Angio-Associated Migratory Cell Protein (AAMP) Regulates the Hippo/YAP Pathway and Mitochondrial Functionality to Drive Osteosarcoma Metastasis

Abstract Background: Osteosarcoma (OS) is the prevalent form of primary bone cancer among adolescents, but the 5-year overall survival rate for patients with a metastatic or recurrent OS is under 20%. Angio-associated migratory cell protein (AAMP) is known to be a key regulator of cellular migration, yet its role in the context of OS metastasis has yet to be firmly established.Methods: Bioinformatics analyses were used to explore the association between AAMP and YAP expression and the prognosis of OS patients, and to evaluate differences in AAMP expression in patients with primary OS, recurrent OS, and pulmonary metastatic OS. Immunohistochemical (IHC) staining was additionally performed to compare AAMP levels in primary OS and pulmonary metastatic OS patient samples. Lentiviral transduction was further used to establish OS cell lines in which AAMP or YAP had been stably knocked down or overexpressed. OS cell migration and invasion were assessed using wound healing and Transwell assays. Proteins associated with the mitochondria, the epithelial-mesenchymal transition (EMT), YAP, and its target proteins were assessed in OS cell lines via Western blotting. OS cell lamellipodia were detected via phalloidin staining. Mitochondrial morphological characteristics were assessed via transmission electron microscopy following the knockdown of AAMP. An ATP kit was employed to measure ATP levels in OS cells in which AAMP had been knocked down. Animal model studies were used to confirm indices associated with OS cell lung metastasis following AAMP knockdown. Results: Patients with metastatic OS exhibit higher levels of AAMP expression that are correlated with poorer patient prognosis. Knocking down AAMP suppressed the migratory, invasive, and EMT activity of analyzed OS cell lines. AAMP was found to regulate CFL1 and thereby control OS cell protrusion. AAMP knockdown was further found to promote OS cell mitochondrial dysfunction and decreased intracellular ATP production, with these AAMP knockdown cells exhibiting impaired migratory and invasive activity as a consequence of YAP inhibition. Consistently, the knockdown of AAMP suppressed the in vivo metastasis of OS cells. Conclusions: Together, these data highlight a model wherein AAMP can promote OS cell migratory and invasive activity by regulating YAP and mitochondrial functionality. The AAMP/CFL1/YAP signaling pathway may thus represent a viable therapeutic target for efforts aimed at suppressing the metastatic progression of OS.