Cross-species microRNA expression patterns identify potential therapeutic targets in osteosarcoma

Osteosarcoma is the most common primary bone tumour in both humans and dogs. In both species, osteosarcoma displays a marked propensity for pulmonary metastasis, making canines a robust and clinically relevant translational model of the disease. With current standard-of-care treatment, the 5-year survival rate for humans with localized osteosarcoma is approximately 60-70%, but falls to around 20-30% for patients presenting with metastatic disease. In dogs, amputation followed by chemotherapy yields a median survival time of roughly 10-12 months, with fewer than 20% surviving beyond two years. Despite incremental improvements in supportive care, therapeutic strategies for osteosarcoma have remained largely unchanged for more than three decades in both species, highlighting the need for novel prognostic indicators and therapeutic targets. MicroRNAs (miRNAs) are small, non-coding RNAs that can function as tumour suppressors or oncogenes. They are expressed across diverse tissues and are known to exhibit dysregulation in cancer. In this study, 20 osteosarcoma cell lines (6 human and 14 canine), derived from both primary and metastatic tumours, were evaluated for key malignant behaviours using a series of in vitro functional assays. These included measurements of proliferation (doubling time), migration (scratch and transwell assays), anchorage-independent survival (anoikis assay), invasion (drop invasion assay), and colony formation (clonogenic assay). RNA was subsequently isolated from each cell line, and expression of 48 candidate miRNAs was quantified using real-time quantitative polymerase chain reaction (RT-qPCR). Each miRNA was correlated with measured behaviours using Pearson's r and false discovery rate (FDR) analysis. Ten miRNAs were significantly associated with at least one behaviour at p < 0.05 following FDR correction. Notably, miR-708-5p demonstrated significant correlations with multiple malignant phenotypes, including doubling time, migration, and colony formation. MiRNA expression profiles, therefore, revealed several candidates associated with malignant behaviour, suggesting that select miRNAs may contribute to disease progression and represent promising targets for future therapeutic development.