HIF1A and brain neoplasm: ROS-mediated AMPK activation induced HIF-1α expression and transactivation to simultaneously increase the transcriptional expression of the three SSP genes as well as the expression of genes for glucose transporters and glycolytic process, thereby enhancing glucose uptake, glycolytic flux, and de novo serine and glycine biosynthesis to promote the survival and proliferation of GBM cells and brain tumor growth under the brain microenvironment of restricted serine/glycine (Fig. 7D and E).