A miR-30 Guided Molecular Profiling of Canine Osteosarcoma and Extraskeletal Osteosarcoma Reveals Non-Seed Regulatory Divergence

Osteosarcoma (OS) and extraskeletal osteosarcoma (EOS) in dogs exhibit histological similarities but differ in anatomical origin, which poses a challenge to diagnostic accuracy. We adopted a marker-first strategy to enhance molecular classification by selecting RUNX2, KPNA2, and SATB2, three validated immunohistochemical (IHC) markers, as primary targets. Bioinformatic screening identified the miR-30 family as the only miRNA group predicted to coordinately regulate RUNX2, KPNA2, and SATB2, justifying its prioritization for expression analysis. RT-qPCR on FFPE tissues from 14 OS, 19 EOS, and 10 healthy controls revealed that miR-30a was significantly downregulated in OS and inversely correlated with RUNX2 nuclear expression, confirmed by IHC. MiR-30e also showed high diagnostic accuracy, while miR-30b and miR-30c distinguished EOS from OS. Non-seed interaction modeling (i.e., outside the canonical "seed" region, spanning nucleotides 2-8 of the miRNA) suggested divergent regulatory affinities within the PI3K/AKT/RUNX2 axis among miR-30 family members. MiR-30a and miR-30e exhibited the highest diagnostic power (LR⁺ 7.7 and 6.8, respectively), supporting their role as biomarkers. These results highlight a miR-30-centered regulatory axis with relevance for diagnosis and molecular stratification of canine osteogenic tumors.