By using Ru5a, a structural analog of Ru5 incorporating a photo-affinity tag, we identify that mitochondrial ATP synthase (ATPase) is the most important molecular target of Ru5. The findings from subsequent studies indicate that Ru5 functions as an ATPase inhibitor, resulting in mitochondrial dysfunction and subsequently leading to ferroptosis and epithelial-to-mesenchymal transition (EMT) inhibition in cancer cells (Scheme 1B). Here, DNAH8 is linked to cancer.