Hypoxia induces hypoxia-inducible factor (HIF)-1α expression, which stimulates glycolysis in Tregs through the upregulation of the glucose transporter and glycolytic enzymes and suppression of mitochondrial respiration.93 HIF-1α-deficient Tregs have impaired migration but increased immunosuppressive function in mice with brain tumors.93 Here, HIF1A is linked to brain neoplasm.