KDR and osteosarcoma: VEGFR2 (vascular endothelial growth factor receptor 2), the main VEGF-A receptor involved in angiogenesis and vasculogenesis, and PD-L1, expressed in 64.5% and 35.5% of osteosarcoma cells, respectively, were associated with a pro-metastatic effect in the lungs, and tumor growth [30].