Monoamine oxidase A (MAOA), primarily known as a mitochondrial enzyme in the brain (Kolla and Bortolato, 2020) and as an immune checkpoint in antitumor therapy (Wang et al., 2021), also negatively regulates the Trp metabolism-mediated anti-ferroptotic pathways that promote tumor growth (Liu et al., 2023). Here, MAOA is linked to neoplasm.