cancer

Gene fusions are well-known drivers of cancer and are potent targets for molecular therapy. An emerging spectrum of human tumors harbors recurrent and pathognomonic gene fusions that involve the transcriptional coactivator YAP1 (which encodes the protein YAP) or its paralog WWTR1 (which encodes the protein TAZ). YAP and TAZ are frequently activated in cancer and are the transcriptional effectors of the Hippo pathway, a highly conserved kinase cascade that regulates diverse functions such as organ size, development, and homeostasis. In this review, we discuss the tumors that have YAP, TAZ, or other Hippo-dysregulating fusion proteins; the mechanisms of these fusion proteins in driving their respective tumors; and the potential vulnerabilities of these chimeric oncoproteins across cancers of many origins. Furthermore, as new YAP1 and WWTR1 gene fusions are discovered, we provide a framework to predict whether the resulting protein product is likely to be oncogenic.