In tumor tissue, intermittent blood supply leads to an alternating situation of lack-of-oxygen and reoxygenation, which causes oxidative stress.23, 36 Hypoxia induces a HIF-1α-dependent accumulation of lipid droplets and decreased FAO in tumor cells, whereas the hypoxia-reoxygenation leads to increased FAO in MCF-7 breast cancer cells, thereby providing reduced power to protect against accumulation of ROS.37 Current studies further demonstrated that HIF-1 inhibited two enzymes in FAO, the medium- and long-chain acyl-CoA dehydrogenases MCAD and LCAD. The gene discussed is HIF1A; the disease is breast cancer.