KDR and osteosarcoma: KEGG analysis showed that KDR_EC was enriched in HIF‐1, VEGF and platelet activation signalling pathways (Figure 6B) as they highly expressed the VEGF receptors FLT1 (VEGFR1) and KDR (VEGFR2) and the neovascular development biomarkers PLVAP and MCAM (Figure 6C),44 suggesting that these cells are involved in angiogenesis of osteosarcoma TME.