TGFB1 and osteosarcoma: It is now known that TGFβ1 promotes EMT through Smad‐dependent transcriptional regulation of HMGA2, which further induces expression of the important EMT‐associated transcription factors Snail, Slug, and Twist.8 Our previous report showed that human apurinic/apyrimidinic endonuclease 1 (APE1) promotes transcriptional activation of TGFβ1 expression in osteosarcoma cells.9 We have clearly shown that APE1 knockdown downregulated TGFβ1 mRNA, intracellular protein, and secretion levels, which further attenuated in vitro angiogenesis.