HIF1A and osteosarcoma: Hypoxia rapidly stabilised HIF-1α and HIF-2α in all three osteosarcoma cell lines and the corresponding up-regulation of CA IX protein levels (Figure 2A), Glut-1 mRNA levels (Figure 2B) and levels of secreted VEGF-A (Figure 2C), indicates that it is transcriptionally active in these cell lines.