The YAP1 signaling inhibitors, verteporfin and CA3, suppress the mesothelioma cancer stem cell phenotype.

Molecular Cancer Research 2019 Novemver 15 [Link]

Eckert RL, Kandasamy S, Adhikary G, Rorke EA, Friedberg JS, Mickle MB, Alexander HR


Mesothelioma is an aggressive cancer that has a poor prognosis. Tumors develop in the mesothelial lining of the pleural and peritoneal cavities in response to asbestos exposure. Surgical debulking followed by chemotherapy is initially effective, but this treatment ultimately selects for resistant cells that form aggressive and therapy resistant recurrent tumors. Mesothelioma cancer stem cells (MCS cells) are a highly aggressive subpopulation present in these tumors that are responsible for tumor maintenance and drug resistance. In the present manuscript, we examine the impact of targeting YAP1/TAZ/TEAD signaling in MCS cells. YAP1, TAZ and TEADs are transcriptional mediators of the Hippo signaling cascade that activate gene expression to drive tumor formation. We show that two YAP1 signaling inhibitors, verteporfin and CA3, attenuate the MCS cell phenotype. Verteporfin or CA3 treatment reduces YAP1/TEAD level/activity to suppress MCS cell spheroid formation, matrigel invasion, migration and tumor formation. These agents also increase MCS cell apoptosis. Moreover, constitutively-active YAP1 expression antagonizes inhibitor action, suggesting that loss of YAP1/TAZ/TEAD signaling is required for response to verteporfin and CA3. These agents are active against mesothelioma cells derived from peritoneal (epithelioid) and patient-derived pleural (sarcomatoid) mesothelioma, suggesting that targeting YAP1/TEAD signaling may be a useful treatment strategy. Implications: These studies suggest that inhibition of YAP1 signaling may be a viable approach to treating mesothelioma.