LncDARS-AS1 Regulates ATP1A1 Stability and Enhances Na⁺/K⁺ ATPase Activity to Promote Osteosarcoma Metastasis

Osteosarcoma, the most prevalent malignant bone tumour in children and adolescents, exhibits aggressive pulmonary metastasis and poor prognosis. This study identifies LncDARS-AS1 as a key regulator of metastasis via modulation of ATP1A1, the catalytic subunit of Na⁺/K⁺ ATPase (NKA). Transcriptomic analyses, validated by qPCR in 217 osteosarcoma RNA samples, reveal that LncDARS-AS1 is significantly upregulated in metastatic lesions and associated with adverse clinical outcomes. Functional assays confirm that silencing LncDARS-AS1 suppresses osteosarcoma proliferation and metastasis in vitro and in vivo. Mechanistically, LncDARS-AS1 directly binds ATP1A1, preventing its interaction with the UBQLN4 and subsequent proteasomal degradation, thereby enhancing NKA activity. Protein-RNA interactions were validated using ChIRP, mass spectrometry, molecular docking, and molecular dynamics simulations. Functional NKA activity was assessed using ion-sensitive fluorescent indicators and enzymatic assays. Additionally, digoxin, a cardiac glycoside targeting NKA, effectively inhibited tumour growth and metastasis at clinically safe concentrations. These findings uncover a novel LncDARS-AS1/ATP1A1 axis that promotes osteosarcoma metastasis through inhibition of ubiquitin-mediated degradation and provide a rationale for repurposing digoxin in osteosarcoma therapy. ATP1A1 emerges as a promising target for anti-metastatic intervention.