ROS play important roles in cancer cell signalling,39 proliferation40 and the regulation of apoptosis,41 as well as cancer cell invasion and migration.42 Integrin-mediated changes in mitochondrial function that result in an increase in ROS production constitute an important mechanism of migration.43 Increased levels of ROS then serve as important mediators (activators) of Src and FAK signalling to regulate cell motility. This evidence concerns the gene PTK2 and cancer.