In support of their proposition, when human MDA-MB-231 or murine EO771 breast cancer cells expressing mitochondrial catalase (mCAT) to neutralise reactive oxidative stress (ROS) were injected directly into the hindlimb muscles of mice, 6 out of 19 treated animals examined 6 weeks later developed a tumour signal compared to 1 out of 19 mice administered with control cancer cells. Here, CAT is linked to neoplasm.