Role of the Hippo-YAP/TAZ Pathway in Epithelioid Hemangioendothelioma and its Potential as a Therapeutic Target

Epithelioid hemangioendothelioma (EHE) is a rare malignant vascular tumor arising from vascular endothelial cells. This study delves into the molecular mechanisms underlying EHE, with a specific focus on the Hippo-YAP/TAZ pathway. EHE is characterized molecularly by transcriptional co-activator with a PDZ-motif (TAZ)-calmodulin binding transcription activator 1 (CAMTA1) or Yes-associated protein (YAP)-transcription factor E3 (TFE3) fusions. YAP/TAZ, a transcription co-activator, binds to transcription factors and regulates gene expression. The YAP/TAZ and its upstream Hippo pathway are involved in cell proliferation and cell contact inhibition, regulating organ size and carcinogenesis. In addition to oncogenic effects, dysfunction or gene duplication of the Hippo pathway results in a poor prognosis due to epithelial-mesenchymal transformation of epithelial cells, stem cell transformation, and increased drug resistance. Notably, the TAZ-CAMTA1 fusion is specific to EHE, and genetic alterations in the Hippo pathway other than this fusion gene are absent in EHE. The TAZ-CAMTA1 fusion is a promising therapeutic target. This review summarizes recent advances in EHE, focusing on the role of the Hippo-YAP/TAZ pathway in EHE and its potential as a therapeutic target for drug development.