HIF1A and neoplasm: Mitochondrial-produced ROS have been recently involved in metastatic dissemination of cancer cells, as shown by Ishikawa et al. These authors described how replacing the endogenous mitochondrial DNA in a weakly metastatic tumour cell line with mitochondrial DNA from a highly metastatic cell line enhanced tumour progression through increased production of ROS and HIF-1α stabilization [1].