Mitochondrial one-carbon metabolism maintains redox balance during hypoxia.

Mitochondria generate high levels of reactive oxygen species (ROS) to activate protumorigenic signaling pathways. In parallel, the mitochondria must also increase their antioxidant capacity to lower ROS levels and prevent cancer cell death. In this issue of Cancer Discovery, Ye and colleagues demonstrate that serine catabolism through one-carbon metabolism within the mitochondrial matrix is necessary to maintain this redox balance.