Thirdly, many of the network hubs identified during exposure to continuous hypoxia were not differentially expressed during cyclical hypoxia (Figure 5, Table 1), including the most densely connected node, Fos (FBJ osteosarcoma oncogene), and several other key transcriptional regulators such as early growth response 1 and 2 (Egr1, Egr2), and TATA box binding protein (Tbp). This evidence concerns the gene EGR2 and osteosarcoma.