YAP/TAZ inhibition reduces metastatic potential of Ewing sarcoma cells

Abstract

Ewing sarcoma (EwS) is a highly metastatic bone cancer characterized by the ETS fusion oncoprotein EWS-FLI1. EwS cells are phenotypically highly plastic and switch between functionally distinct cell states dependent on EWS-FLI1 fluctuations. Whereas EWS-FLI1high cells proliferate, EWS-FLI1low cells are migratory and invasive. Recently, we reported activation of MRTFB and TEAD, effectors of RhoA and Hippo signalling, upon low EWS-FLI1, orchestrating key steps of the EwS migratory gene expression program. TEAD and its co-activators YAP and TAZ are commonly overexpressed in cancer, providing attractive therapeutic targets. We find TAZ levels to increase in the migratory EWS-FLI1low state and to associate with adverse prognosis in EwS patients. We tested the effects of the potent YAP/TAZ/TEAD complex inhibitor verteporfin on EwS cell migration in vitro and on metastasis in vivo. Verteporfin suppressed expression of EWS-FLI1 regulated cytoskeletal genes involved in actin signalling to the extracellular matrix, effectively blocked F-actin and focal-adhesion assembly and inhibited EwS cell migration at submicromolar concentrations. In a mouse EwS xenograft model, verteporfin treatment reduced relapses at the surgical site and delayed lung metastasis. These data suggest that YAP/TAZ pathway inhibition may prevent EwS cell dissemination and metastasis, justifying further preclinical development of YAP/TAZ inhibitors for EwS treatment.

Ewing Sarcoma—Diagnosis, Treatment, Clinical Challenges and Future Perspectives

“…In addition, EWS-FLI1 low cells are more chemoresistant, upregulate immune modulators PD-L1 and PD-L2, are resistant to T-cell mediated apoptosis, and upregulate angiogenic switch genes in response to Wnts [337,338]. We found MRTFB/YAP/TAZ/TEAD signaling as a master gene regulatory pathway specifically activated in EWSR1-FLI1 low cells [336], and treatment of EwS xenografts with the YAP/TAZ inhibitor verteporfin tended to reduce lung metastases in an orthotopic limb amputation xenograft mouse model [339]. In line, a recent study immunohistochemically identified an association of high YAP/TAZ expression with poor prognosis in a series of 55 tumors [340].…”

“…Increasing tissue stiffness is a major component promoting transforming oncogene function [356], and one may therefore speculate that it also impacts on aggressiveness of bone metastatic disease. Hippo/YAP/TAZ signaling serves as the major cellular mechanosensor of the metastatic niche microenvironment, and increased YAP and TAZ protein expression and activity have recently been associated with low EWSR1-FLI1 levels and adverse disease outcome in EwS [336,339,340].…”

“…Removal of the tumor-bearing limb allows longer survival of the animal and the growth of spontaneous metastases. This approach was used to further demonstrate the importance of EphA2 [392] to show the anti-metastatic effect of treatment of the mice with the WNT pathway signaling inhibitor, WNT974 [396,397]. Another aspect of metastasis biology that has been explored is the role of immune cells, including the role of M2 macrophages promoting EwS [398]; the effect of expanded human NK cells in controlling primary and metastatic EwS [399].…”

Hot Spot Analysis of YAP-TEAD Protein-Protein Interaction Using the Fragment Molecular Orbital Method and Its Application for Inhibitor Discovery

“…The following primary antibody was used for PLA assay: YAP (63.7; Santa Cruz Biotechnology), TEAD (D3F7L, Cell signaling). Cells were then subjected to proximity ligation assays using the Duolink™ In Situ Red Starter Kit Mouse/Rabbit (DUO92101; Sigma-Aldrich/Merck) and following the manufacturer's instructions [58].…”

Unraveling the IGF System Interactome in Sarcomas Exploits Novel Therapeutic Options

“…Recent findings in Ewing sarcoma demonstrated that TEAD triggers cytoskeletal riorganization in cells characterized by low levels of EWS-FLI1 fusion protein [235] and this is relevant considering that there are data indicating that low EWS-FLI1 levels might promote Ewing sarcoma migration, invasion and metastasis [228]. Published data suggested that TAZ might play a relevant role in metastatic onset [235].…”