Abstract A07: Role of YAP/TEAD and YAP/Smad signaling pathways in osteosarcoma tumor growth and lung metastasis dissemination
Authors: Morice Sarah , Mullard Mathilde , Renault Sarah , Amiaud Jérôme , Brion Régis , Corre Isabelle , Gomez-Brouchet Anne , Redini Françoise , Verrecchia Franck 
Published: September 2020

Abstract
Osteosarcoma (OS) is the main malignant primary bone tumor in children and adolescents for whom the prognosis remains poor, especially when metastases are present at diagnosis. Because Hippo/YAP cascade plays a crucial role in cancer progression, we investigated its implication in OS development. Using proximity ligation assay and immunoprecipitation approaches, and promoter/reporter assays, we demonstrated a functional interaction between YAP and the transcriptional factor TEAD-1 in OS cell lines. To understand the specific role of this YAP/TEAD-1 interaction to regulate OS tumor growth, we generated OS cells that overexpressed a YAP protein able (YAP127A) or not able (YAP94A) to interact with TEAD-1. Using in vitro experiments and a preclinical model of OS, we demonstrated that YAP overexpression stimulates respectively OS cell proliferation and tumor growth only when YAP is able to interact with TEAD-1. Furthermore, the overexpression of YAPS94A reduces specific TEAD-1 transcriptional response and in vivo tumor growth. In contrast, the ability of YAP to stimulate OS cell migration does not depend on its ability to interact with TEAD-1. In addition, the effect of YAP overexpression (YAPS94A and YAPS127A) on OS cell migration is associated with cytoskeleton reorganization. Since we previously demonstrated the crucial role of the TGF-β/Smad3 signaling pathway in OS migration and metastatic development, we study the interaction between YAP and Smad3 in OS cells. Using proximity ligation assay and immunoprecipitation approaches, and promoter/reporter assays, we demonstrated a functional interaction between YAP and the transcriptional factor Smad3 in OS cell lines regardless of YAP’s ability to interact with TEAD-1. Finally, we investigated the effect of verteporfin, identified as an inhibitor of the Hippo signaling pathway, on OS progression. In vitro and in vivo experiments showed that verteporfin inhibits YAP/TEAD-1 cascade, OS cell proliferation, and reduces primary tumor growth. In addition, verteporfin reduces in vivo lung metastases development. In this context, in vitro experiments demonstrated that verteprofin inhibits the TGF-β/Smad3 cascade and the response of TGF-β key targets involved in the metastasis dissemination process. Together these results demonstrate that YAP/TEAD-1 interactions are crucial in OS tumor growth and suggest that YAP/SMAD3 interactions are involved in OS lung metastasis dissemination. Furthermore, we show that verteporfin may be a promising therapeutic strategy against tumor progression of OS, specifically against lung metastasis dissemination.
Citation Format: Sarah Morice, Mathilde Mullard, Sarah Renault, Jérôme Amiaud, Régis Brion, Isabelle Corre, Anne Gomez-Brouchet, Françoise Redini, Franck Verrecchia. Role of YAP/TEAD and YAP/Smad signaling pathways in osteosarcoma tumor growth and lung metastasis dissemination [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr A07.