AMPK Signaling Regulates Epithelioid Hemangioendothelioma Cell Growth

<b>Background/Objectives:</b> Epithelioid Hemangioendothelioma (EHE) is an ultra-rare, metastatic vascular sarcoma with limited therapeutic options. The hallmark of EHE is a chromosomal translocation that produces the <i>WWTR1-CAMTA1</i> gene fusion, encoding the aberrant transcriptional regulator TAZ-CAMTA1. Given its central role in the EHE initiation and progression, TAZ-CAMTA1 represents a compelling therapeutic target. <b>Methods and Results:</b> In this study, we identified AMP-activated protein kinase (AMPK) as one of several proteins capable of repressing the TAZ-CAMTA1 transcriptional activity in NIH3T3 and HEK293 cell lines. The pharmacologic activation of AMPK inhibited the proliferation of EHE cell lines without inducing apoptosis; however, in contrast to the NIH3T3 and HEK293 models, AMPK activation in EHE cells unexpectedly increased the TAZ-CAMTA1 expression and activity. Notably, elevated TAZ-CAMTA1 expression was also associated with reduced EHE cell growth, suggesting that the induction of TAZ-CAMTA1 may be one mechanism by which AMPK suppresses EHE growth. Additionally, we found that AMPK inhibits mTOR activity and that direct mTOR inhibition also suppresses EHE cell growth. <b>Conclusions</b>: Together, these findings demonstrate that AMPK activation impairs EHE viability through dual mechanisms: by promoting TAZ-CAMTA1 expression and by inhibiting mTOR signaling. This work highlights AMPK as a potential therapeutic target in EHE and supports the growing body of evidence favoring mTOR inhibitors as promising treatments for this rare cancer.