EGR1 Mediates Riluzole-Induced Apoptosis in Osteosarcoma via the Yap/p73-Bax Signaling Axis

Osteosarcoma (OS), although rare, is the most common primary bone cancer, primarily affecting individuals aged 10-30 years. Despite therapeutic advances, survival rates have remained stagnant for decades. Recent studies show that Riluzole, a glutamate receptor antagonist, induces apoptosis in OS cells both in vitro and in vivo. Our previous work demonstrated that Riluzole increases reactive oxygen species (ROS), activating c-Abl kinase, which phosphorylates Yes-associated protein (Yap) at tyrosine 357. This modification promotes nuclear translocation of Yap and interaction with p73, enhancing Bax expression and inducing apoptosis. Early Growth Response 1 (EGR1), a zinc finger transcription factor often linked to apoptosis in other cancers, is significantly downregulated in OS. Here, we investigated the role of EGR1 in Riluzole-mediated apoptosis across OS cell lines and patient-derived xenografts (PDX). In this study, we show that Riluzole upregulates EGR1 expression in all OS cell lines. Chromatin immunoprecipitation followed by qPCR confirmed that EGR1 directly binds to the Bax promoter along with Yap/p73, enhancing Bax expression. Immunohistochemistry of in vivo xenograft tumors from Riluzole-treated mice revealed increased EGR1 and cleaved caspase-3 levels, indicating elevated apoptosis, while reduced NUMA expression suggested diminished tumor proliferation. Together, these findings reveal a novel mechanism where Riluzole promotes apoptosis through upregulation of EGR1, which then cooperates with YAP/p73 to activate Bax expression. These insights establish Riluzole as a promising therapeutic intervention for OS treatment through modulation of the EGR1/Yap/p73/Bax signaling axis.