TGFB1 and osteosarcoma: Zhang et al. reported that TGF-β1 signaling and a hypoxic environment induced CSC phenotypes in a non-CSC population and that the blockage of TGF-β1 signaling inhibited the dedifferentiation and clonogenicity of osteosarcoma cells and reduced CSC self-renewal capacity, suggesting that CSCs may be yielded from differentiated cells [70].