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

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.