The miR-16-1-3p suppresses proliferation and invasiveness via the MDM2-p53 axis in TGF-β1 signaling in osteosarcoma

The TGF-β signaling pathway has both tumor-suppressive and metastasis-promoting effects in cancer, yet the molecular determinants governing this switch remain unclear. Here, we investigated the miR-16-1-3p/MDM2/p53 axis as a potential regulator of TGF-β/Smad signaling output in osteosarcoma. miR-16-1-3p overexpression alone markedly reduced the proliferative and clonogenic potential of U2OS cells, while its combination with TGF-β treatment strongly enhanced G1-phase arrest and nearly abolished tumor growth capacity. miR-16-1-3p inhibited TGF-β-induced actin remodeling and epithelial-mesenchymal transition (EMT)-associated changes. While TGF-β promoted both 2D and 3D migration, miR-16-1-3p overexpression, alone or combined with TGF-β, counteracted its pro-migratory effects. Mechanistically, miR-16-1-3p reduced MDM2 expression and stabilized p53, which was associated with enhanced p21 induction and suppression of proliferative responses under TGF-β stimulation. Co-administration of TGF-β and miR-16-1-3p markedly increased cisplatin sensitivity in wild-type U2OS cells and reduced tumor nodule volume, Ki67 expression, and metastasis in the chicken chorioallantoic membrane model. Collectively, these findings suggest that miR-16-1-3p biases TGF-β signaling output toward anti-growth responses, while attenuating pro-migratory effects through MDM2 inhibition and p53 stabilization, providing a mechanistic rationale for improving therapeutic responses in osteosarcoma.